HYPNOSIS

ABSTRACT

     A comprehensive theory of hypnosis is presented which attempts to explain the three main aspects of hypnosis in terms of principles of condi­tioning and inhibition.  (1) Hypnotic induction is explained as a conditioning procedure for producing an inhibitory set. (2) Hypnotic phenomena (increased responsiveness to suggestion) occur because this set can inhibit stimuli (both sensory and cognitive) which would ordinarily contradict the suggested response. (3) Post-hypnotic behavior changes are explained as occurring through a process of higher-order conditioning; this conditioning being facilitated by the inhibitory set which inhibits stimuli that would be incompatible with the new association. The theory is felt to be broad enough to cover not only hypnosis and suggestion, but also such related areas as persuasion, the placebo effect and faith, as well as throw added light on the area of conditioning.

A THEORY OF HYPNOSIS: AN EXPLANATION OF HYPNOTIC
INDUCTION, HYPNOTIC PHENOMENA, AND
POST-HYPNOTIC SUGGESTION ¹

Alfred A. Barrios

Self-Programmed Control Center, Culver City, CA

            Throughout the years many extraordinary phenomena have been at­tributed to the effects of hypnosis and great claims made as to its efficacy in therapy. Yet, in spite of such claims, it seems that there continues to be relatively little interest shown in it by the psychological and psychiatric community. Why?

            It is felt that the reason for the continued apathy toward hypnosis is not that the claims made for it are untrue or exaggerated, but that it is still virtually an unknown. This unknown quality has led to the arousal of fears (an innate response to an unknown), many misconceptions and various unjust criticisms, and, consequently, rejection or avoidance of the area. What we are in need of, then, is a rational theory or explanation of hypnosis, one that will tie it down to known laws and facts. and, thus, help us to make the most of this vast, unexplored area. The following theory is presented as an attempt at achieving this goal.

           The theory will be divided into three major sections, one each for what is felt are the three major aspects of hypnosis. Each section will start off with definitions of terms, then the major hypotheses and their corollaries will be presented together with available evidence in support of them, followed by suggestion for further tests.   There are a total or seven hypothesis making up the theoretical system. Hypotheses I - III deal with the first aspect, the hypnotic induction   Hypotheses IV and V deal with the second aspect, hypnotic phenomena.  Hypotheses VI and VII deal with the third aspect, post hypnotic suggestion. The reason for dividing the theory into three sections is to emphasize the fact that when one attempts to explain hypnosis, he has to do more than just explain hypnotic phenomena. He has also to explain how the hypnotic state was produced and how hypnosis can produce post-hypnotic behavior changes. Most previous theories deal only with hypnotic phenomena, per se.

            The overall explanation presented will he based mainly on principles of conditioning and inhibition delineated in the postulates. Briefly, hypnotic induction will be explained as the conditioning of an inhibitory set, a set which increases responsiveness to suggestion by inhibiting stimuli and thoughts incompatible with a suggested response. The various hypnotic phenomena, including the phenomenon of post-hypnotic suggestion, will then be explained in terms of this set.

The theory presented herein was part of a doctoral dissertation completed in 1969 at the University of California, Los Angeles.  The work was supported in part by a Public Health Ser­vice fellowship (MPM-l3, 264-cl) from the National Institute of Mental Health, Public Health Service.

BASIC POSTULATES

       One of the major purposes of any theory or explanation should be to tie the phenomena to be explained down to known laws. This can be done by first stating the known laws and then showing how the theory (the system of hypotheses explaining the phenomena) can be deduced from these laws or can be shown to be compatible with them. In what follows, we will present the known ''laws'' (the postulates) that the theory of hyp­nosis will be tied down to.

       As the reader goes through the postulates, he should keep in mind that at the present stage the science of psychology has not yet advanced to the point where we can really speak in terms of “laws, “ in the sense of firmly established and accepted laws.  Thus, he is not expected to accept absolutely the validity of the postulates. However, it is felt that sufficient evidence will be presented to show that these postulates are reasonable approximations to established laws. How close an approxima­tion they are will, to a large extent, be mirrored by how valid are the hypotheses and corollaries deduced from these laws. Thus, if the hypo­theses of the present theory are tested and validated, then the validity of the postulates themselves will be further strengthened.

Postulate I.                                Reciprocal Inhibition

            When an organism is attending or responding to one Stimulus, there will be a

reciprocal inhibition of incompatible stimuli and responses.

            Sherrington (1906, 1940) was one of the first to discover the phenomenon of reciprocal inhibition. He found that “incompatible movements such as turning the eyes to the right and left are so controlled in their nerve centers that with increased activity of one muscle goes decreased activity of its antagonist. The same type of inhibition is observed in human attention and distraction, since in attending to one object, you cease attending to another.” (Woodworth and Schlosberg, 1954, p. 669).

            The latter contention is supported by the work of Hernández-Peón (1959) who has shown that when an organism is attentive to one stimulus other stimuli impinging upon it tend to be inhibited.  This centrifugal inhibition of afferent sources has been demonstrated for all sense modalities  (Lindsley, 1961). Which stimulus will be most likely to be attended or responded to (and, therefore, which stimuli will be inhibited) in a given situation will depend on a number of different factors, such as: stimulus intensity, novelty of the stimulus, acquired significance of the stimulus, sense modality, etc. (Berlyne, 1960). Some types of stimuli, then will have preference or dominance over others, and they, in turn, will have dominance over others, and so on, thus forming a “stimulus dominance hierarchy” (SDH).

Corollary 1:     If a dominant stimulus is itself inhibited or eliminated, those stimuli below it in the hierarchy which it was reciprocally inhibiting will now be responded to more strongly.

Postulate II.                                 Cognitive Stimuli

            Behavior is determined by cognitive stimuli as well as sensory stimuli.

            We know that an organism's behavior in a given situation can be determined by certain innate behavior patterns. A pin prick will evoke a pain response (withdrawal of the injured part, crying out, heart racing, palms sweating, etc.); salt on the tongue will elicit salivation; stimulation of the erogenous zones will evoke certain patterns of physiological res­ponses; etc. Such stimulation seems to trigger “built-in” or  innate patterns of behavior.  But we also know that organisms do not always make the same response to the same stimulus. Learning or conditioning can and does play a very big part, especially with humans, in modifying be­havior. For example, the response resulting from stimulation of the erogenous zones will vary from individual to individual as a result or the individual's previous experience; i.e., his previous conditioning.  If a person has been taught that sex is something dirty and bad, he could easily respond with feelings of disgust or guilt rather than with the normal (“built in”) sexual response. Thus, we can say that stimulation can also trigger “acquired” or learned patterns of behavior.

           One way of conceptualizing this modification of behavior by learn­ing is to think of the organism as reacting not only to sensory stimuli but reacting as well to what may be called memory, recorded. or “cog­nitive” stimuli. A sensory stimulus can be defined as coming to the organism via the sensory pathways. A ''cognitive stimulus" will herein be defined as a stimulus emanating from engrams (permanent traces or recordings of past experiences in the brain). It is postulated that this stimulus is as potentially capable of initiating and directing behavior as any sensory stimulus. This means, for instance, that a stimulus dominance hierarchy can be made up of both sensory and cognitive stimuli.

            These engrams are felt to he formed through a process of conditioning (see Postulate III, below) and are triggered by the conditioned stimulus. This conditioned stimulus can be either a sensory stimulus or another cognitive stimulus. For example, the thought of a steak (a cognitive stimulus) can be triggered by the smell of a steak cooking (a sensory stimulus) or the thought of a particular restaurant specializing in steaks (a cognitive stimulus).

            Under the heading of cognitive stimuli we would find such things as thoughts, images, beliefs, sets, values, attitudes, ideas, etc. A cognitive stimulus can also be looked upon as the equivalent of  Hull's (1933) “pure stimulus act”, Tolman's (1932) “expectancy”, Osgood's (1948) “representational mechanism”,  etc.

            The reason for using the term “cognitive stimulus'' rather than such terms as “expectancy,”  “thought,” or “cognition” is that inclusion of the term "stimulus'' more strongly implies action.  In the past, cog­nitive theorists have been usually criticized for leaving their subjects ''lost in thought''.

            Support for the contention that permanent records of previous ex­perience (engrams) are stored in the brain comes from at least two sources. First, there is the work done by Penfield (1954) where he has reported that electrical stimulation of the temporal cortex of humans causes the subject to experience images so vivid that they are difficult to tell from reality. These hallucinations are reenactments of actual experiences from the recent or distant past. (“Both old and recent memories are evoked with equal ease.'')                                                         

     ''In general, the recollections produced by stimulation seem to be as clear as   they would be seconds after the experience. In fact, they are apparently as clear as they were during the ex­perience.. . It is an episode in which action goes forward and the patient is an actor. He may seem to see and hear and react as well.'' (p. 99)

             The work of Penfield ties in with clinical reports that brain tumors in the temporal cortex can also lead to complex and elaborate hallucina­tions (Weinberger and Grant, 1940). It is proposed that the irritation due to the tumor and the electrical stimulation both serve to trigger the engram which, in turn, leads to the hallucinations.

             A second source of evidence in support of the existence of engrams which might be used is the recent work which implicates RNA in the process of memory storage. These studies, summarized in a number of recent articles and books (Brazier, 1964; Landauer, 1964; Gaito and Zavala, 1964;  Jacobson, 1966), suggest that previous experiences are recorded  in the brain by restructuring of the RNA molecule. According to Landauer (1964), for example, when two stimuli, the CS and US, are paired, RNA representing the CS enters the neurons activated by the US. The result of incorporating the new RNA, which represents the CS, alters the recipient. or US cells, so as to make them more likely to fire in the presence of the spreading electrical activity generated by the CS. Thus, the engrams we are talking about could be thought of as the restructured RNA molecules that have entered the neurons normally activated by the US. A cognitive stimulus would be the stimulation propagated by the al­tered US cells upon stimulation by the CS.

            One very important implication from the above engram concept is that all recorded experiences are subject to “replay” if the appropriate engram is triggered. Extinction or forgetting would be explained in terms or an interference hypothesis; that is, “replay” would fail to occur if there were more dominant stimuli present which led to responses incompatible with the response evoked by the CS.  If these competing responses could be eliminated, then the appropriate engram could be trig­gered (i.e.. the appropriate cognitive stimulus could be evoked).

Postulate III.                                          Conditioning

            If an organism attends to two stimuli occurring in close contiguity, these two stimuli will become associated so that upon later oc­currence of the first stimulus the reaction to the second will occur.

            This postulate is essentially the “S-S Contiguity” interpretation of conditioning with the added stipulation that the organism must be aware of or attentive to the two stimuli. This awareness or attention addendum has recently been shown to be necessary by a number of investigators: Guthrie (1959); Speilberger (1962) Dulany (1962); Maltzman (1966); and Trabasso and Bower (1968). Thus, according to this postulate, (1) association occurs between stimuli and not a stimulus and response as called for by the S-R approach; and (2) contiguity of the attended stimuli is the necessary and sufficient condition for conditioning to take place and not drive or need reduction as called for by the “Law of Effect” approach. It is the authors opinion that the evidence indicates that this is the more general and parsimonious of the three major systematic points of view that have dominated the psychology of learning (namely, the S-S Contiguity, the S-R Contiguity and the S-R Effect approaches).

            As pointed out, the S-S Contiguity approach says first of all that association occurs between stimuli and not between a stimulus and a response. This, of course, does not mean that a stimulus cannot become associated with a response. The S-S position would explain an association between a stimulus, S₁ and a response, R₂, by positing that the  association takes place between S₁ and S₂ where S₂ is a stimulus which normally evokes R₂. It is felt the S-S position is more general than the strict S-R approach because as well as explaining association between stimuli and responses, it can also explain the formation of associations between stimuli where no visible response is involved. (One of the major shortcomings or the S-R position, we feel, has been that it is more difficult for S-R theorists to conceive of conditioning taking place when no visible response is known to occur.) Evidence in support of the conten­tion that associations can take place between stimuli without necessitating a response comes from a number of areas of study. Among them are: (1) sensory preconditioning, (2) perceptual learning, and (3) learning without overt response. An extensive review of these areas can be found in Kimble (1961).

            In addition to saying that associations take place between stimuli, Postulate III states that contiguity of the stimuli in the focus of attention is the necessary and sufficient condition for the association to take place. This is opposed to the “Effect” position which proposes that, in addition to contiguity, some form of drive or need reduction is necessary for the association to take place. Although there is no denying that reward or drive reduction can facilitate conditioning, there is considerable evidence to show that conditioning can, however, still take place without the neces­sity of drive reduction.

            The evidence against a strict “Effect” position comes from several areas of study (also reviewed in Kimble, 1961). These are: (1) the latent learning studies, (2) the saccharine studies, (3) the exploration studies, and (4) the brain stimulation studies, in addition to the sensory precondi­tioning and perceptual learning studies already mentioned.

Corollary 2:              Whatever would raise the stimuli to be paired in the stimulus dominance hierarchy should facilitate the conditioning.

              This follows from the postulate since the latter states that the CS and US must be in the focus of attention to be paired. If there are other, more dominant, stimuli present, this condition will not be met.²   Thus, anything that would inhibit competing stimuli should facilitate conditioning.

Corollary 3:   Words can act as conditioned stimuli which can evoke cogni­tive stimuli mediating responses similar to those evoked by the original unconditioned stimuli.

              Pavlov was one of the first to recognize that words could act as conditioned stimuli.

              ''Obviously for man speech provides conditioned stimuli which are just as real as any other stimuli. . . . Speech on account of the whole preceding life of the adult, is connected up with all the internal and external stimuli which can reach the cortex, signaling all of them and replacing all of them, and therefore it can call forth all those reactions of the organism which are normally determined by the actual stimuli themselves.” ­(Pavlov, 1960, p. 407)

            That words can act as conditioned stimuli is supported by a number of experiments. As pointed out by Platinov (l959), Vasileyva found that he could condition a stable defensive motor response to the word ''bell''.  Hudgins (1933) was able to condition the pupils of his subjects eyes to contract upon thinking the word ''contract''.  Menzies (1941), by associating the word ''crosses'', with immersion of the hand in cold water, was able to condition his subjects so that when they said the word “crosses” a drop in the temperature of the hand resulted. This contention is also concurred with by Hull:

                    “In the suggestion experiments the words of the experimenter presumably are merely performing the function served by the ar­bitrary sounds, temperatures, etc. (conditioned stimuli) in the conditioned reflex experiments.” (Hull. 1933, p. 280)

An interesting point to ponder is that the reinforcing effects of the drive reducers (such as food and sex) might themselves be subsumed under a stimulation explanation of reinforcement. This is the case if we consider the possibility that it is the drive reducer’s resulting stimulation of arousal which plays the major role in reinforcement rather than reduction of a drive, per se. This seems to fit in with the position taken by Sheffield's  (1966) ''Drive Induction” and Miller's (1963) ''Go-Mechanism” explanation of drive reduction in conditioning. The reason that most drive reducers can be such effective reinforcers could be that they are stimuli which, due to their high arousal value, would be placed high in a stimulus dominance hierarchy, as well as place any stimulus they become associated with high in the hierarchy.

           That words can evoke responses similar to those evoked by the un­conditioned stimuli they are a substitute for is also supported by the available evidence.  For instance, Schultz (1950), Vandell, Davis and Uugston (1943), Max (1937), and Jacobson (1938), among others, “have shown quite satisfactorily that thought can give rise to specific patterns of muscular tension and activity, particularly in those muscles that are symbo­lically represented in the thought in question." (Weitzenhoffer, 1953, p. 246).  There are also a number of experiments where it has been shown that various physiological and perceptual responses can be evoked by means of waking suggestion. These are best summarized in Barber’s two review articles on the physiological effects of suggestion (1961, 1965). Among the responses he reports evoked by waking suggestion, we find such things as heart acceleration and deceleration, color blindness, deafness, autonomic changes. salivation, analgesia, and allergic dermatitis. (Heart acceleration, for example, could be produced by words associated with fear-producing stimuli; i.e., by suggesting something fearful.)

Corollary 4:  A reciprocal inhibitory response can be conditioned like any other response if it occurs contiguously with the conditioned stimulus.

            First of all, we know that an inhibitory response can be conditioned just like any other response.  For example, Pavlov (1960), referring to experiments in his laboratory by Volborth, concluded that “if an inhibitory stimulus is applied simultaneously and repeatedly for short periods of time together with some neutral stimulus, the latter also develops an inhibitory function of its own.” (p. 106; see also p. 404)

           Under Postulate I we saw that when an organism is responding to one stimulus, there occurs a reciprocal inhibition of any stimuli that would lead to incompatible responses.  The case in favor of the contention that this type of inhibitory response can be conditioned is very nicely presented by Wolpe (1958) in his book, Psychotherapy by Reciprocal Inhibition.  For example, among other things, he refers to Pavlov’s experiment where a strong electric current was made the conditioned stimulus for a feeding response in a dog:

                    “The current was in time gradually increased (with feeding) until it was extremely strong, but even then no defensive reaction was manifested.  In other words, the pathways normally connecting the electrical stimulus with the defense reaction had become inhibited.  It would appear that at every stage of the experiment the performance of the feeding response involved a reciprocal inhibition of the mild defense reaction aroused by the electrical stimulus.After many repetitions of the procedure, in the course of which the current was gradually stepped up, so great a degree of conditioned inhibition of the defense reaction to the current was established that even very strong electrical stimuli were unable to evoke that reaction, but evoked only the feeding response.”  (Wolpe, 1958, p. 30)

            The important thing to note here is that in conditioning the feeding response, the inhibitory response --inhibition of the defense reaction-- was simultaneously being conditioned.

            Wolpe also cites as evidence various experiments done on cats whereby neurotic anxiety reactions were overcome by opposing them with feeding reactions.  To this evidence can be added Watson’s “Peter and the Rabbit” experiments wherein a phobia of rabbits was gradually extinguished by having the child eat his meals in the presence of the feared rabbit.  (Watson, 1957, pp. 172 - 175)  Wolpe’s position is apparently supported by at least one learning theorist.  Osgood discussing what he refers to as “an hypothesis of reciprocal inhibition of antagonistic reactions” states that

            Simultaneous with every increment in excitatory habit tendency in the association of a given stimulus with a given reaction, there is also generated an equal increment of inhibitory habit tendency in the association of the same stimulus with the directly antagonistic reaction.  In other words, simultaneous with learning any response, the S is also learning not to make the directly antagonistic response.  (Osgood, 1948, p. 150)

Corollary 5:  If a set to inhibit certain stimuli is conditioned to a given CS, the presence of this CS will facilitate the occurrence of any response that would ordinarily be interfered with by these stimuli.

            This corollary is derived from Postulates I and III.  It is given substantial support by the work of Harlow on learning sets and error factor theory (Koch, 1959).  In a number of experiments he has shown that when monkeys are given a series of different discrimination problems to learn, a “learning set” is gradually established which facilitates the making of new, different, discrimination responses.  (The CS referred to in the postulate in this case would be any stimulus or stimuli which are always present from problem to problem, such as the presence of the experimenter himself.)

            Harlow explains this facilitation in terms of learned (conditioned) inhibition.  He proposes a hypothesis similar to Wolpe’s --that in learning to make a particular response the organism learns to inhibit all interfering or incompatible stimuli, or what he calls error factors (EF’s).  In fact, he goes so far as to say that “learning is nothing but suppressions or inhibitions of EF’s”  (Koch, 1959, p. 526).  Harlow feels that when the monkey is asked to make a new discrimination response, this learned inhibition of EF’s facilitates the making of the new response.  This is because many of the EF’s inhibited in learning the previous problems are potential interferers of the new response as well.

            Also in support of Corollary 5 is the fact (as pointed out by Harlow) that in most learning experiments the investigator often finds it quite advantageous to “adapt” his animals to the experimental situation prior to the start of the learning.  “...Psychologists have been doing this for decades, e.g., ‘adapting’ rats on a straight-away before training them on a multiple unit maze, thereby doubtless reducing error-producing factors in advance of the ‘learning’ situation.” (Koch, 1959, p. 526).  This adaptation procedure can be looked upon as the establishment of a conditioned inhibition of irrelevant responses.  This conditioned inhibition is evoked in the learning situation by the stimuli that are common to both the adaptation trials and the learning trials.

                            EXPLANATION OF HYPNOTIC INDUCTION (HI)

            In the following an attempt will be made to explain hypnotic induction in terms of the principles of conditioning and inhibition outlined in the above postulates.  It will be shown how the hypnotic induction can be explained as the conditioning of an inhibitory

set --a set which increases responsiveness to suggestion by inhibiting stimuli (sensory and cognitive) incompatible with the suggestion.  This explanation will then be condensed into three major hypotheses and evidence presented in their support.  Finally, some of the major individual factors that can influence the hypnotic induction, such as prestige, expectation, fears, and age, are discussed and their roles explained in terms of the theory.

            The first step in the explanation will be to define the terms to be used, then we shall attempt to fit the HI into a conditioning paradigm.

Definitions

Suggestion

            The definition of suggestion given in Warren’s (1934) dictionary is as follows:  “A suggestion is a stimulus, usually verbal in nature, by which an individual seeks to arouse activity in another by circumventing the critical, integrative functions.” (p. 267)  The following is the definition of suggestion given by McDougall (1908, p. 100):  “Suggestion is a process of communication resulting in the acceptance with conviction of the communicated proposition in the absence of logically adequate grounds for its acceptance.”  Hull defines suggestion as follows:  “...A true suggestion response is one in which the subject’s own symbolic process, instead of becoming active either in facilitating or resisting the tendency to action naturally arising from the experimenter’s words, remains passive so far as the particular act suggested is concerned.”  (Hull, 1933, p. 307)

            Lindzey (1954, p. 27), summarizing a number of definitions of suggestion, states:

                      “In these and in similar definitions, attention is called to some arbitrary restriction in the determinants of behavior.  The individual is not employing all relevant ideas, nor his full intelligence.  Granted that suggestion proceeds according to the laws of association (conditioning), still we must also allow for the blocking of normal  association, so that the end result in behavior is due to a selected field on determinants.”

           The definition of suggestion which will be used in the present paper is as follows:

A suggestion is a stimulus or set of stimuli, usually verbal in nature, by which one    individual (1) evokes a cognitive stimulus in another, and (2) at the same time evokes an inhibitory set which tends to inhibit stimuli (sensory or cognitive) incompatible with the cognitive stimulus evoked.³

           The only major difference between this definition and the previous ones mentioned is the addition in the parentheses--that sensory stimuli, as well as cognitive stimuli tend to be inhibited by the inhibitory set.  All of the above definitions seem to stress the inhibition of cognitive stimuli and do not mention inhibition of sensory stimuli.

           It should be stressed that both hypnotic and waking suggestion have an inhibitory set component.  The only difference between hypnotic and waking suggestion is that for a given individual, the former should have a larger inhibitory set component as a result of the hypnotic induction.  The size of the inhibitory set for waking suggestion will vary from individual to individual depending on certain factors, such as prestige for example, (these are discussed in a later section).  This means that for a particular suggestion, the response could be greater for one individual in the waking state than for another individual in the hypnotic state.

Hypersuggestibility

Hypersuggestibility is defined as a state where the cognitive stimulus evoked by a suggestion is responded to more readily or strongly than usual because the usually competing stimuli have been reduced or inhibited.

(The usual responsiveness to suggestion could be predetermined for each individual.)

            There are, of course, numerous ways other than hypnotic induction for bringing about a state of hypersuggestibility.  For example, sensory deprivation is known to lead to such a state (Jackson and Pollard, 1962; Jackson and Kelly, 1962; Pollard, Uhr and Jackson, 1963).  The hallucinogenic drugs (e.g., LSD and mescaline), which act as inhibitors, are also known to produce states of hypersuggestibility (Barrios, 1965; Sjobert, 1965; Solursh and Rae, 1966).

Hypnosis

Hypnosis is defined as a state of hypersuggestibility arrived at by means of a hypnotic induction.

³ It should be mentioned that the evocation of the cognitive stimulus alone will cause a certain amount of inhibition of competing stimuli just as the evocation of any stimulus would.  However, in a suggestion we find the additional inhibitory “aid” of the inhibitory set.

            It is a hypersuggestible state (i.e., more suggestible than normal) because when a suggestion is given, the inhibitory set part of suggestion for a given individual is greater in scope that it is in the normal state.

Hypnotic Induction (HI)

   Hypnotic induction is defined as the giving of two or more suggestions in succession so  

that a positive response to one increases the probability of responding to the next one.

            That the author is not alone in his feelings that a positive response to a series of suggestions or assertions leads to a state of hypnosis is illustrated by the following statements made by Skinner (1957):

                        "With respect to a particular speaker, the behavior of the listener is also a function of what is called belief (a term very similar to suggestibility). ...Our belief in what some one tells us is similarly a function of, or identical with, our tendency to act upon the verbal stimuli which he provides. If we have always been successful when responding with respect to his verbal behavior, our belief will be strong. ... (pp. 159-160)

                  "The listener reacts to the behavior of a given speaker to an extent determined by the consequences of past reactions. The speaker can build confidence or belief by saying many things which are obviously true or quickly confirmed or by resorting to rhetorical devices. ... (p. 365)

                  "Various devices used professionally to increase the belief of a listener (for example by salesmen or therapists) can be analyzed in these terms. The therapist may begin with a number of statements which are so obviously true that the listener's behavior is strongly reinforced. Later a strong reaction is obtained to statements which would otherwise have led to little or no response. Hypnosis is not at the moment very well understood, but it seems to exemplify a heightened ‘ belief  ‘ in the present sense." (p. 160)

           From the definition of HI used in the present paper, then, the reader can begin to see the fairly broad scope of the theory of hypnosis presented in this paper. It can not only be used to explain the phenomenal effects of hypnosis, in the accepted sense of the term, but also the hypnotic effects (persuasibility) of salesmen, lawyers, politicians, etc.; the hypnotic effects (placebo effect) of psychotherapists and doctors of medicine; and even the hypnotic effects (faith) of ministers and faith healers.                                                                

            This definition of HI does not differentiate between waking suggestions and trance or sleep suggestions. That is, we can conceive of the "formal hypnotic induction" suggestions of eyelid closure, drowsiness, sleep, etc., as just so many more waking suggestions. "Sleep suggestions, " however, may, in addition, further aid the hypnotic induction since the sleep-like state thus produced may provide for even greater inhibition of stimuli competing with the suggestions. ⁴ As Hull puts it,

     "It is a very general custom of hypnotists to give suggestions of relaxation while inducing the trance. ... The present hypothesis assumes that this relaxation has the effect more or less completely of suppressing the spontaneous activity of the

symbolic thought processes. With this suppression should disappear the control normally exercised by symbolism over the lower levels of activity. This should leave the latter more completely exposed to the influence of suggestive stimuli from outside sources. ..." (Hull, 1933, p.310)

Hypnotic Induction in a Classical Conditioning Paradigm

     In this section, we will attempt to show how the hypnotic induction is actually a conditioning process.

Understanding the Conditioning Paradigm

            Before we show how the hypnotic induction fits into the conditioning paradigm we must first be sure we understand the conditioning paradigm. First of all, as pointed out in the conditioning postulate, for a process to be called conditioning it must involve two stimuli presented together contiguously and in the focus of attention. In classical conditioning the two stimuli are usually referred to as the CS and the UCS. The CS is usually some neutral stimulus (i.e., no observable response is evoked or at least not the response to be conditioned) and the UCS is a stimulus which evokes some innate response (e.g., food --salvation; shock --withdrawal). However, and this is an important point to keep in mind, there is nothing that says that the UCS has to evoke an innate response. The UCS, or second stimulus in the pair, can be one that evokes a learned or previously conditioned response. In classical conditioning, this is referred to as higher-order conditioning and as Hebb (1949) has pointed out, most conditioning in the mature organism is of this higher-order variety.

⁴ It should be stressed that in the present theory sleep suggestions are not a necessary condition for hypnotic induction. Thus, the use of the term "hypnotic," which means "tending to produce sleep," is perhaps misleading and it might be appropriate to eventually change it.

            Another thing to keep in mind is the nature of the response conditioned (the CR). We know that in a conditioning situation the experimenter (E) is not always interested in the entire response to the UCS. He usually focuses on one component of the UCR which he is interested in associating with the CS. Usually, this component is some positive response (e.g., salvation, eye-blink, withdrawal, etc.). However from our reciprocal inhibition postulate, we know that occurring with each positive response there is also a reciprocal inhibitory response. Now, in applying the conditioning paradigm to hypnotic induction, we will be focusing on the inhibitory component rather than the positive component.

            Finally, a third thing to keep in mind is that the CS need not be something as obvious as a bell ringing, but can also be the very presence of the experimenter and  any action on his part which is repeated prior to each time the UCS is presented.

            Now let us indicate specifically what the CS, UCS, UCR, CR, the trials and reinforcement are:

The Various Classical Conditioning Components in the HI

            The conditioned stimulus (CS) is the following general stimulus situation: The hypnotist making a suggestion during a hypnotic induction.

            The unconditioned stimulus (UCS) is the particular words of the hypnotist evoking the cognitive stimulus which leads to the particular suggested response. This UCS, of course, is a "second-order" UCS in that it evokes its response as a result of previous conditioning and not innately.

            As an illustration of the distinction between this CS and UCS (since at first glance they do appear to be indistinguishable), let us take the suggestion, "You will now feel your arm pulled up. " The CS would be the first part of the suggestion; i.e. the hypnotist saying the words, "You will now..." which essentially would precede each suggestion in the hypnotic induction series. The UCS would be the specific suggestion "... feel your arm pulled up. " The CS is always the same. The UCS varies with each suggestion.

            The unconditioned response (UCR) is the reciprocal inhibition of stimuli incompatible with the particular suggested response. This inhibitory response occurs automatically when the suggested response occurs. Three of the major classes of stimuli inhibited would be the following: (1) specific stimuli in direct contradiction to the suggested response: for example, if it is suggested that the subject see a watermelon on a table that is actually empty, the sensory stimulus "empty table" would be in direct contradiction to the image "watermelon on table;" (2) general irrelevant but attention-catching stimuli like a door slamming or an itch; and (3) certain general negative attitudes (e.g., skepticism) and fears (e.g., fear of the unknown) which interfere with theconditioning during hypnotic induction in a number of ways. (This will be discussed further in a later section.)

            The conditioned response (CR) is the following response: Inhibition of stimuli incompatible with the previous suggested responses. This CR is evoked upon the presentation of the CS--i.e., when the hypnotist makes a suggestion(4). It can be measured directly in terms of inhibition of competing stimuli (e.g., see Hernández-Peón, et al 1960) or it can be measured indirectly by measuring the increase in strength of the suggested response, since according to the stimulus dominance hierarchy postulate, by inhibiting competing stimuli the inhibitory set would increase response to the suggestion.

            A trial would be considered that period during which a suggestion is made and the suggested response occurs. Each trial need not necessarily be thought of as involving a different type of response. When a suggestion is repeated (and each suggestion is usually repeated a number of times in most hypnotic inductions), a trial can be thought of as taking place with each repetition. Each repetition would be expected to lead to a stronger response and thus a greater inhibitory set.

            Reinforcement is regarded here in terms of a contiguity point of view. As pointed out in the conditioning postulate3 all that is necessary for conditioning to take place is that the two stimuli (the CS and the UCS) occur contiguously and in the focus of attention.

(4) It could very well be that this conditioned inhibitory response will not appear to be a discreet one, that is, evoked only when the hypnotist makes a suggestion, but may instead appear to be a continous one, present even between suggestions. This would best be explained in terms of generalization. The inhibitory response, rather than become associated specifically with the CS we have designated (i.e., the hypnotist making a suggestion), may also become associated with other components of the whole hypnotic setting as well.

Analysis of the HI in Terms of the Classical Conditioning Components

            Let us now look at the hypnotic induction in the above terms.

            First suggestion (first trial). When the initial suggestion is responded to (i.e., when the first presentation of the UCS leads to its response), a certain proportion of stimuli incompatible with the suggested response are reciprocally inhibited (the UCR). This inhibition is conditioned to the hypnotist making a suggestion (the CS) so that when the hypnotist makes his next suggestion (when the CS is presented again) a conditioned inhibitory response (the CR) is evoked; i.e., those stimuli inhibited during the response to the first suggestion are now automatically inhibited prior to the response to the second suggestion.

            Second suggestion (second trial). Since a certain proportion of competing stimuli will now automatically be inhibited when the hypnotist makes a suggestion the probability of evoking the next suggested response is increased. When this second suggestion is positively responded to, another proportion of incompatible stimuli will be inhibited. As was the case in the first trial, this inhibitory response becomes conditioned to the CS so that on the succeeding trial an even greater proportion of competing stimuli arc now inhibited, thus further facilitating the response to suggestion.

            Succeeding suggestions (succeeding trials). Each succeeding suggestion positively responded to will now add to the proportion of incompatible stimuli inhibited until, conceivably, a point is reached where all incompatible stimuli are automatically inhibited when the hypnotist makes a suggestion. (It is as if S's focus of attention were gradually being narrowed more and more until the only stimuli reacted to were the cognitive stimuli evoked by the hypnotist.) This would be called a 'deep" state of hypnosis.

            The hypnotic induction is ended by suggesting that S will "awaken” or come back to normal, whereupon the inhibitory set which has been developed during the induction becomes inhibited itself. That the hypnotic conditioning can be so quickly “extinguished" by such a suggestion should not be so surprising to those who are familiar with the part that cognitive factors can play in extinction (e.g., see Spence, 1963).

            It should be mentioned that very often in a hypnotic induction, after getting a positive response to a suggestion, the hypnotist will then remove the suggestion. For example, after getting a positive response to the suggestion, "Your arm will become as stiff and rigid as a steel bar, the hypnotist usually follows with, "Your arm will now loosen up and is now no longer rigid. " Knowing this, one might be inclined to think that such removal or reversal of the suggestion would undo the conditioning of the inhibitory set accomplished by that suggestion. Actually, this apparent paradox can be explained if we realize that most of the stimuli that would have to be suppressed in order for the first suggestion (“stiff arm”) to be responded to would be the same as those that would have to be suppressed for the second suggestion (“loose arm”). For example, there is the attitude of skepticism (a cognitive stimulus), the suppression of which would facilitate both responses.

            This paradox of reversal learning has been explained in a similar manner by Harlow and his Error-Factor theory. As Harlow points out, “…discrimination learning and reversal are not antithetical processes. So far as EF elimination is concerned, the two learning problems have more in common than at variance." (Harlow, 1959, p. 522) If we under stand Harlow correctly, error-producing factors (EF) can be looked upon as what we refer to as incompatible stimuli or stimuli that lead to wrong responses. Thus, he is saying that the discrimination and discrimination reversal problems, although involving apparently opposite responses, require suppression of many similar incompatible stimuli.

Instant Hypnosis

            Very often we see or hear of a hypnotist putting a subject under hypnosis instantaneously by merely snapping his finger or whispering certain key words in the subject's ear. This type of instant hypnosis most likely occurs as a result of the subject being previously hypnotized and given the post-hypnotic suggestion that he will go back under hypnosis upon a given cue. The inhibitory set developed during the hypnotic induction is conditioned to this cue by means of this post-hypnotic suggestion (see section below on post-hypnotic suggestion) and thus re-evoked when the cue is presented.

            Instant hypnosis, however, can also occur without the subject directly being hypnotized previously by the hypnotist. This can happen when the subject has heard of or seen the hypnotist's great effectiveness and believed it. In a sense, this subject is already hypnotized or conditioned by having heard or seen the positive responses achieved by the hypnotist, (This is discussed further in the section on prestige, below.)

Self-Hypnosis

            A self-hypnotic induction can be explained in much the same way as the hypnotic induction above. The only major difference in this case is that the subject plays the part of both the hypnotist as well as the subject. To put it in terms of the conditioning paradigm, the only major difference is that in self-hypnosis the CS is the following stimulus situation: “the subject giving himself a suggestion during a hypnotic induction” rather than “the hypnotist making a suggestion during a hypnotic induction”.

            There is also instant self-hypnosis. It is explained in the same way as the first type of instant hypnosis, except that the cue the subject is given is a self-induced one. He is also told that in this state he will be able to give himself suggestions in the same way as the hypnotist has, including the suggestion to awaken.

The Explanation of HI in Three Hypotheses

            The above explanation of hypnotic induction can be condensed into three major hypotheses. In this section we shall look at the evidence in support of these hypotheses, as well as suggest further tests.

Hypothesis I: Hypnotic induction is a conditioning process.

            Hull and his coworkers provide a good portion of the evidence bearing on the validity of this hypothesis. In his chapter, “Hypnosis Regarded as Habit,” Hull (1933) proposes that if hypnosis results from a conditioning process, or is a "habit phenomenon” as he prefers to refer to it, it should display certain characteristics common of habit phenomena. (We are making the assumption that habits are types of conditioned responses.) Hull points out six such common characteristics: (1) practice in an act facilitates its subsequent performance; (2) the rate of facilitation in the practice activity is more rapid early in the practice than later; (3) a period of disuse is followed by a partial loss of the facilitation resulting from practice; (4) other things being equal, the loss of facilitation following disuse is less where the original repetitions were widely spaced than where closely spaced; (5) with the resumption of practice this is recovered, the new practice curve showing a picture of negative acceleration; and (6) the amount of loss resulting from disuse is recovered with less practice than was required for its original acquisition.

            In two experiments by Kreuger (1931), one of Hull's associates, it was found that hypnotic induction did indeed display the above characteristics.

            Hull also presents as corroborative evidence a number of experiments showing that waking suggestion (which in the present paper is felt to be essentially equivalent to hypnotic suggestion) has “habituation effects parallel to those shown by Kreuger to be characteristic for the process of hypnotization.” (Hull, 1933, p. 343) These include the experiments of Hull and Huse (1930), Williams (1930), and Patten, Switzer and Hull (1932).

            In concluding the chapter “Hypnosis Regarded as Habit,” Hull states:

   “Such a remarkable and detailed conformity of the phenomena hypnosis to the known experimental characteristics of ordinary habituation can hardly be accidental and without significance. The indications would seem to be that whatever else hypnosis may be it is--to a considerable extent, at least--a habit phenomenon and that quite possibly this hypothesis may furnish the basis for an ultimate understanding and explanation of its hitherto largely inexplicable characteristics. '' (Hull, 1933, p. 347)

            The reader might question the use of Hull's evidence in support of Hypothesis I on the grounds that the latter hypothesis is referring to the conditioning of "an inhibitory set," not a particular response as proposed in Hull's postulate. Actually, there is no real discrepancy here. The author is of the opinion, like Harlow and Osgood, that

"Simultaneous with every increment in excitatory habit tendency in the association of a given stimulus with a given reaction, there is also generated an equal increment of inhibitory habit tendency in the association of the same stimulus with the directly antagonistic reaction" (Osgood, l948, p. 150)

Iand, thus, that both are directly related.

Hypothesis II: The response conditioned during the HI is an inhibitory set, a set which tends to inhibit stimuli incompatible with the response suggested by the hypnotist.

            This hypothesis is, of course, founded to a great extent on Corollary 4 of the postulates, which states that inhibitory responses can be conditioned.

            There are a number of corollaries to Hypothesis II; we shall look at three of them.

Corollary 1: Reactivity to competing stimuli should decrease as the HI progresses.

            This is what we would expect if HI involves the conditioning of an inhibitory bet, and consequently the gradual increasing of the inhibitory set as the HI progresses.

            The results of an experiment by Hernández-Peón , et al (1960) appears to support this corollary. These investigators found that the HI resulted in the diminution of the forearm flexor response elicited by tactile stimulation. (This tactile stimulation can be looked upon as a competing stimulus.) It is interesting to note their interpretation of the results:

"All procedures for inducing hypnosis require the focusing of attention upon the experimenter's verbal stimuli with obliteration of irrelevant stimuli (competing stimuli)…. It does not seem unreasonable that during the hypnotic state itself, the thresholds of perception for modalities other than the auditory are raised by the postulated centrifugal sensory inhibition at lower levels of the central nervous system. ...

”Our results fall in line with the above mentioned hypothesis although sometimes the size of the skin reflex remained unchanged during hypnosis, in most of the experiments a more or less intense diminution was induced by the hypnotic state per se. ...

“Our results agree with those of Scars (1932), Dynes (1932), and Doupe et al. (1939) who recorded during hypnotic anesthesia partial, but significant reduction of non-voluntary physiologic reactions to pain such as the psycho galvanic reflex, respiratory, cardiac, and vasomotor responses." (pp. 37 and 40)

Corollary 2: Increasing the inhibitory response paired with the CS on each trial should facilitate the conditioning (facilitate the hypnotic induction).

            This corollary would help explain how sleep suggestions facilitate the hypnotic induction. Sleep suggestions would produce an added inhibitory response which would summate with the one produced by a positive response to a suggestion, resulting in stronger inhibitory responses with each suggestion.

            The point that sleep suggestions could evoke sleep-like responses was brought out by Pavlov (1960) when discussing methods of hypnotic induction:

“At present the more usual method consists in the repetition of some form of words, describing sleep, articulated in a flat and monotonous tone of voice. Such words-are, of course, conditioned stimuli which have become associated with the state of sleep. In this manner any stimulus which has coincided several times with the development of sleep can now by itself initiate sleep or a hypnotic state.1.” (pp. 404 - 405)

            It should be mentioned that there are at least two possible difficulties with the use of sleep suggestions in a hypnotic induction. First, there is the possibility that the sleep suggestions might be too effective; i.e., the subject might literally fall asleep, which would mean a loss of contact between the hypnotist (H) and the subject (S). One possible way to avoid this is for H to suggest that S will continue to hear his voice even though going into a “deep sleep". The other difficulty is that the sleep-like state produced might interfere with the responsiveness to other suggestions, especially any requiring an alert, awake state. This difficulty might be avoided if prior to such suggestions H suggests that S will be wide awake and very much alert although in a deep state of hypnosis.

            Corollary 2 would also explain why devices which focus S's attention will facilitate the in. As Hernández-Peón (1959) and others have shown, a major component of the attention response is the inhibition of competing stimuli. Any means, then, whereby H can get S to focus his attention (suc as having S look at a shiny crystal or a spinning spiral) should add to the inhibitory response and thus aid the HI.

Corollary 3: The more stimuli brought under the control of the inhibitory set with each succeeding trial (with each suggestion), the more effective the HI and thus the greater the increase in general suggestibility.

            From this we can make at least two predictions:

            (1) The greater the overlap among the stimuli incompatible to two suggestions3 the greater will be the increase in response to the second suggestion when the first one has been positively responded to. This, of course, can be stated another way--the more similar the second suggestion to the first, the greater the increase in responsiveness to the second suggestion when the first one has been positively responded to.

            (2) A hypnotic induction which only involved getting a positive response to the same suggestion over arid over again, or to a series of similar suggestions would not lead to as great an increase in general suggestibility as a hypnotic induction which involved getting a positive response to a series of different suggestions. (Increase in suggestibility would be measured by the increase in responsiveness to a set of suggestions different from those used in the induction.)

            Parenthetically, it should not be inferred from this corollary that for a suggestion to be positively responded to all the stimuli competing with suggested response must be covered by the inhibitory set. One should not forget that it is a combination of the inhibitory set and the strength of the cognitive stimulus evoked which determines the probability of a positive response to a suggestion. Also, there can be degrees of positive response, depending on how many competing stimuli have been inhibited.

Hypothesis III: A positive response to a suggestion will induce within the responding person a more or less generalized increase in the normally existent tendency to respond to succeeding suggestions.

            Hull (1933, pp. 313-314) points out two studies in support of this hypothesis (Caster and Baker, 1932; and Jennes, 1933). Caster and Baker

“took with a stop-watch the suggestion times required to produce lid-closure in ten subjects, (1) preceding positive response to arm suggestion and (2) following such response. Under these conditions the hypothesis demands that the trance induction time following the arm movement should upon the whole be less than that preceding the response to arm suggestion.”

This hypothesis was confirmed in seven out of ten subjects. Jennes (1933), repeating this experiment with some improvements, confirmed the hypothesis in eight of nine subjects.

            The above findings seem to fit in with the reports of a number of investigators:

“Schilder and Kauder (1927), for instance, have pointed out that a number of earlier investigators as well as they themselves had found it efficacious to give their subjects some waking suggestions easy of execution before attempting to hypnotize them. This appeared to facilitate the process.” (Weitzenhoffer, 1953, p. 40)

            Opposed to Hypothesis III we find the results of two of Hull's own experiments (Hull et al., 1933; Fatten et al., 1932). In these experiments he attempted to see if a positive response to one waking suggestion would increase the responsiveness to a second waking suggestion. His results indicated no such increase, thus contradicting the hypothesis. In commenting on the apparent contradiction between these two experiments, and the Caster and Baker and Jennes experiments, Hull states:

“It is difficult to reconcile the results of the two groups of investigations. The problem involved is of such central importance that the experiments should be repeated with judicious variations to make certain whether or not some hidden defect of technique may not have produced this seeming inconsistency, particularly between the study of Jennes (1933) and that of Hull et al. (1933). . . No question in the whole subject of hypnosis and suggestibility is in such urgent need of critical experimentation. (Hull, 1933, p. 393)

            A thorough analysis of the two negative experiments by hull et al. (1933) and Patten et al. (1932) uncovers what well might be a "hidden defect of technique". Both experiments used the following two suggestions:

(l) that the head would rail forward on the chest, and (2) tInt the arm3 which was suspended by a special device, would sway forward (from side to front). The order of these suggestions was, of course, alternated. In both the Hull et al. and Patten et al. experiments, it was found that giving the head suggestion first actually seemed to interfere with the response to the subsequent arm suggestion rather than facilitate it. This, of course, was in direct contradiction to the hypothesis that positive response to direct suggestion, as such, evokes a generalized hypersuggestibility. The possible defect of technique that might explain such contradictory results is the distinct possibility that arm movement might naturally be interfered with more when the head is in the bent-over-on-chest position than when straight up. To illustrate this the reader need only try it himself. If he holds his arm extended then lets his head come down, he will notice that as the head comes down, the arm will also come down a bit as the center of gravity is shifted. This greater pull downward on the arm might explain the longer time for it to sway forward in response to the arm suggestion. This possible explanation is given further support when we see that no such interference with the head suggestion was reported by Hull et al. (1923) when the arm suggestion was given first, and what is more, Batten found that when the arm suggestion was given first, the head suggestion tended to be facilitated (seven out of ten S's).

            The following are a number of corollaries to Hypothesis III, a test of which would be a further test of the hypothesis.

Corollary 4: If a positive response to a suggestion will increase responsiveness to the next suggestion, then a negative response should decrease responsiveness.

            This can easily be tested by giving the subjects in one group one or more very difficult suggestions (i.e.. suggestions with a low probability of being initially evoked) prior to a test suggestion and comparing their response to this test suggestion with that of a second group that does not first get the difficult suggestions.

         Corollary 5: If a series of suggestions are given to the subject, the probability of
         inducing a state of hypnosis will be greater if the suggestions are given in a gradually
         increasing order of difficulty than if they are given in random order.

            This would be predicted since the probability of a positive response to any individual suggestion, according to the theory, is greater the greater the number of positive responses to

previous suggestions, and this is maximized if the suggestions are given in gradually increasing order of difficulty. Each positive response increases the probability of success in the following suggestion.

            It is interesting to look at some of Barber's results in this light (1961, 1965). In a number of studies he has shown that a good many hypnotic phenomena can be gotten by means of waking suggestion, without the need of a "hypnotic induction". (What he considers a hypnotic induction is mainly the giving of sleep or relaxation suggestions.) However, if one looks at Barber's studies, one finds that he usually gives his waking suggestions in a series (sans the "hypnotic induction") usually in gradually increasing order of difficulty. It might very well be that part of the reason for the high percentage of hypnotic-like responses he reports is that he has actually put some of the S's through a hypnotic induction, at least according to its definition in the present paper. In other words, responding positively to the previous suggestion(s) increases the probability of responding to the next one.

Corollary 6:    A hypnotic state can be facilitated if, along with each of the first few suggestions given in the hypnotic induction, the actual sensory stimuli which would ordinarily evoke these suggested responses accompany the suggestions without the subject's knowledge.

            This should be done in such a way that the subject is not aware of the "artificial" cause of the responses so that he will ascribe them solely to the hypnotist's suggestions. It is felt that this can be done, if the sensory stimulus is kept close enough to threshold, almost the point of being sub-threshold. The response to the sensory stimulus would summate with that to the cognitive simulus (evoked by the suggestion) to lead to the overall response.

            The response could be "artificially" induced in a number of ways. For instance, the suggestions that the eyes are going to get tired can be helped if a slight strain is placed on them by having S look at an object at a difficult angle. Or the suggestion that S was going to feel cold could be reinforced by actually lowering the temperature of the room somewhat.

            It is interesting to know that an experiment somewhat along these lines has already been run. This is the "abstract conditioning" experiment of Corn-Becker et al. (1949), where a series of "artificially reinforced" suggestions led to a definite positive response to a subsequent "nonreinforced" suggestion. The main difference between Corn-Becker's experiment and the type proposed by the corollary is that Corn-Becker did not attempt to keep the reinforcing stimuli close enough to threshold, and thus the S's were quite aware of the external cause of the responses and did not think that they were due solely to E's suggestions. One might say that in Corn-Becker's experiment any conditioned inhibitory set was conditioned to the stimulus pattern "Experimenter plus External Stimulation," whereas in the experiment proposed by the corollary the CS would be just "Experimenter" (or Hypnotist). The likely reason that Corn-Becker did get a positive response to the "nonreinforced" suggestion at the end of the series was because of stimulus generalization; i.e., having been conditioned to a stimulus pattern (Experimenter plus External Stimulation), S will still respond to a component of that pattern (Experimenter). However, it would be predicted that such a generalized response would not be as strong (both in terms of amplitude and ease of extinction) as one where the CS is the same one used during the conditioning. Nevertheless, this approach to facilitating HI bears further investigation. It might have the advantage over the "sub-threshold approach" of not attempting to deceive the subject. If deception were detected by a subject, it could produce irrevocable damage to his attitude toward hypnosis.

     Individual Difference Factors Influencing Hypnotic Induction

            In this section we shall list some of the individual difference factors that have been purported to influence HI and attempt to show how their role can be explained in terms of the theory.

     Voluntary Attention (Concentration)                                   

            That people differ in their ability to voluntarily suppress irrelevant stimuli (ability to concentrate) is fairly obvious. We also know that the greater the ability of S to concentrate on H’s suggestions the greater the probability of responding positively to them.  Thus, we would predict that the greater a subject’s ability to concentrate, the greater the probability of success of the HI.

Prestige

            It is fairly well accepted that the more prestige the H has in the eyes of the subject the better his chances of success.  It is felt that this is so because the statements, commands or suggestions of a person with prestige tend to be questioned less; i.e., such a person evokes a greater inhibitory set to begin with.  People, in general, have been previously conditioned to accept at face value the statements of someone who is an authority in his field.  That is, an inhibitory set which inhibits contradictory stimuli has been previously conditioned (much in the same way as in the hypnotic induction process).  This is so because what the authority says has usually turned out to be true.  The more a person is known to be an expert the greater the unquestioning acceptance of his statements (i.e., the greater the inhibitory set).  Thus, when a person hears of a particular hypnotist’s great successes (or witnesses them), this prestige factor or inhibitory set is evoked by the hypnotist and thus aids the HI.  This could be tested by seeing the effect of hypnotizing a shill or previously determined good subject in front of the prospective subject.  At least one experiment has supported the contention that prestige can increase the chances of success in hypnotic induction, that of Das (1960).

            It is felt that if a waking suggestion is effective, it is often, to a great extent, dependent on this prestige factor.

            Related to the prestige effect is the concept of transference as it is used by psychoanalysts in explaining hypnosis.  The latter feel that one of the major factors involved in a hypnotic induction is a transference effect; that is, the subject in going under hypnosis is actually reacting to the hypnotist as he would to his parents when a child.  The prestigeful influence of the parent is “transferred” to the hypnotist during the process of hypnotic induction according to this view.  It could be that certain characteristics of the hypnotist and his hypnotic induction might, through generalization, evoke the child-parent type of prestige effect which could then interact with the hypnotic induction to facilitate it.  How big a factor it will play in the hypnotic induction will be determined by how similar to his parents the subject perceives the hypnotist as being.  It should be pointed out that this transference could also hurt the hypnotic induction if the patient had developed a negative reaction pattern to his parents.

Subject’s Expectation

            The expectation of being hypnotized can have a number of different effects on the hypnotic induction.  First of all, there may be a negative effect produced if the subject has a great fear of hypnosis.  Or, conversely, if he is an adventuresome person and enjoys exploring the “unknown,” it may have a positive effect.  (These effects will be discussed below in the section on fears.)

            A second effect that expectation can have is that of focusing S’s attention on the appropriate CS-CR contingency.  That is, as a result of the expectancy of being hypnotized, the S may be more likely to correctly ascribe the occurrence of the “strange” phenomena to the hypnotist than to some external cause.  For example, if the suggestion of coldness is given in a non-hypnotic setting, S is more likely to ascribe any subsequent feeling of coldness to the possibility that someone has lowered the temperature of the room.  If he doesn’t associate the positive response (and thus the inhibitory response) with the hypnotist (the CS), then the desired conditioning does not take place.  The idea that focusing attention on the contingency would facilitate conditioning is given considerable support by recent studies on the effect of awareness on learning (e.g., Eriksen, 1962).  These studies indicate that the more the subject is aware of the correct contingency the better the conditioning if his attitude is positive. 

            Parenthetically, it might be mentioned that if it is important that the responses be ascribed to the appropriate CS (the hypnotist or “Experimenter”, we should then expect that a subject will be less likely to be hypnotized if he performs the suggested response voluntarily just to please the hypnotist.  If he does this, he would not ascribe the responses to the hypnotist but to his own volition, and thus would defeat the purpose of the HI.

            A third way expectation can influence the hypnotic induction is if S has a certain preconceived notion of what hypnosis is like.  One example of how this can have a negative effect on the hypnotic induction is where the subject incorrectly expects that hypnosis is some state of unconsciousness or sleep.  When he finds himself still aware of things or awake, he thinks that he is not hypnotized.  This negative thought can, of course, have a braking effect on the hypnotic induction.  Such a negative effect can be eliminated, it would seem, by means of a pre-induction talk where S is told that hypnosis is not a state of seep nor unconsciousness and where he is given some idea of what to actually expect.  Another expectation that can hurt a hypnotic induction is one where the subject believes that being hypnotized means responding to every suggestion in the HI.  If a person fails to respond to one for some reason, even after he has successfully responded to the previous ones, he may decide that he is no longer hypnotized and at that point may stop responding to all succeeding suggestions.  To eliminate this, as part of the pre-induction talk, the subject should be told that because of individual differences, there may be some suggestions that work very well for some people but not for others, and, therefore, it should not bother him if he doesn’t respond to a suggestion; in such a case, he should just wait for the next one.

            A subject’s expectation of what hypnosis is like can influence the hypnotic induction in other ways.  For example, if a subject is told that catalepsy of the dominant hand occurs when one goes under hypnosis (Orne, 1959), then as S feels himself being put under, he is also indirectly being given the suggestion of catalepsy of the dominant hand.  This response can, in turn, influence the hypnotic induction, as do any positive responses to previous suggestions.

            This last aspect of expectation has played a major role in the “goal-directed” (white, 1941) and “role-playing” (Sarbin, 1950) theories of hypnosis.  These theories state in essence that hypnotic behavior is a meaningful, goal-directed striving, its most general goal being to behave like a hypnotized person as this is continuously defined by the hypnotist and understood by the subject.

            In two recent experiments by Barber and Calverley (1964b, 1965), the overall effect of expectation of hypnosis was found to have a positive effect. They found that higher scores on the Barber Suggestibility Scale are obtained when the experimental situation is defined as hypnosis rather than as control.

Fears

            Fear of the unknown, mistrust of the hypnotist, fear of revealing "inner secrets," etc., are all examples of fears that can interfere with the hypnotic induction. Because of such fears, any positive response to suggestion during the hypnotic induction would be fear-producing and, thus, tend to be avoided or suppressed, and in this way, interfere with the conditioning of the inhibitory set.⁶ (A pre-induction talk aimed at allaying S's fears should facilitate the hypnotic induction.) Conversely, an attitude of adventuresomeness on the part of the S would probably lead to facilitation of the hypnotic induction. That this seems to be the case is given support by the work of Hilgard (1967). He reports a positive correlation between adventuresome and hypnotic susceptibility.

Motivation

            It is fairly obvious that if a subject is not very much interested in being subjected to a hypnotic induction, his chances of positively responding are much less. In one study by Barber and Calverley (1966) it was shown how important the factors of boredom and disinterest are in affecting S's responsiveness to a hypnotic induction. By repeating the same monotonous HI procedure over a period of eight days, the experimenters produced a significant drop in suggestibility.

Attitudes

            The fact that certain attitudes can influence the HI is fairly well accepted (Weitzenhoffer, 1953, p. 283). For example, in a recent study (Dorcus, 1963) it was found It is true that indications of fear are considered a good sign by some hypnotists (e.g., Gindes, 1951) since this would probably indicate a high degree of expectancy of being hypnotized. However, all things being equal, i.e., if people are matched on degree of expectancy of being hypnotized, it would be predicted that the greater the fear, the greater the interference. that by means of a pre-induction talk aimed at eliminating the interference of certain known negative attitudes (these can be thought of as competing cognitive stimuli), the experimenter was able to hypnotize the six presumably unsusceptible subjects. In this regard, we can also consider the work of Barber. In one study, for example, Barber and Calverley (1964a) found that by manipulating S's attitude towards the task at hand (a suggestibility test) they were able to significantly affect S's suggestibility score in the expected direction. Pre-test instructions aimed at producing a negative attitude led to a considerable drop (almost down to 0) in responsiveness.

            We will now discuss three typical attitudes that might influence the induction and attempt to explain how in terms of the theory.

            One negative attitude which often interferes with hypnotic induction can be called, for want of a better term, "non-submissiveness," or a strong desire to be in control of oneself all the time. This would lead to a decrease in the probability of a positive response to the suggestions of the hypnotist, and thus interfere with the HI, since the desire for self-control would be incompatible with giving up control to the hypnotist. This interference can best be eliminated if the hypnotist does not take the authoritarian attitude as his approach. Many people have the misconception that hypnosis invariably means losing control to someone else. This need not be the case. It can be worked so that the only person gaining greater control over the subject is the subject himself. This can be done by instructing the subject during the pre-induction talk that the hypnotist should be looked upon as an instructor who is merely showing him a technique whereby he can gain greater control over himself, greater control over his involuntary side. He is told that he can reinterpret each suggestion given by the instructor by replacing "you" with "I". For example, if the instructor tells the subject "you will now feel your arm being pulled up," the subject can be telling himself, "I will feel my arm being pulled up." He can also be told that he does not have to respond to a particular suggestion if it annoys him for some reason, and that he can always feel free to "awaken" at any point if he so wishes.

            Still another way of eliminating this problem might be to let the subject hypnotize himself completely. Instead of the H giving S the series of suggestions, S could give them to himself after learning what the series is. This method might have other advantages as well in that S could set his own pace. He would go on to the next suggestion only after succeeding on the previous one. Often, a hypnotist may not spend enough time on a particular suggestion, or, conversely, he might spend too much time on it. (In self-hypnosis, as in hetero-hypnosis, a response is usually considered positive only if it occurs involuntarily.)

            Another common interfering attitude is what can be called the "rational" attitude. Too strong a desire to have a rational explanation for everything can lead the S to ascribe any positive response to "more rational causes" than the hypnotist's suggestions; e.g., "My arm came down because it would naturally get heavy being in such a position for so long," or, "My eyes closed because they would naturally do so after staring so long," etc. And as already pointed out, it is important that the S be focused on the correct CS-CR contingency; that is, he should ascribe a positive response to the hypnotist's suggestions. This negative attitude can best be eliminated if the subject is given a reasonable explanation for hypnosis in the pre-induction talk. For example, it should be stressed that no trickery need be involved in hypnosis; that words can actually evoke such phenomena naturally; that hypnosis is a state where words have a much greater effect because of the highly increased concentration, etc.

           A third common attitude which can interfere with the hypnotic induction is an attitude of skepticism. Skepticism can be thought of as a conditioned set to inhibit response to suggestions and is felt to be a result of a conditioning process where suggestions have been negatively reinforced somewhere in the past of the subject. Such an inhibitory set would naturally interfere with a positive response to H's suggestions and thus interfere with the conditioning process taking place during the HI. Elimination of this skeptical attitude can be helped by making sure that the initial suggestions in the HI have a high probability of success (e.g., the "chevreul pendulum" suggestion--see Weitzenhoffer, 1957).

Imagination

            We would expect that the greater a subject's imagination, i.e., the greater the ease of evoking vivid imagery to begin with, the greater the probability of responding to suggestions and, therefore, the greater the susceptibility to hypnotic induction. This seems to be supported by the available evidence. Hilgard (1967), for example, reports positive correlation's between childhood fantasy and involvement in reading, and hypnotic susceptibility.

            However, there may be limits to how great a part an initial vivid imagination may play, for a subject may conclude that the positive response to a suggestion is due to his own vivid imagination and not the hypnotist's doing. He might remember that he has been able to evoke similar responses when using his own imagination. And, as has been mentioned, it is important that S ascribe the positive responses to the hypnotist.

Age

            According to Weitzenhoffer's review of the area, suggestibility and hypnotic susceptibility at first increase with age, reaching a peak at the ages of seven to eight, then decreases gradually to the age of twenty, when it begins to level off (Weitzenhoffer, 1953, p.76). The reason that suggestibility varies in this way with age can be traced to certain factors that vary with age. One of these is language ability. Since hypnosis is dependent to a great extent on the conditioned response evoked by words, we can understand why very young children whose language ability is not yet well developed would make very poor subjects, and thus, why we would expect an initial gradual increase in suggestibility with increasing age.

            An explanation for the gradual decline in suggestibility after the age of eight is that with continued increasing age the number of cognitive stimuli competing with a suggestion increases (i.e., knowledge increases with age), and a corollary to the Reciprocal Inhibition or Stimulus Dominance Hierarchy postulate is that the more stimuli in the hierarchy, the lower the probability of any one of them being reacted to. These competing cognitive stimuli develop in a number of ways. First, we know that with increasing age the number of possible cognitive stimuli evoked by a word increases.  For example, the word “house” has been associated with more and more houses as the person gets older; thus, if the suggestion is given, “You will now see a house,” there will be competition among the many “house” images, with a resultant weakening of any one finally singled out.  Also, with increasing age there will be a greater number of possible contradictory cognitive stimuli evoked by a suggestion; i.e., the S has more information available with which to verify or contradict the suggestion.  Finally, there is the fact that with increasing age there is the development of skepticism.  As pointed out above, skepticism can be thought of as a conditioned process where suggestions have been negatively reinforced; i.e., people learn in time that not everything anyone says is true.

Summary

            To summarize the above briefly, an attempt has been made to explain hypnotic induction as the conditioning of an inhibitory set --the set to inhibit stimuli (sensory or cognitive) incompatible with a suggestion given by the hypnotist. The hypnotic induction procedure, defined as the giving of two or more suggestions such that a positive response to one will increase the probability of responding to the next one, was placed in the conditioning paradigm, with the CS, UCS, UCR, CR, trials and reinforcement clearly delineated.

            The explanation of hypnotic induction was put in the form of three major hypotheses: (1) hypnosis is a conditioning phenomenon; (2) the response conditioned during hypnosis is an inhibitory one; and (3) a positive response to one suggestion increases the probability of responding to the next one. Evidence was presented in support of these hypotheses and further experimentation proposed. Numerous suggestions, deducible from the theory, for improving the success of HI were interspersed throughout.

            Finally, some of the major individual factors that can influence the HI were discussed included concentration, prestige, expectation, fears, attitudes, imagination, and age.

EXPLANATION OF HYPNOTIC PHENOMENA

            An attempt will be made to show that all hypnotic phenomena can be explained in terms of the following two hypotheses: Hypotheses IV--a suggestion leads to the desired response by first evoking a cognitive stimulus which is connected with that response; and Hypothesis V--the inhibitory set evoked by a suggestion facilitates the suggested response by inhibiting stimuli competing with the cognitive stimulus. This explanation holds for all suggestion phenomena, whether the suggestion is given in the hypnotic state or in the normal state. The reason that hypnotic suggestions lead to stronger responses than normal suggestions is that the inhibitory set is made more effective after a hypnotic induction.

             In what follows we will first analyze a number of hypnotic phenomena in terms of this explanation and then look at the evidence in support of it. (Most of the examples of hypnotic phenomena that will be given are referred to in Weitzenhoffer's (1953) extensive review of the field.) This, of course, will not be an exhaustive list of hypnotic phenomena, but should be enough so that the reader will be able to apply  the explanation to other hypnotic phenomena not covered.

Hypnotic Phenomena

Hallucinations

            A hallucination is herein defined as a highly vivid image which is incongruous with the present sensory and/or cognitive environment ("reality"). An image is defined as a cognitive stimulus emanating from an engram or recording of a previously experienced sensation or combination of sensations. Since engrams can be of any sense modality, images can also be in any sense modality. This is important to remember, as one often associates the term image with only visual images.

            A hallucination occurs as a result of a suggestion because (1) an image (a cognitive stimulus) is evoked and (2) an inhibitory set is also evoked, one which inhibits competing stimuli in the Stimulus Dominance Hierarachy (one which inhibits “reality”) sufficiently so that the image rises to the dominant position in the hierarchy.

           As an example of how the explanation works, let's say the suggestion were given to a subject that there was a watermelon on an obviously empty table. First of all, an image of the watermelon on the table would be evoked by this suggestion, since words can act as conditioned stimuli triggering engrams. However, this image ordinarily would tend to be quickly suppressed by the more dominant incompatible stimuli present. The very sight of the empty table, i.e., the incompatible sensory stimulus "empty table," would most likely be enough to suppress the image. In addition, there might also be cognitive stimuli in contradiction, such as the knowledge that watermelons weren't in season, or the remembrance that no watermelons had been carried into the room, etc. If, however, these incompatible, competing stimuli could be suppressed or eliminated, then, according to

the theory, a highly vivid image of the watermelon on the table would occur (an image so vivid that if one were to eat a piece of this imaginary melon, we would find all the responses associated with the eating of a real melon - salivation, gastric secretions, enzyme production, etc.). Hypnosis facilitates the production of hallucinations because its strong inhibitory set helps in the suppression of those contradictory stimuli.

Age Regression

            Age regression induced through hypnotic suggestion is a phenomenon very similar to hallucinations induced through hypnotic suggestion. There are two main differences, however. First, whereas age regression involves the evoking of a specific image or related set of images which are recordings of an actual event that has taken place in S's past, a hallucination can involve combinations of such images forming a new and not previously experienced precept (such as the image of an animal with a lion's body and a giraffe's head). Second, a hallucination is often projected onto the present sensory environment (e.g., "You will see a red number 7 on the wall." The "7" is imaginary, (but the wall is real), whereas in age regression, the present environment tends to be replaced entirely by the set of images evoked.

Control of Physiological Responses

            Hypnosis can be looked upon as a state where one has greater control over involuntary responses. Most physiological responses are considered in this class. Among the physiological responses reported to have been controlled by hypnosis we find the following: basal metabolism (Platinov, 1959, p. 110); blood sugar level (Platinov, 1959, p.113; Weitzenhoffer, 1953, p. 135); enzyme secretion, gastric acidity, and secretion of bile (Weitzenhoffer, 1953, p. 135); water metabolism and temperature regulation (Platinov, 1959, pp.161, 169); blister formation (Hadfield, 1917; Schneck, 1953, p. 263; Ulman, 1947); hunger contractions (Lewis and Sarbin, 1943; Scantlebury et al., 1942); and heart rate (Schneck, 1953, p. 262).

            An example of how such mechanisms can be controlled by means of hypnosis has already been given above. We saw how the suggestion of eating a hallucinatory watermelon would be expected to lead to certain