Suggestion

BIBLIOGRAPHY

The concept of “suggestion” originally was intimately associated with hypnos and was introduced in the mid-nineteenth century by Alexandre Bertrand in France and James Braid in England as an explanation of hypnotic phenomena. It thus replaced the theory of animal magnetism and other fluidistic theories. Suggestion became a universally recognized psychological concept during the famous controversy between the schools of Salpétriére and Nancy in the 1880s and 1890s.

Hypnotic suggestion . Early usage of the word “suggestion” referred to very specific phenomena. By monotonous verbal phrases, sometimes accompanied by eye fixation, hand movements before the eyes or handstrokes on the forehead (”passes”), or regular soft sounds, a sleeplike, hypnotic state was induced in the subject, and in this state different phenomena were produced: catalepsis, contrac-tures, automatic movements, anesthesia, analgesia, hallucinations, illusions, posthypnotic amnesia, posthypnotic actions, etc. The automatic and uninterested way in which these suggested acts are performed has generally been emphasized as a characteristic of hypnotic suggestion.

As long as the term “suggestion” was used exclusively in connection with hypnosis, we can assume it related to functionally rather homogeneous phenomena. However, this narrow concept of suggestion did not prevail with time. Gradually, miscellaneous phenomena with some similarity to hypnotic suggestion were included in the concept of suggestion.

Expansion of the suggestion concept . Social scientists soon found it useful to incorporate the hitherto exclusively medical concept of suggestion into their theories of social interaction. Such well-known sociologists as Gabriel Tarde, Scipio Sighele, and Gustave Le Bon regarded suggestion as the basic mechanism in social process. These authors considered suggestion in its different forms as a unitary phenomenon. Manifestations of suggestion in different contexts were believed to differ in degree, not in kind. Such pioneers of social psychology as Edward A. Ross and William McDougall also viewed different suggestion phenomena as parts of a continuum. In addition to hypnosis, induced illusions, impressionability through leading questions, uncritical beliefs, conformity to fashion, and mass suggestion were mentioned as examples of suggestion. Everyday suggestion acts were considered less-pronounced forms of the same kind of behavior that could be observed in hypnotized individuals. [See Le Bon; McDougall; Ross; and Tarde.]

Testing and experimental psychology . During the 1890s the awakening interest in individual differences and efforts to measure these differences also included considerable concern for the individual’s suggestibility. Probably as many suggestibility tests as intelligence tests were constructed in the decades around the turn of the century. This is a noteworthy fact, which bears witness to the importance attached to suggestion at that time.

The expansion of the suggestion concept that can be traced in medicine and in the work of the early sociologists and social psychologists is somewhat paralleled in differential and experimental psychology. It is possible to follow the way in which the term “suggestion,” operationally defined in tests or experimental procedures, successively covered wider and wider functional areas. After having first been limited to the production of simple motor and sensory reactions, the suggestion experiments and tests gradually included more complex phenomena, such as change of judgment, opinion, and attitude.

Analysis of the suggestion concept

The question naturally has arisen whether all the phenomena called suggestion and suggestibility really belong together functionally or have been arbitrarily brought together by some superficial similarities.

Qualitative analysis . On the basis of qualitative analysis, Asch (1952) has sought to refute the interpretation of suggestibility in terms of automatisms and baseless beliefs, analogous to the mechanisms in hypnosis, that has often been applied to behaviors shown by the subjects in prestige-suggestion experiments. By means of introspective analysis Asch has attempted to demonstrate that the subject’s reactions in such experiments are sensible and reasonable, quite different from the uncritical and automatic actions of a hypnotized individual.

Correlation and factor analysis . A quantitative way of determining the extent of the relations between the functions tapped by different suggestibility tests has been the analysis of correlations between the tests. Some early groping efforts were made (e.g., Brown 1916; Aveling & Hargreaves 1921). No clear pattern appeared, however, in these studies, which embraced rather small numbers of variables. More extensive factor analyses have been made by Eysenck (1943; 1947) and Stukát (1958). In the Eysenck studies two factors were identified: “primary” and “secondary” suggestibility. Primary suggestibility has been characterized by Eysenck (1947, p. 165) as execution of a motor movement after the experimenter has repeatedly suggested to the subject that such a movement will occur, without the subject’s conscious participation in the movement. Typical of the tests that define this factor is Hull’s body-sway test, where the subject stands straight with his eyes closed and listens to repeated verbal suggestions to the effect that he will fall forward. Other primary-suggestibility tests involve hand or arm movements, such as “hand rigidity” and “arm levitation.” The tests that belonged to this factor were rather highly intercorrelated, and they also correlated clearly with hypnotizability.

Eysenck’s notion of secondary suggestibility is characterized by the subject’s perceptions being influenced by indirect suggestions. This factor had very high loadings in “heat illusion” and “progressive weights” tests, for example. In the former test an electric current is sent through a metal wire, heating it by degrees. The subject holds the wire and is told to report as soon as he feels it getting warmer. The test is repeated, but this time no current is sent through the wire, although the subject believes that it is. In Binet’s progressive-weights test, the subject lifts a series of weights, of which only those in the first sequence are successively heavier, while the rest are of the same weight. The subject’s tendency to judge the equal weights as successively heavier constitutes the measure of his suggestibility.

On the whole, the secondary-suggestibility tests showed less functional unity than the tests of primary suggestibility. While the latter had an average correlation of .50, the corresponding figure for the former was only .15.

The possibility of a “tertiary,” or “prestige,” type of suggestibility has also been discussed; this refers to procedures in which the individual’s attitude changes when he is told the attitude of experts or a majority. In Stukát’s factor analyses the existence of a primary-suggestibility factor was convincingly verified. The primary-suggestibility tests had a clear personality-trait character: they had high reliability coefficients and there were consistently high intercorrelations between different tests in spite of considerable situational variations. The primary-suggestibility factor was largely unconnected with other types of suggestibility. [See Factor analysis.]

Other results of factor analysis were less clearcut. Some group factors seemed to be related to Eysenck’s secondary suggestibility, being characterized by the influence of an experimentally and impersonally induced set upon cognitive functions, but they were functionally too narrow to warrant an identification with it. Other factors were interpreted as personal or prestige suggestibility. The fact that these group factors, impersonal as well as personal, were intercorrelated, was a basis for ah interpretation on the second-order level. The feature common to these related factors is that they all represent tests in which different subjective influences, such as set, expectation, and need for conformity, direct the individual’s perceptions, memory, and judgments. This second-order factor can be regarded as a secondary-suggestibility factor, but it apparently covers a broader functional area than the secondary-suggestibility factor in Eysenck’s analyses.

It thus seems reasonable to distinguish between two kinds of suggestibility: a “primary” form, found in hypnosis and in ideomotor acts of an automatic character which are produced by monotonous verbal stimuli; and secondary suggestibility, characterized by the influence of different experimentally induced subjective factors upon cognitive functions. These influences can be personal or social as well as impersonal (e.g., expectation). In this broad sense, the secondary form includes prestige suggestibility, which thus does not constitute an independent, “tertiary” category.

Concomitants of suggestibility

Suggestibility and age . Suggestibility has usually been assumed to decrease with age, at least during the individual’s developing years. This belief has been experimentally corroborated for secondary suggestibility but not for primary suggestibility. Cohn and Dieffenbacher (1911) and Messer-schmidt (1933a) found that suggestibility decreased with age among children who were tested with different “illusion” tests. No such age trend appeared, however, between the ages of 5 and 16 in another of Messerschmidt’s studies (1933b). In Stukát’s investigation (1958), different age gradients appeared for primary- and secondary-suggestibility tests. The slope was steeper for secondary tests of a personal kind (e.g., leading questions, majority suggestions) than for tests with an impersonal influence (e.g., a weight-comparison test similar to Binet’s). The age curves for prestige-suggestibility tests likewise have shown considerable decrease between the ages of 6 and 18.

In Barber and Calverley’s study (1963), children had higher composite scores on a number of tests of primary suggestion. The “adult” level was reached at 14 to 15 years of age. Instructions designed to produce positive motivation resulted in adults’ manifesting a suggestibility level similar to that of children.

Suggestibility and sex . Comparisons between males and females have been made in a great number of investigations. Girls and women have most often been found to be more suggestible than boys and men, both in primary and secondary suggestibility. As to primary suggestibility, women exceeded men in hypnotic susceptibility, although the differences were not significant (e.g., Barry et al. 1931). Aveling and Hargreaves (1921) reported that girls were more suggestible than boys on tests of hand rigidity and arm levitation. Eysenck (1947) reports that neurotic women were significantly more suggestible than neurotic men on the body-sway test but that there was no difference between sexes in normal subjects. In a number of primary-suggestibility tests, Stukát (1958) found more, but not a significantly higher degree of, suggestibility among females than among males; this was the case for children as well as adults.

A very extensive study of sex differences in secondary-suggestibility tests was performed by Brown (1916), who administered 26 different tests to college students, assessing such things as liminal sensations. Most of the differences were indicative of greater female suggestibility, and some of the differences were significant. Other studies have revealed similar results (e.g., Stukát 1958). A few authors report no differences (e.g., Cohn & Dieffenbacher 1911). Thus, in general, females are somewhat more suggestible than males, and mostly so perhaps in personal and prestige secondary suggestibility. The intraindividual differences of each sex are, however, considerably greater than the intersex differences. [See Individual differences, article onsex differences.]

Suggestibility and neuroticism . The controversy between the Salpêtrière and Nancy schools fundamentally concerned the question of whether suggestibility was a pathological “stigma” present only in hysterical neurotics (Salpêtrière) or a normal trait characterizing all individuals (Nancy). A large body of clinical and experimental data showing that everybody is suggestible to some degree has settled this controversy in favor of the Nancy school. There is, however, a related question, namely, whether neurotics are more suggestible than normal subjects. Here the results have been inconsistent.

Using the body-sway test, Eysenck (1947) found neurotic patients more suggestible than normal ones, while other studies (e.g., Baumgartner 1931) showed no differences with the same test. Nor did Stukát (1958) find any consistent differences between normal persons and neurotics on a number of primary-suggestibility tests. The results of the relatively few studies that have included tests of the secondary type reflect somewhat higher suggestibility among neurotics (e.g., Stukát 1958). There is some evidence that neurotics are more easily influenced by prestige suggestions. Although neurotics constitute a rather heterogeneous group of individuals, such traits and symptoms as anxiety, inferiority feelings, lack of confidence, etc., are predominant in most groups of neurotics. These characteristics probably account for greater need to conform and greater willingness to submit to the expressed opinions of other people. In addition to such relatively constant traits, the greater suggestibility of neurotics may be partly caused by the specific situation in which they happen to be. The fact that a person suffers from acute disturbances and that he is hospitalized may increase his suggestibility, especially in situations that are connected with his illness.

Suggestibility and personality . Parallel to, and sometimes intermingled with, the discussion and study of suggestibility and neuroticism is the question of the relation between suggestibility and personality type. Most often suggestibility has been associated with hysteria and hysterical personalities. The assumed greater suggestibility among hysterics has been ascribed to different mental mechanisms by different authors. Janet (1919) explained it in terms of the hysteric’s disposition to shrink his sphere of consciousness, to dissociate, and to be unable to synthesize mentally. According to Janet, this makes the hysterical mind fragmentary and an easy prey to suggestion. Bleuler (1916) has emphasized the vivid and labile affec-tivity of hysterics, whose emotions are far more important than their intellectual processes. However, Bleuler also points out that hysterics are characterized not only by positive but also by negative suggestibility and autosuggestibility. [See Hysteria.]

The experimental studies that have examined the belief generally held by clinicians that there is a close association between suggestibility and hysteria have provided somewhat inconsistent results. On the whole, however, they have not given much support to traditional belief with respect to either primary or secondary suggestibility.

Lindberg (1940) found higher secondary suggestibility (olfactory and visual) in hysterics than in asthenics and syntonics but a lower degree than was found in a group of oligophrenics. Kehlet and Paerregaard (1956) found more secondary suggestibility in female hysterics than in female non-hysterics. Eysenck (1943) and Stukát (1958) report no differences in a number of different suggestibility tests, both primary and secondary. In Stukát’s investigation the most suggestible groups were oligophrenics and asthenics. A few studies refer to the relation between different Rorschach indices and suggestibility. In his Psychodiagnostics (1921) Rorschach maintained that there is a connection between emotional lability, primarily represented by color-form (CF) responses, and “affective” suggestibility. This belief has been only partially substantiated by experimental research. Linton (1954) correlated cojudge suggestibility in the autokinetic situation with several Rorschach measures. The suggestibility variable had its highest correlation with the ratio of color-to-movement responses (C:M), and the result thus to some extent supported Rorschach’s hypothesis. On the other hand, Stukát (1958) found no consistent relations between different Rorschach indices or patterns and a number of suggestibility tests. [See Projective methods, article onthe rorschach test; and the biography of Rorschach.]

Theories

Primary suggestibility . Weitzenhoffer (1953) has classified existing theories of primary suggestibility, including hypnosis, according to what is assumed to be the basic process; there are thus neurophysiological, dissociation, conditioned-response, and transference theories. Of these, the existing neurophysiological theories must be considered quite unsatisfactory. The basic mechanism behind suggestibility has been said to be inhibition of the ganglion cells in the brain (Heidenhain 1880), a functional dissociation between nerve cells (Sidis 1898), or a shift of nervous energies from the central nervous system to the vasomotor system (McDougall 1926), but the empirical support for these hypotheses is weak. The transference theories are likewise based on meager empirical evidence. They can be said mainly to express the often reported experience that in hypnosis an emotional relation between the hypnotist and his subject is often developed. Most of these theories are formulated in psychoanalytic terminology, which makes it difficult to link them to general psychological concepts. The theories that lay emphasis on dissociation (e.g., Janet 1919; Sidis 1898) no doubt touch upon a central factor in primary suggestibility. The observations of hypnotic behavior, as well as of waking suggestion situations, bear witness to the automatic and disintegrated character of the individual’s actions, which are strikingly different from normal conscious and “willed” behavior. However, as has been pointed out by Hull (1933), the dissociation is more apparent than real, and the autonomy of the dissociated elements is often far from complete. Another criticism that can be directed against the dissociation theories is that they have been mainly superficially descriptive, that is, not integrated with larger and well-established systems, and are therefore of a limited explanatory value.

The theories that seem to be most satisfactory are those which interpret primary suggestibility in terms of conditioned response. Pavlov (1927) regarded suggestibility as the most simple form of the typical conditioned reflex in man. Among others, Welch (1947) has elaborated this idea. He calls attention to the striking similarity between the initial stages of hypnosis induction (and waking suggestions of the body-sway type) and an ordinary conditioning experiment, as illustrated in the paradigm (Figure 1). [See Learning, article onclassical conditioning.]

While Welch believes that such a simple conditioning model may satisfactorily explain the early phases of primary suggestibility, a more complicated process involving abstract conditioning seems to be necessary to explain other hypnotic phenomena. Although the conditioning theories leave a great deal of the primary-suggestibility phenomena

unexplained, there is some empirical support for them in the significant correlations that have been found between suggestibility and conditionability (Stukát 1958).

Secondary suggestibility . McDougall defined suggestion (in situations where it was clear that he meant secondary suggestibility) as a “process of communication resulting in the acceptance with conviction of the communicated proposition in the absence of logically adequate grounds for its acceptance” (1908, p. 97). This conception of suggestibility as nonlogical behavior is representative of most older theories. In opposition to this “suggestion doctrine,” Asch (1952) has maintained that suggestion is most often a rational process. According to Asch’s qualitative analysis of the subject’s responses to prestige suggestions, the individual does not change his judgments or evaluations arbitrarily but because there is a change in the object of judgment. The source of prestige provides a context in which a statement can be interpreted. The subject’s reaction toward prestige suggestions is ordinarily not a passive, automatic, and uncritical acceptance, analogous with the behavior of a hypnotized individual; rather the subject acts sensibly and does as well as is possible in a vague and difficult situation.

Leaving aside the question of the rational or irrational character of suggestible behavior, Sherif (1936) and Coffin (1941) have also emphasized that a suggestion primarily functions as a frame of reference. If the external stimulus situation is well structured, the frame of reference is almost completely made up of the properties of the objective situation. If, on the other hand, the situation is vague and unstructured, organization still takes place, but now internal factors, such as set, attitude, etc., are important determinants. This makes it reasonable to include secondary suggestibility among the large group of phenomena that have been intensively studied under the headings “central dynamics of cognition,” “central directive state,” “functional determinants,” etc. A large number of studies have adequately established that cognitive functions are determined not only by the objective stimulus situation but also by various internal factors, such as needs, past learning, and mental set.

Postulating that secondary suggestibility is a special case of the central dynamics of cognition, Stukát has derived a number of hypotheses which have been experimentally tested. The results clearly support the hypotheses that, in secondary-suggestibility situations of a personal type, the suggestion effects are greater when (1) there are a greater number (up to a certain limit) of unanimously influencing individuals; (2) the social status of the influencing individual is higher; (3) the influencing individual is older in relation to the subject (among children and adolescents). Further, he verified the hypotheses that (4) reproof tends to increase and praise to decrease an individual’s suggestibility toward propositions from other persons; (5) an individual is more suggestible if the atmosphere of the situation is anxiety-arousing than if the situation is calm. As to impersonal secondary suggestibility, it was found that (6) an individual’s suggestibility is greater when his expectation is greater. For secondary suggestibility in general, (7) a high negative correlation exists between the degree of stimulus structure and the subject’s tendency to yield to suggestions.

These results are in rather close agreement with the findings from several other investigations. Asch (1956) and Rosenberg (1961) have reported an increase in conformity when the number of cojudges increased up to four. Higher-partner prestige has been found to increase conformity tendencies (Rosenberg 1961). Interestingly, it has been found (e.g., Harvey & Consalvi 1960) that the second-status member, the one only one step from the top, was significantly more conforming than either the leader or the lowest-status man. Investigations (e.g., Di Vesta 1959) have shown the effects of prior reinforcement: previous success engenders greater resistance to social influence, while failure has an opposite effect. Stimulus structure as a factor in suggestibility has been demonstrated in studies where conformity was greater for the more difficult than for the easier items in tests when the subjects were given incorrect hints (e.g., Coffin 1941). Other experimental studies (e.g., Di Vesta 1959) have further confirmed the “functional determinants” character of secondary suggestibility (or “conformity” or “persuasibility”), since they have demonstrated that the individual’s tendency to yield to social influences is related to such variables as subjective certainty, confidence, dependency, and self-esteem. [See Groups, especially the article ongroup formation.]

Thus, the secondary-suggestibility phenomena, which have often been regarded as specific and isolated from other psychological functions, can be included naturally in the more general field of functional determinants in cognition. As a consequence of such an integration, the same explanatory concepts can be used for secondary suggestibility as for this wider area. Stukát (1958) has applied the “hypothesis theory” of Postman and Bruner to secondary suggestibility. The central concept in the theory is “hypothesis,” that is, “expectancies or predispositions of the organism which serve to select, organize, and transform the stimulus information that comes from the environment” (Postman 1951, p. 249). The stronger the hypothesis, the less is the amount of appropriate stimulus information required to confirm it. The hypothesis strength is postulated to be determined by a number of factors, namely, the frequency of past confirmation of the hypothesis, the number of alternative hypotheses available, motivational and cognitive support, and consensual validation. There is good general agreement between this model and the data from the experimental studies of secondary suggestibility mentioned above. A limitation of the theory as an explanatory device for suggestibility is its failure to take account of the fact that social influence (“consensual validation”) can act both as a motivational factor and as a source of cognitive information. A good deal of recent experimentation and discussion has aimed at determining the relative effect of “normative” and “informational” influence (e.g., Di Vesta 1959). Although the results so far have given more evidence about the importance of motivational than of rational cognitive factors in conformity behavior, this question still constitutes an interesting problem.

Karl-Gustaf StukÁt

[Directly related are the entries Attitudes, article onattitude change; Brainwashing; Conformity; Hypnosis; Persuasion. Other relevant material-may be found in Moral Development; and in the biographies of Charcot; Janet; Mesmer.]

BIBLIOGRAPHY

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Barber, Theodore X.; and Calverley, David S. 1963 “Hypnotic-like” Suggestibility in Children and Adults. Journal of Abnormal and Social Psychology 66:589-597.

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