Can unconscious intentions be more effective than conscious intentions? Test of the role of metacognition in hypnotic response

While several theories assume that responses to hypnotic suggestions can be implemented without executive intentions, the metacognitive class of theories postulate that the behaviors produced by hypnotic suggestions are intended and the accompanying feeling of involuntariness is only a consequence of strategically not being aware of the intention. Cold control theory asserts that the only difference between a hypnotic and non-hypnotic response is this metacognitive one, that is, whether or not one is aware of one's intention to perform the relevant act. To test the theory, we compared the performance of highly suggestible participants in reducing the Stroop interference effect in a post-hypnotic suggestion condition (word blindness: that words will appear as a meaningless foreign script) and in a volitional condition (asking the participants to imagine the words as a meaningless foreign script). We found that participants had equivalent expectations that the posthypnotic suggestion and the volitional request would help control the conflicting information. Further, participants felt they had more control over experiencing the words as meaningless with the request rather than the suggestion; and they experienced the request largely as imagination and the suggestion largely as perception. That is, we set up the interventions we required for the experiment to constitute a test of cold control theory. Both the suggestion and the request reduced Stroop interference. Crucially, there was Bayesian evidence that the reduction in Stroop interference was the same between the suggestion and the volitional request. That is, the results support the claim that responding hypnotically does not grant a person greater first order abilities than they have non-hypnotically, consistent with cold control theory.

Suggestions in Court

Although Münsterberg introduces this chapter with a clinical case study involving posthypnotic suggestion, the focus is on suggestibility and reconstructive memory processes broadly, including the role of individual differences (e.g., age, gender) and alcohol intoxication, which he supports with both experimental evidence and anecdotal observation. The documentation of suggestibility effects is one of the most significant contributions of modern research on eyewitness memory and has yielded important, now widely used, experimental approaches. False memories, in today’s parlance, are essentially the same as what Münsterberg calls pseudo-memories, and they have been demonstrated in a variety of situations and shown to have behavioral consequences. Consistent with Münsterberg’s impression, individual differences in suggestibility are key, especially age differences, with children and elderly adults both being more suggestible than young adults. The present chapter reviews experimental research on suggestibility, with the exception of hypnosis, to be treated in the next chapter.

Does unconscious control depend on conflict?

Unravelling the mechanisms that trigger cognitive control is a central question in cognitive science. Cognitive conflict is closely associated with the activation of cognitive control, helping individuals to follow their own goals. In this study, we examined whether the association of conflict and control holds when people are not aware of their intentions (i.e., they experience involuntariness regarding their behaviours). To induce unconscious control, we employed a posthypnotic suggestion (word blindness: that words will appear as a meaningless foreign script) on highly suggestible participants, a manipulation which has previously been shown to halve the Stroop interference effect. To alter the amount of conflict, we manipulated the proportion of incongruent, congruent and neutral Stroop trials between blocks in two experiments. The analyses revealed that the Stroop effect was reduced by the suggestion in the high conflict conditions (conditions with 33% or more incongruent trials), and barely at all in the low conflict conditions (conditions with 10% incongruent trials) compared to no suggestion conditions, thus, supporting the idea that a certain amount of conflict is required to activate unconscious control. This finding can also be interpreted in light of the two competing accounts of the word blindness effect (de-automatisation of reading and response competition models). The results imply that conflict between the response options occurs even in the suggestion condition and so the word blindness suggestion does not influence semantic processing as the de-automatisation of reading account postulates, rather, it is more likely that the suggestion facilitates the reduction of response competition.

The Induction of Synaesthesia in Non-Synaesthetes

In this chapter we review research examining the induction of synaesthesia with training, posthypnotic suggestion, and pharmacological agents in non-synaesthetes. Each of these methods has been shown to produce different aspects of synaesthesia, but none have produced experiences that have been corroborated using neuroimaging assays. Nevertheless, the close parallels between induced and congenital synaesthesias have the potential to illuminate different facets of this condition. We argue that training may be a valuable model for studying the learning mechanisms underlying congenital synaesthesia, posthypnotic suggestion may have greater utility in the experimental manipulation of this condition, and the administration of pharmacological agents may serve as a useful tool for studying the development of synaesthesia or for large-scale studies of induced synaesthesia. Induced synaesthesias also raise important questions regarding espoused criteria for demarcating synaesthesia from other phenomena.