Accounting for hypnotic phenomena via motivation and experimenter demands.

Abstract

When completing time judgement (intentional binding) and word-based attention tasks (Stroop) following specific hypnotic suggestions, individuals of higher hypnotic suggestibility have been found to perform in a manner not achievable without suggestions. Cold Control Theory (CCT) in contrast asserts that behaviour carried out following hypnotic suggestion is driven by the same mechanisms utilized in voluntary action such that one can achieve with voluntary action whatever is achieved under suggestion but that under suggestion the individual is affected by a reduced awareness of intention. To investigate this tenet of CCT, two experiments were carried out to explore the potential role of performance expectation (Experiment 1) and in-group demand characteristics (Experiment 2) in suggestion fulfilment among individuals of higher suggestibility. Self-reported beliefs of performance expectations in an intentional binding experiment involving a suggestion for modified performance were gathered from 19 medium suggestibility and 10 high suggestibility participants. The experiment revealed no evidence for specific strategic responding under suggestion, upholding CCT’s prediction of modified awareness of intention. The effect of in-group demand characteristics was then tested using 13 participants of unknown suggestibility, 6 higher suggestibility participants and a further 9 participants in a control condition. The manipulation among the latter group was found to affect Stroop task performance in a manner alike that previously attributed to a suggestion for altered performance. Bayesian evidence for this finding was weak yet compelling. It is argued here that the findings of Stroop interference effects, such as within Palfi et al. (2021), may be the product of in-group demand characteristics. The current study proposes that in-group demand characteristics may more broadly drive suggestion fulfilment while still abiding a process of Cold Control.