Look into my eyes: Pupillometry reveals that a post‐hypnotic suggestion for word blindness reduces Stroop interference by marshalling greater effortful control

Abstract

The mechanisms underpinning the apparently remarkable levels of cognitive and behavioural control following hypnosis and hypnotic suggestion are poorly understood. Numerous independent studies have reported that Stroop interference can be reduced following a post‐hypnotic suggestion that asks participants to perceive words as if made up of characters from a foreign language. This effect indicates that frontal executive functions can be more potent than is generally accepted and has been described as resulting from top‐down control not normally voluntarily available. We employed eye tracking and pupillometry to investigate whether the effect results from voluntary visuo‐attentional strategies (subtly looking away from the word to prevent optimal word processing), reduced response conflict but not overall conflict, Stroop effects being pushed from response selection to response execution (response durations) or increased proactive effortful control given enhanced contextual motivation (as indexed via pupil dilation). We replicated the reduction in Stroop interference following the suggestion despite removing any trials on which eye movements were not consistent with optimal word processing. Our data were inconclusive with regards to conflict type affected by the suggestion in the latency data, although preserved semantic conflict was evident in the pupil data. There was also no evidence of Stroop effects on response durations. However, we show that baseline‐corrected pupil sizes were larger following the suggestion indicating the socio‐cognitive context and experimental demands motivate participants to marshal greater effortful control.

The nature and persistence of the effects of posthypnotic suggestions on food preferences: The final report of an online study

“…Notably, a number of studies have shown that (post-)hypnotic suggestions are implemented through top-down modulations (Terhune et al, 2017 ), require attention allocation (Tobis and Kihlstrom, 2010 ), and require cognitive effort (Parris et al, 2021 ). Further, the relationship between food-related PHSs and executive functions (requiring cognitive effort) has also been demonstrated (Ludwig et al, 2014 ; Zahedi et al, 2020a ).…”

Cognitive simulation along with neural adaptation explain effects of suggestions: a novel theoretical framework

“…This can be translated into the feeling that suggestions cause better performance with the same effort as before rather than conducting an action without attributing it to the direct exertion of volition. As suggested by SATH, under the influence of direct verbal suggestions, participants may perform a cognitive task with less reactive cognitive control and more proactively and consequently more efficiently (Zahedi et al, 2019(Zahedi et al, , 2020bParris et al, 2021), which would feel comparatively effortless.…”

Do Task Sets Compete in the Stroop Task and Other Selective Attention Paradigms?

“…Since undertaking the phonological/phonetic encoding of the irrelevant word occurs automatically in the sense that it is obligatory (with both manual and vocal responses), phonetic encoding of the colour name would be delayed. Moreover, since the phonetic information from the irrelevant word is not the needed response, control would likely be needed to prevent it interfering further (especially with a vocal response Stroop task) and control of automatic processes can be effortful (Diede & Bugg, 2017;Entel & Tzelgov, 2020;Parris, Hasshim & Dienes, 2021). This added level of interference in the colour naming process for congruent relative to non-lexical, non-pronounceable letter strings would also add another point at which noise could interact 4 However, Kinoshita et al (2017)'s study potentially confounds the orthographic similarity and pronounceability of their pronounceable nonwords (such as HIX) and non-pronounceable consonant nonwords (such as HDK).…”

“…Since undertaking the phonological/phonetic encoding of the irrelevant word occurs automatically in the sense that it is obligatory (with both manual and vocal responses), phonetic encoding of the colour name would be delayed. Moreover, since the phonetic information from the irrelevant word is not the needed response, control would likely be needed to exclude it and prevent it interfering further (especially with a vocal response Stroop task) and control of automatic processes can be effortful (Diede & Bugg, 2017;Entel & Tzelgov, 2020;Parris, Hasshim & Dienes, 2021).…”

“…And this process apparently delays colour naming in the Stroop task. Moreover, the outputs of this obligatory process of grapheme-to-phoneme conversion and the phonetic processing would need to be controlled, and control over automatic processing is effortful (Diede & Bugg, 2017;Entel & Tzelgov, 2020;Parris, Hasshim & Dienes, 2021). Here again then, task conflict need not be invoked; the divergence in pupil sizes might merely reflect: 1) the amount of processing that is required for each stimulus type with the greatest amount of effort required for the stimuli with the greatest levels of processing, and/or; 2) the control required to prevent the irrelevant information from further delaying computation of the phonetic code for the colour name.…”