Can hypnosis displace the threshold for visual consciousness?

Abstract

To test the specific effects of hypnosis on the attentional components of visual awareness, we developed a posthypnotic suggestion for peripheral visual inattention inspired on the “tunnel vision” symptom of the Balint Syndrome. We constructed a dual-target visibility and discrimination paradigm, in which single-digit numerical targets were placed both on the hypnotically affected peripheral space and on the remaining undisturbed central area. Results were 3-fold: (i) when compared to participants of Low hypnotic susceptibility (Lows), highly susceptible participants (Highs) presented decreased subjective visibility; (ii) Highs did not show dual-task interference from peripheral targets (an effect of unconscious processing) during hypnotic suggestion to not attend them, but Lows did; (iii) nevertheless, when asked to execute a discrimination task over these same targets, Highs performed with the same accuracy as Lows. These results suggest that the hypnotic manipulation of visuospatial attention did produce an experiential change in Highs, but not one that could be mapped onto interference at a single (conscious or unconscious) level of processing. Rather, we posit that Highs simultaneously displayed (i) a fluctuation in awareness of peripheral targets coherent with the suggestion and (ii) a control strategy that involved removing hypnotically unattended targets from the task set whenever task instructions would allow for it. In light of these findings, we argue that hypnosis cannot be used as a tool to restrict the processing of otherwise supraliminal stimulation to subliminal levels.

Hypnotic suggestions cognitively penetrate tactile perception through top-down modulation of semantic contents

“…Previous studies on the influence of hypnotic suggestions on a visual oddball paradigm have shown that a suggested visual blockade can decrease performance, as well as decrease strength of the correlated P3b signal 21 , a signal associated with frontal-parietal memory load 22 , but found no significant changes in earlier components. Another study, implementing a “tunnel vision” suggestion found that highly suggestible participants reported lower visibility of stimuli, but no change in task performance, indicating that the suggestion’s influence was limited to attendance 23 .…”