Suggestion overrides automatic audiovisual integration

• We investigate whether suggestion can de-automatize audiovisual integration in speech perception.
• Ten highly and ten less hypnotically suggestible individuals perform the classic McGurk task.
• We provide a posthypnotic suggestion to prioritize the auditory input whilst crisply viewing the video.
• Posthypnotic suggestion reduces McGurk illusions in highly but not less suggestible individuals.
• We show that suggestion overrides the automaticity of audiovisual speech perception.

Cognitive scientists routinely distinguish between controlled and automatic mental processes. Through learning, practice, and exposure, controlled processes can become automatic; however, whether automatic processes can become deautomatized – recuperated under the purview of control – remains unclear. Here we show that a suggestion derails a deeply ingrained process involving involuntary audiovisual integration. We compared the performance of highly versus less hypnotically suggestible individuals (HSIs versus LSIs) in a classic McGurk paradigm – a perceptual illusion task demonstrating the influence of visual facial movements on auditory speech percepts. Following a posthypnotic suggestion to prioritize auditory input, HSIs but not LSIs manifested fewer illusory auditory perceptions and correctly identified more auditory percepts. Our findings demonstrate that a suggestion deautomatized a ballistic audiovisual process in HSIs. In addition to guiding our knowledge regarding theories and mechanisms of automaticity, the present findings pave the road to a more scientific understanding of top-down effects and multisensory integration.