What is it about?
Typical and learned contexts of objects in environment can form expectations about what is likely to be perceived in certain circumstances. Our experiments show that these expectations are powerful in causing people to perceive ("hallucinate") objects that are actually not present. Normal people without neuropsychiatric diagnosis are easily prone to such contextually induced "hallucinatory" experiences. This occurs primarily when attention is directed away from where the illusory perceptual object is experienced and/or when the visual conditions are noisy or ambiguous.
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Why is it important?
The results are important because they show that (1) experiencing someting that is not actually present is a quite common phenomenon, (2) peoples reports about what they perceive can not be trusted too much, (3) it is not difficult to purposely induce such illusory perceptions, (4) the currently highly influential theoretical account of cognition -- the predictive coding approach -- has variable experimental support, (5) in what and how we perceive the top-down processes in the brain substantially modulate the bottom-up input signals.
Perspectives
Studying individual differences in the propensity to "hallucinate" may help advance pre-clinical applications of population screening. When combined with genotyping, variations in "hallucinatory" experiences in neurotypical and patient populations may help advance our understanding of the origins and predispositions to neuropsychiatric vulnerabilities. As the subjective experience of an actually absent object is a kind of "pure" conscious experience, combining this behavioral experimental paradigm with brain imaging must help us to understand the brain mechanisms of consciousness better.
Professor Talis Bachmann
Tartu Ulikool
Read the Original
This page is a summary of: It’s all in your head: Expectations create illusory perception in a dual-task setup, Consciousness and Cognition, October 2018, Elsevier,
DOI: 10.1016/j.concog.2018.09.001.
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