Do expectations change raw sensations?

Lens adapted to this topic: Why reported effects may not prove raw sensation changes

The strongest dissent does not deny that expectations affect experience reports or brain activity. It questions whether this demonstrates a change in raw sensation at an early sensory stage. Effects may arise through attention, task demands, perceptual interpretation, awareness, or response criteria, and individual differences and expectation–stimulus congruence complicate simple top-down accounts. The evidence therefore supports modulation of experience, but not necessarily a single mechanism.

• Critics argue that evidence for cognition directly changing perception is often confounded with effects on attention, judgment, or reporting.
• Experimental design issues make it difficult to determine whether expectations alter sensory processing directly or indirectly through attention.
• Expectation effects vary across individuals, complicating claims about a uniform change in raw sensation.
• When expectations and pain input conflict, sensory input can receive greater weighting, limiting assimilation of experience to expectation.
• Bayesian accounts explain why prior expectations contribute to perceptual processing, but this functional dependence does not by itself establish that expectations alter the raw sensory signal.

Featured sourceThe Effects of Expectations on Perception: Experimental Design Issues and Further Evidencebostonfed.org4 sourcesView sources