Attending is a cognitive process that incorporates a person’s knowledge, goals, and expectations. What we perceive when we attend to one thing is different from what we perceive when we attend to something else. Yet, it is often argued that attentional effects do not count as evidence that perception is influenced by cognition. Two arguments often given to justify excluding attention; both of these arguments are highly problematic.
- The first is arguing that attention is a post-perceptual process reflecting selection between fully constructed perceptual representations.
- The second is arguing that attention as a pre-perceptual process that simply changes the input to encapsulated perceptual systems.
The current evidence supports the thesis that what we know routinely influences what we see, that the same sensory input can be perceived differently depending on the current cognitive state of the viewer, and that phenomenologically salient demonstrations are possible if certain conditions are met.
Taken together, there are several conclusions.
First, it is not possible to characterize attentional effects as non-semantic changes in input of the kind that occur when we look at one location versus another. Rather, attention can and often does operate over dimensions that we normally think of as reflecting meaning and these attentional effects should be counted as genuine instances of CPP (cognitive penetrability of perception).
Second, the possibility of exogenously cueing one’s knowledge in real time to bias how something is perceived strongly suggests that under normal circumstances what we see is reflecting our endogenous cognitive state.
Third, to understand why these effects often lack the “wow factor” common to the best visual illusions, it is useful to work through the effects through the lens of predictive coding.
Knowledge ought to change what we see to the extent that it provides a better hypothesis of the sensory data.