If we consider perceptions as arising from predictive processes, we must consider the manner in which the underlying expectations are formed and how they are applied to the sensory data. We provide examples of cases where expectations give rise to unexpected and unlikely perceptions of the world. These examples may help define bounds for the notion that perceptual hypotheses are direct derivatives of experience and are used to furnish sensible interpretations of sensory data.

It is proposed that symmetry of stone tools may derive from perceptual similarity rather than from cognitively more complex awareness of symmetry. Although encodement of shapes necessarily involves symmetry (as evidenced by the confusability of enantiomorphs), it does not imply awareness of symmetry. Responses of relatively simple organisms, such as bees, support the notion that the processes involved are likely to be perceptual.