What determines visual cue reliability?

Visual environments contain many cues to properties of an observed scene. To integrate information provided by multiple cues in an efficient manner, observers must assess the degree to which each cue provides reliable versus unreliable information. Two hypotheses are reviewed regarding how observers estimate cue reliabilities, namely that the estimated reliability of a cue is related to the ambiguity of the cue, and that people use correlations among cues to estimate cue reliabilities. Cue reliabilities are shown to be important both for cue combination and for aspects of visual learning.