The sequential judgment of proportion

Ss gave percentage estimates of proportion, which were revised after each event during the presentation of a sequence of binary events. Responses exhibited constant errors of overestimation of proportions greater than.5 and underestimation of proportions less than.5. Both verbal and nonverbal responses were used, the constant error being somewhat greater for nonverbal responses. There was a tendency for the constant error to decrease as the number of events between revisions was increased.