Perceptual equivalents of confirmation biases and framing effects are observed in subjects` estimates of feature numerosity. Subjects are asked to estimate the percentage of display items that have a particular feature. Features either are randomly distributed or are spatially clustered such that features of the same type tend to be close. Subjects systematically overestimate the prevalence of features in clustered displays. The pattern of results is best explained by a regional salience bias: Features tend to be more salient if they belong to regions that have a high concentration of instruction-mentioned features. The regional salience bias is contrasted with a feature salience bias: Features tend to be more salient if they are mentioned in the instructions. The relations among the observed perceptual bias and traditional confirmation biases, numeric estimation, and attention are discussed.