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 are either 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 patten 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 consentration of instruction-mentioned featurcs. The regional salience bias is contrasted with a feature salience bias: features tend to be morc salient if they arc mentioned in the instructions. The relations between the observed perceptual bias and traditional confirmation biases, numeric estimation. and attention are discussed.