The nature of perceptual classification was investigated in children ranging between 4 and 10 years, and in young adults. Triad classification task responses were categorized as consistent or inconsistent with several classification rules, including: overall-similarity, size-dimensional, brightness-dimensional, pure identity, and all combinations of a switch from one rule to another midway through the experiment. The rule with the highest proportion of responses consistent with it reflectd each person's best-fitting rule pattern. The higher this value, the higher the assumed consistency of rule usage. Data from the majority of individuals in every age group conformed best to one of the three dimensional rules. In addition, the consistency values for individuals' best-fitting rule became significantly higher as age increased. It is concluded that most children have a tendency to attend selectively to one stimulus dimension when making perceptual classification judgments. The developmental trend in perceptual classification does not appear to be a holistic-to-analytic shift; instead, it is a trend toward greater consistency in following a given classification rule.