The development of identity as a privileged relation in classification: When very similar is just not similar enough

Abstract

Young children classify by overall similarity the same stimuli that older children and adults classify by part identity. This developmental trend is typically discussed in terms of a shift from comparing wholes to comparing parts. The present study investigates if the trend reflects more than one developing ability. The results of Experiment 1 showed that, in the absence of a part identity relation, older children classify by wholes, not parts. Experiment 2 demonstrated a developmental trend from classifying by similarity to classifying by identity and showed that absolute identity classifications are made more readily than overall similarity classifications by older but not by younger children. Experiment 3 investigated adults' use of absolute identity and showed that identity classifications reflect a strategically imposed and thus shiftable criterion by which stimuli may be classified. In conclusion, the results of the present study suggest that the developmental trend from overall similarity to part identity classifications involves a shift from comparing wholes to comparing parts, and also involves a shift from classifying by similarity to classifying by identity. The revised description of the developmental trend may be related to the trend from conceptual representations based on characteristic features to representations based on defining features.