The cognitive basis of classification in very young children: an analysis of object-ordering trends.

1--3 year-olds' ability to conceptually interrelate objects was studied. 8 children each at 12, 18, 24, 30, and 36 months were given 7 free classification tasks. Each task contained a scrambled array of 8 objects from 2 classes. Spontaneous manipulations were analyzed to determine (1) whether children sequentially contacted similar objects above chance level and (2) to what extent objects from 2 classes, rather than just 1, were selected. Children at each age sequentially selected similar objects above chance in some tasks. Initially such sequences were accompanied by a tendency to manipulate only 1 class of objects throughout a task, but this single-class bias declined significantly with age. Selection of only 1 class can be accounted for by perceptual salience. Selection by similarity involving 2 classes is less likely explained by salience and more likely explained by a strategy in which individual items are conceptually compared. Classification based on conceptual comparisons of the items being selected may emerge over the second and third years, even though children engage in class-consistent behavior earlier.