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Flexible and Context-Dependent Categorization by Eighteen-Month-Olds


  • This work was supported by an Economic and Social Research Council U.K. Grant (R000239112) and by a European Commission Grant 514562 (NEST). We are very grateful to the parents and infants who participated in these studies. We are also deeply indebted to Hoben Thomas for the time he has taken in sharing his expertise using finite mixture models, Michael Thomas for numerous discussions, and Agnes Volein for helping to collect the data.

concerning this article should be addressed to Denis Mareschal, School of Psychology, Birkbeck University of London, Malet Street, London WC1E 7HX, U.K. Electronic mail may be sent to


One hundred 18-month-olds were tested using sequential touching and following 4 different priming contexts using sets of toys that could be simultaneously categorized at either the basic or global level. An exact expression of the expected mean sequence length for arbitrary categories was derived as a function of the number of touches made, and a finite mixture model analytic method was also used to explore individual variability in categorization. Toddlers could categorize flexibly and spontaneously selected the level of categorization as a function of the prior prime. Perceptual Variability emerged as a predictor of the level at which infants subsequently categorized. The infants were also able to classify objects as members of both basic- and global-level categories simultaneously.