chapter04 OUP028–29/mareschal (Typeset by SPi, Delhi) 65 of 98 November 11, 2006 10:1 Chapter 4 Why let networks grow? Thomas R. Shultz, Shreesh P. Mysore, and Steven R. Quartz ‘Let it grow, Let it grow.’ Grateful Dead, 1973, Eric Clapton, 1974, Boogie Brown Band, 2003 Introduction Beyond the truism that to develop is to change, the process of developmen- tal change itself has been relatively neglected in developmental psychology. Methodologically, most behavioural studies have traditionally utilized a cross- sectional approach. This has revealed a great deal about how certain behav- ioural and cognitive abilities differ at various points in development, but it tends to reveal less about the developmental processes that operate to trans- form those cognitive and behavioural abilities. A variety of factors account for the lack of explanations of developmental change, ranging from the method- ological challenges their study entails to principled, learning-theoretic argu- ments against the very existence of such developmental processes (Macnamara, 1982; Pinker, 1984). Among the most influential arguments against developmental change was Chomsky’s (1980) instantaneity argument that starts with the null hypothesis that children are qualitatively similar learners to adults and supposes that development is instantaneous, in the sense that there are no time dependen- cies in development. Departing from this view and supposing that children are initially more restricted learners only results in weakening their acquisi- tion properties. The upshot is that less is less, and development only reduces learning capability. Thus, as a sort of charity principle, one ought to at least start with the hypothesis that children do not differ substantially from adults, because explaining development is difficult enough without having to do so with greatly diminished learning ability.