The Piagetian approach to intellectual development (Piaget & Inhelder, 1969; Piaget, 1952) has come under increasing critcism in the recent literature for its readiness to interpret children's performance in terms of the presence, or absence, of underlying operational structures whilst ignoring the contribution of social influences in the immediate situation; critics have argued that we risk seriously underestimating the cognitive skills available to the young child if we overlook these influences (Magarrigle & Donaldson, 1975; Donaldson, 1976; Smedslund, 1977; Sinha & Walkerdine, 1978). The young child fails the various Genevan tests of operational thinking, they suggest, not because he lacks the necessary logical competence but because he misinterprets the intention of the experimenter. Drawing on Macnamara's (1972) account of language acquisition, McGarrigle & Donaldson (1975) argue that children rely heavily on the non-verbal features of any social interaction (including psychology experiments) to interpret the other person's intended meaning. ‘Preoperational’ children fail in conservation experiments, they suggest, because the situation involves a conflict between the formal logic of the problem and the social logic of the context: the adult refers behaviourally to length when he rearranges a row of objects, but then refers linguistically to number when he poses the question. In their study of number conservation the objects were not rearranged intentionally by the experimenter but ‘accidentally’ through the actions of a ‘naughty’ teddy bear ‘trying to spoil the game’ as a consequence, 68 per cent of a group of 4–6 year olds conserved, compared with only 41 per cent in the control condition.