From the 1960s, there was some shift of attention among developmental psychologists from Chomsky's generative model of Universal Grammar towards alternative explanations involving data-based investigation of children's spontaneous speech. Interest continued in the developmental constructivism of the Swiss psychologist Jean Piaget (1896-1980), whose theorizing about the capacities of pre-school children began in the 1920s. Piaget posited the existence of all-purpose cognitive skills switched on by regulatory and auto-regulatory mechanisms at each stage of the child's development. Piaget and his Geneva School argued that the child passes through a series of uniform stages, always following the same sequential order.