Development of time quantification: integration and nonintegration of beginnings and endings in comparing durations.

This study investigated how children handle time information when deducing durations of events. In an elaboration of the commonly used choice paradigm to study children's time concepts, pairs of durations were presented in a 4 beginning lags X 4 ending lags design in 2 different problem series. Children's task was to equalize the durations of the 2 events by restarting 1 event for a certain time. The normative rule, quantification of duration differences in beginnings and endings and their integration by addition or subtraction, began to predominate at the age of 10 years and was the only rule employed by 13-year-olds. In contrast, almost all 7-year-olds simplified the task to an ordinal level. 4 different nonalgebraic rules were identified, each placing more importance on endings than on beginnings. Neither young children's tendency to simplify nor older children's capacity to quantify could be detected in previous studies, because they investigated time concepts on an ordinal level only. In light of the present findings, previous notions on the development of time concepts in children have to be reevaluated.