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Three studies investigated how young children use duration indicators (hour-glass or metronome) and employ counting to estimate brief durations. The first experiment showed that 4-5-year-old subjects were very accurate when trained to produce a response for a set duration (DRRD 10 s J in the presence of a luminous array composed of small diodes, that went from green to red to indicate the target duration. A rapid decline in performance after the suppression of the clock indicated that during training, subjects of this age only relied on the signal of the last diode turning red to give their response. In the second experiment, 4-5 and 6-year-olds were trained to space their responses using a critical duration (DRL 5 s) with an auditory-visual metronome, which produced a flash and a beep every 800 ms, then with the metronome beating every 1 200 ms. Efficiency of performance was comparable in the two age groups. However, waiting times were adjusted to the critical delay only for the 6-year-olds. Furthermore, accuracy was impaired when the metronome rate was changed. This suggested that 6-year-olds counted the number of beats, whereas 4-5-year-olds made a global estimation. In the third experiment, 7-year-old children were asked to reproduce the durations (3 s, 5 s or 8 s) of the illumination of a bulb or the intervals (3 s, 5 s or 8 s) between two flashes of light. In both cases, estimations of« counter subjects » were more accurate than those of « non- counter subjects». A questionnaire, however, did not show any direct relationship between use of a counting strategy and comprehension of principles of time measurement (the necessary constancy of counting rhythm and of counted units during estimation and reproduction phases) . The current results suggest the interest of further research associating the maturation of internal timing mechanisms (as assessed by mean and variance of preferred motor tempo or of counting rhythm) and development of concepts of time measurement.
