Development of time concepts: differentiating clock and calendar from apparent durations.
To investigate the role of perception and stress on time concepts, the real-time and apparent durations of common events varying in length from 30 s to 4 years were rated by kindergarten through 12th-grade pupils, college students, professors, and stress-impaired adults (N = 1,788). The events were pleasant, neutral or unpleasant; either directly perceptible and of specific duration or perceptually vague; and happened either to oneself or to someone else. Second graders differentiated apparent from real-time durations and, therefore, already had an abstract concept of time. As predicted from differentiation theory (Gibson, E. J., 1969; Gibson, J. J., 1966, 1983), longer durations were acquired later than shorter ones; perceptually-vague durations were acquired later than clearly perceptible ones of similar length; and, as Neisser (1976) also suggested, stress did not lead to regression, nor did the personal-impersonal dimension make a difference during childhood.