Introduction

In 1928, at the first International Congress of Physics and Philosophy in Davos, Switzerland, Piaget heard Einstein presenting his theory of relativity on physical time. From then, he tried to demonstrate that psychological time is intrinsically related to the physical time defined by Einstein: "The hypothesis that I want to defend is that psychological time depends on the speed or the movements with their speed" (Piaget, 1946). Thus, during several decades, Piaget and a whole generation of psychologists investigated, with sophisticated methods, the development of the ability to judge time in children as a result of the development of the capacity to logically reason about time.

In parallel, researchers accumulated data from animals and human adults showing their abilities to accurately estimate time, and that the subjective time is linear with the objective time. Then they proposed models of temporal information processing, according to which the raw material for time judgments comes from an internal mechanism similar to that of a clock. Recently, developmental psychologists have become aware of the utility of these models to better understand the interval timing abilities in children, and have decided to break with the dominant Piagetian theory. Thus, they made an effort to reconsider interval timing in children within the framework of the most completely developed model of interval timing, the scalar timing theory (e.g., Gibbon et al., 1984). First, they submitted children to the tasks related to this theory, in order to provide empirical data on age-related changes in timing. Then they examined different potential sources of developmental changes at each level of the temporal information processing.

7.2 INTERVAL TIMING IN CHILDREN: PROCEDURES AND MODELING OF DATA

7.2.1 Temporal Bisection in Children

Recent studies have adapted for the temporal bisection procedure, initially used with animals (e.g., Church and Deluty, 1977; Meck, 1983), and later modified for human adults (e.g., Allan and Gibbon, 1991; Wearden, 1991) [young children (e.g., Droit-Volet and Wearden, 2001, 2002; Gautier and Droit-Volet, 2002a; McCormack et al., 1999; Rattat and Droit-Volet, 2001)]. In the temporal bisection task, the children generally received three experimental phases: pretraining, training, and testing. In the pretraining, they were presented a short and a long standard duration in the form of a sound or a visual stimulus (e.g., blue circle). Then they were trained on successive blocks of trials to press one button after the short standard duration and another one after the long standard duration. In this training phase, a correct response resulted in the appearance of a smiling clown, and an incorrect one of a frowning clown, as illustrated in Figure 7.1. The training terminated when the child made no errors during a block of trials (i.e., eight trials, four for each standard). The number of the training blocks required to discriminate the short from the long standard decreased with age; the 3-year-olds took at most three or four training blocks, the 5-year-olds up to two or three, and the 8-year-olds, as the adults, one or two training blocks. Thus, the simple learning of two standard durations took longer in the younger children. After a successful training block, the children were given a testing

Correct response Incorrect response

FIGURE 7.1 The smiling clown (positive feedback) and the frowning clown (negative feedback) presented on the center of the computer screen after a correct response and an incorrect response, respectively, in both the temporal bisection and temporal generalization procedures.

Correct response Incorrect response

FIGURE 7.1 The smiling clown (positive feedback) and the frowning clown (negative feedback) presented on the center of the computer screen after a correct response and an incorrect response, respectively, in both the temporal bisection and temporal generalization procedures.

8-year-olds

Stimulus duration (sec)

Human adults

Stimulus duration (sec)

FIGURE 7.2 Psychophysical functions obtained from the 3-, 5-, and 8-year-olds in a temporal bisection task in two anchor duration conditions (1/4 and 2/8 sec) (Droit-Volet and Wearden, 2001), with an example of temporal bisection function obtained from the human adults derived from Wearden (1991). (From Droit-Volet, S. and Wearden, J., J. Exp. Child Psychol, 80, 142-159, 2001.)

8-year-olds

Stimulus duration (sec)

Stimulus duration (sec)

Human adults

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