ABSTRACT
IN studying the evolution of child thought we frequently encounter the problem of how proportions come to be understood. In the case of speed and movement this idea is involved as soon as two successive movements have to be compared over different times and distances, say 5 cm. in 1 second and 10 cm. in 2 seconds. 2 Similarly, with children's judgements of probability, the idea of proportions is directly implied in granting the same degree of probability to two favourable cases out of four, as to three favourable out of six possible cases. 3 In both these very divergent fields, the idea of proportion does not appear to be fully developed until the level of formal operations is reached (Stage IV), although it is, of course, developing all through the earlier stages, especially as regards the simpler cases.
