I. Problems of the present study and historical review of the previous studies;The present study attempts to clarify experimentally the development, as well as situational difference, of visual size constancy in early infancyPrevious studies on the development of visual size constancy made by Frank, Beyrl. Burzlaff, Akishige, Thouless. Weber & Bicknell, Locke, etc. used very rarely infants who were younger than one year of age. Subjects of Frank's study (8), for instance, were 30 young children, of whom 29 are older than one year.Ruth M. Cruikshank's experiment, under the direction and planning of Brunswik (6) used 73 babies from 13 to 49 weeks old. The present study starts with the criticism of her experiment. She set up three stimulus situations, A B and C, using two rattles large (57cm long) and Small (19cm long). In A, the smaller rattle was presented at 25cm distasce from the eyes of the subject, while in B, the larger one was shown 75cm far, and in C, she presented the larger rattle 75cm far. She assumed that “equal reactions to situations A and B, but lack of equivalence for Situation C would represent the positive aspect of size constancy” (p. 336). We might derive from this assumption the major premise that the subject would show the same response to the object of the same apparent size. This premise was criticized in the present study which started in an attempt to experimentally test the assumption that the infant might prefer the object of the larger apparent size. Even if the premise derived from Cruikshank's assumption was admitted, Acritical study of the learning curves in her study showed that she was not so positively in her attempt to clarlfy the developmental aspect of visual size constancy.The present study tries to show the developmental as well as situationally differential aspects of visual size constancy in early infancy. It comprises nine experiments.II. Method(a) Subjects: 457 babies 12 weeks to one year of age.(b) Conditions of stimulus situation and procedure.The first Second and third experiments used two red toy-gold-fish made of celluloid, one 10cm and the other 17.5cm long. The 4th, 5th, 6th and 7th experiments used two red tiny balls, (one 0.25cm and the other 0.45cm in diameter). These objects were presented, at distance 17.4cm from the eyes of the babies.The babies were assumed to show the preference to respond to the objects of the larger apparent size. In the 2nd aud the sixth experiments we presented the larger object at a distance farther from the subject than the smaller one. trying to make the size of the retinal image of the former iden ical with that of the latter. It was assumed in our experiment that if the subjects showed the preference of the larger object over the smaller one, then the existence of visual size constancy would be positively proved.III. Result.(1) The children in early infancy prefered the larger object under the situation set up in the present experiments. The preference of the larger toy gold-fish began at the 5th month of age while the preference of the larger red ball at the 6th month.(2) The tendency to prefer the larger ball was greater than the inclination to prefer the larger toy-gold-fish. The preference of the larger ball showed rapid development after the 11th month of age.(3) Cruikshank's experiment on the development of visual size constancy did not assume the babies' preference of thelarger object This is one of the short-comings of her study.(4) In the2nd experiment, the development of visual size con stancy, although very slight, was found after the 6th month of age when the red toy-gold-fish was used as the stimulus object.(5) In the 6th experiment, the development of visual size constancy was clearly found at the 6th month of age and was much more clearly observed after the 8th month.(6) The difference between these two modes of development in size constancy observed
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