Abstract
In many studies it was demonstrated that the cerebral palsied children had poor perforemance on the figure perception in comparing with normal children. This was partly because of their behavioral characteristics such as "distractibility" (external distraction of figure-background perception). This study was intended to examine the effects of the external stimuli on the figure perception relating to the following points. 1) Are there differential effects of external stimuli among spastic, athetotic and normal children? 2) What effects will be brought about due to changing conditions of the external stimuli? 3) Do the external stimuli decrease their distracting effects in accordanance with presenting them repeatedly? Furthermore, the relationship between external distraction of attention and disorder of figure-background perception was discussed. Those points were examined in the Experiment I with single-figure perception and in the Experiment II with figure-background perception. Method Subjects were 30 normal, 30 athetotic and 30 spastic children. Figure stimuli were 24 single-figure stimuli selected from Peabody Picture Vocabulary Test, and 14 figure-background stimuli overlapped with geometric figure. The external stimuli were 8 small lamps set on the outside edges of the screen. They were presented by following conditions; 1) simultaneously with figure stimuli, 2) starting to light a little before presenting the figure stimuli (.125 sec. in single-figure perception; .25 sec. in figure-background perception), 3) starting to light a long before presenting the figure stimuli (.25 sec. in single-figure perception; .5 sec. figure-background perception). Result and discussion 1) Cerebral palsied children made higher distracting error ratio than normal children both in the single-figure perception and the figure-background perception. It was suggested that the distracting effects would be related with orienting reflex to the external stimuli. 2) When the external stimuli were started to present a long before the figure stimuli, ther was no distracting effects. It was suggested that the foreperiods of the external stimuli might come into action of signaling stimuli. 3) It was found that the frequency of distracting errors were decreased in accordance with repetition to the external stimli. This might be due to habituation to the external stimuli. 4) There was no significant difference in the distracting effects between clinical types. But in the figure-background perception, there was significant difference. Therefore, it was suggested that the external distraction of attention and the disorder of figure-background perception were mutually independent ones.
