[Visual nonverbal set in preschool- and schoolchildren].

Visual set for perception of unequal circles was formed in 5-6-year-old preschool- (n = 30) and schoolchildren (n = 43). Children of 5.3-6.1 years old formed a less rigid set than 9-10-year-olds. The reaction time to a probe stimulus significantly depended on the set stability and stage. The role of structural maturation of the frontal cortical areas in set formation and stability is discussed. The factor of set rigidity was shown to be significant for cognitive activity.