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THIS CHAPTER is devoted to studies in the development of the cognitive processes involved in perceiving, thinking, and learning. It focuses on how and when these processes evolve, the factors that influence their formation, and their effects on the intellective functioning of the child. Development of the Perception of Physical StimuliDuring the past decade there has been increasing interest in the effects of central and intervening processes on the act of perceiving. The construc tion of theories and models of perceptual mediation has not been matched by empirical research, however, and a number of exciting hypotheses have been put forward that are still in need of adequate testing. In the absence of any broad, longitudinal studies, several reviews will be noted before empirical investigations are discussed.WohlwilΓs (1960a) analysis was limited to experimental investigations involving noncognitive, nonconceptual tasks. A decrease in the perceptual assimilation of objectively different stimuli was noted as a correlate of increasing age, while the distorting effects of contrast were found to in crease. Apparently, as the child becomes better able to discriminate, the very contrast between the differentiated stimuli of which he has become newly aware serves to produce distortions. This suggests a growing relativism and a corresponding reduction in the importance of the absolute properties of the stimulus. Other trends noted by Wohlwill were a tendency, increasing with age, to relate a stimulus to its spatial framework and a sharp drop in errors of spatial localization of body orientation. In all instances the im provement of perceptual discrimination was accompanied by the onset of centralized controls, which stabilized and simplified perceptual patterns, sometimes at the expense of objectivity (veridicality). The need for this simplicity can be inferred from another trend identified by Wohlwill, who noted that the young child requires more redundancy in a pattern to per ceive it correctly and prefers perceptual modes that provide a minimal scope of information. The question of whether or not age, learning, and the emer gence of central controls and regulatory mechanisms actually increase veridicality was singled out as the most significant open question to be faced.Bevan (1961) posed a theory of the evolution of perceptual frames of reference that was founded primarily on differentiation rather than associa tion. He pointed out that perceptual development is characterized by pro-451 at NORTH DAKOTA STATE UNIV LIB on July 1, 2015 http://rer.aera.net Downloaded from