The orthogenetic principle in the perception of ‘‘forests’’ and ‘‘trees

This study explores possible links between ontogenetic and microgenetic change (Werner, 1948, 1957) in the perception of stimuli with multiple levels of structure. Visual search for targets defined by local versus global structure was examined in observers aged 6, 8, 10, and 22 years. Perceptual access to each level of structure was varied by using pattern elements of same (easy) or opposite contrast polarity (hard); attentional processes were isolated from sensory processes by varying the number of display items. The results showed large improvements with age in search rates for global targets, with search rates for local targets being more constant over age. This pattern held regardless of whether perceptual access to a target was easy or hard. These results support the view that the perception of local and global structure involves different underlying processes. KEY WORDS: Visual search; local perception; global perception; perceptual development; othogenic principle; visual attention. The orthogenetic principle, that development proceeds from an initially undifferentiated state to one of increasing specialization, and finally to the coordinated integration of specialized components (Werner, 1948, 1957), is a central tenet of modern developmental theory. Its legacy is evident in current research on human development, including that con-cerned with brain anatomy and physiology (John