A potentially important source of cognitive developmental variance is that associated with basic cognitive-processing efficiency. Discrepant findings from several studies have failed to establish convincingly whether developmental change exists in basic processing efficiency. Employing 2 different experimental tasks, memory and visual scanning, which permit the isolation of a theoretically similar process, that is, search, we examined age effects on the search-processing parameter after analyzing it for convergent and discriminant validity. Each of the 96 subjects at 4 ages (9, 11, 13, and 15 years) completed both experiments. Validity evidence was obtained through a comparison of process and task intercorrelations, which revealed the former to be significantly more related than the latter (p less than .001). Also, significant age effects (p less than .001) were obtained for the search-processing parameter in both tasks, which provides evidence for the development of basic cognitive-processing efficiency.