High speed memory scanning in mental retardates: evidence for a central processing deficit

Third-grade, high-school, and adult normal subjects and two diagnostic categories of educable mental retardates (cultural familials and encephalopathies) were tested in a Sternberg-type “memory scanning” recognition task. All five groups showed the characteristic linear increase in correct reaction time as the number of items in the memorized set increased. The slopes of the linear functions, however, were steeper for the two retardate samples than for the normal samples, suggesting a central processing deficit which could not be attributed to a lag in development.