This study determined which intellectual abilities account for IQ changes over the school year. All the Head Start subjects involved in the study (35 boys and 33 girls, mean age 44.1 months) lived in poverty under conditions of urban deterioration. The subjects were initially given the Standord-Binet Intelligence Scale in the fall and were tested again 6 months later. Tasks from the Binet were grouped according to categories: comprehension, verbal ability, performance, drawing, visual perception, and memory. The findings indicated that in the overall shift in the pattern of cognitive abilities, change in two categories (visual perception and comprehension) accounted for the rise in IQ encountered during the Head Start year. (CS)