Visual search for single and combined features by children and adults: possible developmental inferences

Visual search time was measured in four groups of children 4 to 10 years of age and in young adults, as a function of display size for both target present and target-absent conditions. The slopes of regression lines in a simple search (search for \ within /) were compared with those obtained in within-dimension conjunction target searches, within either homogeneous (search for the inverted T within Ts) or heterogeneous distractors (search for arrow within Ys and inverted Ys). Analysis indicated that simple search was always preattentive (slopes near 0) after 5 years of age and serial (with positive slopes) before this age. Searching within heterogeneous distractors apparently involved element-by-element scrutiny and focal attention in all groups whereas searching within homogeneous distractors required distributed attention, perhaps based on parallel grouping of distractors in adults, though distractors were focally attended to by children.