Mentally retarded and nonretarded individuals' attention allocation and capacity

Eighteen mentally retarded individuals, 20 nonretarded children, and 20 nonretarded adults were exposed to three conditions of an auditory detection task. In the location condition single random nonsimultaneous English letters were presented to both ears. Subjects reported the letters to one preassigned ear. In the meaning condition rapidly presented backward letters containing infrequent target (forward) letters were presented to one ear. Subjects reported the target letters. In the both condition rapidly presented backward letters containing infrequent target (forward) letters were nonsimultaneously presented to both ears. Subjects reported the target letters to one preassigned ear. The retarded subjects and nonretarded children reported significantly fewer target letters across the location, meaning, and both conditions. These groups also demonstrated slower reaction times (RTs) relative to the adult group; however, their RTs remained constant across conditions. We concluded that developmentally immature populations are less efficient at attentional allocation and have a more limited attentional capacity.