Allocation of attention and task difficulty.

Individuals with and without mental retardation did a dual task procedure designed to investigate how task difficulty influenced the allocation of attention. The primary task required semantic category decisions. Subjects sorted cards according to whether the object pictured on the card belonged to a target category. The easy decision task used basic level categories (horse and hammer). The difficult decision task used superordinate categories (animals and tools). While making decisions, subjects were required to signal detection of auditory probes. Response times to the probes were used to index attention to the primary task. Subjects without mental retardation allocated more attention to the difficult task. Those with mental retardation gave similar attention to the easy and difficult tasks. Possible explanations for their failure to allocate attention in accordance with task difficulty were discussed.