Attentional resource demands of stimulus encoding for persons with and without mental retardation.

Speed of encoding differences between individuals with and without mental retardation were examined to determine whether they stem from an automatically executed cognitive process or from encoding processes that require attentional resources. In Experiment 1, encoding functions were generated for physical identity and name identity encoding while subjects retained a full memory load or half memory load. Size of memory load influenced encoding times for all subjects. However, the pattern of group differences suggested that subjects with mental retardation allocated fewer attentional resources to encoding, even though encoding may require more of their resources for efficient execution. These conclusions were supported in Experiment 2, in which resource allocation was assessed using response times to auditory probes placed at various locations in the semantic encoding and decision task.