EFFECTS OF TARGET PROBABILITY AND MEMORY DEMANDS ON THE VIGILANCE OF ADULTS WITH AND WITHOUT MENTAL-RETARDATION

The vigilance of young adults with mild mental retardation and without mental retardation was compared in two experiments in which observers performed two memory demanding, cognitively based, 60-minute tests. I n Experiment 1, target probability was 5% or 30% with a 1.5-second eve nt rate. Detection by observers with mental retardation declined more rapidly than did that of observers without mental retardation in both target probability conditions; further, their response criterion becam e increasingly more conservative. In Experiment 2, target probability was 10% or 30% with an 8-second event rate. Observers with mental reta rdation detected fewer targets under both target probability condition s. Subjects' response criterion differed as a function of level of int elligence from the onset of the vigil and did not change with time on task. Intelligence-related differences in vigilance were explained in terms of subjects' information-processing abilities.