Visual masking, mental age, and retardation

Automatic processing in mildly retarded and nonretarded persons

Mildly retarded adults, equal mental age nonretarded children, high mental age nonretarded children, equal chronological age nonretarded adults and young nonretarded adults were required to perform a priming task (letters/digits) in which some primes were masked (visual noise mask) at just below detection levels to assess automatic processing. The critical (just below detection level) prime-mask stimulus onset asynchronies (SOAs) were established individually for each subject using the method of limits and reassessed after the experimental trials. The mean critical SOA for each of the five groups was comparable and the critical SOAs remained stable across the 120 experimental trials for all groups. The nonretarded adult subjects demonstrated semantic, categorical and orthographic priming. The mildly retarded, the equal-MA and the high-MA groups failed to demonstrate priming, and in fact, demonstrated superior performance for prime-target conditions which should have been poorest. This finding was discussed in terms of the level of specificity engendered in the priming task. Under the mask procedure, the nonretarded adult groups demonstrated semantic (letter) priming and orthographic priming, suggesting that letters (not digits) function as an analog to words which were employed in earlier masked prime lexical decision tasks. The mentally retarded, the equal-MA and the high-MA groups again failed to demonstrate priming under the mask procedure.

Read-out times from iconic memory in normal and retarded adolescents

The method limits was used to obtain an estimate of read-out times for a sample of 12 normal and 12 retarded subjects matched on chronological age. The procedure required tachistoscopic presentation of a stimulus array (2, 4, or 6 digits) for a variable duration, followed by a post-stimulus. The subject's task was to recall the digit indicated by the cue. The results indicated that read-out time (a) increased as the number of digits increased, (b) was longer for retardates relative to normals, and (c) decreased with practice for both intelligence groups. The implications of a read-out deficit in retarded individuals were discussed.