Automatic and effortful processing by mentally retarded and nonretarded persons.

Automatic and effortful processing by brain-injured and cultural-familially mentally retarded and nonretarded persons were compared in a letter priming task. Both retarded groups responded considerably slower than did the nonretarded group. Inhibitory effects due to a prime stimulus and facilitative effects following brief presentations of prime stimuli were similar for all groups. Facilitative effects remained at the same level for the nonretarded group but clearly continued to increase for the retarded groups along the longest presentation intervals. The findings were interpreted as showing similar automatic processing effects in all groups. Effortful processing by retarded persons, on the other hand, was slower to develop and possibly greater than that by nonretarded persons.