Two studies examined the effectiveness of pupillary measurements to indicate cognitive processes in educable mentally retarded (EMR) and nonretarded elementary and high school students. In the first study, pupillary scores from 20 nonretarded and 10 EMR students were measured for two conditions of an auditory task: listening and remembering. Results indicated that while younger Ss and retarded Ss remembered a comparable number of words under instructions to remember and to listen, older nonretarded Ss retained significantly more words in the remember than the listen condition. The second experiment investigated the sensitivity of pupil size measurement to differences in digit processing by 10 EMR and 11 regular class high school students. Pupil size differences as a function of the instructional condition were not revealed consistently across trials. (CL)