This paper reports on three studies within a 6-year longitudinal study which explored the use of Piagetian sensori-motor substages as a curriculum base for individuals with profound mental retardation (MR). In the first study, a simple observational inventory, the Cognitive Marker Natural Observational Tool (CM-NOT), was developed and evaluated with 20 caregivers, most with little formal education, who evaluated the cognitive skills and secondary processing differences in 38 individuals with profound MR. Caregivers were relatively successful in using the measure, as demonstrated by 86 percent agreement with earlier clinical assessments of the same individuals. The use of electroencephalographic (EEG) reports to analyze behavioral and language differences was the focus of the second study. Participants (n=31) with profound MR were assessed by caregivers using the CM-NOT and the results were compared with EEG reports. Areas of seizure activity matched predicted behavioral/language dysfunction 82 percent of the time. The third study showed that nine out of ten individuals with profound MR demonstrated an increase in pulse rate and behavior when in a highly stimulated environment. The report includes a chart of cognitive milestones for infants, illustrations of regions of the human brain and their functions, and a sample CM-NOT test form. (Contains 21 references.) (CR)