Stability of cognitive performance in assessment situations was investigated in a group of 18 children with Down's Syndrome (DS) aged 6 months to 4 years. Two widely used tests of early cognitive development were presented: the Mental Scale of the Bayley Scales of Infant Development and a series of Piagetian object concept tasks. Both sets of tasks were presented in the same testing session, with testing repeated one to two weeks later. Both qualitative and quantitative aspects of performance were recorded. Even when overall scores were similar, patterns of pass/fails were very different in the two testing sessions. Successes showed poor stability over sessions with fails often occurring by default, the result of a refusal to engage fully in a particular task. This pattern of results suggests: (1) that single-session testing may not adequately assess cognitive status in DS children; (2) that the relationship between performance and competence may be unstable in such children, and (3) that "slow development" theories may not adequately describe cognitive development in young children with DS.

Two different strategies for teaching discrimination to Down's Syndrome (DS) and non-handicapped children were compared for relative efficiency: trial-and-error and errorless learning. Two types of discrimination tasks were used, shape and nonsense figure tasks. A pre-test was used to match children for pre-existing ability. Errorless learning proved to be the superior training strategy in each group, both during training and in post-tests. DS children responded poorly to trial-and-error training in both absolute and relative terms. Although order of presentation of training conditions had little effect on performance in the non-handicapped group, an interesting differential effect emerged in the DS group: initial trial-and-error training adversely affected subsequent performance in the errorless task while initial errorless experience enhanced subsequent trial-and-error performance. It would appear from these results that errorless learning may be useful as a "primer", increasing motivation to learn in more conventional learning situations. ..Piagetian infanisearch tasks. Am. J . ment. Defic., 92 (2). 169-177.

This research was supported by ESRC Linked Studentship C00428725008and MRC Project Grants G9011079N/ G9311518N. Thanks are extended to Rachele Walker for assistance with data collection, to all of the children who participated in the studies, and to the teaching staff of Lothian Region special schools who generously -and uncomplainingly -allowed us to play havoc with their timetables.