Effects of age on learning ability: contributions from the animal literature.

For both ethical and practical reasons, animal subjects are becoming increasingly important tools for life span developmental researchers. Selected studies from the animal literature which have important implications for the study of learning in a life span context are reviewed. Specific issues discussed include task difficulty, genotype effects on life span learning processes, perseveration, and early versus later experience. It was concluded that 1) the hypothesis that task difficulty has a greater effect on senescent animals relative to younger animals generally is supported by the current literature, 2) genotype is a highly relevant variable for life span developmental research, but little work has been dirrected toward how genotype affects behavior within specific environmental contexts, 3) perseveration is very likely an important factor in poorer performance among aged subjects, but it has not been adequately studied in relation to physiological correlates, earlier precursors, or genotype, 4) the issue of the importance of early versus later experience has not been resolved, but research in this area promises much information with regard to potential modifiers of a decline in learning ability with increasing age.