Age differences in the acquisition and retention of concurrent discriminations by monkeys

The performances of adult and aged macaque monkeys were compared on several tasks requiring acquisition and retention of concurrent object discriminations. Cross-sectional and longitudinal comparisons between 11-year-old and over-20-year-old animals were conducted on the acquisition of several 16-problem concurrent tasks, and after 2 weeks, retention by the different age groups was also evaluated. Although the retention tests indicated no age-related impairment, acquisition tests showed that aged animals made reliably more errors-to-criterion than did adult animals. The relative contributions of intersession and intrasession improvement and preference phenomena were considered and contrasted to some previously reported age-specific outcomes. Although the present results affirmed the contention that old animals were selectively impaired on intersession task requirements, some earlier interpretations of preference effects were questioned. Old animals did not show a potentiation of specific object preferences; rather, they tended to be nonsystematic in maintaining their selection of initially preferred objects. Concurrent discrimination was indicated to be a behavioral measure that is, under appropriate circumstances, selectively sensitive to aging and may offer an appropriate comparative model of information-processing characteristics.