Resumen de Individual Response Strategies in List Learning by Orangutans

Karyl B. Swartz, Sharon A. Himmanen

• Two orangutans learned eight lists of items in a recognition memory procedure that allowed the list items to be reported in any order. In a previous study using this same procedure, the orangutans developed a spatial response strategy that was applied to acquisition of novel lists. The purpose of the present study was to determine whether serial order information would supersede the already established response pattern. One subject maintained the established response strategy while the other showed a gradual weakening of that pattern that appeared as lists were acquired. Neither subject demonstrated a serial position effect although serial order information may have affected the shift in response strategy. The obtained individual differences are striking in light of previous studies that have shown quantitative differences but no qualitative differences in serial learning by monkeys and orangutans.