How the great apes (Pan troglodytes, Pongo pygmaeus, Pan paniscus, Gorilla gorilla) perform on the reversed reward contingency task II: transfer to new quantities, long-term retention, and the impact of quantity ratios.
We tested 6 chimpanzees (Pan troglodytes), 3 orangutans (Pongo pygmaeus), 4 bonobos (Pan paniscus), and 2 gorillas (Gorilla gorilla) in the reversed reward contingency task. Individuals were presented with pairs of quantities ranging between 0 and 6 food items. Prior to testing, some experienced apes had solved this task using 2 quantities while others were totally naïve. Experienced apes transferred their ability to multiple-novel pairs after 6 to 19 months had elapsed since their initial testing. Two out of 6 naïve apes (1 chimpanzee, 1 bonobo) solved the task--a proportion comparable to that of a previous study using 2 pairs of quantities. Their acquisition speed was also comparable to the successful subjects from that study. The ratio between quantities explained a large portion of the variance but affected naïve and experienced individuals differently. For smaller ratios, naïve individuals were well below 50% correct and experienced ones were well above 50%, yet both groups tended to converge toward 50% for larger ratios. Thus, some apes require no procedural modifications to overcome their strong bias for selecting the larger of 2 quantities.
Uher
Jana
J
Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany. uher@primate-personality.net
Call
Josep
J
D000818:Animals; D001245:Association Learning; D002755:Choice Behavior; D003210:Concept Formation; D004193:Discrimination Learning; D005260:Female; D006071:Gorilla gorilla / Q000523:psychology*; D007266:Inhibition, Psychological; D008297:Male; D009042:Motivation; D019974:Pan paniscus / Q000523:psychology*; D002679:Pan troglodytes / Q000523:psychology*; D011148:Pongo pygmaeus / Q000523:psychology*; D011340:Problem Solving; D011597:Psychomotor Performance; D012153:Retention, Psychology; D012193:Reversal Learning; D012201:Reward; D013045:Species Specificity; D014163:Transfer, Psychology