Conditional discrimination using 3-dimensional objects by a chimpanzee (Pan troglodytes): tests for derived stimulus relations

A female chimpanzee (Pan troglodytes) was trained on the conditional-discrimination task using 3-dimensional objects under a face-to-face experimental setting. In Experiment 1, the subject was required to pick up the correct comparison object, take it to the sample object, and construct a new paired-object with a specific action. After acquisition of the task, derived stimulus relations (associative symmetry) were tested. The subject showed a significant emergence of symmetry only when the spatial arrangements of stimuli were changed between the baseline and test trials. In Experiment 2, the subject was tested under the condition where the action to constructed paired-object was common to all stimuli. The subject showed significant above-chance performance in the transitivity test, but not in the symmetry tests. The present results are generally consistent with previous studies in chimpanzees that show weak evidence for the emergence of symmetry.