Apes know that hidden objects can affect the orientation of other objects.

Area of Science:

• Primate cognition
• Animal behavior
• Comparative psychology

Background:

• Great apes possess complex cognitive abilities.
• Understanding object orientation and its relation to reward is crucial for survival.
• Previous research suggests apes can associate visual cues with food availability.

Purpose of the Study:

• To investigate whether great apes infer the causal reason for an object's inclined orientation.
• To determine if apes associate inclination with reward presence or understand the underlying cause.
• To explore the limits of their reasoning in such tasks.

Main Methods:

• Presenting bonobos, gorillas, and orangutans with inclined vs. flat boards, with food as a hidden reward.
• Observing choices when board orientations changed (inclined to flat).
• Testing reasoning with supported vs. unsupported inclined boards and varied reward sizes/types.

Main Results:

• Subjects consistently preferred inclined boards, indicating an association with reward.
• Apes failed to identify unsupported inclined boards, suggesting a lack of causal reasoning in that context.
• When presented with two rewards of different value, apes chose the board with greater inclination (larger reward) but ignored food type, even when it was less preferred.

Conclusions:

• Great apes infer the reason for board inclination, not just associate it with reward presence.
• Their reasoning has limitations, particularly when causal cues are ambiguous.
• The study highlights sophisticated, yet constrained, inferential abilities in great apes regarding object-reward relationships.