Clark’s nutcrackers’ (Nucifraga columbiana) ability to discriminate knowledge states of human experimenters during an object-choice task

Abstract

The present thesis examined whether the corvid, Clark’s nutcracker, is able to discriminate knowledge states between human experimenters based upon gestural cues using an object-choice task. To do so, the knowledge state of two experimenters was manipulated – one experimenter was informed, and the other uninformed, as to the location of a hidden food reward. To find the reward, the birds had to use the gesture of the informed experimenter and refrain from using the unreliable gesture of the uninformed experimenter. The nutcrackers responded to the gesture of the informed experimenter at above chance levels when simultaneously presented with the uninformed experimenter’s gesture. When the uninformed experimenter’s gesture was presented alone, the birds continued to follow the gesture. These results suggest the birds learned the gesture was meaningful, perhaps by associative learning, yet when this mechanism was not reliable the nutcrackers based their choices on the knowledge states of the experimenters.