Figure 1: Experimental apparatuses and setup.
(a) Chimpanzees in the GO group (blue food box on left) could release a peg, allowing food to be shaken out, whereas those in the NO-GO group (green food box on right) would prevent food from being shaken out. (b) In the test conditions, recipients would sit in front of the food box (left of image) and actors would face them across a keeper’s corridor (right); the peg was attached to the mesh of the actor’s room (right).
