Figure 10. DN performing full nut-cracking action demonstrations.

(A) subjects’ attention was gained by calling their given name; (B) hammer was to eye-level and (C) brought down on the nut as many times as required until it cracked; (D) the cracked nut (both shell and kernel) are provided to the target subject by a keeper. Subject in this demonstration was the female (C9) to the left of DN—holding onto the mesh in A-C; keeper rolled the nut to C9 in D (hand feeding, even by keepers, is not permitted at the testing institution).