Table 1.

The Canister Lid Colours And Contingencies For Experiment 1

	Canister colours/contingency
Monkey	B → A	A → B
P	Purple	Yellow
H	Green	Blue
T	Purple	Blue

Note: A monkey selected from two canisters with coloured lids. Choice of one canister resulted in a half vegetable followed 4 s by a grape (B → A), and choice of the other resulted in a grape followed 4 s later by a half vegetable (A → B). Monkeys were given different colours in the experiments to avoid colour confounds.