Table 3.

The chimpanzees solved the task 279 times in the five 100% sessions, an average of 55.8 rewards per individual per session. The ‘potentially obtainable’ column is calculated by multiplying the reward rate by the chimpanzees’ actual performance in the 100% condition. Example: if 55.8 is the theoretical maximum rewards an individual could obtain on average across sessions, multiplying this number by the 80% rate equals a potentially obtainable amount of 44.6 rewards. The table shows that chimpanzees could have obtained far more rewards in the 80%, 60%, 40%, and 20% conditions if they had simply pulled the bars at the same rate as they did in the 100% condition.

Rate	Total successful trials	Actually obtained average rewards per individual per session	Potentially obtainable average rewards per individual per session
100%	279	55.8	NA
80%	57	10.3	44.6
60%	18	2.9	33.5
40%	8	1.3	22.3
20%	0	0	11.2
0%	0	0	0