The zookeeper concludes that Jocko’s silence was meant to keep the other chimpanzees from taking his food. This conclusion is based on two observations: how Jocko uttered food barks that led to his bunch of bananas being taken away by other chimpanzees, and how, the next day, Jocko stayed silent after being given a banana. From the fact that Jocko stayed silent after a previous experience where his food was taken away, the zookeeper concludes that his silence was a strategy to avoid the same outcome.

The zookeeper's conclusion rests on a number of assumptions: for example, that chimpanzees have the memory and other capacities to learn from a single past experience. But the biggest assumption here is that Jocko's silence was not just a response to a different quantity of food. To figure out if Jocko was making a decision to stay silent, we would want to know that the conditions in both scenarios were pretty much equal. But on the first day, he was given an entire bunch of bananas, and the next day was only given one. Perhaps if he had been given a bunch of bananas on the second day, he would have barked again.