Sophisticated abilities may arise from the maximisation of simple rewards in complex environments.

There's a You're Wrong About podcast episode that essentially makes the case that in order to communicate with sign language, Koko the gorilla had simply learned gestures for rewards with a more sophisticated framework than what we typically see in research. Obviously, that's an oversimplification, but there's a wonderful debate about the whole thing.

According to our hypothesis, the ability of language in its full richness, including all of these broader abilities, arises from the pursuit of reward. It is an instance of an agent's ability to produce complex sequences of actions (e.g. uttering sentences) based on complex sequences of observations (e.g. receiving sentences) in order to influence other agents in the environment (cf. discussion of social intelligence above) and accumulate greater reward [7].

If reward is enough, and seeking reward is a singular universal mechanism for the development of intelligence, it would seem that either side of the Koko argument is moot. The "Koko was only responding to rewards" camp is in fact just echoing the sentiment that Koko is demonstrating general intelligence. Therefore, that cannot by itself stand as an argument that Koko had not demonstrated general intelligence. In contrast, arguing that Koko did demonstrate a high level of intelligence would simply be reiterating the counter argument that Koko manifested sophisticated abilities through the maximization of rewards in complex environments.