Ape is a corner case, they're the only species we know of that share to a limited extent the enlarged forebrain that humans have.
A single outlying data-point hardly disproves a theory, and even so, you can't possibly know that the monkey knew what he was doing. It could just be mimicry. Your thinking about what the monkey is thinking is distinctly the distinguishing trait of human psyche I'm talking about.
EDIT: Also relevant. Operant theory can explain seemingly "intelligent" behaviour as random or observed and mimicked actions that are then reinforced by the environment [0]
Your monkey's behaviour could be explained in a similar vein to that which explains "cargo cult" behaviour [1].
Now, you could say that this is indeed "intelligent" behaviour, but then again a dog can be trained to open a door, and pigeons can be trained to orient themselves based on a clicker [2]. But what I'm talking about here is what distinguishes human intelligence from other forms of life on this planet.
