Why Monkeys Can Only Count to Four

David Goldenberg of MinuteEarth explained an experiment he conducted with monkeys in which he found that they processed the amount of apples presented to them using relative comparison. This is a way of thinking that perceives the size of the mass rather than counted quantity of items in front of them.

It makes sense for an animal to be able to discern small differences between amounts. But when there are lots of things out there, knowing the exact number isn’t as important – it’s more about knowing when the amounts are different enough to matter.

In other words, the monkeys could see when the apples were reduced from three to two, but could not perceive the difference when the amount of apples were increased from four to five.