The intelligence of monkeys is the result of millions of years of evolution in a complex social environment. They are smart not because they have a large brain in itself, but because their brain is adapted to solving specific tasks: survival in a group, foraging for food, and manipulating conspecifics. Social Brain: The Main Driver The most convincing theory explains primate intelligence by social complexity. Living in a group requires remembering dozens of relationships, tracking alliances, deceiving, and detecting deception. The more complex the society, the larger the brain. Social Brain Hypothesis. The size of the neocortex, that is, the new cortex, in primates correlates with the size of the group they live in. Monkeys living in large groups are smarter than those living in small ones. Politics and Manipulation. Monkeys form coalitions, take revenge, reconcile, and deceive. For example, baboons are capable of tracking who is friends with whom and who owes whom for years. Understanding Other Minds. Some monkeys understand that others can make mistakes or not know something. This is called theory of mind and is considered the foundation of complex social behavior. Tools and Ecology The second factor is the need to obtain hard-to-reach food. Use of Tools. Chimpanzees use stones to crack nuts, sticks to catch termites, and leaves as sponges for water. This requires planning and training. Extractive Foraging. Fruits, nuts, insects hidden in hard-to-reach places require ingenuity. Monkeys whose diet includes such resources demonstrate more complex behavior. Anatomy and Brain The monkey brain is disproportionately large compared to the body. In chimpanzees, it weighs about four hundred grams — less than a human, but the structure is very similar. Prefrontal Cortex. Responsible for planning, self-control, and decision-making. The prefrontal cortex in primates is much bet ... Read more