How the Brain Works With Monkeys

Often mischievous and playful, monkeys are fascinating creatures that evolved to live in complex societies in the treetops. They display a wide variety of social strategies that help them form strong bonds, raise young, and problem-solve in their environment. These characteristics make them fun to observe—and they also made them excellent subjects for studies that reveal how the brain works.

Monkeys use facial expressions, body movements, and vocalizations to communicate with one another in their large groups. They groom one another—which looks like kissing to us—to show affection or make up after fighting, and they grumble, howl, bark, moan, squeak, and chatter. Staring down at other monkeys can mean “stay away,” and the sharp, piercing calls of howler monkeys can be heard from 2 to 3 miles (3 to 5 kilometers).

Most monkeys are arboreal, living in tropical rainforests of Asia, Africa, and Central and South America. Some, such as spider monkeys, have prehensile tails that grip branches and allow them to move gracefully from tree to tree. Others, such as baboons and some mangabeys, are terrestrial and live on the ground in forest savannas or mountain regions.

Monkeys are the most highly social mammals and almost all species live together in families or troops. Some breed seasonally; for example, guianan squirrel monkeys in South America give birth between September and November after a gestation period of seven to 7.5 months. Other monkeys—like baboons and some mangabeys—give birth throughout the year, and newborns are helpless, staying clinging to their mothers for up to two years as they learn to forage.