Monkeys and their human cousins don't necessarily see the world the same way, according to new research from the Peruvian Amazon and a clever experiment from a lab in Scotland. In fact, some monkeys, even within the same species, see things differently from one another. The research suggests that various forms of sight may confer a range of survival advantages. "As humans, we tend to think all creatures perceive the world the way we do, but that isn't the case," said Andrew Smith, a primatologist at the University of Stirling in Scotland. For nearly a decade, Smith and his colleagues have ventured into the Peruvian Amazon to study how different types of sight affected the foraging behavior of New World monkeys called tamarins. Humans have so-called trichromatic, or three-color, vision. So do Old World species such as chimpanzees, gorillas and orangutans. Trichromats have three types of light sensitive cells in the retina, fine-tuned to wavelengths that appear blue, green and red.

But New World monkeys have a broad range of vision types. Every howler monkey, for example, is trichromatic. The owl monkey is monochromatic, seeing only in black and white. Among tamarins and spider monkeys, all males are dichromats—they can't perceive reds or greens. But females split 60-40 between three- and two-color vision.

"You can have six individuals from the same species, even the same family, who see the world in six different ways," Smith said.


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