“Don’t shoot till you see the whites of their eyes!” That was an order given by Colonel William Prescott to the Colonial soldiers at the Battle of Bunker Hill during the American Revolution. The reason for the order was not to get close to the British soldiers to get to know them, but because the Colonial Army was low on ammunition and Prescott wanted to make sure it wasn’t wasted. Seeing the whites of the eyes may be dangerous in warfare, but it’s valuable for communication.
Human eyes come in various colors, such as blue, brown, or green, but that refers to the iris. The area surrounding the iris is called the sclera. In humans, the sclera is white, or at least close to white. That makes us different from other animals, since most mammals have dark eyes. The question is, why are the whites of the eyes the way they are?
In 1997, Shiro Kohshima, a Japanese biologist at Kyoto University, compared the eyes of primates and found that only humans had white in their eyes. He proposed that the white sclera helps us communicate because the contrast between the white and the dark pupils makes it easier to tell where someone is looking. Parents can often tell if their child is telling the truth by whether the child is looking at the parent. When someone looks away, it may mean they are hiding something. The whites of the eyes tend to draw our attention away. When someone looks us directly in the eye, it helps us to bond with that person. Thus, the white sclera helps us communicate or avoid communicating.
In 2007, Michael Tomasello, a psychologist at Duke University, expanded on Kohshima’s theory, developing a cooperative eye hypothesis. He said that the whites of the eyes help us determine what someone is focused on because we are sensitive to where a person is looking. Tomasello conducted experiments on human infants, gorillas, chimpanzees, and bonobos. He did this by looking at the ceiling with only his eyes, only his head, or both, to see how humans and primates would react.
Tomasello found that human infants followed the researcher’s eye direction three times more often when he glanced toward the ceiling with his eyes only than when he tilted his head upward with his eyes closed. He found that the primates did the opposite. For them, following the head movement was more important than following eye movement.
From an early age, humans are very sensitive to eye contact. Within the first few days, babies looked longer at faces that were directed at them. In two to four months, babies learn to follow where others are looking. You can hold the attention of babies by looking directly at them. When the parent looks at an object and names it, this helps the infant connect the name to the object, improving language skills.
Even though some people’s eyes are not as white as others’ due to age, health, or race, humans do show more of the sclera than other animals do. Experiments with humans and chimpanzees indicate that the whites of the eyes enable both humans and chimpanzees to better determine the gaze direction of humans than that of chimpanzees.
The bottom line is that humans have more white in their eyes, giving our eyes greater contrast that draws attention to where we are looking, helps us communicate, helps infants learn language terms, helps us determine the status of someone’s health, and helps us to bond with someone we care about. We can be thankful that God has given humans this exceptional gift, but it may not have been an important factor in helping the Americans win the Revolutionary War.
— Roland Earnst © 2026
Reference: popsci.com