Even when blind from birth, sightless people understand how others see the world in the same way that sighted people do -- though they have never personally experienced a single visual image, according to a new study conducted by researchers from the Massachusetts Institute of Technology and Johns Hopkins University.
What's more, the information is recorded and processed in the same way by the same areas of the brain, whether a person is blind or can see, the research, published in the October issue of the journal Cognition, determined.
The findings speak to the brain's remarkable ability to process information from various sources and reach the same understanding, said Marina Bedny, an assistant professor of psychological and brain sciences at Hopkins and one of the three researchers who conducted the study.
"As long as the information is coming in, it doesn’t really matter how it’s coming in," she said. "It can be coming in through your eyes, or it can be coming in through your nose." The human brain, she added, is "a device that really evolved to get important information out of the world by hook or by crook."
The researchers told 13 sighted and 9 blind people 32 stories. Each story was 13 seconds long. Some stories described a person who comes to believe something as a result of seeing it, including a friend's worried face or someone's handwriting. Other stories described a person coming to believe something as a result of hearing it, including a worried voice or someone's footsteps. Half the stories involved an event that would make the character feel bad and the other half would make him or her feel good.
"Blind people’s inferences about how other people see provide a window into a fundamental question about the human capacity to think about one another’s thoughts," the researchers wrote. "What are the mechanisms used to think about someone else’s mind?"
The researchers found no differences in the way blind and sighted people absorbed and understood the information. This argues that the blind do not have to "simulate" a concept by having their own first-hand experience of it to understand it. Rather they are taking in the information from a wide variety of cues, including the descriptions of others, and coming to similar conclusions about the way other people view the world, a concept known as "theory of mind."
"Blind people can't be doing it through simulation," Bedny said. "There has to be a mechanism other than simulation. They have to have an abstract theory of mind."
"You can know lots and lots [about] the ways that the minds of other people work without having had this experience yourself," she added.
When the researchers scanned the brains of members of both groups, they found similar activity in the same parts of the brain that process such information, which helped confirm their conclusions.