From Greek mythology to The Matrix to TV’s Kung Fu, blindness has often been connected with the ability to see the future or “the force” or whatever power is associated with the deprivation of vision in that particular text. But in the real world, are blind people’s brains any more acute than those of sighted people?
In the new documentary Algorithms, which hits theaters in New York and Los Angeles today, a handful of visually impaired boys from India strive to prove that they can play chess with the best. Guided by their own blind master, chess champion Charudatta Jadhav, who believes there’s no reason why blind people can’t rise to become grand masters, the film chronicles the boys over a three-year-period as they compete in the World Junior Blind Chess Championship in Sweden in 2009 and Greece in 2011.
Sloan Science and Film spoke with Daniel Goldreich, an associate professor in the Department of Psychology, Neuroscience & Behavior at Canada’s McMaster University and a leading researcher into the sensory acuity of blind people, spatial intelligence and the general plasticity of the brain.
Sloan Science and Film: There’s a commonly held notion that when a person is blind, their other senses become heightened. How scientifically accurate is this idea?
Daniel Goldreich: When I first got into my research, this idea was fairly unclear and controversial. It’s only been in recent years that we’ve brought precise modern sensory testing methods to that question. When I got into this, I thought I was going to disprove this cliché. But much to my surprise, my results started indicating that blind people do have a better sense of touch, depending on what tasks you’re talking about.
For example, they do seem to have better tactile-spatial acuity: so the ability to define structural details with their fingertips, at least in the way we’ve tested that ability: which is to press surfaces against the stationary finger. Blind people are better. Everyone gets worse with age, probably because we lose sensory receptors in the fingers, and that happens to blind people at the same rate as sighted people. But if you look at it with respect to age, a blind person of a given age is like a sighted person twenty years younger. We’ve also looked at vibrational tasks, where you can see how quickly the brain comes up with a tactile perception. And there, blind people are faster, particularly those who were born blind and can read braille proficiently.
SSF: So are there differences in brain functioning or changes in the brains of the blind?
DG: That’s one of the things that attracted me to this field in the first place. There’s a lot of interest among neuroscientists about changes in the brain with the loss of a sensory input, or with the over-reliance on one sensory system. There were early monkey experiments in the 1970s and ‘80s that looked at what happens if a monkey loses a finger. There’s a representation of the whole body on the surface of the parietal lobe of the brain, which is called the somatosensory homunculus. It’s a one-to-one topographical map from the body to the brain. It turns out if you lose a finger, the map changes shape, so the neurons that used to respond to that finger get filled in by the other fingers, so the fingers next to it on the map grow larger. This plasticity reflects a change in the brain that’s responding to the environment. And if you over-stimulate a finger, like what might happen in braille reading, that finger grows larger. Collectively, those are forms of plasticity in the somatosensory cortex, which lead a lot of neuroscientists to be interested in whether blind people are better at certain tasks.
And then there’s this other cool thing called cross-modal plasticity. The visual area of the brain is in the back of the brain in the occipital lobe, which receives input from the retina. When people become blind, especially at an early age, it appears that this primary visual area of the brain starts to respond to non-visual senses, so there’s this whole sensory substitution going on. So someone who is blind has their whole somatosensory area with possibly bigger fingertips and they’re also driving what would normally be the visual area of the brain with the sense of touch, so they have lots of extra neurons responding to nonvisual senses.
But it’s complicated. It seems clear that blind people are better on a number of these things, but there’s always this outstanding question of whether it’s because they’re blind, and then the visual cortex gets taken over by other senses, or because they practice more. Or both. Chess-playing is a good example: If you took a sighted person who was sighted all the time except they were blind-folded when they played chess, could they develop the same skills? That’s the experiment you’d have to do.
SSF: What about spatial intelligence, which might help explain an aptitude for chess?
DG: I think that’s been less well studied. It’s certainly true that when blind people navigate it’s quite impressive. They basically have to have a map in their brain. I’ve asked blind people, “How do you walk from your apartment to downtown?” The answer is, “I count blocks, I listen to sounds, there’s a grading on this particular block, etc.” So there’s a lot of memory involved and a lot of holding things in the brain spatially. I know of a study at the University of Montreal where they tested people on spatial navigation. And they also did MRI studies of the hippocampus in the brain, which is involved in acquiring new memories and spatial navigation. They reported that a different part of the hippocampus was larger in blind people. This is a part that’s not necessarily involved with spatial navigation, but memory acquisition. So there is some evidence that blind people are better, but it’s not clear whether it’s a practice effect or it has to do with plasticity due to vision loss.
But the study also did a digit span task: basically how many digits you can remember. Most people can only remember seven, like a telephone number, and beyond that, performance really begins to fall. And they did that as a control in this study, and the result showed that there was no difference between blind and sighted people. So my guess is that memory is not automatically heightened in blind people.
SSF: Is there any scientific evidence to suggest that blind people are actually smarter than sighted people?
DG: I’ve met a lot of blind people in my lab. They are fascinating and it’s really impressive what people can do without sight, especially people who are born blind who so naturally navigate through their environments. I’ve met blind people who walk faster than me. I’ve met blind people who downhill ski or drive cars. But I think they are about as wise as anyone else.
SSF: What about math and logic and computational processes?
DG: I think it’s a different realm. I know that when people learn math, there is the concept of the number line, and that’s been studied by cognitive psychologists. So we think of 0 and 1 being to the left of larger numbers. There are psychological tests that show this. This is something that might show up. If someone is blind from birth and they may have never learned the number line, would that affect their mathematical abilities? But I don’t think of math and vision as being related.
SSF: The documentary is set in India, by the way, and I wonder whether there might be differences in blind people in North America and other countries. Could there be a social aspect at play here, as well?
DG: Well, the cause of blindness may be different in other counties. I know in India there are a lot of congenital cataracts and the lens gets clouded over and destroys useful vision. But that’s less of a problem in Western countries, where this is often operated on. In North America, the causes of blindness tend to be things that are not curable surgically. And that might affect the talents that blind people develop. There are differences between losing all vision and having cataracts, where you still have light perception. So the impact on the brain may be very different. And there are, of course, cultural differences in the way blind people are treated differently in other countries.