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How Did Our Brains Get So Brilliant?

• September 10, 2013 • 10:00 AM

(PHOTO: AGSANDREW/SHUTTERSTOCK)

Two words: open architecture.

Modern human brains evolved over the last two million years while confronting the survival challenges of African grasslands. So how do our savannah-derived brains perform high-flying cognitive feats—like reading, learning chess, and doing theoretical physics—that seem totally unrelated to our ancestral environment?

Our brains are remarkably general problem solvers. Human children quickly learn and execute new cognitive tasks that the world’s smartest chimpanzee could never learn, even after years of training. Some of our cognitive skills are consequences of our unique ability to use language, but language is only part of the answer. The real secret to our brain’s success is what engineers call open architecture, or, as Tufts University neuroscientist Maryanne Wolf has put it, a “protean capacity to make new connections among structures and circuits originally devoted to other more basic brain processes.” The open architecture of the human brain is why humans from all cultures can learn to read, write, and do math.

These brain modules are found in animals ranging from fish to rats, and taken together, they encode important abstract concepts of Euclidean geometry.

For example, when we learn to read, our brain creates new connections between specialized neural modules for vision, hearing, and language. These specialized modules evolved long before the availability of reading material, but our flexible brains rig up connections between them to build a new and cognitively sophisticated function.

Another cognitively challenging skill is geometrical reasoning, which involves mentally manipulating features of shapes and lines, and transposing those mental transformations onto our surroundings. Recent work by Harvard psychologist Elizabeth Spelke and her colleagues shows that, like reading, our geometrical intuitions are also a result of the brain’s open architecture. We have uniquely human geometrical skills that are cobbled together from two evolutionarily ancient brain modules shared with nearly all other vertebrates.

These two core brain modules are a navigation module and a shape recognition module. The navigation module enables us to orient ourselves spatially by registering the orientation and relative distances of walls and other features of our surrounding area. With the shape-recognition module, our brain intuitively uses angles and lengths to register the shapes of small 2-D and 3-D objects. Both of these brain modules are found in animals ranging from fish to rats, and taken together, they encode important abstract concepts of Euclidean geometry: orientation, distance, length, and angle. But individually, each module uses only a limited set of geometrical features, and non-human animals show a limited ability to integrate these modules.

A simple example: If someone handed you a map of a triangular room and pointed out a position on that map, you’d have no trouble navigating to that spot. This task of transposing the triangle from the map onto the real space around you feels deceptively simple, but under the hood, you draw on both your navigation and your shape-recognition modules as you mentally manipulate the sides, angles, and orientation of the triangle on the map to guide yourself through the triangular room.

Young children have functioning navigation and shape-recognition modules, but, as Spelke and her colleagues found, those modules don’t talk to each other yet. To show this, the researchers had four-year-old children use a map to find a particular spot in two different triangular “rooms” (made with movable partitions): one in which the walls were not touching, so there were no corners (and hence no visible angles), and one with just corners, but no main walls (and hence no walls for judging relative distances).

In most cases, the children could navigate the room with no corners, but they had more trouble in the room that had only corners. In other words, the children did well when they could use their navigational module to gauge the distances between walls, but they were less skilled at using the angles of the corners-only room to fill in the missing sides of the room’s shape. Spelke and her colleagues concluded that “tests of map understanding show no evidence of integrated representations of distance and angle.” These children’s brains could process distances to navigate their surroundings, and they could process angles when presented with pictures of shapes, but they couldn’t put the two modules together.

The open architecture of our African savannah brains is the secret behind many of our uniquely human cognitive feats. The cost is the long years of childhood, during which we wire together specialized brain modules as we learn to speak, read, write, draw shapes, and generally do what adults manage without effort. Scientists are discovering their complex neural underpinnings of these tasks, discoveries that show us how children learn skills such as reading and geometrical reasoning and, ultimately, how we can help children who struggle to learn better.

Michael White
Michael White is a systems biologist at the Department of Genetics and the Center for Genome Sciences and Systems Biology at the Washington University School of Medicine in St. Louis, where he studies how DNA encodes information for gene regulation. He co-founded the online science pub The Finch and Pea. Find him on Twitter @genologos.

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