A recent post on Current Developments in Behavioral Science summarized the latest research showing that babies have to learn to perceive and avoid the apparent dropoffs called "visual cliffs." Even though they can see, their lack of experience with depth perception and the dangers of heights puts them at risk.
While that's taken for granted these days, I was reminded of two related findings even more dramatic. The first can be illustrated by an example from anthropologist Colin Turnbull's classic, The Forest People, in which he describes his time living with the Pygmies of what's now the Democratic Republic of the Congo. On his first trip away from his dense jungle home into large open spaces, Turnbull’s friend Kenge thought distant objects like animals really were as small and bug-like as they appeared. His background had not provided suitable experience in perspective, showing how important learning from consequences is to this essential skill. Presumably, as children we have to learn this too. Anyone remember their experience?
Then there's the line of research on blind people whose sight has been enabled. Way back in the 17th century, John Locke speculated that such people
who were blind from birth would be unable to visually discriminate shapes without some
experience. He appears to have been right (and that's also the case for many blind people who'd previously had sight, but not for many years).
In one recent case study, a young woman born blind had her sight partially restored in one eye at the age of 12. According to her parents, only after months of learning was she able to acquire skills such as the ability to recognize people visually (Ostrovsky, Andalman, and Sinha, Psychological Science, 2006). These researchers summarized current views about these skills as "learned over time through experience" (p. 1013). For a less positive example tracking the ups and downs of the process in detail, neurologist and author Oliver Sacks described the case of "Virgil" in An Anthropologist on Mars. As Sacks pointed out, unfortunately, a number of the re-sighted never attain anything close to normal vision, and some understandably become depressed.
Talk about depressing, some experts used to think that most re-sighted blind people would never be able to use their vision properly because of irreversible changes in their brains. Let's hang on to some hope, though: Clearly some can. And, while the extensive brain plasticity that we now celebrate is far from unlimited, perhaps new help for rehabilitation may come from the introduction of methods from the science of consequences--much as has been the case for stroke victims (described in Chapter 4 of my book).