Jonathan Dobres

the amazing thing

I’m taking a class about professional issues in psychological science, in other words, a class in how to be a real scientist. Giving talks is as much a part of the professional life of a scientist as running a lab and applying for grants, so yesterday was talk day. The goal was to give a talk about your research lasting no more than ten minutes, and I hit it on the dot. The talk was generally well-received, which was gratifying, as it will likely evolve into my eventual dissertation defense. Then the professor spoke. “Really great job,” she said, “but, Jon, why should I care about this topic?”

Ah yes. That. I knew I had forgotten something. To be fair, I’m not likely to give this talk to audiences who are utterly unfamiliar with the topic in question, which in this case is something called perceptual learning. But I’m hedging here. I can play devil’s advocate with myself until the sun implodes, but really, I should have just found an extra thirty seconds to explain why my field matters. Good scientists explain their work clearly and concisely. Great scientists—your Carl Sagans, Oliver Sackses, Steven Pinkers, and Albert Einsteins—make the point of their work so obvious and accessible that anyone can understand it.

To the above list of Great Scientific Communicators we should certainly add Dr. Jean Berko Gleason. Dr. Gleason is one of the world’s preeminent psycholinguists, and if you don’t know what a psycholinguist is, I’ll let her explain. All those clips are wonderful (and yes, she is exactly like that in person), particularly for how clearly she explains herself. Multiple branches of nuanced research laid out—zip, boom, bonjour—in half a minute. After watching those clips no one is left wondering why psycholinguistics is an important field. We all understand why Dr. Gleason has allowed psycholinguistics to fill her life, and how it’s relevant in our own.

So what about my field? What’s perceptual learning?

Perceptual learning is a process by which we get better at perceiving things over time. We’re not interested in changes in strategy or decision making (usually), rather, true perceptual learning means that you are literally getting better at seeing. With practice, you can become more sensitive to contrast, motion, or a thousand other things. Take my dentist, for example. Since I’m a graduate student with a bargain basement dental plan, my dental work is performed by fourth and fifth year students at my university’s dental school. Before the end of every visit, a supervising dentist double-checks the student’s work. During one recent checkup, my student dentist told his supervisor that he hadn’t found any cavities in my mouth. The supervisor took one of her tiny metal hooks in hand and glanced it over my molar for what could not have been more than a second. “There’s some decay there. We’ll need to schedule a follow-up to treat it.” She, the experienced dentist, had seen plainly what the less experienced student could not, because her extensive training had made her more sensitive to the tiny precursor of a cavity on my tooth.

It’s not just dentists, of course. Radiologists have to hunt through murky x-rays to find fractured bones and dangerous tumors. Baggage screeners need to be able to spot a knife amongst shampoo and sweaters. Jewelers peer inside diamonds, looking for perfection. Perceptual learning makes the difference between an amateur and an expert.

Perceptual learning is important because it demonstrates that experience and practice can create dramatic change in the brain. If you have a stroke, can we help you recover? Yes. As the developed world grows older on average, what can we do to protect the brain from the ravages of age? Back in ‘86, two researchers showed that you could turn an eighty year old into a twenty year old, given enough practice. We spend increasingly large amounts of time playing video games. Some decry this as a waste of time, a habit fated to create a nation of ADHD-addled zombies. But the science says video games improve our visual capacities. Hell, what are you doing right now? How did you get so good at reading? How are you able to process letters, words, and whole sentences with such blinding speed? In part, reading is a product of perceptual learning.

Over the summer, I participated in a colleague’s experiment, one that involved what’s called a texture discrimination task. Imagine a grid of horizontally dashed lines. Somewhere in the grid, off in your peripheral vision, three of the dashed lines have been turned into diagonal slashes. Sometimes the slashes are arranged vertically in the grid, and sometimes horizontally. The whole stimulus is displayed for a fraction of a second, and your job is to say whether the slashes were vertical or horizontal. On the first day of the experiment, the task was impossible. My performance was so poor that I might as well have had my eyes closed. It was the same story on the second day. After three weeks of training, however, my performance bordered on perfect. The exciting thing, the amazing thing, was that I could feel my perception changing over time. What had once been impossible became trivially easy. The slashes, once as jumbled and fleeting as a snowflake in a blizzard, now jumped out at me as clearly as a snowball in summer.

As scientists we can argue at length about why and how my perception changed. Was it a low-level change in highly specific sets of neurons, or was it a broader change in the way I allocate attention? Will this transfer to other tasks, and what does that mean? Was I detecting the slashes, or filtering out the horizontal lines? It’s easy to get bogged down in the methodology and specifics, and lose sight (har har) of the big picture. Whatever the reasons, there is no doubt in my mind that my perception changed over those three weeks, simply as a result of diligent practice. That’s an amazing thing, a powerful thing. That’s why I do what I do.