How We Learn: The Surprising Truth About When, Where, and Why It Happens

by Benedict Carey

Interleaving. That’s a cognitive science word, and it simply means mixing related but distinct material during study. Music teachers have long favored a variation on this technique, switching from scales, to theory, to pieces all in one sitting.

Certainly any material taught in a single semester, in any single course, is a ripe target for interleaving. You have to review the material anyway at some point. You have to learn to distinguish between a holy ton of terms, names, events, concepts, and formulas at exam time, or execute a fantastic number of perfect bow movements at recital. Why not practice the necessary discrimination skills incrementally, every time you sit down, rather than all at once when ramping up for a final test?

self-administered perceptual training is possible with minimal effort. Most important, I’ve used it to show that PLMs are meant for a certain kind of target: discriminating or classifying things that look the same to the untrained eye but are not.

In short: Sleeping and waking adjust themselves to the demands and risks of our life, not according to what the health manuals say. The other theory is that sleep’s primary purpose is memory consolidation. Learning. In recent years, brain scientists have published an array of findings suggesting that sleep plays a critical role in flagging and storing important memories, intellectual and physical. Also (yes) in making subtle connections—a new way to solve a tricky math problem, for example, or to play a particularly difficult sequence of notes on the viola—that were invisible during waking.

The preponderance of evidence to date finds that sleep improves retention and comprehension of what was studied the day before, and not just for colored eggs. It works for vocabulary. Word pairs. Logical reasoning, similar to what’s taught in middle school math. Even the presentation you’ll be giving at work, or the exam that’s coming up at school. For all of these, you need to memorize the details of important points and to develop a mental map of how they fit together. The improvements tend to be striking, between 10 and 30 percent,

REM: These storms of neural firing appear to aid pattern recognition, as in the colored egg experiment, as well as creative problem solving and perceiving relationships that weren’t apparent during the day, as in a difficult calculus problem. It likely plays the largest role, of all the stages, in aiding percolation. People still get these benefits from sleep sans REM—just not to the same degree. REM is also involved in interpreting emotionally charged memories.

Walker describes REM as “a nighttime therapy session.”

“Stage 2 seems to be the single most critical stage for motor learning,”

Stages 3 and 4: These two are usually lumped together in learning research as slow-wave or deep sleep. This is prime retention territory. Starve people of deep slumber, and it doesn’t just dim their beauty; they don’t get the full benefit of sleep-aided recall of newly learned facts, studied vocabulary, names, dates, and formulas.

Mastering a subject or skill may not be as urgent as avoiding some saber-toothed cat, but over a lifetime our knowledge and skills become increasingly valuable—and need to be continually updated. Learning is how we figure out what we want to do, what we’re good at, how we might make a living when the time comes. That’s survival, too.

Learning crests during waking hours, giving way to sleep at the moment of diminishing returns, when prolonged wakefulness is a waste of time. Sleep, then, finishes the job. I’ve always loved my sleep, but in the context of learning I assumed it was getting in the way. Not so. The latest research says exactly the opposite: that unconscious downtime clarifies memory and sharpens skills—that it’s a necessary step to lock in both. In a fundamental sense, that is, sleep is learning.

We all “know” we need to be organized, to develop good, consistent study routines, to find a quiet place and avoid distractions, to focus on one skill at a time, and above all, to concentrate on our work. What’s to question about that? A lot, it turns out.

About the only thing we can control is how we learn. The science tells us that doing a little here, a little there, fitting our work into the pockets of the day is not some symptom of eroding “concentration,” the cultural anxiety du jour. It’s spaced study, when done as described in this book, and it results in more efficient, deeper learning, not less.

Let go of what you feel you should be doing, all that repetitive, overscheduled, driven, focused ritual. Let go, and watch how the presumed enemies of learning—ignorance, distraction, interruption, restlessness, even quitting—can work in your favor. Learning is, after all, what you do.