There is a phenomenon whereby, as soon as you start thinking about something, you see it everywhere.

I started thinking about repetition when Radiolab asked me to address a listener’s comment from the website. After hearing the Loops show, Sarah wrote, “I'm curious if anyone has ever studied loops in toddlers. I often watch my 20-month-old daughter repeat the same activity over and over and over. I assume the repetition is meant to teach her.”

So I started mulling repetition in children, and suddenly: there was repetition, over and over and over again. Everywhere.

Repetition, broadly construed, is in everything. It’s in our breath, and our pulse. It’s sunrise, sunset. It’s spring summer fall winter. The tides, cell division. Bad habits, and good ones. The daily grind. Annoyingly repetitive thoughts. It’s in music, art, dance, architecture. Religion, history. Doodling, nail-biting, toe-tapping, smoking. Menstruation, masturbation, sex. Rhythm is repetition. Rhyme is repetition. Repetition has power -- there's a universal attraction to it. And it can be transformative: religions use extreme repetition to transport believers. Dervishes whirl themselves into transcendence. Monks chant their way closer to God. Recite enough rosaries and the words start to slip out of their shells.^¹

Apart from how strangely ubiquitous repetition is, what really drew me in was the realization that while it can be powerful, transformative, even therapeutic -- repetition has a dark side. There's a threshold beyond which it goes from being soothing and predictable to being maddening and pathological. It’s almost as if there's a Goldilocks amount -- too little and you have a disorganized mess, too much and you have madness, or its close cousin, ecstasy.

ROCK A BYE, BABY

Our love affair with repetition starts early. Children have a seemingly infinite appetite for it. It’s in their songs, their stories, their games. Their love of the rocking chair, and the swing. It’s the inevitable conclusion of nearly every book and game -- that incessant refrain, “Again! Again!”

I called Joshua Sparrow, professor of child psychiatry at Harvard Medical School and co-author of the book, Touchpoints 3 to 6, part of the best-selling series on children’s development, and he had much to say on the subject of children’s repetition. As Sarah surmised, the most straightforward reason children engage in repetition is basic practice -- just as musicians repeat difficult passages again and again, trying to bypass conscious thought entirely, to get the music right into their fingers. When a child utters a new word for the first time, she’s doing much the same thing. The simplest utterance involves coordinating a host of separate actions; scores of muscles in the lips, tongue, jaw, not to mention extremely subtle breath control. (The voice is such a complex instrument that it makes the French horn look like child’s play.) When she lights on the correct combination... Eureka! And it wouldn’t make sense to do it just once -- you don’t get a robust neural pathway that way. By repeating something again and again, children are pruning and shaping the brain’s intricate neural topiary.

Then there’s repetition that’s not quite as, well, repetitive. It’s repetition with variation; sometimes nearly imperceptible variation. This type of repetition is actually an endless series of subtle experiments. As in: “What happens when I bang this with my fingers closed? How about open? Okay, what if I use a bit more force? Now less? What if I turn my arm this way? And that way?” Ad infinitum, ad nauseum. This tireless investigation is the means by which children figure out how the world works, and master the principles of mass, inertia, and gravity.

With this second kind of “theme and variation” repetition, they’re also experimenting on themselves, and in the process developing what some scientists call their "sixth sense," proprioception. The nerves in our muscles and tendons are constantly signaling our brains about where we are in space. So children use endlessly repetitive experiments to figure out how to control their marionette bodies.

And then there’s another kind of repetition, more accurately termed “repetitive behavior,” whose purpose is strangely twofold: it can calm an anxious child, or stimulate a bored one. Children in “under-enriched” environments might engage in self-stimulating behaviors -- known as "stimming" -- like covering and uncovering their ears, for instance, or blinking rapidly, or repeatedly tapping surfaces. Overstimulated, tired, or scared children may rock, suck their thumbs, even bang their heads. (It’s a horrible thing to see your child banging his head on the floor, and utterly confounding to then learn that it’s "perfectly normal;” nearly one in five developmentally typical children will purposely and repeatedly bang their heads on a hard surface.) And since even normal developmental milestones -- learning to crawl, walk, talk -- are thought to be somewhat stressful to a child, Sparrow and his colleagues have found that such repetitive behaviors peak during developmental transitions.

When such repetitive behaviors are very persistent, however, and very intense, and when they don’t seem to doing anything for the child: attention must be paid.

A SCRATCH IN THE RECORD?

Firstly, extreme repetitive behavior might signal a developmental disorder, such as autism. In fact, repetitive behavior is one of the official diagnostic criteria of autism, which is why pediatricians will often ask parents seemingly strange questions like whether their children do a lot of spinning, or spend an inordinate amount of time flapping their hands.²

Extreme repetitive behavior can also be a normal response to an abnormal environment. It’s one of the ways children respond to serious neglect and abuse. Intensely repetitive behavior is so common among foster children, for instance, that foster parents are often warned to look out for it.

But pathologically repetitive behavior is not confined to the autistic, or to the abused, or to children. It can be indicative of any number of clinical conditions, including schizophrenia, Tourette Syndrome, Parkinson’s disease, and obsessive-compulsive disorder. Nor is it confined to humans. Animals in captivity, especially those in very small or very boring cages, do it all the time, often injuring themselves in the process. Birds pluck out all their feathers. Tigers pace. Elephants swing their trunks, and endlessly sway, as if to some unrelenting internal waltz. In fact, animals engage in a kind of repetitive behavior that veterinarians call “overgrooming” -- horses bite their flanks until they bleed, cats lick off their fur -- suggesting that some repetitive behaviors may be evolutionarily laudable activities gone haywire. And there are plenty of human counterparts, like dermatilomania and trichotilomania, disorders that stem from the idle urge to pick at a scab or pluck a hair, respectively, and end in painful self-mutilation.

OUT OF THE CRADLE ENDLESSLY ROCKING

Strangely, though, even when repetitive behaviors seem to be doing far more harm than good -- when a child has been banging her hand for years, for instance, and develops serious injuries -- there’s evidence that they may be somehow useful. When Robin Gabriels, a child psychologist at the University of Colorado, monitored stress hormones in autistic children, she found that children who engaged in the most intensely repetitive behaviors (who weren’t necessarily the most severely autistic) had the lowest stress levels. Some speculate that repetitive behaviors might help to distract from other, more disturbing sensations. Sparrow treats people who repetitively cut themselves, and he says they almost always describe it as a way to organize general feelings of despair into one specific feeling, or to create a sensation so intense that it blocks out all others. In another study, Gabriels worked with a severely autistic nine-year-old girl who was violently banging her head. It turned out that she had terrible dental problems. When the dental problems were resolved, the head banging stopped. To widen the scope a bit, the simple fact that mild forms of repetitive behaviors are found in mildly stressed people, and extreme forms of repetitive behaviors are found in extremely stressed people, would seem to suggest that repetition is generally comforting, and that some people need a lot more comfort than others. Perhaps we’re sort of dipping our toes, as needed, into the waters of predictability.

James Bodfish, professor of psychiatry and pediatrics at the University of North Carolina, who studies repetitive behaviors, is officially skeptical of the notion that pathological repetition has any substantive similarity to normal repetition. In a recent phone conversation, however, he allowed himself to ponder the broad appeal of repetition. Humans yearn, says Bodfish, for reassuringly predictable patterns. We are, as the philosopher William James had it, “mere walking bundles of habits.” You might even say that the default setting for our brains is forming habits, and automatizing functions. You need repetition to establish patterns, and you need patterns to achieve variation. A brain that’s suffered some insult -- be it environmental or genetic -- can revert to a repetitive state, says Bodfish. It gets stuck.

Even in the most benign repetition, however, there's a threshold beyond which madness lies. But where exactly is the threshold? When does a song go from danceable to maniacal? When do those mildly annoying repetitive thoughts actually drive you crazy? When does the earworm become chronic, insomnia-inducing Broken Record Syndrome? When does a drop of water become torture?

And in its benign form, repetition is enchantment, and grace. Glory be for the hypnotic lullaby, the incantatory poem, the elegant arcade. All praise to the magic of the rocking chair.

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Notes

1. "In Zen they say: If something is boring after two minutes, try it for four. If still boring, try it for eight, 16, 32, and so on. Eventually one discovers that it's not boring at all but very interesting," said composer John Cage, as quoted in this very interesting essay on repetition in music.

2. Here I'm stepping into a minefield. The last thing I want to do is add to a parent’s sea of worries, so, Dear Parents, please know that most repetition -- even repetition that seems utterly bizarre on its surface -- is perfectly normal. Pathological repetition is on an entirely different scale. Sparrow says that one sign that repetitive behavior might be problematic is that it's very persistent and not very soothing. A developmentally normal one-year-old, he says, might bang her head on the floor a bit and thereby manage to move herself across some threshold so she's able to sleep.