Boredom: The one weird trick of baby science

If monkeys could become bored, they would become human.
— Johann Wolfgang von Goethe, German polymath (1749–1832)

One reason I started studying baby laughter is that I was bored of making them bored. Most of modern baby science is built on one ingenious invention called the habituation paradigm. It involves making babies bored and then trying to surprise them again. This experimental design has been used in thousands of experiments with babies. It is the first thing we think of when designing any new study. It is incredibly versatile because it exploits the fact that babies get bored with anything and everything. Babies have an attention span measured in seconds. Scientists like to measure things, so everyone is happy.

The idea of boredom, as English speakers understand it, was invented by the Victorians. In her 2015 book The Book of Human Emotions, historian Tiffany Watt Smith explains that the word first appears in English in 1853   as a derivative of the French word bourrer, to stuff or force-feed. It occurs in Charles Dickens’s Bleak House when Lady Dedlock is ‘bored to death’ by her lonely life. Of course, the experience of being bored existed before we had a word for it. For millennia, languages have had words to describe when things are tedious or irksome. I have not been able to find the original German version of the Goethe quote above, so I am not entirely sure what he thought was happening to humans and not monkeys. In the French it translates as s’ennuyer, a reflexive verb literally meaning to annoy oneself. Interestingly, bourrer is a transitive verb, which means it gets done to something or someone. To be bored is to be fed up. Tiffany argues that the upper- and middle-class Victorians needed a word for boredom when too much leisure time was forced upon them.

In habituation experiments, baby scientists fill babies so full of an idea that they become bored of it. Then we see what it takes to revive them. We already encountered the habituation method in the previous chapter, where Denis and Bob were testing babies’ knowledge of cats and dogs. Given how important it as a method, it is worth going through it in greater detail. The fact that the method is effective reveals a lot about how babies’ brains work.

First we must look at a brain 5 million times smaller than ours, because habituation is a universal property of brains. Understanding this fact was worthy of a Nobel Prize, which was won by Eric Kandel in 2000. The brains he looked at belonged to Aplysia californica, the California sea hare, a type of slug. Weighing in at several kilograms and made up of around 35 centimetres of mottled reddish-brown sliminess, they are exceptionally ugly creatures. Nonetheless, Kandel considers them beautiful and their beauty is in their brains. Their entire nervous system has only 18,000 neurons, 50 times smaller than a bee brain. Aplysia brains are tiny but their neurons are giant. Each one can be 50 times larger than mammalian neurons and are so massive you can see them with the naked eye. This made them an ideal laboratory animal for Kandel to study how learning happened.

Kandel was interested in learning and memory, which are closely intertwined. When learning to do something new, you encode it in your memory. Eric Kandel was the first person to work out how this happened at a neuronal level (Kandel, 1976). He did this by teaching his slugs to ignore him. If you poke an Aplysia with an electrode, it reflexively withdraws the gill and siphon on its back as a defensive measure. Kandel would wait until the slug went back to normal and then he would poke it again … and again … and again. Eventually, the slug would come to ignore the pokes, learning not withdraw its gill. Kandel looked at the chain of neurons that controlled the initial reflex and how they changed as the slug habituated. The exact details of the cellular process are not important right now, but isn’t it good to know you can get a Nobel Prize for annoying slugs?

Habituation experiments with babies are somewhat different. We certainly do not poke babies with electrodes, we cannot peer directly into their brains and babies are way cuter than slugs. But the earliest experiments were conceptually very similar to Kandel’s work. The pioneer of infant habituation, Les Cohen, like Kandel, was working in the early 1970s. He would sit babies opposite a screen in a darkened room with few distractions. Then he would show them a picture like a simple chequerboard and measure how long it was until the baby looked away. Then he would show them the same picture again … and again … and again. Babies, like slugs, got bored. They looked longest at the start but less and less over time (Cohen, 1972).

This is exactly as you would expect. The weird trick in the title of this section is what you do once the babies are bored. We normally define boredom (aka habituation) as a 50% decrease in average looking. To determine this, we keep a running average of babies’ looking from the first two pictures compared to the most recent two pictures, using an average because babies can be quite unpredictable. They may easily get distracted by a parent, by their socks or by random baby thoughts. Once they are bored, we test them by showing something different. After a dozen dogs we could show them a cat. After a succession of female faces, we could show a man. If the babies perk up and look longer, it indicates they understand there is a difference. If they stay bored, they are probably not noticing the difference.

Using this method, we can ask babies all kinds of questions and they can answer. We can ask about perception of colour or size or orientation, about categories of animals or people, about concepts like number and relations like sameness or ‘in front of’. Using sounds instead of pictures you can test what babies understand about speech or music. Babies can tell dogs and cats apart by five months. At around four to six months babies not only learn to tell male from female faces, but they can know the difference between emotional expressions like happiness, sadness, anger and disgust. Habituation shows cases where young babies can discriminate things older babies and adults cannot. For example, six-month-olds can tell one monkey face from another, a task that ten-month-olds and adults fail. Likewise, at six months babies can discriminate the speech sounds of all languages but by a year they hear only those relevant to their native tongue. This is an example of perceptual narrowing and we will revisit it in the chapter on language (Maurer & Werker, 2014).

One important refinement of this method is to include something super-exciting at the very end. This is to check the babies are still paying attention, as they sometimes zone out. In my Ph.D. I was habituating babies to some rather dull shapes, which looked like outlines of a house with a big white arrow on it. Each one was slightly different. I was interested in whether the babies learned the average. The trouble is, the babies might know the difference but could be so bored they just do not care any more. Therefore, all my habituation experiments ended with a photo of a bunny rabbit. My experimental results were mixed but I could very strongly conclude that babies like bunnies.

Once I had survived my Ph.D., I decided to celebrate by getting my left arm tattooed with various images from my research. Naturally I had to include the rabbit, although with a nod to my time-perception research, I transformed it into the White Rabbit from Alice’s Adventures in Wonderland, carrying a large pocket watch to measure how quickly I made the babies bored.

This is excerpt of my book, The Laughing Baby. Taken from Chapter Eight: Surprise!