In the late 1970s, psychologists Andrew Meltzoff and Keith Moore reported that newborn babies could copy a range of facial expressions, including tongue protrusion, mouth opening and lip pursing. Surely such an achievement could only be due to clever genes; after all, it's impossible to imagine how babies could learn to produce the expressions they see on the faces around them, just a few hours or days after birth. According to Meltzoff and Moore, their findings indicated that we must be born with a cognitive mechanism that connects 'felt but unseen movements of the self with the seen but unfelt movements of the other'.
However, worrying cracks began to appear in Meltzoff and Moore's picture as soon as their findings were published in Science magazine – and these cracks have been spreading ever since, in fine but disfiguring lines. From the outset, other experts on child development were unable to replicate the results. They found that newborns copies sticking out their tongues, but not other facial gestures – so perhaps instead of an elaborate imitation mechanism, it was a simple reflex in response to stimulation. Evidence that older infants don't copy any facial gestures, not even tongue protrusion, supported that interpretation.
Further doubts arose when it was discovered that adults can't imitate facial expressions without something called 'mirror experience.' Experiments have shown that people who film themselves and then try to copy their own facial expressions simply by looking at a frozen image on the screen do no better on their tenth attempt than on their first. The only way they improve is with 'mirror experience' – if they watch a reflection of their face as they are trying to recreate the expression. It seems that, in order to learn imitation, we need to see, as well as feel, what we are doing. If we were born with a cognitive mechanism that connects seeing another person's gesture with the sensation of replicating it ourselves, we should be able to improve our imitation without 'mirror experience'.
For several decades, child psychologists have watched the flaws in Meltzoff and Moore's work becoming more apparent, without ever abandoning their belief in it. One of the reasons for this is that Meltzoff portrays Homo imitans – a species born able to mimic – in beautiful, compelling prose. Additionally, every loving parent is drawn to the idea that if you stick out your tongue at a newborn, the baby likes to return the compliment. In the scientific world, the concept of an imitation instinct swiftly became a foundation stone. By the 1990s, it was supporting other claims about how the mind is shaped by the genes. Researchers might have realized that, if the imitation instinct was discredited, other treasured ideas would fall apart.
But there were also practical considerations. When small babies are not asleep, they are often inattentive; when they're alert, they're often absorbed in things around them, but not by the things a researcher wants them to look at. In each study of newborn imitation, only a small number of babies stayed attentive for long enough to be analyzed. This sampling, along with small variations in experimental procedure, could have produced misleading results. So, until recently, the idea of a newborn imitation instinct was still scientifically plausible.
However, a study led by Virginia Slaughter at the University of Queensland in 2016 was so large and thorough that it finally undermined this argument. Slaughter and colleagues studied an unprecedented number of babies at one, three, six and nine weeks old. They tested for imitation for nine gestures, following gold-standard procedures. They found evidence for just one: tongue protrusion. In every other case, the babies were no more likely to produce the gesture after seeing it done than they were if they saw something else. Of course, you can't prove a negative – that no newborn baby has ever been able to imitate. But in the aftermath of the Queensland study, we have no good reason to believe that newborns can copy gestures or, therefore, that humans have an instinct for imitation.
What we're left with instead is a wealth of evidence that humans learn to imitate in much the same way as we pick up other social skills. In a 2018 study at Birkbeck College in London, Carina de Klerk and her colleagues discovered that a baby's capacity to imitate depended on how much parents had imitated its facial expressions. The more parent copies a baby's facial gesture, the more likely the baby is to imitate it. But the effect highlighted here doesn't generalize. Parents who copy babies' smiles make the infants better at imitating smiles, but not at copying hand movements. This specificity is important because it shows that a simple learning mechanism is involved: babies associate the feel of their own mouth opening with the sight of another mouth opening. Being imitated doesn't make babies think that imitation is a good idea, or give them the capacity to imitate any action they like. Rather, parental imitation gives the baby 'mirror experience', an opportunity to connect a visual image of an action with the feeling of doing it.
In the space of a few decades, it's become clear that imitation is not a cognitive instinct and is not in our genes. Rather, children learn to imitate through interaction with other people. Adults and peers help them to do this, not only by copying what the child does, but through games, songs and rhymes that synchronize actions, by reacting in the same way and at the same time (for example, 'Ooh, what's that?'), and, in most cultures, by allowing the child to spend time in front of actual mirrors, while building up the range of movements that they can copy in future. Whether the mirror is real or metaphorical, 'mirror experience' is what makes children imitations.