Show me your tongue baby
Rhesus monkey babies ape - at least the facial expressions of their peers and researchers. And thus refute assumptions that only humans and great apes are capable of such early social practice.
The new neighbor comes over with her youngest. You greet each other, take a look in the pram - and are delighted when the little one throws back his own beaming smile. A baby's smile opens doors and hearts for him - most people don't care that many of the little ones' reactions, especially in the first few months, are only imitations of what they are currently perceiving.
Accordingly, the spontaneous imitation reflex that children show in the first three months of their lives and in which they imitate facial expressions such as a smile or opening the mouth is considered by many experts to be the first element in children's attempts at interaction. The reflexive imitation of facial expressions, which is later lost, serves to build social bonds - and ensures the infant the sympathy of the people on whom he depends.
Almost thirty years ago, the first studies on these early childhood abilities, which are already present immediately after birth, were carried out - a small sensation for the experts at the time, as it was assumed up until the 1960s that babies did not have much are more than incapable, needy, somehow still incomplete little adults. Another surprise followed two years ago: not only human babies, but also newborn chimpanzees imitate facial gestures - and within the first five weeks they are no different from humans.
And now Pier Ferrari from the University of Parma and his colleagues are coming up with a new study, according to which newborn rhesus monkeys can also mimic facial expressions such as opening their mouths or sticking out their tongues. The imitation of gestures would not only be an ability of humans and their closest relatives, as was previously assumed, but a more widespread mechanism of early childhood learning.
The scientists presented different facial expressions to 16 newborn rhesus macaque monkeys on the first, third, seventh and 14th days of their young lives and filmed the monkeys' reactions. In particular, within the first few days, they imitated the sticking out of their tongues and the opening of their mouths – gestures that are important elements of social interaction in the macaque world. The animals also showed this behavior when dealing with other rhesus monkeys. However, other gestures - such as opening the eyes or opening the hands - which evoke imitation in human babies were followed with interest but not imitated by the little ones.
Already from the seventh day this behavior decreased again, to finally stop in the second week of life. The window for this form of interaction is therefore very limited in macaques. However, despite the short time span and limited range of responses, Ferrari and his colleagues still see a strong resemblance to the behavior of human and infant chimpanzees: all three groups have similar knee-jerk imitation abilities within a given developmental period.
The fact that these last for different lengths of time is explained by Ferrari with the different lengths of development phases of the infants: while human children depend on their caregivers for years, rhesus monkeys begin to explore the environment for a short time at the age of one week - so it's just that it is logical that at this point people are no longer aping, but communicating correctly.