Rejection is underlined in almost everyone by a side-to-side shaking of the head; the origin of the gesture may be in the most tender childhood
You may have heard that in some countries around the world, for example Bulgaria and parts of Albania, people nod their heads in disapproval and shake their heads from side to side to indicate agreement. That is, unlike most of the world, but they are exceptions to a rule that applies in many different cultures, even in those that have not had previous contact with others.
The English naturalist Charles Darwin wondered during his travels why this gesture is found all over the world. In his 1872 book “The Expression of the Motions of Mind in Man and Animals,” he formulated an interesting theory. In babies, the first act of denial is the refusal of food, specifically when they turn their head from the mother’s breast to the side indicating that they don’t want it anymore, and then do the same when trying to feed them with a spoon.
Darwin’s theory seems plausible when you consider that babies have little motor control over their neck muscles, so their heads need to be supported, for example, during breastfeeding. Also, babies cannot turn off their sucking reflex. So if they want to stop eating, they need to turn their heads.
However, whether this is the origin of the movement of the head to say no is more difficult to prove empirically. On the one hand, head bobbing occurs, with very few exceptions, in all cultures of the world. However, the exceptions do not disprove Darwin’s theory, as we know that many innate behaviors can be “overwritten” by cultural impositions.
For example, in Turkey, people throw their heads back in rejection, for example, when they don’t want to do something, but keep moving their head from side to side to show disagreement, for example, with an opinion.
According to Darwin’s theory, even children born deafblind must shake their heads to express their disapproval, although they have never witnessed such a gesture, and the few studies of gestures in deafblind children suggest that this is also the case.
As if that were not enough, this gesture is not only observed in humans. Other mammals that suckle their young in a similar way, especially primates closest to us like bonobos, also shake their heads to express rejection.
However, other monkey species do not. This could be because, in these cases, the rejection is expressed simply by the output. Nodding is a more advanced and more social way of expressing rejection or disagreement, because at least we stayed there.