It has long been observed that mothers tend to cradle their babies over their Left shoulder. In the past, it has been suggested that this is merely so they can keep their right hand free for other tasks (if righthanded). But the “positional bias” is not uniquely human: scientists have observed that infant mammals prefer to stick closely to their mother’s right – so as to observe her with their left eye. The researchers, from Australia and Russia, studied 11 wild mammals ranging from reindeer to whales, and found that about 75% of the time, when infants approached their mothers from behind, they did so from the right. They also noted that at times of stress, the mothers positioned their young on their left – even, in one observed case, when that meant putting their infant between themselves and the danger. The researchers believe the bias is down to the fact that in mammals, signals picked up by the left eye are sent to the right side of the brain, which is responsible for processing social cues and building relationships. Thus holding babies to their left helps mothers respond to them appropriately, and bond with them. Researcher Yegor Malashichev, of Saint Petersburg State University, said that the bias was so widespread, it was likely to be “ancient and really basic”.