We’re approaching the winter solstice: days are short, nights are long, and people are more likely to feel down. While seasonal affective disorder - recurring depression thought to be caused by a lack of light - is a well-documented phenomenon, less serious cases of the winter blues also abound, and can be contagious. Glum postures and movement patterns can result in bad moods being unconsciously passed on from one person to another, thanks to a group of cells called mirror neurons.
As their name suggests, as well as controlling the body’s movements, this system is also sensitive to the behaviour of others: if you see someone moving in a sad way, these cells will react as if you are moving in the same way as them, which can bring you down, too.
However there is hope in the face of this snowball effect of doom and gloom. Some neuroscientists have argued that mirror neurons are the basis for empathy, and in fact simply holding a pencil in your mouth will activate your smile muscles and make you feel a little happier. This will unconsciously be picked up by people around you.
Dr Daniel Glaser is director of Science Gallery at King’s College London
