Debate about universal facial expressions goes big
laugh? To what extent do your facial movements depend on the situation you are in whether you are in a formal meeting, say, or at home with your family? And do other people around the world express anger in such situations in the same way? These questions are at the centre of a contentious scientific debate about the nature of emotion that has raged for more than a century. On page 251, Cowen et al. enter the fray. The authors used a type of machine learning to investigate whether people adopt the same facial expressions in similar contexts across cultures. Their results are sure to be the subject of lively discussion. The universality debate is central to an understanding of the nature, causes and functions of emotions. The universality hypothesis proposes that people around the world consistently use certain configurations of facial muscle movements to specifically express instances of a certain category of emotion. For example, people are said to frown in sadness consistently enough (and frown infrequently at other times) for frowning to be recognized as the expression of sadness the world over. The same goes for scowling in anger, smiling in happiness and so on. Such expressions are thought to have evolved to signal emotional information in contexts that posed fitness challenges for our hunter gatherer ancestors. Sometime in our evolutionary past, the hypothesis goes, our ancestors capitalized on specific, universal emotional expressions as a means of communicating those challenges to one another, helping them to survive and reproduce. There is considerable debate about whether the published empirical evidence provides support for the universality hypothesis. A large body of literature seems to back it up, but these studies have been consistently criticized for methodological problems. Furthermore, a growing number of experiments