The understanding of when, where and how to control emotional expressions according to cultural expectations (see figure below). Consequently, there is a large cultural (and individual) variation in such rules (e.g., shaking the head from side-to-side to indicate ‘no’ is common, but in Greece it can be done by titling the head backward and lowering the eyelids, while the Aryor√©o of Paraguay signal ‘no’ by blending wrinkling the nose with closing the eyes and pursing the lips). While they vary across cultures, their use differs among social groups within a culture. The term ‘display rules’ was coined by Paul Ekman and Wallace V. Friesen in 1979 to capture attempts at managing involuntary emotional expressions, especially in face, that involve amplifying, attenuating, covering or inhibiting them (see figure below). The eye-brow flash, discovered by Irenus Eibl-Eibesfeldt in 1972, lasting about 0.6 seconds, is found in other primates, and is generally used in most cultures as a greeting response or as part of flirtation, and as such amounts to a ‘yes’ in favour of social contact. In Japan, however, it is inhibited as it is considered to be an indecent facial expression. In general, the Japanese repress or mask a lot of affect displays found in western cultures. Sometimes, according to Ekman’s leakage hypothesis, the human body leaks information about an emotion, even when actors are unaware of it and despite the display rules governing it. Displays are considered to be subject to a process of learning. Thus, how children learn display rules, and the age at which they first use them appropriately, has generated much research. While imitation is clearly involved, they also require the child to have a theory of mind. As a consequence, autistic children can show evidence of not having acquired display rules for emotional expression.
