<正> It may look like a 'yawn' but any primate expertknows this monkey’s expression is really a threat. Simi-larly, when a monkey 'grins' or 'smiles', it is notin fact expressing pleasure: it is signaling fear of submmis-sion. The faces monkeys make are an important partof their communications with each other, but peoplehave traditionally-and wrongly-interpreted those expressions