Facial expression of pain: an evolutionary account: Amanda C de C Williams, PhD, University of London —

“This paper proposes that human expression of pain in the presence or absence of caregivers, and the detection of pain by observers, arise from evolved propensities. The function of pain is to demand attention and prioritise escape, recovery and healing; where others can help achieve these goals, effective communication of pain is required. Evidence is reviewed of a distinct and specific facial expression of pain from infancy to old age, consistent across stimuli, and recognizable as pain by observers. Voluntary control over amplitude is incomplete, and observers better detect pain which the individual attempts to suppress than to amplify or to simulate it.”

And: Laughter? It’s a funny business: “We laugh more frequently than we eat, sing or have sex. So why do we know so little about it?” Telegraph UK