Wincing in pain or gasping from laughter? Neuroscience explains the Kuleshov Effect: how altering the context behind a facial expression may lead the viewer to confuse agony with ecstasy.
the Kuleshov Effect: http://vimeo.com/8082147
The Findings. Check out Figure 1: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1810228/