Figure 1.

Original frames, subtracted frames, and entropy values during the emergence of a smile (adapted from Bowers et al., 2006). Figure 1a shows the original frames from the course of a facial expression from a neutral (baseline) expression through a smile. Figure 1b shows the subtracted frames which were derived by subtracting corresponding pixel intensities of adjacent images. Figure 1c shows a plot of the summed pixel difference changes (entropy) as the expression appears over time, with labels marking the tone cue, beginning of facial movement, peak entropy (most rapid movement change), and end of facial movement.