A recent study by Walker and his colleagues examined how rest — specifically, rapid eye movement, or REM, sleep — influences our ability to read emotions in other people's faces. In the small analysis of 36 adults, volunteers were asked to interpret the facial expressions of people in photographs, either following a 60- or 90-minute nap during the day or with no nap. Participants who had reached REM sleep (when dreaming most frequently occurs) during their nap were better able to identify expressions of positive emotions such as happiness in other people, compared with participants who did not achieve REM sleep or did not nap at all. Those volunteers were more sensitive to negative expressions, including anger and fear.
Wish Fulfillment? No. But Dreams (and Sleep) Have Meaning - TIME