1. a psychological characteristic featuring a relative absence of empathy toward and emotional support of others.

2. a thermal sensation produced by a stimulus that is below skin temperature. Exposure to low temperatures may affect physical and mental health. Research indicates that reaction time, tracking proficiency, tactile discrimination, and other types of performance begin to deteriorate at temperatures of 13 °C (55 °F) or below. Studies of cold effects on social behavior have produced conflicting evidence of both increased and decreased aggression.