Recent research has linked behavioral intentions and threat-related expressions. However, studies of motion are confounded with the size of stimuli. Therefore, in the current study, we used apparent motion (toward or away), by means of an optical illusion, to examine pure expressions of anger and fear and ambiguous expressions comprised of 50/50 facial blends of the anger and fear expressions. We hypothesized that anger would be more easily recognized from faces made to appear as if they were approaching an observer, whereas fear would be more easily recognized from faces made to appear as if they were withdrawing from an observer. The results for pure expressions are consistent with these predictions. Ambiguous expressions (blended 50% anger and 50% fear) were more frequently labeled as fear, regardless of apparent motion (approach or avoidance). These findings suggest that apparent motion, in the form of approach or avoidance, influence the detection of unambiguous threat-related facial expressions.
