This study assessed the extent to which happy and sad facial expressions displayed by infants and adults elicit motoric approach and avoidance responses in viewers. Participants were asked to pull a joystick toward (approach response) or put it away from (avoidance response) their body in response to facial stimuli (sadness and happiness expressed by infants, female adults, and male adults) presented on a computer screen. They also rated the degree to which they themselves would want to help/become involved with the stimulus person. The results showed that both sadness and happiness elicited faster approach than avoidance responses, irrespective of participants' gender and whether the stimulus depicted an infant, female adult, or male adult. We also found that the motivation to help and become involved in response to infants' sad expressions was linked to delayed avoidance. The different functions of the emotional expressions of infants and adults are discussed.

Key words: facial expression; sad; happy; approach-avoidance behavior; motivation