Pleasant stimuli typically elicit greater electromyographic (EMG) activity over zygomaticus major and less activity over corrugator supercilii than do unpleasant stimuli. To provide a systematic comparison of these 2 measures, the authors examined the relative form and strength of affective influences on activity over zygomaticus major and corrugator supercilii. Self-reported positive and negative affective reactions and facial EMG were collected as women (n = 68) were exposed to series of affective pictures, sounds, and words. Consistent with speculations based on known properties of the neurophysiology of the facial musculature, results revealed a stronger linear effect of valence on activity over corrugator supercilii versus zygomaticus major. In addition, positive and negative affect ratings indicated that positive and negative affect have reciprocal effects on activity over corrugator supercilii, but not zygomaticus major.

Prior research has shown that perceived social isolation (loneliness) motivates people to attend to and connect with others but to do so in a self-protective and paradoxically self-defeating fashion. Although recent research has shed light on the neural correlates of social perception, cooperation, empathy, rejection and love, little is known about how individual differences in loneliness relate to neural responses to social and emotional stimuli. Using functional MRI we show that there are at least two neural mechanisms differentiating social perception in lonely and nonlonely young adults. For pleasant depictions, lonely individuals appear to be less rewarded by social stimuli, as evidenced by weaker activation of the ventral striatum to pictures of people than of objects, whereas nonlonely individuals showed stronger activation of the ventral striatum to pictures of people than of objects. For unpleasant depictions, lonely individuals were characterized by greater activation of the visual cortex to pictures of people than of objects, suggesting their attention is drawn more to the distress of others; whereas nonlonely individuals showed greater activation of the right and left temporoparietal junction to pictures of people than of objects, consistent with the notion that they are more likely to reflect spontaneously on the perspective of distressed others.As a social species, humans create emergent organizations beyond the individual-structures that range from dyads, families, and groups to cities, civilizations, and cultures. These emergent structures evolved hand in hand with neural and hormonal mechanisms to support them because the consequent social behaviors helped these organisms survive, reproduce, and care for offspring sufficiently long that they too reproduced (Cacioppo & Patrick, in press;Dunbar & Shultz, 2007). The multimodal neurophysiological processes involved in the execution of an action, for instance, give rise to parallel neurophysiological sensorimotor processes in the observer of these actions (Rizzolatti & Craighero, 2004). This mirror neuron system appears to play a role in a variety of social processes including mimicry, synchrony, contagion, coordination, and co-regulation (e.g., Rizzolatti & Fabbri-Destro, in press; Semin & Cacioppo, in press).Empathy for another person's pain is also associated with many of the same neural mechanisms associated with one's personal experience, including activation of the dorsal anterior cingulate (dACC), thalamus, and anterior insula (Decety & Lamm, in press-a;Jackson, Rainville, & Decety, 2006). In an illustrative study, Jackson, Meltzoff, and Decety (2005) found that the level of activity in the dACC was strongly correlated with ratings of the intensity of pain experienced by the observed person, a result reminiscent of Eisenberger, Lieberman, and Williams ' (2003) exclusion was strongly correlated with activity in the dACC. In the case of empathy and of social pain, evolutionarily older neural mechanisms appear to have been co-opted to ...

Corrugator supercilii muscle activity is considered an objective measure of valence because it increases in response to negatively valenced facial expressions (angry) and decreases to positive expressions (happy). The authors sought to determine if corrugator activity could be used as an objective measure of positivity-negativity bias. The authors recorded corrugator responses as participants rated angry, happy, and surprised faces as "positive" or "negative." The critical measure of bias was the percentage of positive versus negative ratings assigned to surprised faces by each participant. Reaction times for surprise expressions were longer than for happy and angry expressions, consistent with their ambiguous valence. Participants who tended to rate surprised faces as negative showed increased corrugator activity to surprised faces, whereas those who tended to rate surprise as positive showed decreased activity. Critically, corrugator responses reflected the participants' bias (i.e., their tendency to rate surprise as positive or negative). These data show that surprised faces constitute a useful tool for assessing individual differences in positivity-negativity bias, and that corrugator activity can objectively reflect this bias.

Psychological stress has been known to have negative effects on health since the work of Cannon (1929) and Selye (1956). Contemporary research suggests that negative emotional reactions to stressors can also be detrimental to health, but that emotion management can foster healthy coping (Lazarus & Folkman, 1984). Those who ignore the occasional aggressive driver on the morning commute, for example, avoid the negative COACTIVATION OF POSITIVE AND NEGATIVE EMOTIONS 213