Humans and other animals pay attention to other members of their groups to acquire valuable social information about them, including information about their identity, dominance, fertility, emotions, and likely intent. In primates, attention to other group members and the objects of their attention is mediated by neural circuits that transduce sensory information about others and translate that information into value signals that bias orienting. This process likely proceeds via two distinct but integrated pathways: an ancestral, subcortical route that mediates crude but fast orienting to animate objects and faces; and a more derived route involving cortical orienting circuits that mediate nuanced and context-dependent social attention.

Macaques, like humans, rapidly orient their attention in the direction other individuals are looking. Both cortical and subcortical pathways have been proposed as neural mediators of social gaze following, but neither pathway has been characterized electrophysiologically in behaving animals. To address this gap, we recorded the activity of single neurons in the lateral intraparietal area (LIP) of rhesus macaques to determine whether and how this area might contribute to gaze following. A subset of LIP neurons mirrored observed attention by firing both when the subject looked in the preferred direction of the neuron, and when observed monkeys looked in the preferred direction of the neuron, despite the irrelevance of the monkey images to the task. Importantly, the timing of these modulations matched the time course of gaze-following behavior. A second population of neurons was suppressed by social gaze cues, possibly subserving task demands by maintaining fixation on the observed face. These observations suggest that LIP contributes to sharing of observed attention and link mirror representations in parietal cortex to a well studied imitative behavior.gaze following ͉ imitation ͉ joint attention ͉ mirror neurons ͉ shared attention P eople naturally and intuitively share attention with each other. In a laboratory setting, people respond more quickly to targets that are the object of another's attention, even when this social cuing is brief or consistently misleading (1-3). Monkeys' attention also follows the gaze of others (4), and the similar magnitude and time course of gaze following by rhesus macaques and humans (5) implicates shared neural mechanisms. The ability to follow gaze is believed to be an important foundation for theory of mind (6, 7); thus, the neural processes governing gaze following are relevant both to the evolution of social cognition (8-10) and to clinical disorders, such as autism, associated with social attention deficits (11)(12)(13)(14). Although gaze following involves automatic ''mirroring'' of other's mental states, to our knowledge, mirror neurons (15, 16) for visual orienting have not previously been identified.Current evidence suggests that identification of where other individuals are looking is accomplished by neurons along the superior temporal sulcus (STS) (17)(18)(19)(20) (22), as well as the parietal cortex (28). These observations invite the simple hypothesis that gazefollowing behavior is mediated by a relatively straightforward system, beginning with the STS and proceeding directly to the attention-and gaze-control networks. Although intuitively appealing, this model raises several important questions.First, gaze-following behavior fits poorly into existing models of attention (1, 2), which dichotomize the underlying mechanism as either reflexively driven by exogenous stimuli or endogenously guided by internal goals (29, 30). Although there is some evidence that specific neural circuits mediate these processes (31-33), the precise contributions of neurons within different b...

Animals as diverse as arthropods [1], fish [2], reptiles [3], birds [4], and mammals, including primates [5], depend on visually acquired information about conspecifics for survival and reproduction. For example, mate localization often relies on vision [6], and visual cues frequently advertise sexual receptivity or phenotypic quality [5]. Moreover, recognizing previously encountered competitors or individuals with preestablished territories [7] or dominance status [1, 5] can eliminate the need for confrontation and the associated energetic expense and risk for injury. Furthermore, primates, including humans, tend to look toward conspecifics and objects of their attention [8, 9], and male monkeys will forego juice rewards to view images of high-ranking males and female genitalia [10]. Despite these observations, we know little about how the brain evaluates social information or uses this appraisal to guide behavior. Here, we show that neurons in the primate lateral intraparietal area (LIP), a cortical area previously linked to attention and saccade planning [11, 12], signal the value of social information when this assessment influences orienting decisions. In contrast, social expectations had no impact on LIP neuron activity when monkeys were not required to make a choice. These results demonstrate for the first time that parietal cortex carries abstract, modality-independent target value signals that inform the choice of where to look.