For more than a century, social psychologists have been trying to understand how the presence of conspecifics—perhaps the most fundamental invariant of behavior in many, if not all, animal species—affects behavior. Although this issue, traditionally referred to using the term social-facilitation-and-impairment effects, has generated much interest, the impact of social presence on attentional mechanisms—especially those related to executive attention—has been mostly ignored, as have the neural bases of these phenomena. Here, we describe a series of findings indicating that social presence may have strong effects on attentional mechanisms and may even play a key role in the modulation of neuronal activity. Not only do these findings provide new reasons to pay constant attention to the social environment of cognition, but they also have important implications for the practice of psychological science.