The role of flexibility in personal space preferences.

Editor's Note: These short, critical reviews of recent papers in the Journal, written exclusively by graduate students or postdoctoral fellows, are intended to summarize the important findings of the paper and provide additional insight and commentary. For more information on the format and purpose of the Journal Club, please see Review of Holt et al. Personal space is generally defined as the area individuals maintain around themselves into which others cannot intrude without arousing discomfort (Hayduk, 1983). It is a dynamic perception that plays an important role in social communication and behavior across species (Hayduk, 1983; Graziano and Cooke, 2006). Social crowding, or the presence of high population density, is related to personal space in that it reduces the area available for individuals to maintain without intrusion. There is evidence that social crowding produces both behavioral and physiological changes in rodents (Grippo et al., 2010) and nonhuman primates (Judge and De waal, 1997). In humans, personal space has been demonstrated to be important in pathogen avoidance (Peng et al., 2013), social dominance and hierarchies (Aono, 1981), and social attachment (Kaitz et al., 2004). Because awareness of personal space appears to play an integral role in a wide range of behaviors across species, a better understanding of its mal-leability across different contexts can expand our understanding of behavior in many realms. The neural mechanisms underlying the dynamic regulation of personal space remain poorly understood. Research in nonhuman primates has provided evidence that attention to near space is represented in the ventral intraparietal area and a polysensory zone in the precentral gyrus (Graziano and Cooke, 2006). Similarly , evidence from humans suggests a representation of near space in parietal and frontal areas, including the intrapari-etal sulcus, inferior parietal lobe, and parts of the premotor cortex (for review, see Brozzoli et al., 2014). However, this literature primarily focuses on the presence of a stationary object within near surrounding space and does not address movement of objects within that space, or more importantly, the monitoring of an approaching object versus a withdrawing object. Additionally, previous studies have not answered the question of whether specific areas respond to personal space intrusion by conspecifics versus objects. Holt et al. (2014) extend this literature, finding that the dorsal intraparietal sulcus and ven-tral premotor cortex demonstrate greater responses to approaching faces than to withdrawing faces. However, when contrasting approaching cars to withdrawing cars and approaching spheres to withdrawing …