Psychological and physiological evidence for an initial ‘Rough Sketch’ calculation of personal space

Abstract

Personal space has been defined as “the area individuals maintain around themselves into which others cannot intrude without arousing discomfort”. However, the precise relationship between discomfort (or arousal) responses as a function of distance from an observer remains incompletely understood. Also the mechanisms involved in recognizing conspecifics and distinguishing them from other objects within personal space have not been identified. Accordingly, here we measured personal space preferences in response to real humans and human-like avatars (in virtual reality), using well-validated “stop distance” procedures. Based on threshold measurements of personal space, we examined within-subject variations in discomfort-related responses across multiple distances (spanning inside and outside each individual’s personal space boundary), as reflected by psychological (ratings) and physiological (skin conductance) responses to both humans and avatars. We found that the discomfort-by-distance functions for both humans and avatars were closely fit by a power law. These results suggest that the brain computation of visually-defined personal space begins with a ‘rough sketch’ stage, which generates responses to a broad range of human-like stimuli, in addition to humans. Analogous processing mechanisms may underlie other brain functions which respond similarly to both real and simulated human body parts.

Personal space increases during the COVID-19 pandemic in response to real and virtual humans

“…The discomfort levels as a function of distance followed a power law fall-off, as previously (Tootell et al, 2021) in all four cases (to real humans, before and during the pandemic, respectively: R 2 0 71 = . and 0 67 .…”

“…A one-way ANOVA [F(246,248) = 5.698, p = 0.004] revealed that in Cohort 1, the size of personal space (measured with respect to real humans) was significantly larger in the group assessed during the pandemic compared to both: (1) those assessed in early 2020 [t(69) = −3.076, p = 0.003] and (2) those assessed more than 6 months before the pandemic [t(209) = −3.238, p < 0.001; Figure 1]. As expected (Tootell et al, 2021), in Cohort 2, the size of personal space with respect to real humans was highly correlated with the size of personal space to virtual humans (avatars) across individuals, for both the passive and active trials, both before [passive trials: r(17) = 0.625, p = 0.004; active trials: r(17) = 0.644, p = 0.003] and during [passive trials: r(10) = 0.958, p < 0.001; active trials: r(10) = 0.790, p = 0.002] the COVID-19 pandemic.…”

“…This VR procedure measures personal space in response to virtual simulations of humans (“avatars”) but is otherwise identical to the SDP conducted with real humans. VR-based measurements of personal space with respect to avatars have been shown to correspond closely to those measured to real humans in vivo ( Iachini et al, 2016 ; Tootell et al, 2021 ).…”

“…In Cohort 2, discomfort in response to personal space intrusions was also measured, in addition to personal space size. First, personal space size was calculated independently in each individual subject for each of the two SDP modalities (real and virtual), using the average personal space size measured in the active trials of that visit, which are slightly more stable than the passive trials ( Tootell et al, 2021 ). Then multiples of each individual subject’s personal space size (25, 50, 100, 200, and 400%) were calculated.…”

“…In humans, the dimensions of personal space are moderately influenced by a number of situational, social, and psychological factors, including gender, age, social status, cultural norms, and psychological characteristics ( Hayduk, 1983 ; Uzzell and Horne, 2006 ; Kennedy and Adolphs, 2014 ; Holt et al, 2015 ; Iachini et al, 2016 ). However, when many of these situational factors are controlled within a laboratory setting, the preferred distance that a given individual maintains from others remains remarkably stable over repeated measurements ( Hayduk, 1981 ; Tootell et al, 2021 ).…”