Abstract
BackgroundAs social animals we share the space with other people. It is known that perceived extension of the peripersonal space (the reaching space) is affected by the implicit representation of our own and other's action potentialities. Our issue concerns whether the co-presence of a body in the scene influences our extrapersonal space (beyond reaching distance) categorization.Methodology/Principal FindingsWe investigated, through 3D virtual scenes of a realistic environment, whether egocentric spatial categorization can be influenced by the presence of another human body (Exp. 1) and whether the effect is due to her action potentialities or simply to her human-like morphology (Exp. 2). Subjects were asked to judge the location ("Near" or "Far") of a target object located at different distances from their egocentric perspective. In Exp. 1, the judgment was given either in presence of a virtual avatar (Self-with-Other), or a non-corporeal object (Self-with-Object) or nothing (Self). In Exp. 2, the Self condition was replaced by a Self-with-Dummy condition, in which an inanimate body (a wooden dummy) was present. Mean Judgment Transition Thresholds (JTTs) were calculated for each subject in each experimental condition. Self-with-Other condition induced a significant extension of the space judged as “Near” as compared to both the Self-with-Object condition and the Self condition. Such extension was observed also in Exp. 2 in the Self-with-Dummy condition. Results suggest that the presence of others impacts on our perception of extrapersonal space. This effect holds also when the other is a human-like wooden dummy, suggesting that structural and morphological shapes resembling human bodies are sufficient conditions for the effect to occur.ConclusionsThe observed extension of the portion of space judged as near could represent a wider portion of “accessible” space, thus an advantage in the struggle to survive in presence of other potential competing individuals.
Highlights
Substantial evidence suggests that perception of the environment is shaped by our possibility to act, defined in terms of both body morphology [1,2,3,4,5,6,7,8] and energetic costs [9].Regarding the space immediately around us it has been demonstrated that perception of affording features is enhanced when the affording object falls within the reachable space of the onlooker, allowing her to directly interact with it [11]
The aim of the present study was to investigate whether a human body located in the extrapersonal space could influence the self-centred, egocentric space categorization
In the peripersonal space it has been shown that the presence of others is able to modulate our predisposition to act towards a graspable object [16], or to see someone reaching an object with a tool extends our perception of the peripersonal space [12, 18]
Summary
Substantial evidence suggests that perception of the environment is shaped by our possibility to act, defined in terms of both body morphology [1,2,3,4,5,6,7,8] and energetic costs [9] (see [10] for a different view).Regarding the space immediately around us it has been demonstrated that perception of affording features is enhanced when the affording object falls within the reachable space of the onlooker, allowing her to directly interact with it [11]. In the same way, when we see an affordable object the other’s action opportunities modulate our perception: observing someone reaching an object with a tool, makes us to perceive the object as closer [12, 18] This evidence suggests that the human body is a visual stimulus which undergoes a special processing as a source of action, that could be remapped into our own. Results suggest that the presence of others impacts on our perception of extrapersonal space This effect holds when the other is a human-like wooden dummy, suggesting that structural and morphological shapes resembling human bodies are sufficient conditions for the effect to occur. Conclusions: The observed extension of the portion of space judged as near could represent a wider portion of ‘‘accessible’’ space, an advantage in the struggle to survive in presence of other potential competing individuals
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