Conference of the European Society for Cognitive Psychology location:Paphos, Cyprus date:17-20 September 2015
We perceive the distance as reduced when adopting a human body, compared to an object, as reference frame. Previous data suggest that when observing a human body with the potential/intention to walk, we simulate the walking action and this changes our space perception. Moreover, a certain degree of interindividual variability in this effect has been observed, which seems to depend on perspective taking (PT) abilities.
The ventral Premotor Cortex (PMv) is known to be involved in motor simulation (or motor mirroring) and could play a role in the “social scaling” of the extrapersonal space.
Here we performed three different sessions of transcranial Direct Current Stimulation (tDCS) lasting 20 minutes (sham, cathodal, anodal) on the left PMv and we administered the IRI-Interpersonal Reactivity Index- to measure PT.
27 Subjects were divided into two groups (High PT and Low PT) and were asked to judge the location (“Near” or “Far”) of a target object from an egocentric reference frame (RF), or an allocentric RF (either a human body or a static object).
Stimuli were presented with progressively increasing or decreasing target-RF distance until the subject did not report a perceived change from Near to Far or vice-versa.
The results indicate that only in the Low PT group the anodal stimulation reduces the space perception with the human body vs the object, conversely the effect is inverted with the cathodal stimulation. Thus, it seems that the ability to take the other‘s perspective modulates the impact of the left PMv stimulation during the Other-centered extrapersonal space perception. Specifically, the lower is the PT score, the greater is the impact of tDCS stimulation of the left PMv on the “social scaling” of the extrapersonal space.
In conclusion, PT appears to be a prerequisite for the motor simulation to occur and being modulated.