Altercentric Intrusions from Multiple Perspectives: Beyond Dyads

<div><p>Recent findings suggest that in dyadic contexts observers rapidly and involuntarily process the visual perspective of others and cannot easily resist interference from their viewpoint. To investigate whether spontaneous perspective taking extends beyond dyads, we employed a novel visual perspective task that required participants to select between multiple competing perspectives. Participants were asked to judge their own perspective or the visual perspective of one or two avatars who either looked at the same objects or looked at different objects. Results indicate that when a single avatar was present in the room, participants processed the irrelevant perspective even when it interfered with participants’ explicit judgments about the relevant perspective. A similar interference effect was observed when two avatars looked at the same discs, but not when they looked at different discs. Indeed, when the two avatars looked at different discs, the interference from the irrelevant perspective was significantly reduced. This is the first evidence that the number and orientation of agents modulate spontaneous perspective taking in non-dyadic contexts: observers may efficiently compute another’s perspective, but in presence of more individuals holding discrepant perspectives, they may not spontaneously track multiple viewpoints. These findings are discussed in relation to the hypothesis that perspective calculation occurs in an effortless and automatic manner.</p></div

Graphical representation of the interaction <i>number</i> (one avatar, two avatars) by <i>orientation</i> (centered, off-centered) on Inconsistency Ratios.

<p>Error bars represent standard errors of the means.</p

Illustration of the event sequence for matching/mismatching consistent and inconsistent trials requiring self- and other-perspective judgments in the two_avatars_off-centered condition.

<p>Please note that in Italian, English plural words (e.g., avatars) are used in the English singular form (e.g., avatar). Picture adapted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114210#pone.0114210-Qureshi1" target="_blank">[3]</a>.</p

Examples of stimuli used for inconsistent trials.

<p>a) One_avatar_centered; b) One_avatar_off-centred; c) Two_avatars_centered; d) Two_avatars_off-centered. On consistent trials, the avatar(s) saw the same number of discs as the participants; the discs were thus confined to one of the walls.</p

Grip aperture over time for both small and large object.

<p>In Panel A, grip aperture (mm) over time for both the small and the large object. Error bars represent standard errors. In Panel B, example from a representative participant of the index – thumb distance over time for both large (red) and small (light blue) object. Each line represents one trial.</p

X- and z- components of finger plane over time for both small and large object.

<p>In Panel A, <i>x</i> and <i>z</i> components of finger plane at 10%, 50% and 100% of the movement time for both small and large object. In Panel B, example from a representative participant of the thumb and index finger tips position during the action unfolding.</p

X, y, and z-thumb over time for both small and large object.

<p>In Panel A, <i>x-</i> and <i>y-thumb</i> coordinate over time for both small and large object. Error bars represent standard errors. In Panel B, example from a representative participant of a tridimensional representation of the <i>x-</i>, <i>y-</i> and <i>z-thumb</i> coordinate for both large (red) and small (light blue) object. Each line represents one trial.</p

Illustration of a bistable point-light walker.

<p>Illustration of a single frame of the bistable point-light walker (without perspective cues), and the two veridical interpretations with the point-lights superimposed. Whilst both veridical interpretations are equally plausible, observers usually prefer the FV interpretation. Thus, the objectively bistable point-light walker does not correspond to the subjectively bistable one. To obtain <i>subjectively</i> bistable stimuli, we performed a preliminary adjustment task in which perspective cues carrying the information concerning the veridical orientation of the point-light figure were gradually manipulated. On each trial, participants were asked to indicate whether the visually presented stimulus was perceived as FV or FAV. Individual perspective levels were determined by fitting a cumulative Gaussian function to the proportion of FV responses in the different perspective conditions, and selecting the perspective manipulation corresponding to the 30%, 50%, and 70% FV thresholds.</p

Lateral and frontal view of hand model.

<p>In Panel A, the local frame of reference (F_local) determined by using the markers <i>rad</i> (placed on the radial aspect of the wrist), <i>ind1</i> (placed on the metacarpal joint of the index finger) and <i>lit1</i> (placed on the metacarpal joint of the little finger). <i>x-y</i> represents the metacarpal plane, <i>y-z</i> represents the sagittal plane. In Panel B, the finger plane defined as x, y and z components of the thumb – index plane defined as passing through the markers <i>thu0</i> (placed on the trapezium bone of the thumb), <i>ind3</i> (placed on the tip of the index finger), and <i>thu4</i> (placed on the tip of the thumb). Additional markers (not used to compute the variables of interest) were placed on the metacarpal and proximal interphalangeal joints of the thumb, the proximal interphalangeal joint the index finger, and the proximal interphalangeal joint and the tip of the little finger.</p