Spatial Judgments in Egocentric and Allocentric Perspectives

Participants were provided with verbal and written instructions about the experimental procedure and task. They were instructed to memorize the dyads that would be shown one at a time and to answer two different questions: “What stimulus was closest to you?” (egocentric question)—“What stimulus was closest to the bar?” (allocentric question). The kind of question was indicated by a word on the screen. The words were the following: “YOU” was for “What stimulus was near to the body”—“BAR” was for “What stimulus was near to a black bar”.
Training phase: After the instructions, participants were presented with each object and asked to name them. In this way, difficulties and errors due to naming problems could be excluded a priori. Then, participants were trained to use specific keys to provide their response: S for sphere, C for cube; C for cone and P for pyramid. The keys were highlighted on the central part of the keyboard according to a vertical dimension to avoid laterality effects and with the remaining part of the keyboard hidden. Afterwards, participants could start a training session during which they had to provide spatial judgments for 6 dyads (the presented dyads were not included in the testing phase).
Testing phase and Experimental Design: The experiment was organized in blocks. Each block corresponded to a specific spatial judgment and a specific dyad. There were four blocks: ego cube–pyramid; ego cone–sphere; allo cube–pyramid; allo cone–sphere. Blocks were presented in counterbalanced order. Within each block, the order of presentation of trials was randomized. Within the egocentric block, participants had to provide an egocentric spatial judgment (“What object was closest to you”). Within the allocentric block, participants had to provide an allocentric spatial judgment (“What object was closest to the bar”). Each block comprised 16 trials regarding egocentric/allocentric spatial judgments and four distractor questions (total: 64 trials + 16 distractors). The testing phase was administered once for each participant.
We planned a random presentation of distractors in each block, asking participants which stimulus was the tallest one. Distractors prevented participants from understanding the ultimate purpose of the experiment.
Each trial started with the presentation of a fixation cross on a grey screen for 100 ms; immediately after, a blank screen was presented for 1 s; then, the first object appeared for 400 ms and it could be nearest to the body (egocentric condition first) or to the bar (allocentric condition first). Afterwards, the second object appeared for 400 ms, and it could be nearest to the body (egocentric condition second) or to the black bar (allocentric condition second). Then, the virtual desk disappeared and after a 1 s blank, the word indicating the spatial judgement (“you” for egocentric, “bar” for allocentric) appeared (see Figure 2). Participants were instructed to respond as accurately and quickly as possible, although there were no time limits. Mean accuracy and RTs measured the performance.