Frames of reference and categorical/coordinate spatial relations in a "what was where" task

Abstract

The aim of this study was to explore how people use egocentric (i.e., with respect to their body) and allocentric (i.e., with respect to another element in the environment) references in combination with coordinate (metric) or categorical (abstract) spatial information to identify a target element. Participants were asked to memorize triads of 3D objects or 2D figures, and immediately or after a delay of 5 s, they had to verbally indicate what was the object/figure: (1) closest/farthest to them (egocentric coordinate task); (2) on their right/left (egocentric categorical task); (3) closest/farthest to another object/figure (allocentric coordinate task); (4) on the right/left of another object/figure (allocentric categorical task). Results showed that the use of 2D figures favored categorical judgments over the coordinate ones with either an egocentric or an allocentric reference frame, whereas the use of 3D objects specifically favored egocentric coordinate judgments rather than the allocentric ones. Furthermore, egocentric judgments were more accurate than allocentric judgments when the response was Immediate rather than delayed and 3D objects rather than 2D figures were used. This pattern of results is discussed in the light of the functional roles attributed to the frames of reference and spatial relations by relevant theories of visuospatial processing.

Keywords: Categorical/coordinate spatial relations; Egocentric/allocentric frames of reference; Ventral stream; Verbal response.

Fig. 1

Schematic overview of the learning and testing phase. a Participant is seated at the desk with the eyes closed and the experimenter helps him\her to align his\her body midline with the center of the desk; b the experimenter puts a triad on the desk and asks participant to open the eyes and to learn the objects or the figures (not shown here) and their position; c according to the assigned experimental condition, participant has to wait 1.5 or 5 s to receive the instructions about the kind of spatial judgment requested (Ego-Coor or Ego-Cat or Allo-Coor or Allo-Cat). During this time, participant is with eyes closed and the triad is removed; d finally, the experimenter asks for the spatial judgment

Fig. 2

Graph on the left shows the mean accuracy of coordinate and categorical judgments as a function of the egocentric and allocentric reference frames with 2D stimuli. Instead, the graph on the right shows the mean accuracy for the same judgments with 3D stimuli