Verbal Comprehension in Spatial Reference Frames

The Verbal Comprehension in Spatial Reference Frames (VCSRF) task was developed in order to assess the ability to process descriptions of locative spatial relations under different spatial reference frames (SRF). Building on previous classification models of SRF (Carlson, 1999; Levinson, 1996; 2003), the VCSRF was designed to include four distinct conditions: (1) a self-centred and (2) a third-person-centred (relative) SRF, (3) an object-centred (intrinsic) SRF, and (4) an environment-centred (absolute) SRF. While in the self-centred

36 SRF spatial relations are coded egocentrically, relatively to the examinee’s viewpoint,

performance in the other SRF entails spatial perspective transformations involving self-based mental rotations (Kessler & Thomson, 2010; Kessler & Rutherford, 2010; Zacks, 2008; Zacks & Michelon, 2005). In the third-person-centred SRF, spatial relations are defined relatively to another person’s viewpoint, requiring from the examinee to adopt the third- person’s perspective. Switching from a self-centred to a third-person-centred perspective may occur in social contexts, for example in dialogue, enabling the two interlocutors’ mental representations of space to be aligned, and ultimately ensuring optimum communication attainment. The object-centred SRF involves spatial relations defined by the axial orientation of the reference (ground) object, independently of the viewpoint of the perceivers. Finally, under an environment-centred SRF, spatial relations are described with respect to a fixed point in the external environment, independently of the perceivers’ viewpoint or the orientation of the reference object.

Apparatus. The apparatus of this task consisted of a central circular board with a diameter of 18 cm, on which the reference object (a glass or a car miniature in the object- centred condition) is placed, surrounded by a rotating circular board with a diameter of 28 cm, on which the located object (a ball) is permanently placed, based on a third stable circular board with a diameter of 37 cm. The middle board of the apparatus is rotated in order to move the located object into 8 different locations relatively to the reference object, with Location I being directly in front of the participant, and the rest of the locations being equally distributed along the rotating board in a clockwise order (see Figure 3). In the third-person- centred condition, a Lego mini-figure, facing the reference object, is placed directly opposite of the participants’ location (Location V; Figure 4). In the environment-centred condition, an arrow pointing to the North is placed ~ 4 metres away at an angle of 45 degrees to the right of the participants’ position (Figure 4).

Procedure. In each one of the four conditions, participants hear 16 different statements describing spatial relations between the located and the reference objects (e.g., The ball is to the left of the glass), and are asked to judge each statement as true or false. Participants are explicitly given instructions as to which reference frame they should base their judgements on each condition (e.g., in the object-centred condition: This time, you should base your judgments with reference to the car’s perspective). Each reference frame is explained to participants at the outset of each condition. Figure 4 contains a schematic representation of all four conditions in the VCSRF task, along with the general instructions used for the spatial reference frame employed in each condition and a sample statement describing a spatial

37 relation between the located and the reference objects. Table 4 contains all the items used in the VCSRF task.

Scoring. The total number of correctly judged statements in each condition is

calculated as an index of accuracy of performance. There is no time limit in VCSRF, but the time it takes to complete each condition can be measured as an index of speed of

performance.

Figure 3. A schematic representation of the apparatus of the Verbal Comprehension in Spatial Reference Frames task. The middle circular board of the apparatus is rotated in order to move the located object (red ball) into 8 different locations relatively to the reference object (glass; car in the object-centred condition). Each Latin number corresponds to one of the possible locations of the located object. Possible locations are not marked on the

apparatus in order to eliminate the possibility of being used as facilitating cues by the participants.

38

Spatial reference frame Schematic representation Instructions Sample statement

Self-centred Based on your

perspective

The ball is to the left of the glass. (Correct response:

True)

Third-person-centred Based on the other

person’s perspective

The ball is to the left of the glass. (Correct response:

False)

Object-centred Based on the car’s

perspective

The ball is to the left of the car. (Correct response:

False)

Environment-centred Based on the North

(as pointed by the arrow)

The ball is South- West of the glass. (Correct response:

True)

Figure 4. Schematic representation of all conditions in the Verbal Comprehension in Spatial Reference Frames task. The middle board of the apparatus is rotated in order to move the located object (red ball) into 8 different locations relatively to the reference object (glass; car in the object-centred condition). In the third-person-centred condition, a Lego mini-figure, facing the reference object, is placed directly opposite of the participants’ location. In the environment-centred reference frame, an arrow pointing to the North is placed ~ 5 metres away at an angle of 45 degrees to the right of the participants’ position. The third column presents the general instructions used to describe the spatial relations in each condition. The fourth column provides sample statements describing a spatial relation between the located and the reference object.

39 Table 4. Items used in all Conditions of the Verbal Comprehension in Spatial Reference Frames Task

Relative RF Intrinsic RF Absolute RF

Self-centred Third-person-

centred Object-centred Environment-centred Item Loc Statement (CR) Loc Statement (CR) Loc Statement (CR) Loc Statement (CR) 1 III To the left of (T) II Behind & to the

right of (T)

III In front of (T) VI North of (T)

2 VII To the right of (T) V Behind the (F) VIII Behind & to the left of (T)

IV North-West of (F)

3 II In front & to the left of (T)

VII To the left of (T) VI Behind & to the left of (F)

I South-East of (T)

4 V In front of (F) VIII In front & to the right of (F)

IV In front & to the right of (T)

VII North-East of (T)

5 VIII In front & to the left of (F)

III To the left of (F) VII To the right of (F) II South-West of (F)

6 IV Behind & to the right of (F)

VI In front & to the left of (T)

II In front & to the left of (T)

VIII East of (T)

7 VI Behind & to the right of (T)

IV In front & to the right of (T)

V To the left (F) V North of (F)

8 I In front of (T) I In front of (F) I To the left (T) III West of (F)

9 V Behind the (T) VIII Behind & to the left of (T)

IV In front & to the left of (F)

VII East of (F)

10 II Behind & to the left of (F)

III To the right of (T) VIII Behind & to the right of (F)

IV West of (T)

11 VIII In front & to the right of (T)

V In front of (T) III To the left of (F) V North-West of (T)

12 VI In front & to the right of (F)

II In front & to the left of (F)

II In front & to the right of (F)

I South of (F)

13 III To the right of (F) VI Behind & to the right of (F)

I In front of (F) VI North East of (F)

14 IV Behind & to the left of (T)

I Behind the (T) VI Behind & to the right of (T)

III South West of (T)

15 I Behind the (F) IV Behind & to the left of (F)

V To the right of (T) VIII South East of (F)

16 VII To the left of (F) VII To the right of (F) VII Behind the (T) II South of (F)

Note. RF = reference frame; Loc = location of the located object; CR = correct response; T = true; F = false.

3.3 Performance on spatial language measures (Study 1)