Fig 1.
From left to right, the images depict the uncrossed (A), and crossed (B) tools, and a close-up of the end of a tool (C). The tools have red Light Emitting Diodes (LEDs) embedded at the far ends of the tools, and vibrotactile stimulators embedded in the handles. A vertical peg was attached to the far ends of the tools (white oval), which slotted into holes in the wooden board to ensure the position of the tips of the tools was consistent for crossed and uncrossed trials (C). An off-white LED fixation point was positioned with equal distance to the ends of both tools. A webcam was placed in line with the fixation light and the chinrest, which were aligned with participants’ sagittal plane.
Fig 2.
Procedure for each experimental session.
During the sensory manipulation phase the experimenter applied a capsaicin cream (pain condition) or warm-up gel (active placebo condition) to the participant’s dominant arm, or there was no manipulation (neutral condition). During the passive stage (set 1) of the Crossmodal Congruency task (CCT) the experimenter changed the tools between the crossed and uncrossed positions. During the active stages of the CCT (sets 2–4) participants manoeuvred the tools themselves when changing position. The interactive tool-use task involved retrieving and sorting beanbags, using the same tools that were used for the CCT (see Fig 1).
Fig 3.
Crossmodal interference–three-way interaction.
Crossmodal interference shown by Tool Arrangement (uncrossed [U], crossed [C]) and Visual Field (same [S], opposite [O]) for reaction times (A) and percentage error rates (B), on the Crossmodal Congruency Task (CCT), for all participants (n = 30). Crossmodal interference was calculated by subtracting congruent from incongruent reaction times and error rates. Medians are depicted by the centre lines. The box limits indicate the 25th and 75th percentile. The whiskers extend 1.5 times the interquartile range from the box limits. Circles depict individual data points. ** p < .01, *** p < .001.
Fig 4.
Crossmodal interference–four-way interaction.
Crossmodal interference shown by Set (1 [passive], 2, 3, 4) Tool Arrangement (uncrossed, crossed) and Visual Field (same, opposite) for reaction times on the Crossmodal Congruency Task (CCT), for all participants (n = 30). Crossmodal interference was calculated by subtracting congruent from incongruent reaction times. Circles depict individual data points. Medians are depicted by the centre lines. The box limits indicate the 25ht and 75th percentile. The whiskers extend 1.5 times the interquartile range from the box limits. Circles depict individual data points * p < .05, ** p < .01, *** p < .001.