Cross-modal congruency and visual capture in a visual elevation-discrimination task

Participants in this experiment were required to discriminate the elevation of visual target stimuli (upper versus lower) presented to either side of fixation, while simultaneously trying to ignore vibrotactile distracters presented independently from the index finger (up) or thumb (lower) of either hand. The participants’ hands were occluded from view under an opaque screen while the visual targets were situated directly over the hands above the screen. Participants responded more slowly on this elevation-discrimination task when the vibrotactile distracters were incongruent with the elevation of the visual targets (i.e. a “lower” vibration to the thumb during the presentation of an upper visual target) than when they were congruent (presumably due to the competing responses primed by the target and distracter stimuli on incongruent trials). The vibrotactile distracters had less of an effect on performance when a pair of rubber hands was placed on top of the screen, “holding” the target lights, in a posture consistent with that of the participant. Those participants who agreed most strongly with a statement about feeling the vibrations at the location of the rubber hands in a post-congruency task questionnaire evidenced the greatest reduction in the magnitude of the cross-modal congruency effect.