Adapting the Crossmodal Congruency Task for Measuring the Limits of Visual–Tactile Interactions Within and Between Groups

Abstract

The crossmodal congruency task (CCT) is a commonly used paradigm for measuring visual-tactile interactions and how these may be influenced by discrepancies in space and time between the tactile target and visual distractors. The majority of studies which have used this paradigm have neither mea sured, nor attempted to control, individual variability in unisensory (tactile) performance. We have developed a version of the CCT in which unisensory baseline performance is constrained to enable comparisons within and between participant groups. Participants were instructed to discriminate be tween single and double tactile pulses presented to their dominant hand, at their own approximate threshold level. In Experiment 1, visual distractors were presented at -30 ms, 100 ms, 200 ms and 400 ms stimulus onset asynchronies. In Experiment 2, ipsilateral visual distractors were presented 0 cm, 21 cm, and 42 cm vertically from the target hand, and 42 cm in a symmetrical, contralat eral position. Distractors presented -30 ms and 0 cm from the target produced a significantly larger congruency effect than at other time points and spatial locations. Thus, the typical limits of visualtactile interactions were replicated using a version of the task in which baseline performance can be constrained. The usefulness of this approach is supported by the observation that tactile thresh olds correlated with self-reported autistic traits in this non-clinical sample. We discuss the suitability of this adapted version of the CCT for measuring visual-tactile interactions in populations where unisensory tactile ability may differ within and between groups.

Investigating Visual–Tactile Interactions over Time and Space in Adults with Autism

“…It is important to characterise NT participants used as a control group since individual differences in sensory and autistic traits may potentially mask between-group differences on behavioural measures. However, it should be noted that there were no significant correlations between AQ scores and tactile thresholds (although see Poole et al 2015), or the size of the CE at each SOA and position. This suggests that the null effect of group on the temporal modulation of visual-tactile interactions in Experiment 1 was not driven by the NT participants who reported above average levels of autistic traits.…”

“…A previous study reported a significant effect of temporal and spatial modulation of visual-tactile interactions in 13 NT participants (Poole et al 2015). In the present study we aimed to exceed this sample size to find a between groups effect and account for the heterogeneity likely in participants with ASC.…”

“…Tactile stimuli were presented at threshold in an attempt to equate the task difficulty between, and within, the participant groups (Poole et al 2015). To determine tactile thresholds we utilised a non-spatial task which relied on participant's ability to separate vibrotactile stimuli in time and these thresholds did not differ statistically between the groups.…”

“…Secondly, we sought to provide novel insight into the spatial modulation of multisensory interactions in ASC. In order to do so, we used an adapted version of the CCT (Spence et al 1998), somewhat analogous to the flash-beep illusion (Poole et al 2015). Participants were asked to judge whether they felt a single or double tactile vibration while presented with distracting light flashes (Holmes et al 2006).…”

“…There were a number of reasons for adopting this technique: firstly, any confounds relating to differences in tactile performance that may exist between the groups were removed (Blakemore et al 2006;Puts et al 2014). Furthermore, tactile thresholds have previously been found to positively correlate with autistic traits in NT participants (Poole et al 2015), and presenting stimuli at each participant's threshold should also reduce variability in tactile performance within the control group. Secondly, this enabled the CE to be measured through error rates rather than reaction times.…”