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Investigating visual-tactile interactions over time and space in adults with autism.
Supplementary materials
Journal of Autism and Developmental Disorders
Threshold procedure
Participants received successive trials with a particular duration of the period of silence (gap) between double vibrations. The overall duration of single and double pulse stimuli were matched. Performance relative to the target performance level (75% accuracy) determined whether the gap continued to increase, decrease or reverse in direction on subsequent trials. Participants began at the maximum gap size of 200ms and the initial step size corresponded to a 16ms reduction in the gap duration. The procedure came to an end when the participant reached the minimum step size, which corresponded to ±1ms in gap duration. After reaching the minimum step size, 20 further trials were included over which the average of the reversals was taken as the threshold value and their accuracy was checked to confirm that the threshold procedure had constrained their performance (i.e. 75% ± 10).
Breaks were included after 90 and 180 trials. To ensure that the threshold procedure was not unduly long, if the participant had not reached the minimum step size by 180 trials, the program ended and an average of the participant’s reversals since the 90th trial was taken. The procedure continued using this average level at the minimum step size of 1ms for 20 further trials (Experiment 1, ASC n = 1; Experiment 2, ASC n = 1, NT n = 1). Their threshold was taken as the average gap size across these trials.
Practice Procedure
Participants first completed five trials with the gap duration set at 200ms to ensure that they understood the task instructions. Then 10 unimodal trials presented at their threshold. Finally, the third block comprised 36 trials: 20 baseline trials and 16 trials with light flashes, four in each condition with each combination of congruent/ incongruent trials with single/double pulses.
Participants were required to perform at 75% accuracy ±10% in baseline trials on the third block to continue to the experimental task proper. Participants who performed at 60% or 90% accuracy had the gap duration increased or decreased by 1ms and were required to repeat the practice procedure (Experiment 1, ASC n = 3; Experiment 2, ASC n = 3, NT n = 1). Participants who performed outside of these parameters completed a shortened version of the threshold procedure in which they were re-entered at the final step size reached (Experiment 1, ASC n = 3, NT n = 4; Experiment 2, ASC n = 1, NT n = 1). The initial gap size was set at ±8ms on this shortened threshold procedure
Visual only Procedure
Participants completed a short visual task in which they were required to detect a single or double light flash presented from each of the distractor light positions (0cm, 21cm, 42cm and 42cm_opp). Ten light flashes were presented from each position (five single flashes, five double flashes) in a random order. As in the experimental procedure, the LED was stimulated for 80ms for single flashes and double flashes comprised two single 80ms flashes separated by 120ms. Participants were instructed to focus on a central fixation cross, lifting their toe in response to a single flash and heel in response to double.
A mixed ANOVA [Position (0cm, 21cm, 42cm, 42cm_opp) x Group (ASC, NT)] revealed no significant effect of position (F (3, 96) = 2.19, p = 0.95, ηp2 = .064), nor a Group x Position interaction F (3, 96) = .55, p = .648, ηp2 = .017).
Figure S1. Mean percentage error to light flashes in each position for participants with ASC and NT. Error bars represent standard error of the mean.
Figure S2. The AQ scores for the NT participants plotted as a function of scores from each quadrant of the AASQ: sensory seeking, low registration, sensory avoidance and sensory sensitivity. There was a significant positive correlation with sensory avoidance items (see main text for details). To illustrate the spread of scores, the data in the figure is not adjusted for outliers.
Figure S3.The AQ scores for the NT participants plotted as a function of CE at each SOA (Experiment 1; A) and position (Experiment 2; B). No correlation coefficients reached statistical significance in either Experiment 1 (r < .33, p > .178), or Experiment 2 (r < .11, p >.678).