Do sounds near the hand facilitate tactile reaction times? Four experiments and a meta-analysis provide mixed support and suggest a small effect size

Abstract

The brain represents the space immediately surrounding the body differently to more distant parts of space. Direct evidence for this 'peripersonal space' representation comes from neurophysiological studies in monkeys, which show distancedependent responses to visual stimuli in neurons with spatially coincident tactile responses. Most evidence for peripersonal space in humans is indirect: spatial-and distance-dependent modulations of reaction times and error rates in behavioural tasks. In one task often used to assess peripersonal space, sounds near the body have been argued to speed reactions to tactile stimuli. We conducted four experiments attempting to measure this distance-dependent audiotactile interaction. We found no distance-dependent enhancement of tactile processing in error rates or task performance, but found some evidence for a general speeding of reaction times by 9.5 ms when sounds were presented near the hand. A systematic review revealed an overestimation of reported effect sizes, lack of control conditions, a wide variety of methods, post hoc removal of data, and flexible methods of data analysis. After correcting for the speed of sound, removing biased or inconclusive studies, correcting for temporal expectancy, and using the trim-and-fill method to correct for publication bias, meta-analysis revealed an overall benefit of 15.2 ms when tactile stimuli are accompanied by near sounds compared to sounds further away. While this effect may be due to peripersonal space, response probability and the number of trials per condition explained significant proportions of variance in this near versus far benefit. These confounds need to be addressed, and alternative explanations ruled out by future, ideally pre-registered, studies.

VR Setup to Assess Peripersonal Space Audio-Tactile 3D Boundaries

“…The interpretation is that sigmoidal approximation does not put in evidence as threshold for these data. This might be explained by the methodology of some studies which are removing from their results those participants with bad sigmoidal fit (Holmes et al, 2020). Furthermore, since we used stimuli which belong to the far category (130 cm), this could also be an effect of the variability of the multisensory responses between close vs. far audio-tactile stimuli which has been demonstrated by Serino to show higher variability for far stimuli than close ones (Serino, 2016).…”

Peripersonal space in the front, rear, left and right directions for audio-tactile multisensory integration

“…Thus, our results cannot be applied to the PPS of other body parts, and this should be therefore investigated in a future study. A recent study has questioned the existence of audio-tactile interactions in the peripersonal space 66 . Thus, the conditions of emerging effects of peripersonal space are limited by various factors and stimulus parameters; therefore, we must be careful to compare different studies, and systematic pre-registered studies are required in the future.…”

Peripersonal and reaching space differ: evidence from their spatial extent and multisensory facilitation pattern

“…At odds with some previous studies employing auditory or visual looming stimuli (Canzoneri et al, 2012;Finisguerra et al, 2015;Noel et al, 2015;Serino et al, 2015), we used 'static' stimuli briefly and synchronously flashed with tactile ones to avoid the risk of inflating the estimates of multisensory facilitation. In fact, looming stimuli with predictable arrival times induce foreperiod effects that, though not solely responsible for the boosting of touch, may lead to overestimations of the magnitude of the facilitation (Hobeika et al, 2020;Holmes et al, 2020;Kandula et al, 2017).…”

“…We calculated our sample size with G*Power 3.1.9.2, setting the 10*2 (V-Position*Hand Position) within-interaction for a RM ANOVA hypothesizing a power of 0.85, an α = 0.05 and a correlation of 0.5 between the measures. Considering a medium-low effect size (0.20, see Holmes, Martin, Mitchell, Noorani, & Thorne, 2020), we needed to recruit at least 23 participants per study. All participants were right-handed, as evaluated via the Edinburgh Hand-edness Test (mean score 82%).…”