Conscious awareness modulates processing speed in the redundant signal effect

Abstract

Evidence for the influence of unaware signals on behaviour has been reported in both patient groups and healthy observers using the Redundant Signal Effect (RSE). The RSE refers to faster manual reaction times to the onset of multiple simultaneously presented target than those to a single stimulus. These findings are robust and apply to unimodal and multi-modal sensory inputs. A number of studies on neurologically impaired cases have demonstrated that RSE can be found even in the absence of conscious experience of the redundant signals. Here, we investigated behavioural changes associated with awareness in healthy observers by using Continuous Flash Suppression to render observers unaware of redundant targets. Across three experiments, we found an association between reaction times to the onset of a consciously perceived target and the reported level of visual awareness of the redundant target, with higher awareness being associated with faster reaction times. However, in the absence of any awareness of the redundant target, we found no evidence for speeded reaction times and even weak evidence for an inhibitory effect (slowing down of reaction times) on response to the seen target. These findings reveal marked differences between healthy observers and blindsight patients in how aware and unaware information from different locations is integrated in the RSE.

Phasic Alertness and Multisensory Integration Contribute to Visual Awareness of Weak Visual Targets in Audio-Visual Stimulation under Continuous Flash Suppression

“…Interestingly, reaction times in the Visual + Audio condition did not differ from the Single Audio condition when participants reported being unaware of the visual stimulus. These findings are also consistent with the association between subjective awareness and reaction time under CFS with previous findings indicating that for unimodal visual RSE to occur, the participant need to report some level of awareness of masked targets [29]. More importantly, the incidence of aware trials was higher for the combined audio and visual stimuli than for the visual stimulus alone, again contributing to the evidence of the possibility that increased reported awareness is caused by multisensory integration.…”

“…We expected there to be faster responses in the Visual + Audio condition compared to the Single Audio. We expected the slowest performance in the Single Visual condition, as previous findings have shown that a single weak visual target presented under a CFS mask often goes unnoticed, and that if reaction time response is made to its detection it tends to be slow [29].…”

“…The body of literature has overwhelmingly showed that there are behavioural benefits associated with audio-visual stimulation in both healthy observers [1,3,[5][6][7][8][19][20][21] and patient groups [2,[29][30][31]. However, some aspects of how visual awareness is affected by the temporal relationship between signals has yielded discrepant results, specifically when an auditory signal precedes a visual target.…”

Spatial attention modulates multisensory integration: The dissociation between exogenous and endogenous orienting

“…The goal of the present study was to systematically investigate the effect of spatial attention on MSI through two experiments and determine whether and why there were opposite effects of exogenous and endogenous orienting on MSI. We replicated a well-known multisensory advantage (Cederblad et al, 2021; Hershenson, 1962; Lunn et al, 2019; Tang et al, 2016), i.e., faster responses to multisensory stimuli than to unisensory stimuli (Figures 2 and 5). Furthermore, as expected, we found that exogenous and endogenous orienting induced by the directionality and predictability of the cue modulated MSI differently.…”