Multisensory processing in the redundant-target effect: A behavioral and event-related potential study

Abstract

In a typical redundant-target experiment, participants are asked to respond to events of two modalities, which are presented either alone or simultaneously (Miller, 1982). Combined (bimodal) stimuli are called redundant because the same reaction is required for both targets, irrespective of their modality. Reaction times (RTs) to redundant targets are commonly found to be shorter than RTs to simple (unimodal) targets. Two alternative models have been suggested to explain this redundant-target effect (RTE). Separate activation models, or race models, hold that the two components of a bimodal event are processed in separate channels and that the channel that has first finished processing first triggers the response. By analogy, the probability of obtaining a six is higher when two dice are tossed instead of one. Similarly, the probability of getting an RT, t, lower than a given t 0 is higher for bimodal (e.g., auditory-visual, AV) than for unimodal (A or V) stimuli, resulting in a lower mean RT. This effect has been called statistical facilitation (Raab, 1962; see Figure 1). Given the RT distributions to simple stimuli, the redundancy gain that can be explained by statistical facilitation has a clearly defined upper limit, which is described by the race model inequality (Miller, 1982):A race model requires that this inequality should hold for the cumulative RT distributions for both unimodal and bimodal stimuli. If the redundancy gain surpasses that predicted by the race model, rejecting the race model in favor of a coactivation model is justified. Proponents of the latter model disagree with the separate processing view and suggest that information from the two modality channels is integrated at a particular processing level and subsequently processed as a combined entity. This processing stage gains from redundant information, resulting in faster responses to redundant stimuli.The race model is typically sufficient to explain the redundancy gain of healthy participants in simple unimodal detection tasks with two classes of visual stimuli (see, e.g., Corballis, 1998Corballis, , 2002; a weak violation was found by Miniussi, Girelli, & Marzi, 1998, which was, however, not statistically tested). Surprisingly, split-brain patients have displayed redundancy gains larger than those predicted by the race model when bilateral stimuli have been used (Corballis, 1998(Corballis, , 2002Reuter-Lorenz, Nozawa, Gazzaniga, & Hughes, 1995;Roser & Corballis, 2002 Participants respond more quickly to two simultaneously presented target stimuli of two different modalities (redundant targets) than would be predicted from their reaction times to the unimodal targets. To examine the neural correlates of this redundant-target effect, event-related potentials (ERPs) were recorded to auditory, visual, and bimodal standard and target stimuli presented at two locations (left and right of central fixation). Bimodal stimuli were combinations of two standards, two targets, or a standard and a target, presented either from the same or from diff...

A neural network model of multisensory integration also accounts for unisensory integration in superior colliculus

“…Another possibility is that the differing products of multisensory and unisensory integration properly reflect the pooling of information from two independent sources in the former, and the covariance between information sources in the latter. In either case, these data speak to an important caveat in the interpretation of multisensory enhancements as being produced by a "redundant targets effect" (e.g., Miller, 1982;Gondan et al, 2005;Leo et al, 2007;Lippert et al, 2007;Sinnett et al, 2008), as redundant targets from the same sensory modality do not yield equivalent enhancements either physiologically or behaviorally.…”

Verbal-Spatial Cue Conflict: Implications for the Design of Collision-Avoidance Warning Systems

“…This finding indicates that having redundant information can actually speed reaction time (i.e. both verbal and nonverbal/spatial directional cues provide the same information), which is supported by research on multi-modal redundant targets (Bolia, et al, 1999;Gondan, et al, 2005;Tannen, et al, 2004). However, the study did not investigate the effect of an incongruent, or conflicting verbal-spatial directional cue.…”

“…Collision avoidance warning systems are an important component of this effort (Ho & Spence, 2005;Wang, Pick, Proctor, & Ye, 2007). The most effective means by which to alert drivers remains a point of debate, but research has shown that spatial auditory cues speed reaction time to stimuli and that multi-modal directional cues can speed reaction time even further (Bolia, et al, 1999;Gondan, et al, 2005;Tannen, et al, 2004). As a result, much research in this field has focused on the spatial nature and modality of warnings.…”

Impact of contingency manipulations on accessory stimulus effects

“…Such intersensory facilitation effects are quite robust, and they have been replicated in many different settings. For example, intersensory facilitation has been reported in tasks such as Todd's, in which participants must respond to stimuli from any modality (e.g., Diederich & Colonius, 2004;Gondan, Niederhaus, Rösler, & Röder, 2005;Hershenson, 1962;Miller, 1991). Intersensory facilitation has also been reported when instructionally irrelevant accessory stimuli on one modality (i.e., stimuli to which participants need not respond) are presented simultaneously with relevant target stimuli on another modality, especially when the irrelevant accessories are auditory stimuli (Bernstein, 1970;Doyle & Snowden, 2001).…”

“…In order to investigate the impact of contingency manipulations on accessory stimulus effects, we used a visual simple RT task with target stimuli presented to the left of fixation, to the right of fixation, or both-a task that has often been studied to learn about redundancy gain in divided attention tasks (e.g., Corballis, 2002;Gondan et al, 2005;Miller, 1982Miller, , 1986Mordkoff & Miller, 1993;Schröger & Widmann, 1998). In single-target trials, a single rectangle was presented either to the left or to the right of fixation; in redundant-target trials, both rectangles were presented.…”