Redundant visual signals reduce the intensity of alcohol impairment

Background: Humans interact with multiple stimuli across several modalities each day. The "redundant signal effect" refers to the observation that individuals respond more quickly to stimuli when information is presented as multisensory, redundant stimuli (e.g., aurally and visually), rather than as a single stimulus presented to either modality alone. Studies of alcohol effects on human performance show that alcohol induced impairment is reduced when subjects respond to redundant multisensory stimuli. However, redundant signals do not need to involve multisensory stimuli to facilitate behavior as studies have shown facilitating effects by redundant unisensory signals that are delivered to the "same sensory" (e.g., two visual or two auditory signals). Methods: The current study examined the degree to which redundant visual signals would reduce alcohol impairment and compared the magnitude of this effect with that produced by redundant multisensory signals. On repeated test sessions, participants (n = 20) received placebo or 0.65 g/kg alcohol and performed a two-choice reaction time task that measured how quickly participants responded to four different signal conditions. The four conditions differed by the modality of the target presentation: visual, auditory, multisensory, and unisensory. Results: Alcohol slowed performance in all conditions and reaction times were generally faster in the redundant signal conditions. Both multisensory and unisensory redundant signals reduced the impairing effects of alcohol compared with single signals. Conclusions: These findings indicate that the ability of redundant signals to counteract alcohol impairment does not require multisensory input. Duplicate signals to the same modality can also reduce alcohol impairment.