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).