Though we have spent the majority of this module covering the senses individually, our real-world experience is most often multimodal, involving combinations of our senses into one perceptual experience. This should be clear after reading the description of walking through the forest at the beginning of the module; it was the combination of senses that allowed for that experience. It shouldn’t shock you to find out that at some point information from each of our senses becomes integrated. Information from one sense has the potential to influence how we perceive information from another, a process called multimodal perception.
Interestingly, we actually respond more strongly to multimodal stimuli compared to the sum of each single modality together, an effect called the super additive effect of multisensory integration. This can explain how you’re still able to understand what friends are saying to you at a loud concert, as long as you are able to get visual cues from watching them speak. If you were having a quiet conversation at a café, you likely wouldn’t need these additional cues. In fact, the principle of inverse effectiveness states that you are less likely to benefit from additional cues from other modalities if the initial unimodal stimulus is strong enough (Stein & Meredith, 1993).
Because we are able to process multimodal sensory stimuli, and the results of those processes are qualitatively different from those of unimodal stimuli, it’s a fair assumption that the brain is doing something qualitatively different when they’re being processed. There has been a growing body of evidence since the mid-90’s on the neural correlates of multimodal perception. For example, neurons that respond to both visual and auditory stimuli have been identified in the superior temporal sulcus (Calvert, Hansen, Iversen, & Brammer, 2001). Additionally, multimodal “what” and “where” pathways have been proposed for auditory and tactile stimuli (Renier et al., 2009). We aren’t limited to reading about these regions of the brain and what they do; we can experience them with a few interesting examples (see Additional Resources for the “McGurk Effect,” the “Double Flash Illusion,” and the “Rubber Hand Illusion”).