I recently submitted this research proposal to the University of Pittsburgh in order to obtain some funding and the opportunity to present my findings at a University symposium and possibly other, larger get-togethers. I include it here as a roundabout way of describing some of the work that I do as a researcher. -SM
By Sean Moore, Undergraduate Researcher, Sensory Motor Integration Laboratory
When we first learn about the basics of our senses, those five fundamental pathways of assessing our outer world, we learn of their independence from one another. Smell is smell, sight is sight, touch is touch. Each allow us to know and view our world in a fundamentally different way, each gives us a wholly unique experience of interacting with the world, and each pathway distinctive so that our perception can properly influence our decisions. We don’t, as normal, healthy human beings, hear colors, after all; nor do we taste shapes.
However, the cognitive regions of the brain, in all of their expansive and interconnected glory, rarely work as independent systems assessing distinct sensory stimuli. Rather, perception itself is a richly entwined process in which information obtained from one path can be utilized to short-circuit the calculations another route must make. The result is faster, smoother decisions, actions, and updates about the world around us, and we use it all the time: close your eyes for a second and hunt for that beloved mug of coffee on your desk – careful, don’t spill! We are entirely capable of finding the handle, but the action is accomplished in several short jagged burst of motion. But when we open our eyes, and combine our rich visual information, we intercept that steaming vessel with fluidity and pinpoint accuracy.
This integrative ability of the mind is nothing short of astounding. And yet this capacity for cross-talk between sensory centers also gives rise to some fascinating phenomena; cases in which the mind deludes itself, sensing two distinct pieces of information and yet perceiving another that is wholly independent of either. One such phenomenon is known as the McGurk-MacDonald Effect. Discovered accidentally when a videographer in the lab mistakenly produced a clip “in which repeated utterances of the syllable (ba) had been dubbed on to lip movements for (ga), normal adults reported hearing (da).”1 At the time, the implications were enormous: it was entirely unknown that, prior to the film faux pas, that visual processing influenced auditory perception in any way.
While McGurk and MacDonald’s research shed light on a topic that has been explored in-depth about this parallel engagement of sensory processing, little has been elucidated as to precisely what elements of the visual field are altering the speech recognition capabilities of the mind. Is it the disconnect between the micro-expressions of syllable formation and auditory register? Or does the mere sight of the speaker in the corner of your eye, without any conscious ability to read the words on the speaker’s lips induce the effect? It is not clear what fundamental components of the visual stimulus are truly necessary in tricking our mind, and what protions are wholly extraneous.
In analyzing this affect of vision on the perception of sound, subjects will be presented with the visual stimuli in ever increasing ranges of their peripheral vision, and will be asked to relate what they hear. As these tasks arc further into the visual hemisphere, the visual acuity of subjects will be tested by evaluating their ability to discern geometrically similar letters from one another. By comparing one’s relative visual acuity in the periphery to the extent of which the mind is fooled by the trick, it should become clear at what point, if at all, the lack of visual detail extinguishes this audio-visual phenomena.
While the experiment is almost childishly simple, it aims to shed light on some exceedingly intricate neural connections. It may be discovered that this phenomenon is not contained in the higher-level centers of the visual and auditory centers, but may instead be an ingrained connection between vision and speech that arises prior to, and even influences our conscious perception of the illusion. More importantly, this research allows the chance to investigate the underpinnings of one of the many fascinating paradoxes of the mind. It is these things that have in the first place asked to consider “What is it about me that causes this?” Answering these small riddles, in turn, gives great joy in knowing that, in some small way, our understanding of our fundamental existence has been furthered.
McGurk, H & MacDonald, J. “Hearing Lips and Seeing Voices”. Nature, vol. 264, pg. 746-8. 1976. ↩
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