Monday, September 21, 2015

Your Basal Ganglia Don’t Like Brown

My favorite color is blue. Blue like Lake Michigan; like Cerulean Blue, the best type of crayon; like the color of my favorite stuffed animal that I accidentally left on an airplane headed to Amsterdam when I was little; like the sneakers I wore to pieces as a kid.
But why do we have favorite colors? There are a few good places to start in considering that question, including the list of associations I rattled off above. In general, color preference is influenced by personal experience, cultural upbringing and evolutionary history. Experience and culture play a significant role in the development of color preferences—for instance, getting the stomach flu after drinking an orange soda may ruin orange drinks forever, and while in the U.S. white wedding dresses are the norm, other cultures assign different values to the color white, such as mourning. Acknowledging these elements, I’d like to focus on the evolutionary side of color, and with it a sometimes overlooked emotion: disgust.

An evolutionary perspective is an interesting one that also leads to some particularly intriguing tangents. From an evolutionary standpoint, it makes sense why humans have developed aversions to certain groups of colors and attractions to others: survival. There’s a reason few young kids are interested in drab brown sneakers or grayish-green crayons. Those colors more often seen as ugly are ones that are associated with harmful substances such as rot and animal waste, note psychologists Stephen Palmer and Karen Schloss. On the other hand, more attractive colors such as bright, clear blues are associated with valuable items or resources, for instance, clean water.

One factor in determining color preference is, naturally, color aversion—what colors get weeded out? The emotion of disgust is an important factor in survival in that it tells us what to avoid and, as described above, is often linked with color. As researcher and writer Dr. R. Douglas Fields comments, brown tomato juice seems significantly less appealing than the same juice dyed red, simply because of a person’s evolutionary history and learned associations with brown and red objects. Disgust is an emotion of evasion, featuring a characteristic facial expression—a wrinkled nose and brow and a turned-down mouth—that mimics the expression preceding retching. It can also elicit a shudder response or prompt you to stick out your tongue; all these physiological reactions have the goal of getting whatever the disgusting trigger may be as far from you as possible.

While disgust, like other emotions, is likely processed throughout a large network in the brain, rather than in one specific region, two groups of structures have been identified as being particularly important in that processing: the insula and the basal ganglia. The mammalian insular cortex is a small lobe tucked away deep in the Sylvian fissure, which separates the frontal and parietal lobes from the temporal lobe. The basal ganglia, on the other hand, are a set of structures around the thalamus, including the caudate nucleus, putamen, and globus pallidus, that are largely known for their role in the coordination of movement. Researchers at the INSERM Institute in France provided evidence for the role of the insula in the processing of disgust by studying epilepsy patients who had implanted electrodes in preparation for surgery to relieve their condition. The researchers noticed that specific neurons in the insulae were activated when the subjects viewed pictures of disgusted expressions.

Dr. Reiner Sprengelmeyer explored the role of the basal ganglia in disgust in his examination of studies performed with patients suffering from Huntington’s disease, which causes degeneration of basal ganglia structures. Sprengelmeyer explains that several studies have found that Huntington’s patients have difficulty recognizing disgusted faces, as well as vocal stimuli expressing disgust. While the results are not indisputable, he concludes that assessments evaluating the recognition of emotions could be a useful diagnostic tool.

Psychologist Dr. Paul Ekman at one point describes emotions as “having evolved through their adaptive value in dealing with fundamental life tasks,” a wonderfully practical description of sometimes seemingly arbitrary states of mind. The existence of favorite colors, and more generally color preference, provides an interesting insight into the value of disgust and attraction and the mechanisms beneath them. Perhaps my love of the color blue goes beyond a childhood stuffed animal to the evolutionary roots underlying our species.

—Kate Oksas


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