Is my reality the same as your reality?

By: Tatiana Yunadi

You've probably heard of the age-old question - do people perceive colors in the same way, or is their interpretation of "blue" secretly different? While this raises an interesting philosophical question on epistemology, the neurological condition of synesthesia may offer another insight into the underlying question at hand. This phenomenon could be described as an overlap of senses, where individuals perceive one input in multiple ways.

One of its most common forms is grapheme-color synesthesia: perceiving letters and numbers as being colored in consistent, specific ways. A grapheme-color synesthete could see the letter L as orange, for example. There are associators, who see affiliations in their “mind’s eye”, and projectors who see the colors directly on physical graphemes. Interestingly, individuals with this condition do not typically report seeing the same colors in letters and numbers, with most of the research revealing “random” associations between the two senses. Even within their own demographic, they perceive the external world in different shades and hues. To another synesthete, L could be obviously blue, instead. 

Yet, Brang et al.’s study examines large groups of synesthetes, which reveal some commonalities in associations between individuals. They posit that the interaction arises from early perceptual mechanisms while learning alphabets and numbers, prior to the onset of literacy. This raises interesting questions on whether there are commonalities in how the human mind experiences features of graphemes (lines, curves, width) in association with colors – and what could cause these affiliations to differ.

Perceptory conditions are telling of the subjective nature of reality, as the human mind constructs it to be. In a paper studying how psychedelics affect brainwave patterns, Carhart-Harris offers evidence backing the Anarchic and REBUS brain models. These theories suggest that each individual's brain constructs a working model of the external world through 'shortcuts' that they have learned and are continuing to refine. The brain is the human body's most energy-extensive organ, so cognitive shortcuts are useful in limiting expenditure. The tendency towards cognitive biases are part of our biology; they are so ingrained that we may even subconsciously behave in ways that confirm our preexisting ideas.

It doesn't take a neurological condition to perceive the world differently from reality; we are easily deceived by optical illusions. Our brains simulate perceptions based on predictions, and errors help to recalibrate models. Bayesian theory suggests that the brain undergoes a calculation of strength of prior beliefs that may influence interpretations of external stimuli. The posterior, or your internal experience, is a result of the two interactions. We generate models of reality based on 'priors', and as such, our own internal experiences are inherently biased to some extent.

For some individuals who have sustained highly negative stimuli, such as abuse or other traumatic events, the strength of their priors are higher. Just as a synesthete's letters may differ from another's, your blue may not be my blue, and a hug could be interpreted as a hostile act. The gaps in between our understandings of the world is a palpable one, even if its full extent can never be captured; and there's something so human about our inclination to try and capture or express our experiences.

References:

Brang, R. (2011). Similarly shaped letters evoke similar colors in grapheme–color synesthesia. Neuropsychologia, 49(5), 1355–1358.
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Carhart-Harris, F. (2019). REBUS and the Anarchic Brain: Toward a Unified Model of the Brain Action of Psychedelics. Pharmacological Reviews, 71(3), 316–344.