Recently, the topic of “art” came up in my Perception unit. Visual art, specifically.

What is “art”? What isn’t “art”? Who gets to make the distinction? The beholder, the artists themselves, or trained experts and critics?

[The discussion then turned to a superficial critique of subjectivity, relativity, and (perhaps inevitably) postmodernism. I don’t want to debunk this critique in this post. It’s a long and involved topic that comes up quite often when people from traditional scientific professions (and not only) try to tackle new-fangled non-scientific concepts. I’d like to discuss this in a separate entry when I get the time.]

So…art. I think it’s particularly interesting and relevant to discuss visual art as part of a discipline that deals primarily with vision. Vision is one of the earlier- and rapidly-developing senses, and many of its functions develop substantially within the first 6 months after birth (such as binocularity, colour vision, fixation, peripheral vision, visual acuity)1. Fully-abled adults use 40%-50% of the cortex in different kinds of visual processing2, which is more than any other sense.

What is really interesting about vision (and other senses) is how subjective and relative it actually is.

One of the most intriguing facts about visual perception is that as sensory information goes from the eyes to the cortex (bottom-up processing), top-down processing also occurs: previously-acquired information is added to our perception processing, mediating our (re)action. Visual information is also integrated with other sensory input such as sound, information from the vestibular system, etc. This can result in quite different reactions to visual stimuli in different people – ranging from conscious reaction (“I like/dislike this because it reminds me of X”), to harder-to-trace feelings (a certain image/colour evokes a certain mood), to autonomic arousal (for example, an increase in heart rate when trauma-specific images are seen by people who have experienced or witnessed trauma), to motor (sometimes reflexive) actions (blinking, ducking).

Differences also occur at the “bottom-up” level of perception – in the general mechanisms and components of the sensory organs.

I don’t claim that while one person sees the sky as blue, another sees it as octarine-coloured3; or that where I see a dog, you might see an elephant (although it’s true that where I might see a rabbit, you might see a duck). The intra-species differences (even accounting for colourblind, brain injured, psychotic-disordered, or hallucinogen-consuming parts of the population) are minute compared to inter-species differences. While most animals are sensitive to light, they respond to different wavelengths (some animals can sense infrared or ultraviolet light, for example). Humans are sensitive to specific (and pretty narrow) frequency ranges when it comes to light and sound, so inter-personal differences are still bound to our perceptual ranges.

So, while keeping these ranges in mind, here are some of the tricky ways in which visual perception operates. Vision works primarily by locating the edges in an image and filling in the rest, rather than by taking an accurate “snapshot” of the world around us (as some may think). It is quite selective – our peripheral vision is not very good, and even as we “take in” an image, many characteristics are discarded along the way (a sort of context-dependent image compression).

Vision is easily fooled by controlling context, as can be seen through illusions and aftereffects4. Change the contrast, the sequence of a number of images, insert gaps in easily-recognisable shapes, move an image closer or further away from the eye, cycle through different colours, and you will start to see things that aren’t there, or miss things that are there.

In addition, there is significant variability in the number of cone photoreceptors of different types in the human retina from human to human. Cone photoreceptors are mostly responsible for colour vision (and certain types of colour blindness), and their differing population means each person sees colours slightly differently. Colour groups, as known in common usage (the different types of “blue”, for example: navy blue, royal blue, electric blue, baby blue, etc) are constructs created by dividing the visible portion of the electromagnetic spectrum into wavelength ranges and by grouping certain lengths/ranges together (often in a culturally-specific way).

Now also add in cornea and lens shape and irregularities, the progressive weakening of cilliary muscles (which control the stretching or relaxing of the lens to achieve focus of the light) over time, and also (less commonly) disorders or injuries that may affect the visual cortex or other parts of the brain involved in sensory processing, and you can see why vision itself can be considered somewhat subjective.

So, in a nutshell:

Q: Do you see what I see?
A: Not exactly.

So, to summarise, even while barely touching on cultural values surrounding certain modes of expression, or socially-sanctioned or frowned-upon forms of art, or on what constitutes transgression/iconoclasm in art, or personal preference as informed by previous experiences, associations and cultural values, we “see” a difference at the most basic level of perceiving visual information.

No wonder art remains a controversial topic when we can’t even fully assume that what the artist sees is exactly what the viewer/consumer sees is what the art critic sees…

DISCLAIMER: This is my general understanding of how vision works, in a very generic sense. It is not the Word of the Vision Gods, it’s not published elsewhere, and I have not spent years researching and reading about visual perception – so don’t quote me on this, and always do your own research.

1. White, F., Hayes, B., & Livesey, D. (2005). Developmental Psychology. Sydney: Pearson/Prentice Hall.
2. Snowden, R., Thompson, P., & Troscianko, T. (2006). Basic Vision: An Introduction to Visual Perception. Oxford: Oxford University Press.
3. Octarine is Terry’s Pratchett’s imaginary eighth colour, presented in the Discworld series.
4. Here are some great websites on illusions and aftereffects: Akiyoshi’s illusion pages, 84 Optical Illusions & Visual Phenomena and Project LITE.


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