Friday, December 11, 2020

Three Stages of Vision

Vision doesn't occur passively. It's active, constructive, and largely unconscious.

And it doesn't happen all at once. Sometimes it takes a half second to process an image, and sometimes it takes a second or two. 

The light entering our eyes is translated and organized in stages, beginning with simple visual elements and proceeding to higher levels of interpretation. These stages of image processing start in the retina and continue in different parts of the brain.

For us to be able to see the flying white horses, our brain must segment the image and relegate the dark red shapes to the background, rather than vice versa. 

This kind of sorting normally happens unconsciously, but it's easy to intentionally flip the one set of horses from figure to ground and back again. 

Identifying the figure as a mythological flying horse and the whole pattern as a piece of art by M.C. Escher is the final and most sophisticated stage in image processing, involving several areas of the brain.

Eric R. Kandel et al., authors of a textbook on the Principles of Neural Science, describe the process this way:

"The brain analyzes a visual scene at three levels: low, intermediate, and high. At the lowest level, visual attributes such as local contrast, orientation, color, and movement are discriminated. The intermediate level involves analysis of the layout of scenes and of surface properties, parsing the visual image into surfaces and global contours, and distinguishing foreground from background. The highest level involves object recognition. Once a scene has been parsed by the brain and objects recognized, the objects can be matched with memories of shapes and their associated meanings."

Book: Principles of Neural Science by E.R. Kandel, et al.


Diane Greene said...

I always see the white horses first.

Micah said...

This is fascinating. (Thank you. I just ordered the book.) There is another layer to this.

Right now, I am reading the book The Weirdest People in the World, which discusses how people from Weird (i.e. western, industrialized educated, rich, democracies) cultures process information differently. According to the book, when literate people look at painting, they immediately break down the work into its component parts. But, when non-literate people look at an image, they take in the whole image THEN explore it with greater detail.

European audiences for paintings did not become widely literate until the mid-eighteenth century. This would mean that the way you and I experience paintings today is different than how audiences would often read Titian, Rubens, Velázquez, and others. It also may go some way in explaining why some nineteenth-century painters (e.g. Alma Tadema and the Pre-Raphaelites) found audiences for an approach that largely de-emphasized broad patches of color to ones that were filled with detail. Right now, it is just a thought. I hope to explore it more or see someone else do the research.