A set of stimuli from Gerda Smets’ tests of visual complexity. The second row from the top shows approximately a 20 percent level of complexity.
In 1973, the psychologist Gerda Smets ran experiments using electrodes on the scalp (known as electroencephalography, or EEG) to record the level of brain activity produced by exposure to different patterns. She noted that the brain shows the largest response to patterns with about a 20 percent level of complexity.
Newborns will stare for longer at patterns with about 20 percent complexity than they will at others. The biologist E.O. Wilson suggested that this preference might give rise to a biologically-imposed universal beauty in human art:
It may be a coincidence (although I think not) that about the same degree of complexity is shared by a great deal of the art in friezes, grillwork, colophons, logographs, and flag designs…The same level of complexity characterizes part of what is considered attractive in primitive art and modern art and design.
… Once Smets concluded her experiments, she asked participants which images they preferred. There she found no consensus. A larger brain response to 20 percent complexity did not predict anything about her subjects’ aesthetic preferences, which were distributed across the spectrum. When it comes to judging visual beauty, there are no hard-and-fast biological rules.