...Taylor ran experiments to gauge people’s physiological response to viewing images with similar fractal geometries. He measured people’s skin conductance (a measure of nervous system activity) and found that they recovered from stress 60 per cent better when viewing computer images with a mathematical fractal dimension (called D) of between 1.3 and 1.5. D measures the ratio of the large, coarse patterns (the coastline seen from a plane, the main trunk of a tree, Pollock’s big-sweep splatters) to the fine ones (dunes, rocks, branches, leaves, Pollock’s micro-flick splatters). Fractal dimension is typically notated as a number between 1 and 2; the more complex the image, the higher the D.
Next, Taylor and Caroline Hägerhäll, a Swedish environmental psychologist with a specialty in human aesthetic perception, converted a series of nature photos into a simplistic representation of the landforms’ fractal silhouettes against the sky. They found that people overwhelmingly preferred images with a low to mid-range D (between 1.3 and 1.5.) To find out if that dimension induced a particular mental state, they used EEG to measure people’s brain waves while viewing geometric fractal images. They discovered that in that same dimensional magic zone, the subjects’ frontal lobes easily produced the feel-good alpha brainwaves of a wakefully relaxed state. This occurred even when people looked at the images for only one minute.
EEG measures waves, or electrical frequency, but it doesn’t precisely map the active real estate in the brain. For that, Taylor has now turned to functional MRI, which shows the parts of the brain working hardest by imaging the blood flow. Preliminary results show that mid-range fractals activate some brain regions that you might expect, such as the ventrolateral cortex (involved with high-level visual processing) and the dorsolateral cortex, which codes spatial long-term memory. But these fractals also engage the parahippocampus, which is involved with regulating emotions and is also highly active while listening to music. To Taylor, this is a cool finding. ‘We were delighted to find [mid-range fractals] are similar to music,’ he said. In other words, looking at an ocean might have a similar effect on us emotionally as listening to Brahms.
But why is the mid-range of D (remember, that’s the ratio of large to small patterns) so magical and so highly preferred among most people? Taylor and Hägerhäll have an interesting theory, and it doesn’t necessarily have to do with a romantic yearning for Arcadia. In addition to lungs, capillaries and neurons, another human system is branched into fractals: the visual system as expressed by the movement of the eye’s retina. When Taylor used an eye-tracking machine to measure precisely where people’s pupils were focusing on projected images (of Pollock paintings, for example, but also other things), he saw that the pupils used a search pattern that was itself fractal. The eyes first scanned the big elements in the scene and then made micro passes in smaller versions of the big scans, and it does this in a mid-range D. Interestingly, if you draw a line over the tracks that animals make to forage for food, for example albatrosses surveying the ocean, you also see this fractal pattern of search trajectories. It’s simply an efficient search strategy, said Taylor.
‘Your visual system is in some way hardwired to understand fractals,’ said Taylor. ‘The stress-reduction is triggered by a physiological resonance that occurs when the fractal structure of the eye matches that of the fractal image being viewed.’