Illustration by Gluekit.

Why is something beautiful? David Hume argued that beauty exists not in things but "in the mind that contemplates them." And everyone has at some point heard the old saw that beauty is in the eye of the beholder. But Plato had a fanciful answer made to argue for a universal truth: In his world of forms, he claimed there existed a perfect Form of Beauty, which was imperfectly manifested in what we call beautiful. Despite the allure of Plato's metaphorical claim, students of aesthetics have struggled to substantiate it. Evolutionary psychologists have argued that there exist quantifiable, describable, universal aspects to the human capacity for appreciating beautiful forms, perhaps originating in our ancestors' experience on African savannas or in the need to find suitable mates. They have not solved the problem. However, recent work by several researchers at University College London — including the establishment of the first major grant-driven research program for the neurobiological investigation of aesthetics, or neuroaesthetics — has made the first steps toward a unified biocultural theory of art. An object's beauty may not be universal, but the neural basis for appreciating beauty probably is. The researchers' initial discoveries and the increasing formalization of the field promise to open the way for the first time to an understanding of beauty based on something other than speculation.

The first studies of aesthetics and the brain began with the sort of self-experimentation that science doesn't encourage anymore. In the 1920s neurologist Heinrich Klüver documented the hallucinations he experienced while under the influence of mescaline, using four categories: grids, zigzags, spirals, and curves. Noting their similarity to the hallucinations experienced in various conditions, such as migraine, sensory deprivation, and the hypnagogic state that occurs in the transition from wakefulness to sleep, he named them "form constants." These motifs do indeed seem to be constant — they recur throughout history and across cultures, and can be seen, for example, in prehistoric cave paintings, in the girih patterns of the tile mosaics decorating medieval mosques, and in the repeating tessellations of M.C. Escher's impossible figures or the rectangular forms of Mondrian's Compositions. Underlying those patterns, at least in part, are the intrinsic properties of the visual nervous system. Most neurons in the primary visual cortex occur in repeating structures called ocular dominance columns; these in turn are organized into hypercolumns, whose long-range interconnections are arranged geometrically. The spontaneous activity of these neural networks gives rise to the patterns Klüver studied.

The "uglier" a painting, the greater the motor cortex activity, as if the brain was preparing to escape.

Such investigations of the biology of aesthetics, however, had heretofore not been anyone's primary research focus; rather, the investigations have been subordinated to some other work, such as modelling the visual system. Semir Zeki of University College London is pioneering modern neuroaesthetics, and, thanks in part to a £1 million grant from the Wellcome Trust in the UK last autumn, is forging ahead with a research program that tries to establish the neurobiological underpinnings for creativity, beauty, and even love.

Zeki's work has been ongoing for several years. In 2004 he led a neuroimaging study designed to investigate the neural correlates of beauty. Ten participants were shown 300 paintings and asked to classify each of them as beautiful, ugly, or neutral. Paintings rated as beautiful by some of the participants were rated as ugly by others, and vice versa. The participants were then shown the paintings again while lying in a scanner. "Beautiful" paintings elicited increased activity in the orbito-frontal cortex, which is involved in emotion and reward. Interestingly, the "uglier" a painting, the greater the motor cortex activity, as if the brain was preparing to escape. More recently, Zeki has started to collaborate with scholars from the arts and humanities under the guidance of a multidisciplinary advisory board that includes author A.S. Byatt and Jonathan Miller, a physician and opera producer.

Richard Morris, head of neuroscience and mental health at the Wellcome Trust, says Zeki's work "gives insight into what it is to be human." And according to Wellcome senior scientist John Williams, could reveal some of the underpinnings of conditions, such as depression, that are marked by a reduced aesthetic sense.

Elsewhere at UCL, neuroscientist Hugo Spiers is investigating how the brain encodes direction, location, and the dimensions of space — the implications for architecture could be profound. Spiers recently collaborated with artist Antoni Malinowski and architect Bettina Vismann on a project that aimed to explore the relationship between art, architecture, and the brain. Funded by the Wellcome Trust, the project resulted in an installation calledNeurotopographics, which tracked the relationship between movement though space and the activity of the brain. "When someone traverses a space, their brain produces an oscillating, rhythmic pattern," Spiers explains. "We tried to realize this abstract understanding into an everyday reality."

As for architecture, altering space can have a large impact on brain function. Changing the dimensions of an animal's enclosure causes grid cells to alter their scales accordingly, such that the periodicity of their firing, which is observed as the animal moves across a space, increases or decreases. Surprisingly, negotiating a corridor in opposite directions elicits completely different patterns of place-cell activity, so the same space is apparently encoded as two different places. A less surprising but still important finding is that the lack of easily recognizable landmarks causes disorientation. Spiers and his colleagues are now investigating how the brain encodes three-dimensional space. While recording neuronal activity as rats negotiated a spiral staircase, they found that place cells, but not grid cells, respond to changes in height. Thus, the brain seems to encode the vertical and horizontal dimensions in different ways.

Such knowledge of spatial cognition provides an understanding of the brain's response to the built environment and can inform architects as they consider the aesthetic elements and function of a space. "From an architectural point of view," says Vismann, "I find the correspondence between what occurs in the brain and the physical nature of space and spatial navigation fascinating." She expects that understanding the neural bases of spatial perception will inspire projects, inform the design process, and help formulate ways of organizing space.

Future work may elucidate the long-term effects of one's surroundings on brain function and the relationship between aesthetically pleasing spaces and their functionality. What one considers beautiful is, of course, influenced by culture, learning, and experience, and not everything we find beautiful will ultimately be traceable to the structure and function of our brain. The larger question "What is beauty?" still poses a major challenge, but answering it no longer seems so impossible.