On beauty

Beauty, we may assume, has fascinated mankind from its earliest beginnings. As the Oxford Dictionary tells us, beauty is ‘a combination of qualities [. ] that pleases the aesthetic senses, especially the sight’ (Oxford Dictionary 2013). The Italian novelistphilosopher Umberto Eco explained the ‘History of Beauty’ (Eco 2004) throughout the ages to a wider audience. Although highly debated in professional circles, he did bring the concept from art history to the lay public. Not only does Eco follow descriptions and depictions through the ages, but carefully differentiates beauty from attraction and the desire to possess. Although he includes examples from literature and poetry, beauty appears mainly as a visual concept, and critics praise the book for its illustrative examples. Where do we encounter the concept of beauty in physiology? Following the ancient greek tradition, beauty was seen by many a father of modern physiology in the insights that let puzzle pieces fall into place, in experiments whose results, in often unexpectedly simple setups, suddenly unite previously suspected ideas and generate beauty in the coherence of their results. Johannes M€ uller, in the introduction to his work on the law of specific energies of the sense, describes the recognition of the mere beauty in all living things and warns physiologists to not disregard it (M€ uller 1826). On the other hand, this very book may be seen as one important cornerstone on our way towards a scientific basis of the perception of pleasant visual impressions. Until relatively recently, the study of (human) beauty through neurophysiological means was not undebated. In 1932, Arthur Sewell’s ‘Physiology of Beauty’ was met with caution, if not openly rejected: on the one hand, he was praised for ‘applying to aesthetic responses any methods of analysis comparable with those in pure science’, although this approach had so far been ‘ridiculed by the antimechanists’ (ALB 1932). The reviewer for Nature Magazine further argued that it must be realized that ‘the enjoyment of [. ] arts will in no wise be impaired by correct analysis of this enjoyment’ (ibid). Other reviews were far less pleasant, seeing the work as an open attack towards a sphere that inherently belonged to the humanities, especially philosophy (Reld 1932). Less than a century later, the detailed study of not only the perception of beauty and pleasantness, but also of the scientific basis of beauty-based romantic interactions has become rather customary in the scientific literature (Kawabata & Zeki 2004, Ishizu & Zeki 2011, Cooper et al. 2012, Jacobs et al. 2012, K€ uhn & Gallinat 2012). Insights from the study of aesthetic perception have almost become common knowledge: Students do not need to major in Biology to learn about the human preference for (facial) symmetry, which indicates an absence of genetic defects (Little et al. 2011). In the 1870s, Francis Galton observed the increased attractiveness of composite portraits generated from an overlay of photographic images of a number of individuals who, one by one, would not have been regarded as exceptionally beautiful (Galton 1878). Koinophilia, that is, a preference for partners who do not have any unusual, peculiar or deviant features, has been described across species and cultures (Koeslag 1990). Another factor that seems to determine human beauty is sexual dimorphism, which has been linked to reproductive potential (Jasienska et al. 2004), and is not only shown in the society pages of the tabloids on a daily basis, but has already been discussed in the Daily Mail (Utton 2004). Interestingly, some human features are not consistently considered beautiful over time, for example body mass, whose increase is still poorly understood and becoming a major health hazard (Helge et al. 2011, Meyer et al. 2011, Tesauro & Cardillo 2011, Nduhirabandi et al. 2012, Vella et al. 2012). We are drawn, it seems, towards the average, the symmetric and the (sexually) well-defined. What is more, one may ask, what is new? And which techniques and insights have let us learn more about the neural basis of visual aesthetic pleasure to let publications surge during the last decade? Functional imaging has advanced our knowledge on the neural correlates of aesthetic impressions, that is, fMRI (Ishizu & Zeki 2011, Jacobs et al. 2012) or PET (K€ uhn & Gallinat 2012). Understanding of neurovascular coupling processes therein enables exact imaging of neuronal activity (Lecrux & Hamel 2011). Recent studies, and it is pleasing to see that many in this line have been published in Acta Physiologica, have contributed to our general understanding of sensory inputs, often in unexpected contexts (Akiba & Kaunitz 2011, Holzer 2011, Iwatsuki et al. 2012, Kinnamon 2012). Although most sensory inputs do not reach the conscious mind, input and processing in