Jump to ContentJump to Main Navigation
Art, Aesthetics, and the Brain$

Joseph P. Huston, Marcos Nadal, Francisco Mora, Luigi F. Agnati, and Camilo José Cela Conde

Print publication date: 2015

Print ISBN-13: 9780199670000

Published to Oxford Scholarship Online: August 2015

DOI: 10.1093/acprof:oso/9780199670000.001.0001

Show Summary Details
Page of

PRINTED FROM OXFORD SCHOLARSHIP ONLINE (www.oxfordscholarship.com). (c) Copyright Oxford University Press, 2017. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a monograph in OSO for personal use (for details see http://www.oxfordscholarship.com/page/privacy-policy). Subscriber: null; date: 22 November 2017

Towards a Comparative Approach to Empirical Aesthetics

Towards a Comparative Approach to Empirical Aesthetics

(p.385) Chapter 20 Towards a Comparative Approach to Empirical Aesthetics
Art, Aesthetics, and the Brain

Gesche Westphal-Fitch

W. Tecumseh Fitch

Oxford University Press

Abstract and Keywords

Aesthetic proclivities should be studied across human cultures if shared building blocks of human aesthetic experience are to be described. Comparisons with animals are crucial to determine which elements of aesthetic experience are shared with other species and which evolved in humans. Abstract patterns have a special status in the evolution of human visual art, pre-dating representational art, and being less complicated by issues of symbolic meaning. Possible mechanisms by which abstract patterns emerged as aesthetic phenomena are discussed. Aesthetic-like phenomena in animals are studied. Perceptual abilities and the ecology/sociobiology of a species are crucial in the evolution of behaviours that have the potential for gaining aesthetic dimensions. Generative process underlying geometric patterns may be described with the same formalisms as musical and linguistic syntax, hence the production of visual patterns may depend on cognitive resources that also underlie the generation of complex hierarchical structures in music and language.

Keywords:   empirical aesthetics, symmetry, nest-building, patterns, abstract art, body ornament

20.1 Introduction

Aesthetic traditions are ubiquitous in human societies and seem to be a human cultural universal, akin to language and music. Empirical aesthetics is emerging as an area of cognitive research on a par with musicology and linguistics in its potential to reveal fundamental properties of the human mind. Empirical aesthetics as we understand it focuses on the processes underlying the interaction of one or more individuals with an aesthetic stimulus (often visual), during both perception and production of the object. An important aim of this research should be to describe and understand the worldwide human drive to create and surround ourselves with objects that are pleasing to one or more of the senses, in a way that goes beyond their immediate utilitarian function.

There is a rich potential for comparative work in aesthetics. First, differentiating cultural-specific features from universally shared elements necessitates studying aesthetic traditions across a wide range of human cultures. This is analogous to searching for and defining universal features present in all languages (e.g. different word classes such as verbs and nouns), versus language-specific features, such as the Chinese tonal system. In addition to cross-cultural comparisons, comparisons across species are required to distinguish those components of the aesthetic process that are uniquely human from those shared with other species and to discover possible examples of convergent evolution.

In this chapter, we consider some common features of human aesthetic traditions with a particular emphasis on early artifacts incorporating non-representational patterns, and we discuss their possible evolutionary origins. Non-representational patterns and ornaments are present in most, if not all, human cultures. However, they are not a typical research focus in empirical aesthetics, where the main focus has been on Western “high art.” From a cross-cultural view, however, it makes sense to study abstract ornamental patterns due to their ubiquity and relative simplicity (cf. Westphal-Fitch et al. 2012; Westphal-Fitch et al. 2013). We therefore emphasize the importance of geometrical and non-representational patterns here.

Biologically, it seems likely that many low-level perceptual components of the aesthetic process are shared with other species, while certain aspects (e.g. production of repeated hierarchically organized patterns) may well be unique to our own. Such features may also (p.386) be present in other human domains such as music or language, with important implications for our understanding of the nature of the human mind. In this chapter, we review literature on symmetry perception and on nest-building in birds, bees, and primates, two areas where we think known similarities and differences between humans and animals concerning aesthetics can be usefully pursued. It is vital to study not only chimpanzees and other primates (Zaidel et al. 2013), but also species that may have evolved traits convergently, for example birds. In particular, we highlight the need to take the ecology and sociobiology of a species into account in order to understand the mechanisms by which pre-existing traits can become exaggerated and gain social importance beyond their immediate function.

20.2 Pervasive issues in aesthetic inquiry

We begin with a short discussion of the historical development of aesthetics, observing that the sharp distinction between ornament and “high art” is a relatively new phenomenon idiosyncratic to Western European cultures. We also consider a tension at the heart of all aesthetic inquiry, namely that between the broad pan-human universality of aesthetic activity and the wide variety of superficial fashions and traditions that may change rapidly in individual cultures and time periods.

20.2.1 Natural and acquired aesthetics: beyond Kant

Although aesthetics began as a purely philosophical discipline, with the advent of Gustav Fechner’s writings introducing an empirical approach to aesthetics (Fechner 1871, 1876) scientists began to gather data on aesthetic behaviors. This makes empirical aesthetics one of the oldest branches of psychology, dating back to the 1870s.

Our modern Western conception of the fine arts as “high art” phenomena, distinct from ornament and craft, is a relatively new one which emerged in eighteenth-century Europe (Kristeller 1990; Shiner 2001). Prior to that, and hence for the vast majority of human history, no strict distinction was made between art and craft, and in many cultures this distinction does not exist (Anderson 1979). The concept of “aesthetics” as a distinctive kind of appreciation specific to art (as opposed to “good taste” which might apply to any number of things) arose at roughly the same time in Europe.

The word “aesthetics” derives from the Greek “aisthetiko,” meaning sentient or sensory (cf. the medical term “anaesthetic”). Aesthetics was first used as a term to describe appreciation of beauty in 1750 by Alexander Baumgarten (Gregor 1983; Shiner 2001). Baumgarten proposed aesthetics as a second cognitive mode that relies on the senses (cognitio sensitiva) in addition to rational thought. In his model, rational thought is independent of sensory input, but cognitio sensitiva relies mainly on input through the senses. Additionally, Baumgartner differentiates between the natural and artificial (acquired) aesthetic sense. While humans are born with a natural aesthetic sense—Baumgarten calls it a natural disposition of the soul for beautiful thought: dispositio naturalis animi ad pulcre cogitandum (Groß 2001, p. 97)—enculturation leads to a refinement of this sense. (p.387) We interpret this natural aesthetic sense that Baumgarten describes as the aesthetic sense that is shared between all humans, regardless of cultural surroundings, while traits specific to a culture are acquired in a later enculturation process (or refinement, in Baumgarten’s terms) during ontogeny.

Beauty for Baumgarten is a cognitive phenomenon in an aesthetically minded perceiver—beauty is perfect perception, and not a property of the object being viewed (Groß 2001). This is reminiscent of David Hume’s famous statement (Hume 1757): “Beauty is no quality in things themselves. It exists merely in the mind that contemplates them; and each mind perceives a different beauty.”

Baumgarten’s original concept of aesthetics crucially attributes the capacity for aesthetic perception to all humans, with the proviso that enculturation can refine this ubiquitous natural aesthetic sense. This contrasts sharply with the very influential concept of aesthetics proposed by Immanuel Kant, presented in Kritik der Urtheilskraft (Critique of Judgement; Kant 1872).

The key concept for Kant is “disinterested contemplation.” Kant posits that a perceiver needs to lack all interest in the object (e.g. the desire to possess it) for a pure aesthetic judgment of the object to be possible (Kant 1872, p. 50):

… so sagt Jedermann: Hunger ist der beste Koch, und Leuten

von gesundem Appetit schmeckt Alles, was nur essbar ist; mithin

beweist ein solches Wohlgefallen keine Wahl nach Geschmack.

Nur wenn das Bedürfnis befriedigt ist, kann man unterscheiden,

wer unter Vielen Geschmack habe oder nicht … Geschmack ist

das Beurtheilungsvermögen eines Gegenstandes oder einer Vorstellungsart

durch ein Wohlgefallen oder Missfallen ohne alles Interesse.

Der Gegenstand eines solchen Wohlgefallens heisst schön.

Our translation: … people say that hunger is the best cook, and

people with a healthy appetite enjoy everything that is edible. Such

pleasure does not evidence a choice based on taste. Only when

the needs are satisfied can one discern who amongst the many

has taste or not … Taste is the ability to judge an object or

a performance with pleasure or displeasure without any interest.

The object of such a pleasure is called beautiful.

Kant’s view takes a highly restrictive position on aesthetic judgment, differentiating between “pure” (what we today might call “objective”) and “impure” judgments, effectively excluding most perceivers. It is also elitist: if such a pure and disinterested judgment is only available to the few people on this planet whose needs are met entirely, then aesthetic judgment is not available to the majority of humans. For an empirical approach to aesthetics (p.388) seeking broad commonalities between humans, Kant’s view implies an overly restricted working model, and Baumgarten’s previous, more inclusive approach is preferable.

A later movement, influenced by the reports of explorers and adventurers describing the art practices of other cultures from around the world, explicitly argued that the aesthetic capacity is fully shared by all humans, as stated by Franz Boas:

In one way or another esthetic pleasure is felt by all members of mankind. No matter how diverse the ideals of beauty may be, the general character of the enjoyment of beauty is of the same order everywhere. The very existence of song, dance, painting and sculpture among all the tribes known to us is proof of the craving to produce things that are felt as satisfying through their form, and of the capability of man to enjoy them.

(Boas 1955, p. 9)

Indeed, the pervasiveness of ornamental objects and patterns and their similarities in symmetry, repetition, and structure gave rise to the notion that common, describable elements might underlie ornament and that ornament could usefully be described in “grammars” (see e.g. Jones 1856). This approach has been greatly expanded in more recent work by Washburn and Crowe (1988).

20.2.2 The multiple purposes of art

Alois Riegl, in his posthumously published Historische Grammatik der bildenden Künste (Historical grammar of the visual arts) (Riegl 1966) emphasized that humans naturally possess a Kunstschaffenstrieb (a drive to create art) (Riegl 1966, p. 217). Riegl differentiates between three purposes (“Zweck”) characterizing all human artifacts: 1. Schmückungszweck (decoration), 2. Gebrauchszweck (use), 3. Vorstellungszweck (imaginative purpose) (Riegl 1966, p. 217). There may be mainly functional creations with little artistic content (e.g. an arrowhead), and almost purely artistic creations with no actual functional purpose other than decoration and/or representation. The intertwining of function and aesthetics in tools is particularly interesting. Some quite early hominid tools, so-called bifaces (or handaxes) first produced about 1.4 million years ago (Mithen 1996), have a high degree of bilateral symmetry which would have required considerable planning and careful execution. The largest specimens weigh well over a kilogram and are 30 centimeters long (Wenban-Smith 2004), and it is not clear that they could have functioned usefully as tools. Both the size and symmetry of these Achulean handaxes have stimulated discussion about aesthetic or social functions (Kohn and Mithen 1999; Mithen 2003; Nowell and Chang 2009) and the concomitant cognitive abilities required to create them (Mithen 1996) early in human cultural development.

20.2.3 Fechner and non-representational art

Fechner (1876) distinguished between direct and associative factors in aesthetics. Associative factors correspond roughly to Riegl’s Vorstellungszweck, the ideas and associations that an object triggers in the perceiver’s mind. Direct factors are more closely tied to properties inherent in the object, such as symmetry, color, and other formal or material properties. Associative factors can potentially intensify or counteract the effect of the (p.389) direct factors. Therefore, Fechner suggested that in order to identify aesthetic principles, non-representational ornament may be more useful than representational art, because the associative factors in the objects portrayed in representational art can occlude or override the more subtle organizing principles. This is not the case in ornament, where formal organizing principles take center stage. The associations that a portrayed object triggers are very specific to a certain place and time, and thus hinder a comprehensive historical and cross-cultural study of aesthetics. Furthermore, direct factors are likely to be the only ones that can be meaningfully studied across species.

Concerning data collection, Fechner proposed three different methods for empirical inquiry in aesthetics: Wahl (choice), Herstellung (production), and Verwendung (usage in the real world). The underlying assumption is again that aesthetic proclivities can be active in multiple modalities, and thus can potentially be broken down into component parts, some of which are shared across all cultures and potentially across species (although to our knowledge, Fechner does not discuss the latter possibility). Fechner’s three-way approach takes into account that aesthetics is not a simple stimulus/response activity captured by a sender/receiver model. Inevitably, the producer(s) of an artwork/aesthetic object also engage their perceptual proclivities during production. Very often, the finished product differs from what was originally envisioned, presumably due to the effects of feedback from perception influencing production, leading to unexpected results and “happy accidents.”

Biological approaches to aesthetics have only recently been proposed and empirical data from animals is rarely included. Eibl-Eibesfeldt (1988), writing about the biological underpinnings of aesthetics, distinguishes between three layers of perceptual biases that we might find: those that are shared with other species, specifically other vertebrates (level 1), those that are unique to the human species but shared across humankind (level 2), and those that are unique to a specific human culture (level 3). These are important distinctions worth keeping in mind when developing a comparative approach in aesthetics and can, in our opinion, be usefully extended to production biases as well. We hypothesize that Fechner’s associative factors are located at level 3, while direct factors are situated at level 2. If true, this alignment again underscores the relevance of non-representational abstract art to cross-cultural and cross-species inquiry.

The contents of level 1 (aesthetic proclivities shared with other species), remain little studied and poorly understood. However, an increasing body of research on birds, insects, and primates (reviewed below), allows us to form tentative hypotheses about what may be shared among animals.

20.3 Some implications of non-representational human artifacts

Some of the oldest human aesthetic artifacts known are patterned markings on ochre dating back about 70 000 years (Henshilwood et al. 2002; Kuhn and Stiner 2007). Contemporaneous perforated marine shells seem to have been collected and worn specifically for their visual appeal (Henshilwood et al. 2004; Vanhaeren et al. 2006; Bouzouggar et al. 2007). (p.390) Both pre-date paleolithic representations of humans or animals by roughly 30 000 years (Hodgson 2006; Verpooten and Nelissen 2010). This is surprising, because geometric patterns are far rarer than animate beings in the natural world, and animals and fellow humans would have had a high relevance for early human artists. The fact that abstract patterns and ornaments can be found across cultures, including those that have not developed representational art, further supports the idea that decorative abstraction is a basic and direct outlet for the human aesthetic drive, with no general need for representation.

Ochre has been used by humans for at least 100 000 years: quite sophisticated ochre-processing tools from that time have been found at Blombos cave, South Africa, including an abalone shell containing a well-fitting grindstone (Henshilwood et al. 2011). This “toolkit” contained a residue of the mixture used, consisting of ochre, bone and marrow, charcoal and other minerals, indicating that these humans were experienced in producing pigments. Ochre can be used for body painting (and still is in many cultures), but also for tanning, hafting, and other things, so its presence alone does not demonstrate aesthetic activities.

Gastropod shells were used very early on as body decorations; some of the oldest examples known date back 70 000–82 000 years (Henshilwood et al. 2004; Vanhaeren et al. 2006; Bouzouggar et al. 2007). Some of these oldest examples show evidence of having been covered with or come into contact with ochre (Henshilwood et al. 2004; Bouzouggar et al. 2007). Wear marks around perforations in the shell suggest that the shells were suspended from cords, like beads (Bouzouggar et al. 2007). Ornamental shells have been found in locations several kilometres from the nearest beach, and due to their small size they were unlikely to represent a food source. Unlike the shells of molluscs that were used for food, shells used as beads show abrasion marks suggesting that they were collected after they washed up on the beach, rather than caught fresh (Kuhn et al. 2001).

Around 30 000–19 500 years ago, beads began to be fashioned from teeth, bone, stones, and other materials, with further embellishments and patterns engraved into the surface (Dubin 1997). Beads from 38 000–10 000 years ago have been found in Australia, Africa, Russia, India, China, and Europe. Even today, beads are popular as jewellery, continuing one of the oldest aesthetic traditions of humankind.

Darwin (1874) discussed body ornament as the most basic form of art in The Descent of Man, and interprets it mainly as a means to enhance physical features and to increase physical beauty. He (Darwin 1874, p. 577) noted the universality of ornament, suggesting that it is due to a shared cognitive architecture:

Lastly, it is a remarkable fact … that the same fashions …

now prevail, and have long prevailed, in the most distant quarters

of the world. It is extremely improbable that these practices,

followed by so many nations, should be due to tradition from any

common source. They indicate the close similarity of the mind of

man, to whatever race he may belong.

(p.391) Ornaments are produced and appreciated by men and women alike. In contrast, most famous painters, sculptors, architects, musicians, and poets in Western culture were men, which has led some to hypothesize that art production is mainly a male trait (Voland 2003). However, a male preponderance in the arts is most likely due to socio-historical factors specific to Western cultures, where the aesthetic objects produced by women occupied the less-valued domestic and craft domains. Everyday objects that may be subject to aesthetic modification such as weaving, carving, or sewing are produced by both sexes (Shiner 2001), although the allocation to the sexes may vary from culture to culture.

Decorating the body with beads, tattoos, scars, or paint is extremely common (Gröning 1997; Dubin 1997) and is found in men and women alike, as well as in children. Interestingly, symmetrical paintings on the face increase the perceived attractiveness of faces (Cárdenas and Harris 2006). Swaddle and Cuthill (1995) have shown that artificial manipulations of photographs of individual faces to make them symmetrical actually decreases their attractiveness. However, symmetry is preferred in images of faces created from many averaged faces (Perrett et al. 1999). It may be the case that symmetrical face markings are a means to make a perceiver focus on a general global symmetry (akin to averaging facial properties as in Perrett et al. 1999), while drawing attention away from characteristics that define an individual face, and individual facial asymmetries. Cárdenas and Harris (2007) found that women do not rate symmetry of the face or face decorations more highly during the fertile phase of their cycle, suggesting that at least symmetrical ornamentation of the face does not act as a straightforward cue allowing females to assess mate quality or good genes. In addition to looking attractive, body decoration probably always has been a social activity (it is difficult to tattoo or scar oneself, particularly when symmetry and regularity is the goal; see e.g. Figure 20.1), thus weakening the obvious parallel between body ornament and animal courtship displays. Ornaments may thus serve a group cohesion function (see Figure 20.2), or as a means for rapid broadcast of diverse social information to a large number of people beyond immediate associates (Kuhn and Stiner 2007).

Towards a Comparative Approach to Empirical Aesthetics

Figure 20.1 An example of the intricate and highly symmetrical facial tattoos typical of Maori tradition in New Zealand.

Towards a Comparative Approach to Empirical Aesthetics

Figure 20.2 Body ornament is often by necessity applied in a social setting, for example between mothers and children (left) or same-sex dyads, suggesting that aesthetics has a strong social core.

Verpooten and Nelissen (2010) have proposed sensory exploitation in combination with social learning as a mechanism by which representational art evolved in humans. Sensory exploitation is a mechanism on the part of the sender of a signal, manipulating the signal to heighten its salience to the receiver due to pre-existing perceptual biases (Ryan 1998). Verpooten and Nelissen argue that the early rise of non-representational art and geometric patterns can be explained by stimulation of lower (e.g. primary visual cortex) visual areas. It required social learning and rituals, in addition to an emerging mental bias for iconic images (e.g. readiness to detect faces or figures in inanimate matter), for iconic art to emerge in human society. They thus attempt to map the cultural evolution of artistic tradition onto neural processing in the visual system, with abstract patterns being both earlier in history and lower in the hierarchy.

Although intriguing, we find this argument unconvincing. Not only has it been shown that symmetry perception does not primarily activate early visual cortex (Sasaki et al. 2005), but as already observed, abstract art is often a social art form. The postulated “basic” (p.392) manifestations of aesthetic behaviors may be more sophisticated than previously thought, and already involve higher level visual processing and social interactions. Research with animals, whose basic visual system closely resembles that of humans, provides one way to evaluate this hypothesis.

In another attempt to understand the origins of art, entoptic phenomena have been proposed as the trigger for early non-representational art (Lewis-Williams and Dowson 1988; Dronfield 1996). (p.393) These are visual phenomena that arise not from stimulation of the retina by light but from activity within the visual system itself—for example, the flashes and geometrical patterns perceived when pressure is applied to the eyeballs, during exposure to stroboscopic flicker, or the visual aura perceived by many migraine sufferers prior to an attack. Given the similarities in the visual systems across species, this would predict that entoptic phenomena are not unique to humans (although testing this prediction is non-trivial). Thus the question of why only humans have developed the urge to produce abstract geometrical patterns remains open.

Taking a broader view on the motivation to produce aesthetic objects, Deacon (2006) suggests that aesthetics may be part of a general novel cognitive style that evolved in humans, involving a modified motivational system. Such an internal reward system would make it inherently enjoyable to perceive and manipulate certain visual stimuli in a manner that may also apply to music and language. Additionally, Deacon (2006, p. 30) posits that humans have a unique “representational stance” which biases perception towards detecting a symbolic relation between an object and another referent (e.g. interpreting cloud shapes as objects). This would explain the origin of representational art.

Certainly, aesthetic experiences are rewarding, and it seems likely that the brain’s reward system has a reinforcing effect on the production and perception systems underlying aesthetics. However, we suspect that the representational stance did not play an important role initially, given that geometrical patterns seem to be the oldest art forms and lack any obvious iconic representational function (although symbolic reference may arise later—e.g. meander patterns representing Greek culture).

While it may be impossible to reconstruct the pathways by which geometrical patterns arose, the fact that they are expressed so ubiquitously across virtually all cultures as well as in the oldest artifacts suggests that they are part of our core aesthetic sense, and thus make them a good departure point for considering research in other species.

20.4 Animal aesthetics?

At least since the 1950s, claims have been made that chimpanzees and other primates produce “artistic” paintings when provided with paper, paint, and brushes. Other animals which have been claimed to have artistic abilities include elephants, horses, dolphins, and rhinoceros. We see these performances as having limited relevance. Animal paintings are only produced in a captive or domesticated setting, with human encouragement and provisioning of materials, suggesting that these paintings are more likely due to encouragement and rewards by humans than a natural artistic or aesthetic inclination of the animals.

Unfortunately, little solid empirical work in the lab has been done specifically on the types of aesthetic perception that animals might have. However, using training and food rewards, Watanabe, Sakamoto, and Wakita (1995) have shown that pigeons can discriminate between Monet and Picasso paintings and generalize the distinction to new paintings (p.394) by other painters in a similar style. Pigeons can also be trained to distinguish between children’s drawings that had been classified as “good” or “bad” by humans prior to the experiment, based on their own subjective judgment, and generalize to further, novel examples of these categories (Watanabe 2010). Even so, there is no indication that the birds are enjoying these experiences beyond the immediate food reward they receive for successful answers or that they preferred “good” over “bad” paintings. Indicators of enjoyment might be that the bird paused for a longer period of time near a given artwork without receiving a reward, viewed it for a longer time, or might be physiological measures such as lower cortisol levels or lower heart rates when exposed to art. Nonetheless, because pigeons have excellent vision this research is valuable in showing that visual tasks relying on food rewards, measuring actual behavior and using artworks as stimuli can be successfully applied to animals without involving aesthetic appreciation as motivation, as would inevitably be the case with human participants.

Perhaps more convincingly, Watanabe and Nemoto (1998) provided Java sparrows (Padda oryzivora) a choice between perches which either elicited playbacks of Bach and Schönberg or silence. Two of the four birds spontaneously spent more time on the perch that triggered Bach’s music. Accepting that this may reflect some preference on the birds’ part, the question of what aspect of the stimulus is preferred (loudness, tempo, pitch, range, etc.) remains open (cf. Fitch 2006).

Early evidence suggested that non-human primates prefer regular to irregular visual shapes. Rensch (1957) studied visual preferences in a capuchin (Cebus apella) and a vervet monkey (Cercopithecus aethiops, now Chlorocebus aethiops) with stimuli that either contained symmetry on one or two axes (“regular”) or were asymmetrical (“irregular”), and reported a bias in both species towards the symmetrical shape. Anderson, Kuwahata, Kuroshima, Leighty, and Fujita (2005) later conducted a similar study with four capuchin and four squirrel monkeys (Saimiri sciureus) with additional stimuli including (a) images of bilaterally symmetrical versus scrambled faces, and (b) geometrical shapes that were arranged regularly but not in a bilaterally symmetrical fashion versus scrambled shape arrangements. Regular or irregular images were pasted on cards and several of them presented simultaneously to the animal. The first card to be picked up was interpreted as the preferred image. The animals did not receive food rewards. There was a slight preference for regular over irregular patterns, but this was not consistent for all individuals of a species and not always statistically significant. However, even when not significant, the trend tended to be against irregular and for regular patterns. Again, it is not clear that the animals gained any aesthetic pleasure from this task, and there is no evidence that these species produce such regular patterns. Nonetheless these results may indicate a subtle perceptual bias for regularity in other primates that might be utilized and reinforced in human aesthetic artifacts.

Walker (1970) exposed rats to backgrounds ranging from monochromatic gray to black-and-white geometric patterns of varying complexity and found “a general tendency for the animals to move from less complex to more complex stimuli during the day” (Walker 1970, p. 643). As the order of the backgrounds was not counterbalanced, this effect may have merely been due to familiarity or novelty-seeking behavior in the animals.

(p.395) Artificial body ornaments in the form of leg bands change preferences for conspecifics in zebra finches (Taeniopygia guttata) and can have a positive effect on both males and females. Zebra finches have orange-red beaks, and males additionally have orange-red patches in the face. Females prefer males with red bands over unbanded individuals or those with blue and green bands, while males prefer females with black or pink bands (Burley et al. 1982). When males are kept in dyads, those equipped with red bands monopolized food sources and displaced individuals with green bands (Cuthill et al. 1997). Recently, Pariser, Mariette, and Griffith (2010) reported that when wild-caught zebra finches were kept in male-only aviaries, those individuals with red bands gained more weight and sang more than those individuals with green or neutral bands. Seguin and Forstmeier (2012), however, failed to replicate this effect with zebra finches bred in captivity. We note that ultraviolet light seems to play a crucial role in the preference for red, and that artificial lighting may distort the UV information available to the birds (Hunt et al. 1997). This may explain the difference in these two studies.

Studying the aesthetic experience as a monolithic whole in animals and comparing it to that of humans can only provide the coarsest insights into the biology and evolution of the aesthetic sense. Particular species may have similar abilities and proclivities in some parts of the aesthetic process, but not others. We suggest a modular approach: in the visual domain, perception can be broken down into perception of color, symmetry (reflectional, rotational, translational), repetition, Gestalt principles (for an early study see Hertz 1928), and so on. Production could be broken down into production contexts, production self-reward systems (i.e. the effect that producing something has on the producer itself), demonstrating the ability to manipulate objects and use tools, self-adornment versus object adornment, etc. We now explore some commonalities and differences between bees, birds, and primates concerning production (nest-building) and symmetry perception.

20.4.1 Nest-building

Nest-building is an intriguing behavior to examine in the context of aesthetics because it characterizes all great apes, most birds, and many bees and wasps. Not only does nest construction entail a sophisticated use of external material, but in many species cooperation and quality assessment by perceivers play a role as well.

Bees produce a wide range of nests, using sand, leaves, clay, feathers, or wax (von Frisch 1974). The honeycomb produced by honeybees (Apis mellifera) is particularly pleasing to our eye because of its astonishingly regular hexagonal pattern. Many bees work together to produce the comb; a single cell may be constructed by multiple bees by placing wax chips at 120 degrees to each other to form the walls of the cell (von Frisch 1974). The entire comb structure is independently aligned by many bees along a line determined by the earth’s magnetic field. The production of the comb cells is dependent on motor-sensory feedback from bristles on the side of the bee’s neck, and ceases when these are immobilized (von Frisch 1974). The hexagonal shape of the cells can also be found in other species of bees and wasps, which use non-wax building materials, so that the hexagons are unlikely to be (p.396) due to properties of the wax, contra Pirk et al. (2004). This fact taken together with the experimental results reported by von Frisch refute the oft-repeated myth, originating with D’Arcy Thompson (Thompson 1948), that regular hexagonal cells emerge automatically due to physical principles. Instead, these structures seem to require active, precise control of the insect builders themselves.

The majority of bird species build nests and use them for parental care, although the complexity and materials of the structure as well as the social dynamics involved in nest-building and courtship vary considerably (Hansell 2000). While females are typically involved in nest-building, either alone or together with the male, there are some cases where females assess and choose between nests built by males; for example, weaver birds (Ploceidae). Male Village weaver birds (Ploceus cucullatus), native to Africa, construct nests later inspected by females (see Figure 20.3). The nests are attached to branches and consist of interwoven blades of grass. If the female approves, she will line it with grass and mate with the male (Hansell 2000). Thus, the female chooses her mate partially on the basis of the quality of the nest he can construct. Walsh, Hansell, Borello, and Healy (2011) have shown that male Southern Masked weaver birds (Ploceus velatus) become more efficient builders over time. Nests of both species built late in the season are shorter and lighter than early ones (Walsh et al. 2010). This suggests that experience interacts with the birds’ inherent drive to build nests, demonstrating that males are not merely performing an invariant fixed-action pattern. Nest quality may thus reflect not only dexterity and physical prowess, but also the learning ability of the builder.

Towards a Comparative Approach to Empirical Aesthetics

Figure 20.3 Male weaver birds (left) construct elaborate nests that are inspected by the female prior to mating. Male bower birds (right) build bowers that do not function as nests, but serve to attract females. The construction is enhanced with attractive, colorful objects, and the male performs a display for the female, holding objects in his beak.

While nest structures are typically used to incubate eggs, in some cases, the male construction is not related at all to incubation. Bower birds are a small family of birds (Ptilonorhynchidae) native to New Guinea and Australia (Borgia 1986; Diamond 1982), consisting of roughly 20 species. In fifteen of these species (Hansell 2000), males construct bowers in specially cleared courts in the forest (see Figure 20.3). The bower, together with physical displays of the males, serves to attract females (their use or Gebrauchszweck, in Riegl’s terms). A bower is a large structure made from grass and twigs, somewhat reminiscent of a nest, that is built on the forest floor and decorated with various, typically brightly colored, objects. The preferred colors of the objects and construction style of the bower varies widely between species. The bowers are not used as nests; these are built by the female after mating. Rather, bowers are a component of the courtship display, serving to entice and impress the female (Riegl’s Schmückungszweck). There is also competition between males: neighboring males often try to steal objects from rivals’ bowers and/or destroy the bower structure. The dimensions and construction principles of the bowers vary between species, as do the types and colors of the objects used to decorate the bowers.

While bower birds are famous for a behavior that appears purely ornamental, it is not unique to them alone. Other bird species are known to clear courts for their displays (Hansell 2000), and some species such as the superb lyrebird (Menura novaehollandiae) additionally modify the center of the clearing with a mound of earth (superb lyrebird) or a grass tuft (Jackson’s widowbird, Euplectes jacksonii). In the bird-of-paradise species Lawe’s (p.397) parotia (Parotia lawesii), males place selected objects in the clearings, reminiscent of bowerbirds, with the difference that females subsequently remove the objects from the clearings (Pruett-Jones and Pruett-Jones 1988).

All adult great apes (gorillas, chimpanzees, bonobos, and orang-utans) build nests every night, and use them for sleeping and sometimes for social interactions such as grooming (Sabater Pi et al. 1997). The nests also offer protection against predation and wet ground. Individuals build nests that they rarely share with others, with the exception of mothers sharing nests with their infants. Nests are rarely reused and are built anew each evening. As these nests are mostly arboreal—with the exception of gorillas who usually build terrestrial nests (Tutin et al. 1995)—the nests need to be sturdily constructed. An analysis of orang-utan nests showed that the structures are complex, with sturdy branches preferentially used for support, and thinner branches used for interweaving (van Casteren et al. 2012). Nest construction in chimpanzees and bonobos is rapid, taking about a minute for day nests (used during midday rest) and no more than five minutes for night nests. Juveniles begin constructing nests in a playful manner, in preparation for their own “solo” nests that they must construct after weaning (Fruth and Hohmann 1996).

To summarize, nest-building is a behavior that in birds has the potential to be a crystallization point for the emergence of aesthetic production and perception due to its dual productive/perceptive nature, with competition in males driven by female perceptual judgment. In great apes, although nest-building is a universal trait, there is little social pressure for this behavior to become more elaborate or fulfil a courtship function because each individual builds their own nest. In bees, we see that the collaborative construction (p.398) by many individuals biases the group towards a unified production process, leaving no room for individual variation or innovation if the combined effort is to converge on a well-formed structure. Each of these examples shows certain points of contact with human artistic practices, but none possesses all of the relevant features.

20.4.2 Symmetry perception

Symmetry—in particular, reflectional symmetry—is an important element in many visual designs and is a highly salient cue for humans (for an extensive review on human symmetry perception, see Treder 2010).

It has been hypothesized (Møller 1992; Penton-Voak et al. 1999) that symmetrical features and markings can act as indicators of high genetic fitness in humans and other animals (usually in males), with few deviations from a symmetrical ideal (“fluctuating asymmetry”) being indicative of “good genes,” meaning a high ability to deal with developmental stress and hence most desirable to females. However, fluctuating asymmetry has been criticized (e.g. by Palmer and Strobeck 2003), since the measurement of symmetry may be very sensitive to small measurement errors (especially in small traits), and asymmetries may arise for reasons other than developmental anomalies. Furthermore, Johnstone (1994) argues that a preference for symmetry in females can arise in the absence of a link between symmetry in males and genetic fitness.

Neural networks have been implemented to test whether a visual signaling process might inherently be biased towards symmetrical signals, similar to the symmetrical markings often found in animals (Enquist and Arak 1994; Enquist and Johnstone 1997). While bilateral reflectional symmetry does tend to emerge in these models with repeated iterations of initially random visual signals, critics have noted that this effect may be a byproduct of the simplified perceptual models implemented (Dawkins and Guilford 1995; Bullock and Cliff 1997; Kamo et al. 1998). Both biological approaches make interesting and valid points but fall short of capturing (human) symmetry processing in its full generality.

In animals, symmetry preferences have been studied extensively in the context of mate choice and sexual selection (Møller and Thornhill 1998). Far fewer studies have been published that examine symmetry preferences outside of a mate selection context. Since symmetry preferences in humans can be found in many contexts and feature prominently in many, if not most, human artifacts, we review research on symmetry perception in animals beyond the context of mate selection to see whether clues can be found in other species concerning the socio-ecological pressures that might have led to such an expansion of symmetry use in humans.

Honeybees can be trained to discriminate bilaterally symmetrical visual stimuli from asymmetrical stimuli and can generalize to new exemplars (Giurfa et al. 1996; Giurfa and Menzel 1997). Although there was no initial preference for symmetrical images, after exposure those trained to approach symmetrical stimuli performed consistently better and hovered longer and nearer to the stimuli than those trained to approach asymmetrical stimuli. Bees can also distinguish a vertical axis of symmetry from other orientations in bilateral symmetry (Horridge 1996). Bumblebees raised with no exposure to flowers or (p.399) other symmetrical visual stimuli nonetheless show a marked preference (measured by approaches and staying times on the stimulus) for bilaterally symmetrical over asymmetrical images (Rodríguez et al. 2004). Given that these species obtain food from flowers, which are typically highly symmetrical, with more symmetrical flowers containing more nectar than less symmetrical flowers (Møller 1995), it is not surprising that symmetry is a salient cue to these insect species in a foraging context.

Turning to birds, extensive studies have been carried out on symmetry perception in both pigeons and starlings, with contradictory results. Pigeons can distinguish bilaterally symmetrical (with a vertical symmetry axis) from asymmetrical stimuli and generalize to new exemplars (Delius and Habers 1978; Delius and Nowak 1982). However, Huber and colleagues (1999) call into question whether this discrimination was based on an abstract concept of symmetry. Using three types of stimuli classes, they show that pigeons can learn to discriminate between symmetrical and asymmetrical items in two out of three stimuli classes. However, in the successful cases, the birds do not seem to acquire a general concept of symmetry to differentiate the two types of images. Instead, the authors suggest that pigeons use alternative discrimination strategies, the main one being rote learning. Results indicate that pigeons store each training exemplar together with the reward contingency. When viewing novel stimuli, the birds seem to compare the stored exemplars with the novel ones and respond according to a threshold based on stimulus similarity.

A mixed picture is also emerging for European starlings (Sturnus vulgaris). Starlings have a speckled breast, and the difference between the number of dots on each side averages about 9 per cent (Swaddle and Witter 1995). The birds can differentiate between artificial symmetrical and asymmetrical dot patterns where the asymmetry is achieved by moving the dots of one side of a bilaterally symmetrical pattern around randomly without removing them; that is, the number of spots on either side remains the same (Swaddle and Pruett-Jones 2001). However, if the number of dots is increased and the asymmetry is brought about by randomly removing dots from one side of a bilaterally symmetrical image and placing them randomly on the other side (the number of spots on either side differs) birds fail to discriminate between symmetrical and asymmetrical (Swaddle and Ruff 2004), corroborating the findings of Huber et al. (1999) with pigeons.

Similarly, young chicks (Gallus gallus) can be trained to discriminate bilaterally symmetrical stimuli from asymmetrical stimuli (Mascalzoni et al. 2012) but they have a preference for asymmetrical stimuli right after hatching. Furthermore, they preferentially peck on irregular dot arrays deviating from a straight line rather than arrays that are spaced along a straight line (Elliott et al. 2012), suggesting that a capacity to perceive mirror symmetry is not necessarily an indicator of a general preference for regularity and order. Taken together, the studies for pigeons, starlings, and chickens tell a cautionary tale: symmetry detection can be achieved with training and positive feedback under some circumstances, but it is not a robust capacity as it is in humans. The detection of symmetry, if present in a species, may be confined to narrowly delineated circumstances and stimuli types (e.g. mate choice or foraging), rather than indicating a generalized perceptual principle, as it seems to be in humans.

(p.400) The literature on non-human primate symmetry perception is surprisingly sparse. A brain imaging study conducted by Sasaki and colleagues (2005) while participants were viewing radially symmetrical and asymmetrical dot patterns showed that the same areas of extrastriate visual cortex are activated in both humans and macaques (regions V3a, V4d), but that the activation was stronger in humans. There was little to no symmetry-specific activation in primary visual cortex (V1 and V2). These findings suggest that the visual processing of symmetrical stimuli in humans uses similar visual pathways as in other primates.

Waitt and Little (2006) showed macaques symmetrical and asymmetrical versions of conspecific faces, and the animals looked longer at symmetrical faces. Longer viewing time, at least in humans, is usually interpreted as a sign of preference (Langlois et al. 1987; Quinsey et al. 1996). In an eye-tracking study, Kano and Tomonaga (2009) showed chimpanzees and humans images of humans, chimpanzees, and other mammals. The basic scan patterns of images were very similar, focusing mainly on the head and face regions of the images and spending little time on the background. This again suggests that perceptual similarities exist between humans and other primates. To our knowledge no face preference studies have yet been conducted in chimpanzees. However, there is evidence that chimpanzees have no preference for symmetrical versus asymmetrical images of perineal swellings in female conspecifics (Breaux et al. 2012).

Based on the scant data available, one possibility is that the basic perceptual processes involved in symmetry perception may be quite similar in humans and other primates. So far, in all animal species studied symmetry recognition is restricted to particular symmetry types (typically reflectional symmetry) and contexts (mate selection in birds or foraging in bees), which may reflect a shared “canonical neural substrate” (Cohen and Zaidi 2013, p. 2) that relies on relatively simple perceptual mechanisms (Osorio 1996; Cohen and Zaidi 2013) that possibly evolved due to the biological relevance of symmetrical input in certain circumstances. The very broad appreciation of multiple types of symmetry that humans show, particularly involving both the perception and production of geometrical patterns, is to our knowledge unparalleled in the animal kingdom.

Despite the rarity of flexibly generated, creative geometrical patterns in the animal kingdom and their ubiquity in human society, surprisingly little empirical research has focused on human pattern production (although cf. Westphal-Fitch et al. 2012, 2013), and we think that the ability and proclivity of ordinary humans to generate structured and attractive patterns should be an important focus of future work in empirical aesthetics.

20.5 Discussion

Over its long history, aesthetics has grappled with the distinction between a “natural” aesthetic appreciation and further development (or refinement) of aesthetic sensitivities through cultural input.

The aesthetic traditions of a culture may vary over historical time, but while fashions come and go, we suggest that there are some core fundamental biases and proclivities of natural aesthetics that drive humans to produce aesthetic objects and remain unchanged. (p.401) In particular, a very general ability to both perceive and produce symmetrical stimuli appears to be a stable, and biologically unusual, feature of our species. Production of highly ordered but also extremely varied abstract geometrical patterns is, according to current knowledge, unique to our species, as is the production of representational art.

Although there are phenomena reminiscent of aesthetic behavior (e.g. bower building) in the animal kingdom, these nonetheless differ in important ways from those of humans (restriction to certain contexts, males only).The development of symmetrical signals in the animal kingdom is frequent but again typically restricted to specific contexts and forms. Little is known to what extent abstract patterns are perceived in animals, but it seems clear that patterns are not generated in a creative, flexible, and open-ended fashion in non-human species.

20.5.1 Music, language, and art as a cognitive triad

Art, music, and language are cultural phenomena that have a strong social component: language facilitates communication between humans and is typically used in a social setting (there are exceptions such as babbling and self-directed speech). Music is often played or sung in a group, and an audience may be present. Art is less obviously social: although artifacts may be produced and perceived in a solitary setting, often they are produced in a group, particularly in traditional societies. In particular, body art is highly social both in its production and in its later intended perception.

Besides their social functions, we suggest that a further common feature at the heart of the music/language/art triad is the ability to apply generative rules iteratively during their production (i.e. a generative syntax). In the case of visual art, we refer here in particular to abstract geometric patterns. Syntactic rules that govern the combinatorics of words are studied extensively in language, and it is a promising research field in musicology (Temperley 2010).

We argue that some sizeable subset of aesthetic behaviors involving abstract patterns in the visual domain also involves repeated application of generative rules with parallels to musical and linguistic structure (for examples see Figure 20.4).

Towards a Comparative Approach to Empirical Aesthetics

Figure 20.4 The production process underlying two visual patterns produced from basic shapes (squares, triangles) using a rule that only two edges may be joined at each step, as when sewing patchwork. The repeated application of the generative rule results in binary branching structures that show multiple levels of hierarchical embedding. A: The number of nodes is odd, leading to an asymmetrical binary tree, while the nodes in B are even, resulting in a symmetrical, recursive structure. The branching direction in A is arbitrary, but is kept consistent in the diagram for clarity.

Art, music, and language are all produced over time and the generative rules are applied serially during production. The ordering in the visual domain is less strict than in the auditory domain. Production may be restricted to a serial “one element at a time” production style, for example during sewing or beading, when only one joining operation can be executed at a time, but the order in which elements are joined is typically flexible.

A more striking difference between visual art on the one hand and music and language on the other becomes obvious during perception. While listening to speech or music, the stream must be parsed serially over time. Thus, the perceptual process must closely track the production process of the speaker or performer temporally. However, eye-tracking studies show that this is clearly not the case in visual art: perceivers can scan the two-dimensional array (or three dimensions in the case of sculptures) any way and in any order they like, without temporal restrictions. Humans (disregarding certain clinical groups) have a strong tendency to take in the entire artwork or stimulus first, focusing on details (p.402) at a later stage. Also, the perceiver can return their attention to regions that have already been looked at as often as they like. This relatively unconstrained aspect of visual perception versus the temporally bound perception of music and language offers a noteworthy freedom to the perceiver. Of course, this applies to static artwork but not to film or dance, which share the temporal flow of music or speech. It may be that such oppositions between visual and auditory, or static and temporally dynamic input have a profound effect on our aesthetic experience. However, it is also possible that all aesthetic experience shares certain common organizing principles, for example an “aesthetic trajectory” of recognition/surprise and resolution regardless of the medium or temporal dynamics (Fitch et al. 2009). Both possibilities provide issues for exploration in future empirical work.

Language is limited in its generativity by pragmatics and semantics. While it is possible to utter sentences such as “colorless green ideas sleep furiously,” meaningless sentences are not conducive to successful communication, which is usually the goal of speaking. Music and abstract art are not similarly limited by semantics. Music is the most abstract case, and art can be representational (i.e. convey representational meanings) or abstract. Abstract patterns are particularly visually striking, have the longer developmental history (as we have argued above), and are much more widespread across cultures than representational art. Both music and visual art have an additional dimension of flexibility due to the freedom from semantic content (optional in the case of visual art) that language does not typically enjoy outside the narrow domains of linguistic examples or Dadaist poetry.

(p.403) 20.5.2 Outlook

Precisely because of the vast variance in the types of artwork that humans produce, empirical aesthetics needs to cast a wide net to achieve a comprehensive picture of the human aesthetic drive, and to discover features that all cultures have in common. Therefore, we maintain that in the future, empirical aesthetics should in principle incorporate the aesthetic judgments and activities of humans from a wide variety of cultures, and include manifestations of the aesthetic drive that can feasibly be studied in the lab. In particular, we strongly question the notion that it takes special knowledge or formal education to have a fully-fledged aesthetic experience (Fitch and Westphal-Fitch 2013).

In the same way that linguistics, and more recently, musicology have both rejected traditional prescriptive approaches to what is good or bad or right or wrong, empirical aesthetics needs to embrace a non-elitist, cross-cultural approach which recognizes and explores the aesthetic capacity of ordinary humans.

A broad comparative approach to aesthetics both across different human cultures and cross-species comparisons will allow the field to benefit from methodologies and research questions of linguistics and musicology, which have already mostly transitioned from a prescriptive (i.e. normative) to a descriptive approach (e.g. Honing 2011). We suggest that a wholehearted embrace of such a broadly comparative perspective has rich insights to offer into aesthetics, and the intriguing hidden structural similarities of the human cognitive triad of music, language, and art.


An earlier version of this chapter was published as part of Gesche Westphal-Fitch’s PhD thesis “Comparative Studies in Visual Pattern Processing,” University of Vienna. We thank Ludwig Huber for helpful comments. This research was funded by ERC Advanced Grant SOMACCA (230604) and FWF grant W1234-G17 (to W. Tecumseh Fitch).


Bibliography references:

Anderson, R.L. (1979). Art in Small-Scale Societies. Englewood Cliffs, NJ: Prentice-Hall.

Anderson, J.R., Kuwahata, H., Kuroshima, H., et al. (2005). Are monkeys aesthetists? Rensch (1957) revisited. Journal of Experimental Psychology: Animal Behavior Processes 31(1), 71–8.

Boas, F. (1955). Primitive Art. New York, NY: Dover.

Borgia, G. (1986). Sexual selection in bowerbirds. Scientific American 254(6), 92–100.

Bouzouggar, A., Barton, N., Vanhaeren, M., et al. (2007). 82 000-year-old shell beads from North Africa and implications for the origins of modern human behavior. Proceedings of the National Academy of Sciences of the USA 104(24), 9964–9.

Breaux, S.D., Watson, S.L., and Fontenot, M.B. (2012). A free choice task evaluating chimpanzees’ preference for photographic images of sex swellings: effects of color, size and symmetry. International Journal of Comparative Psychology 25, 118–36.

Bullock, S. and Cliff, D. (1997). The role of “hidden preferences” in the artificial co-evolution of symmetrical signals. Proceedings of the Royal Society B 264, 505–11.

Burley, N., Krantzberg, G., and Radman, P. (1982). Influence of colour-banding on the conspecific preferences of zebra finches. Animal Behaviour 30(2), 444–55.

(p.404) Cárdenas, R.A. and Harris, L.J. (2006). Symmetrical decorations enhance the attractiveness of faces and abstract designs. Evolution and Human Behavior 27, 1–8.

Cárdenas, R.A. and Harris, L.J. (2007). Do women’s preferences for symmetry change across the menstrual cycle? Evolution and Human Behavior 28, 96–105.

Cohen, E.H. and Zaidi, Q. (2013). Symmetry in context: Salience of mirror symmetry in natural patterns. Journal of Vision 13(6), 1–9.

Cuthill, I.C., Hunt, S., Cleary, C., et al. (1997). Colour bands, dominance, and body mass regulation in male zebra finches (Taeniopygia guttata). Proceedings of the Royal Society B 264, 1093–9.

Darwin, C. (1874). The Descent of Man and Selection in Relation to Sex. London: William Clowes and Sons.

Dawkins, M.S. and Guilford, T. (1995). An exaggerated preference for simple neural network models of signal evolution? Proceedings of the Royal Society B 261, 357–60.

Deacon, T. (2006). The aesthetic faculty. In M. Turner (ed.), The Artful Mind. Cognitive Science and the Riddle of Human Creativity. Oxford: Oxford University Press, pp. 21–53.

Delius, J.D. and Habers, G. (1978). Symmetry: can pigeons conceptualize it? Behavioral Biology 22(3), 336–42.

Delius, J.D. and Nowak, B. (1982). Visual symmetry recognition in pigeons. Psychological Research 44(3), 199–212.

Diamond, J.M. (1982). Evolution of bowerbirds’ bowers: animal origins of the aesthetic sense. Nature 297, 99–102.

Dronfield, J. (1996). The vision thing: diagnosis of endogenous derivation in abstract arts. Current Anthropology 37(2), 373–91.

Dubin, L.S. (1997). Alle Perlen dieser Welt: eine Kulturgeschichte des Perlenschmucks. Köln: Dumont Buchverlag.

Eibl-Eibesfeldt, I. (1988). The biological foundation of aesthetics. In I. Rentschler, B. Herzberger, and D. Epstein (eds), Beauty and the Brain. Biological Aspects of Aesthetics. Basel: Birkhäuser, pp. 29–68.

Elliott, M.A., Salva, O.R., Mulcahy, P., et al. (2012). Structural imbalance promotes behavior analogous to aesthetic preference in domestic chicks. PLoS One 7(8), e43029.

Enquist, M. and Arak, A. (1994). Symmetry, beauty and evolution. Nature 372, 169–72.

Enquist, M. and Johnstone, R.A. (1997). Generalization and the evolution of symmetry preferences. Proceedings of the Royal Society B 264, 1345–8.

Fechner, G.T. (1871). Zur Experimentalen Aesthetik. Leipzig: Breitkopf & Härtel.

Fechner, G.T. (1876). Vorschule der Ästhetik, Vol. 1. Leipzig: Breitkopf & Härtel.

Fitch, W.T. (2006). The biology and evolution of music: a comparative perspective. Cognition 100, 173–215.

Fitch, W.T., von Graevenitz, A., and Nicolas, E. (2009). Bio-aesthetics and the aesthetic trajectory: A dynamic cognitive and cultural perspective. In M. Skov and O. Vartanian (eds), Neuroaesthetics. Amityville, NY: Baywood, pp. 59–102.

Fitch, W.T. and Westphal-Fitch, G. (2013). Fechner revisited: towards an inclusive approach to aesthetics. Behavioral and Brain Sciences 36(2), 140–1.

Fruth, B. and Hohmann, G. (1996). Comparative analyses of nest building behavior in bonobos and chimpanzees. In R.W. Wrangham, W.C. McGrew, F.B.M. deWaal, et al. (eds), Chimpanzee Cultures. Cambridge, MA: Harvard University Press, pp. 109–28.

Giurfa, M., Eichmann, B., and Menzel, R. (1996). Symmetry perception in an insect. Nature 382, 458–61.

Giurfa, M. and Menzel, R. (1997). Insect visual perception: complex abilities of simple nervous systems. Current Opinion in Neurobiology 7(4), 505–13.

(p.405) Gregor, M.J. (1983). Baumgarten’s “Aesthetica.” The Review of Metaphysics 37(2), 357–85.

Groß, S.W. (2001). Felix aestheticus. Die Ästhetik als Lehre vom Menschen. Würzburg: Königshausen & Neumann.

Gröning, K. (1997). Decorated Skin. A World Survey of Body Art. London: Thames & Hudson.

Hansell, M. (2000). Bird Nests and Construction Behaviour. Cambridge: Cambridge University Press.

Henshilwood, C., d’Errico, F., Vanhaeren, M., et al. (2004). Middle Stone Age shell beads from South Africa. Science 304, 404.

Henshilwood, C.S., d’Errico, F., van Niekerk, K.L., et al. (2011). A 100 000-year-old ochre-processing workshop at Blombos Cave, South Africa. Science 334, 219–22.

Henshilwood, C.S., d’Errico, F., Yates, R., et al. (2002). Emergence of modern human behavior: Middle Stone Age engravings from South Africa. Science 295, 1278–80.

Hertz, M. (1928). Wahrnehmungspsychologische Untersuchungen am Eichelhäher I. Zeitschrift für Vergleichende Physiologie 7(1), 144–94.

Hodgson, D. (2006). Understanding the origins of paleoart: the neurovisual resonance theory and brain functioning. PaleoAnthroplogy 54–67.

Honing, H. (2011). Musical Cognition. A Science of Listening. New Brunswick, NJ: Transaction Publishers.

Horridge, G.A. (1996). The honeybee (Apis mellifera) detects bilateral symmetry and discriminates its axis. Journal of Insect Physiology 42(8), 755–64.

Huber, L., Aust, U., Michelbach, G., et al. (1999). Limits of symmetry conceptualization in pigeons. Quarterly Journal of Experimental Psychology 52(4), 351–79.

Hume, D. (1757). Four Dissertations. London: A. Millar.

Hunt, S., Cuthill, I.C., Swaddle, J.P., et al. (1997). Ultraviolet vision and band-colour preference in female zebra finches, Taeniopygia guttata. Animal Behaviour 54, 1383–92.

Johnstone, R.A. (1994). Female preference for symmetrical males as a byproduct of selection for mate recognition. Nature 372, 172–5.

Jones, O. (1856). The Grammar of Ornament. London: Day & Son.

Kamo, M., Kubo, T., and Yoh, I. (1998). Neural network for female mate preference, trained by a genetic algorithm. Philosophical Transactions of the Royal Society B 353, 399–406.

Kano, F. and Tomonaga, M. (2009). How chipanzees look at pictures: a comparative eye-tracking study. Proceedings of the Royal Society B 276, 1949–55.

Kant, I. (1872). Kritik der Urtheilskraft. Berlin: L. Heimann’s Verlag.

Kohn, M. and Mithen, S. (1999). Handaxes: products of sexual selection? Antiquity 73, 518–26.

Kristeller, P.O. (1990). Renaissance Thought and the Arts: Collected Essays. Princeton, NJ: Princeton University Press.

Kuhn, S.L. and Stiner, M.C. (2007). Paleolithic ornaments: implications for cognition, demography and identity. Diogenes 214, 40–8.

Kuhn, S.L., Stiner, M.C., Reese, D.S., et al. (2001). Ornaments of the earliest Upper Paleolithic: new insights from the Levant. Proceedings of the National Academy of Sciences of the USA 98(13), 7641–6.

Langlois, J.H., Roggman, L.A., Casey, R., et al. (1987). Infant preferences for attractive faces: rudiments of a stereotype? Developmental Psychology 23, 363–9.

Lewis-Williams, J.D. and Dowson, T.A. (1988). The signs of all times: Entoptic phenomena in Upper Paleolithic art. Current Anthropology 29(2), 201–45.

Mascalzoni, E., Osorio, D., Regolin, L., et al. (2012). Symmetry perception by poultry chicks and its implications for three-dimensional object recognition. Proceedings of the Royal Society B 279, 841–6.

Mithen, S. (1996). The Prehistory of the Mind. London: Thames and Hudson.

(p.406) Mithen, S. (2003). Handaxes: The first aesthetic artefacts. In E. Voland and K. Grammer (eds), Evolutionary Aesthetics. Berlin: Springer, pp. 261–275.

Møller, A.P. (1992). Female swallow preference for symmetrical male sexual ornaments. Nature 357, 238–40.

Møller, A.P. (1995). Bumblebee preference for symmetrical flowers. Proceedings of the National Academy of Sciences of the USA 92, 2288–92.

Møller, A.P. and Thornhill, R. (1998). Bilateral symmetry and sexual selection: A meta-analysis. The American Naturalist 151(2), 174–92.

Nowell, A. and Chang, M.L. (2009). The case against sexual selection as an explanation of handaxe morphology. PaleoAnthroplogy 77–88.

Osorio, D. (1996). Symmetry detection by categorization of spatial phase, a model. Proceedings of the Royal Society B 263, 105–10.

Palmer, R.A. and Strobeck, C. (2003). Fluctuating asymmetry analyses revisited. In M. Polak (ed.), Developmental Instability: Cause and Consequences. Oxford: Oxford University Press, pp. 279–319.

Pariser, E.C., Mariette, M.M., and Griffith, S.C. (2010). Artificial ornaments manipulate intrinsic male quality in wild-caught zebra finches (Taeniopygia guttata). Behavioral Ecology 21(2), 264–9.

Penton-Voak, I.S., Perrett, D.I., Castles, D.L., et al. (1999). Menstrual cycle alters face preference. Nature 399, 741–2.

Perrett, D.I., Burt, D.M., Penton-Voak, I.S., et al. (1999). Symmetry and human facial attractiveness. Evolution and Human Behavior 20, 295–307.

Pirk, C., Hepburn, H., Radloff, S., et al. (2004). Honeybee combs: construction through a liquid equilibrium process? Naturwissenschaften 91, 350–3.

Pruett-Jones, S.-G., and Pruett-Jones, M. (1988). The use of court objects by Lawes’ parotia. The Condor 90, 538–45.

Quinsey, V.L., Kesetzis, M., Earls, C., et al. (1996). Viewing time as a measure of sexual interest. Ethology and Sociobiology 17, 341–54.

Rensch, B. (1957). Ästhetische Faktoren bei Farb- und Formbevorzugungen von Affen. Zeitschrift für Tierpsychologie 14(1), 71–99.

Riegl, A. (1966). Historische Grammatik der bildenden Künste. Graz: Hermann Böhlaus Nachf.

Rodríguez, I., Gumbert, A., Hempel de Ibarra, N., et al. (2004). Symmetry is in the eye of the “beeholder”: innate preference for bilateral symmetry in flower-naïve bumblebees. Naturwissenschaften 91, 374–7.

Ryan, M.J. (1998). Sexual selection, receiver biases, and the evolution of sex differences. Science 281, 1999–2003.

Sabater Pi, J., Vea, J.J., and Serrallonga, J. (1997). Did the first hominids build nests? Current Anthropology 38, 914–6.

Sasaki, Y., Vanduffel, W., Knutsen, T., et al. (2005). Symmetry activates extrastriate visual cortex in human and nonhuman primates. Proceedings of the National Academy of Sciences of the USA 102(8), 3159–63.

Seguin, A. and Forstmeier, W. (2012). No band color effects on male courtship rate or body mass in the zebra finch: four experiments and a metaanalysis. PLoS One 7(6), e37785.

Shiner, L. (2001). The Invention of Art: A Cultural History. Chicago, IL: University of Chicago Press.

Swaddle, J.P. and Cuthill, I.C. (1995). Asymmetry and human facial attractiveness: symmetry may not always be beautiful. Proceedings of the Royal Society B 261, 111–6.

Swaddle, J.P. and Pruett-Jones, S. (2001). Starlings can categorize symmetry differences in dot displays. American Naturalist 158(3), 300–7.

(p.407) Swaddle, J.P. and Ruff, D.A. (2004). Starlings have difficulty in detecting dot symmetry: implications for studying fluctuating asymmetry. Behaviour 141, 29–40.

Swaddle, J.P. and Witter, M.S. (1995). Chest plumage, dominance and fluctuating asymmetry in female starlings. Proceedings of the Royal Society B 260, 219–23.

Temperley, D. (2010). Music and Probability. Cambridge, MA: MIT Press.

Thompson, D.W. (1948). On Growth and Form. New York, NY: Cambridge University Press.

Treder, M.S. (2010). Behind the looking-glass: a review of human symmetry perception. Symmetry 2, 1510–43.

Tutin, C.E.G., Parnell, R.J., White, L.J.T., et al. (1995). Nestbuilding by lowland gorillas in the Lopé Reserve, Gabon: environmental influences and implications for censusing. International Journal of Primatology 16(2), 53–76.

van Casteren, A., Sellers, W.I., Thorpe, S.K.S., et al. (2012). Nestbuilding orangutans demonstrate engineering know-how to produce safe, comfortable beds. Proceedings of the National Academy of Sciences of the USA 109(18), 6873–7.

Vanhaeren, M., d’Errico, F., Stringer, C., et al. (2006). Middle Paleolithic shell beads in Israel and Algeria. Science 312, 1785–8.

Verpooten, J. and Nelissen, M. (2010). Sensory exploitation and cultural transmission: the late emergence of iconic representations in human evolution. Theory in Biosciences 129(2–3), 211–21.

Voland, E. (2003). Aesthetic preferences in the world of artifacts—adaptations for the evaluation of “honest signals?” In E. Voland and K. Grammer (eds), Evolutionary Aesthetics. Berlin: Springer, pp. 239–60.

von Frisch, K. (1974). Animal Architecture. London: Hutchinson.

Waitt, C. and Little, A.C. (2006). Preferences for symmetry in conspecific facial shape among Macaca mulatta. International Journal of Primatology 27(1), 133–45.

Walker, E.L. (1970). Complexity and preference in animals and men. Annals of the New York Academy of Sciences 169, 619–53.

Walsh, P.T., Hansell, M., Borello, W.D., et al. (2010). Repeatability of nest morphology in African weaver birds. Biology Letters 6, 149–51.

Walsh, P.T., Hansell, M., Borello, W.D., et al. (2011). Individuality in nest building: do Southern Masked weaver (Ploceus velatus) males vary in their nest-building behaviour? Behavioural Processes 88(1), 1–6.

Washburn, D.K. and Crowe, D.W. (1988). Symmetries of Culture. Theory and Practice of Plane Pattern Analysis. Seattle, WA: University of Washington Press.

Watanabe, S. (2010). Pigeons can discriminate “good” and “bad” paintings by children. Animal Cognition 13(1), 75–85.

Watanabe, S. and Nemoto, M. (1998). Reinforcing property of music in Java sparrows (Padda oryzivora). Behavioural Processes 43(2), 211–8.

Watanabe, S., Sakamoto, J., and Wakita, M. (1995). Pigeons’ discrimination of paintings by Monet and Picasso. Journal of the Experimental Analysis of Behavior 63, 165–74.

Wenban-Smith, F. (2004). Handaxe typology and Lower Paleolithic cultural development: ficrons, cleavers and two giant handaxes from Cuxton. Lithics 25, 11–21.

Westphal-Fitch, G., Huber, L., Gómez, J.C., et al. (2012). Production and perception rules underlying visual patterns: Effects of symmetry and hierarchy. Philosophical Transactions of the Royal Society B 367(1598), 2007–22.

Westphal-Fitch, G., Oh, J., and Fitch, W.T. (2013). Studying aesthetics with the method of production: effects of context and local symmetry. Psychology of Aesthetics, Creativity, and the Arts 7(1), 13–26.

Zaidel, D.W., Nadal, M., Flexas, A., et al. (2013). An evolutionary approach to art and aesthetic experience. Psychology of Aesthetics, Creativity and the Arts 7(1), 100–9.