Goals

After reading this chapter the student will understand the following.

Introduction

During the Italian Renaissance, painters acted partly as interior decorators, creating frescos, murals and easel paintings with which rich patrons decorated the rooms of their grand villas. The aim was to treat the picture frame as a window opening that offered a captivating glimpse of a realistic visual world. In order to achieve the illusion of a window, artists had to solve the problem of projecting a three-dimensional world onto a flat, two-dimensional picture plane. The problem of perspective projection was solved in the early fifteenth century by Fillipo Brunelleschi and Leon Battista Alberti. Leonardo da Vinci described the solution as follows:

Figure 4.1 illustrates Leonardo’s description. The viewer’s eye is positioned at O, and light rays from the top surface of the cube create a pyramid of sight with its apex at O and base defined by the points ABCD at the corners. A plane surface FGHI (Leonardo’s transparent window) intersects the pyramid to form a perspective projection of the surface, abcd, as a two-dimensional image. The laws of linear perspective define the shape, size and disposition of all the elements in the scene on Leonardo’s window. The image formed on Leonardo’s window corresponds to the image that would be captured by a camera positioned at O (apart from the inversion caused by the camera’s lens). In a sense, therefore, the aim of the representational artist is to create a painting that corresponds to the perspective projection captured by a camera positioned at the eye.

The central thesis of this book has been to argue that a full appreciation of visual art requires a detailed consideration of the visual system’s structure, function and evolution. Even before light reaches the retina, the changes brought about by its passage through the cornea and lens can have visible effects on visual art. Once light energy is converted into neural activity in the visual system, the huge complexity of the central nervous system is brought to bear on the problem of making sense of the retinal image. Visual art is intimately linked with the human capacity to sense light and inextricably bounded by its predispositions and limitations, many of which have firm evolutionary origins. There are manifold ways in which the characteristics of neural processes find expression in the spatial, chromatic and dynamic properties of visual art.

Evolution provides an over-arching theoretical framework for understanding all of human behaviour and offers a reasoned account of the capacity to create and appreciate art. Selection pressure has ensured that the visual system is supremely well adapted to the task of extracting meaning from natural visual images. The demands of optimal tuning and energy conservation have profound consequences for our ability to perceive, retain and appreciate certain spatial details, chromatic variations and dynamic changes in all visual images, including artistic images. Evolution has also equipped humans with a deep interest in nature, in landscape and in biological forms, and this interest finds expression in the enduring preoccupations of visual artists. The impulse to create art may be driven, at least in part, by a desire to advertise genetic quality to potential mates.

Introduction

Assume, as we did at the beginning of the previous chapter, that the aim of the artist is to create a representational painting, which is as close as possible to the light distribution that would be sent to the viewer by the scene itself; a window onto a virtual scene. Even though the artist may be able to use detailed knowledge of perspective projection and optical devices such as the camera obscura, in every case the painting will fall short of an exact facsimile. Instead, it will be a resemblance or approximation to the scene itself. The viewer is almost always aware of the perceptual characteristics of the picture as a flat surface in itself, such as its shape, size and position. The information carried in a picture is also lacking in several important respects, even when the picture is a photograph captured by the highest resolution camera available today or a painting faithfully copied from such a photograph. Natural objects and surfaces have an inherent spatial scale, which we apprehend when we view real scenes. Redwood trees appear massively tall, while the intricate pattern of lichen growing on a rock surface appears tiny. Pictures of objects and surfaces, on the other hand, can be any size; information about absolute scale is lost. In a closely cropped photograph, it may be impossible to distinguish between small ripples in sand, as seen at one’s feet when standing on a beach, and massive sandbanks viewed from an aeroplane. We are able to appreciate absolute scale in real scenes because they have three spatial dimensions (width, height and depth), which carry information about absolute distance. When one’s gaze shifts between real objects, the lens of the eye adjusts its focus to maintain a sharp image (accommodation, described in Chapter 2) and the two eyes alter their convergence angle so that both are directed at the same object. Changes in focus and convergence angle are brought about by muscles inside the eye itself (which control focus) or those attaching the eye to its socket (which control convergence). Sensory information about the state of tension in these muscles provides the visual system with information about absolute depth, which can be used in judgements of absolute size.

Introduction

During the two millennia before the advent of modern conceptual art, with its emphasis on ideas and intellectual qualities, visual aesthetic pleasure was considered to be a core element of one’s experience when viewing visual art. Indeed, beauty was at the very core of the British Aesthetic Movement in art during the late 1800s. Aesthetic judgements are not, of course, restricted to visual art but are also made about natural visual forms such as faces, landscapes and flowers, and about manufactured forms such as buildings and machines. All of these judgements are closely tied to the sensory qualities of the object: its visual attributes such as shape, texture, colour, movement and so on, as well as other attributes such as smell and touch. Moreover, aesthetic judgements are also central in other art forms such as music, literature, opera and dance. Aesthetic judgement is such a fundamental aspect of human experience that it has been considered from the perspective of many different disciplines including philosophy, cultural studies, history and anthropology. This chapter will focus on the insights that can be gained from the scientific perspectives of modern psychology. It will ask how scientific principles can deepen our understanding of aesthetic appreciation in visual art.

Introduction

As Chapter 1 made clear, a major function of painting from antiquity to the nineteenth century was the representation of nature. In this regard, colour is traditionally viewed as an essential component because it brings visual art closer to nature. In 1528, the Renaissance courtier Baldassare Castiglione recorded a conversation on the relative merits of the figurative arts as follows:

Since the earliest cave paintings 30,000 years ago, artists have used pigments to add natural colour to their work. Prehistoric painters used earth pigments such as charcoal bound with water (or saliva) to create yellow ochre, red ochre and black hues. The Egyptians introduced bright greens and blues using pigments derived from natural minerals, which were washed, ground and bound with gum or animal glue to create a painting medium. They also introduced vegetable dyes. Other colours were created by ancient Chinese, Greek and Roman artisans. Various binding agents were used to hold the pigment together as a painting medium, including wax, resin, water and egg. From the fifteenth century onwards, walnut and linseed oil gradually replaced egg as the binding agent preferred by many artists. Acrylic paints became available in the middle of the twentieth century, in which acrylic resin emulsified with water is used as a binder and thinner.

Introduction

The previous chapter concluded that aesthetic preference is tied, at least in part, to utility or affordance. If the human aesthetic sense did evolve as part of a reward system for satisfying certain biologically important needs, then it must be closely linked to visual features in the natural environment. Humans evolved not to function in the environment of modern civilisation, which emerged only in the last few thousand years, but in the environment of the Pleistocene era. For two million years humans existed and evolved as Pleistocene hunter–gatherers. Survival depended on foraging for edible plants and hunting animals. It was a relatively mobile, nomadic existence that relied upon the resources available in the local environment. Bands of hunter–gatherers perpetually moved on to new locations with the changing seasons and with the depletion of local resources. The first point of enquiry in the search for the natural origin of visual aesthetics is this ancient environment. Perhaps the demands of this ancestral lifestyle still drive our aesthetic preferences. The artist Henri Matisse remarked that ‘art imitates nature’. The mimetic theory of art described in Chapter 1 views art as an idealised imitation of nature, a distilled essence of natural aesthetic beauty. To what extent does aesthetic appreciation of art spring from judgements about ancient natural forms? This chapter considers the question from the viewpoint of modern research on landscape preference and visual statistics.

Introduction

Humans are highly visual creatures. Evolution has honed the human brain into a supremely efficient tool for extracting information from visual images, which far exceeds the capabilities of the most powerful computer vision systems available today. The areas of the brain devoted to our visual sense are much larger than the areas devoted to all of our other faculties. Vision begins with an image cast onto the inside surface of the eyes. Large populations of brain cells analyse this image in terms of several essential visual characteristics, including shape, size, texture, colour and motion. These highly complex brain processes underlie all visual experience but they are largely hidden from conscious awareness. The detailed characteristics of brain function must have a profound role to play in our experience of visual art. The aim of this book is to put forward an approach to understanding visual art that is founded on our knowledge of how the eyes and brain function together to create visual experience.

Before we can embark on this task, it is important to define some fundamental terms of reference. Everyone agrees on what we mean by the brain, namely the 1.4 kg jelly-like mass of nerve cells and fibres cradled inside the human skull. The visual system of the brain includes the eyes, the neural pathways connecting the eyes to the brain and all the neurones in the brain that respond primarily to visual stimulation. On the other hand, it is much more difficult to agree on a definition of art. Philosophers continue to debate the virtues of alternative ways to define art; however, one point is clear: any attempt to define artworks in terms of a single characteristic such as their representational properties or their expressive qualities is bound to fail. Counter-examples to single characteristics such as these can always be found. Maps, for example, are representational because they represent the layout of the land but they are not usually considered to be art; human postures have expressive properties but are not usually considered as art unless adopted during an artistic performance such as ballet. On the other hand, it is difficult to consider the collection of Italian Renaissance paintings in London’s National Gallery as anything other than works of art. What about Marcel Duchamp’s ‘Fountain’ (actually a manufactured urinal), or Carl Andre’s ‘Equivalent VIII’ (actually a rectangular arrangement of 120 firebricks)? Are these objects works of art?

Introduction

The outermost surface of the human brain is covered by a thin sheet of neurones called the neocortex or cerebral cortex. The sheet fits inside the skull only because of its extensive folds, rather like an umbrella furled up inside a case. The cerebral cortex is only 3 mm thick but has a total surface area of over 2 m2 when unfolded and contains about ten thousand million (billion) brain cells. It covers the brain like the shell of a nut, or the bark of a tree (cortex means bark or shell in Latin). The cortex is larger in humans than in any other species and is thought to endow us with uniquely human attributes.

The brain is divided vertically front-to-back into two hemispheres, one on each side of the head, which are interconnected by a massive band of nerve fibres called the corpus callosum. Anatomists subdivide each half of the cerebral cortex into four lobes, named as the frontal, parietal, temporal and occipital lobes after the bones that lie above them (Figure 3.1). The frontal lobe is at the front of the head behind your forehead, and the occipital lobe is at the back. The parietal and temporal lobes occupy the territory at the side and top of your head. A key feature of the cortex is specialisation of function. Like a medieval town in which different trades gather in different neighbourhoods – spice merchants here, money lenders there – small, circumscribed regions of the cortex specialise in serving particular mental functions. About one-fifth of the cortical surface is devoted to primary sensations (vision, sound, touch, balance, smell and taste) and to movement control. The rear-most part of the occipital cortex, known as the primary visual cortex (V1), receives input from the eyes and is responsible for vision, while a narrow strip of the cortex running side-to-side over the head from ear to ear receives sensory input from the body surface and mediates our perception of touch. Outside of these primary sensory areas, the remaining four-fifths of the cortex specialises in secondary cognitive functions. Research has shown that each lobe performs a specific set of tasks.

Introduction

This chapter concentrates on how the eye works and how this function impacts on art. To set the scene, it will be useful to know a little about the physical properties of the stimulus for vision, light. The precise physical nature of light has perplexed philosophers and scientists for centuries and is not yet completely understood. Light is a form of energy known as electromagnetic energy because it has both electrical and magnetic properties and it is carried in small packets called photons. The electromagnetic field of each photon has a characteristic vibration frequency that can vary from a few thousand vibration cycles per second to many billions of cycles per second. The standard way of measuring vibration frequency is in terms of the distance between adjacent peaks in the vibrating wave, known as its wavelength. Across the full electromagnetic spectrum, wavelength can vary from extremely short wavelengths that are a fraction of the size of atoms (X-rays and gamma rays, the very highest frequencies) to very long wavelengths that can be many kilometres long (the lowest frequencies). The energy that you can see as light spans only a tiny proportion of the electromagnetic spectrum, corresponding to wavelengths between 400 nm and 700 nm (billionths of a metre). Light wavelength is associated with colour experiences, with the longer wavelengths appearing red or orange and the shorter wavelengths appearing blue or violet. Yellow and green sensations are evoked by middle wavelengths. Electromagnetic energy in the visible band-light is well behaved in the sense that it reflects off most surfaces and can be focused by lenses. As the sense organ for vision, the eye takes advantage of this good behaviour.

Preface

The opportunities for people to engage with visual art are greater now than they have ever been before. In recent years, increasing numbers of people choose to attend major international gallery exhibitions that celebrate visual art both past and present, often at significant cost in terms of time and money. Most houses, shops, restaurants and public buildings display some form of visual art on their walls. It seems that everyone has an opinion about visual art, perhaps a favourite artist, artistic genre or historical era. Where does this universal interest in art spring from? Why have certain visual forms preoccupied artists across generations? What visual qualities underlie our reactions to artworks? Such questions have traditionally been tackled from the perspective of the humanities, especially disciplines such as art history and philosophy.

Psychology is the scientific study of people, the mind and human behaviour. The creation and consumption of visual art is an ancient and universal human activity and, as such, it should also be a prime focus of research in psychology. As a discipline, psychology dates from the mid-nineteenth century, when a small group of European scientists devised new experimental methods for measuring simple human behavioural responses. Over the last 150 years, psychologists have adopted concepts and techniques from a very wide range of scientific disciplines in their quest to understand the human mind and behaviour. Advances in neuroscience have had a crucial impact on psychological theories, providing researchers with fundamental information about the structure and function of the human brain. Mathematics and computer science have supplied deep theoretical principles that help us to understand the information available in visual images and the constraints within which any physical system must operate when trying to make sense of visual information.