Although the term 'composition' is also used in relation to language and music, I use it here only in relation to semiotic modes that are articulated in space. Composition is about arranging elements - people, things, abstract shapes, etc. - in or on a semiotic space - for example, a page, a screen, a canvas, a shelf, a square, a city. As Arnheim (1974, 1982) has shown, it is based on our sense of balance, hence on a very physical and intuitive process, for instance the process of placing something exactly in the centre, or of getting something that is on the right and something that is on the left in perfect balance. But this process is at the same time a semiotic process: 'the function of balance can be shown only by pointing out the meaning it helps to make visible' (Arnheim, 1974:27).
The elements of a picture or page layout are balanced on the basis of their visual weight. This 'weight' derives from their perceptual salience, which, in turn, results from a complex interaction, a complex trading-off relationship between a number of factors: relative size; sharpness of focus - or, more generally, amount of detail and texture shown; tonal contrast - areas of high tonal contrast, for instance borders between black and white, have high salience; colour contrasts - for instance the contrast between highly saturated and 'soft' colours, or the contrast between red and blue; placement in the visual field - elements not only become 'heavier' as they are moved up, but also appear to be 'heavier' the further they are moved towards the left, due to an asymmetry in the visual field; perspective - foreground objects are more salient than background objects and elements that overlap other elements are more salient than the elements they overlap; and also quite specific cultural factors, such as the appearance of a human figure or a potent cultural symbol, which may override pure perceptual salience.
In symmetrical compositions left and right are evenly balanced, but balance becomes more eventful when one side is visually heavier than the other so that the balancing centre has to be shifted away from the geometrical centre of the space. Achieving and maintaining balance in unbalanced situations is a fundamental human experience, a basic given of our existence as biped creatures, and as a result our sense of balance informs all our activities including our semiotic activities. It forms an indispensable matrix for the production and reception of spatially articulated messages. It is also the source of our aesthetic pleasure in composition. The pleasure we derive from moving elements about until the result feels 'just right', orin arranging things to perfection in front of a camera lens, is directly related to the pleasure of almost losing and then regaining balance which we experience as children when we are lifted up and swung through the air, or when we swing on a swing until it moves so high that by right we should fall off, yet still hold on, a pleasure which Freud has famously related to sexuality (1977 : 121). It is even more directly related