What Does Drawing Reveal about Thinking?

Drawings are an integral part of the dialogue a designer conducts with him or herself during design. They are a kind of external representation, a cognitive tool developed to facilitate information processing. Drawings differ from images in that they reflect conceptualizations, not perceptions, of reality. For a particular domain, sketches use a small set of segments or elements that map the critical elements of the domain. It is proposed that the choice of and representation of elements and the order in which they are drawn reflect the way that domain is schematized and conceptualized. Support for this claim is gathered from research on sketch maps, graphs, and geometric analogy solution. Design without drawing seems inconceivable. One view of the role of sketching in design is an iterative, cyclical, dialectic view where sketches serve to instantiate design ideas as well as to stimulate new ones. In each cycle, designers express their ideas externally, on paper, and then examine, interpret, and perhaps reinterpret them. This inspection of the drawings may inspire changes in design ideas, which are put down again on paper to be reexamined again, reconceived, redrawn, reexamined, and so on (for expansion of these ideas, see Goldschmidt, 1989, 1991, 1994; Goel, 1995; Purcell and Gero, 1998; Schon and Wiggin, 1992; Suwa, Gero, and Purcell, 1998; Suwa and Tversky, 1996, 1997). In the experienced designer, consideration of the drawings arouses thoughts about visible aspects of the sketches, of the shapes and arrangements of the design elements, as well as thoughts about aspects of the sketches not directly visible, such as functions and activities enabled by the elements and their spatial arrangements (e.g., Akin, 1986; Goldschmidt, 1989, 1991, 1994; Goel, 1995; Suwa, Gero, and Purcell, 1998; Suwa and Tversky, 1996, 1997; Verstinjnen, Hennessey, van Leeuwen, Hamel, and Goldschmidt, 1998). Drawings are a kind of external representation, one of many cognitive tools invented to facilitate memory and thinking (see discussions by Donald, 1991; Kirsch, 1995 Larkin and Simon, 1987; Norman, 1993; Scaife and Rogers, 1996; Stenning and Oberlander, 1995; Tversky, 1995, in press). Successful external cognitive tools compensate for limitations in human memory and information processing at the same time that they take advantage of them. People are limited simultaneously by the amount of information they can keep in mind and the number of mental operations they can apply to that information. Memory limitations can be reduced by offloading memory to external displays that can be inspected and reinspected. Similarly, mental operations can be facilitated by putting the information relevant to particular operations in spatial contiguity and by taking advantage of people's enormous capacity for recognizing many different patterns (Larkin and Simon, 1987). The way that elements are arranged in space--in groups, orders, or distances--can be meaningful, either iconically or metaphorically (e.g., Kirsh, 1995; Kieras, 1992; Tversky, 1995; in press). These advantages of external cognitive tools are especially available in depictions. Depictions have the added advantage that they can be inspected, discussed, and altered by a group of thinkers, even when distributed over time and space. Drawings are sometimes regarded as externalizations of images. They are both more and less than that. According to the classical view of imagery (e.g., Kosslyn, 1980, 1996; Shepard and Podgorny, 1978), images are like internalized perceptions. They have qualities like perceptible qualities of objects; they are inspected and transformed in ways analogous to inspecting and transforming objects. Indeed, in elegant research it has been shown that imaging activates some of the very brain structures that perceiving does (Kosslyn, Thompson, Kim, and Alpert, 1995). Like perception of objects, images are regarded as having a single, coherent point of view. Furthermore, certain kinds of drawings, like comics or design sketches or route maps, contain extra information not in perceptions and not necessarily in images, such as arrows to indicate directions or squiggly lines to indicate heat rising or annotations in the form of words. Although drawings can be like images, they frequently contradict many of the properties attributed to images. To put it succinctly, drawings reveal people's conceptions of things, not their perceptions of things. How might our conceptions of things differ from our perceptions of them? Children's drawings are an excellent case in point (e.g., Goodnow, 1977; Kellogg, 1969). Consider their early What does drawing reveal 3 drawings of people. All the world over, young children draw people by drawing a circle for a face, with arms and legs extending from it. Does this mean that children perceive that people have 4 limbs and no body, and that the limbs are attached to the head? Certainly not. Rather, a head, arms, and legs are the components of children's early conceptions of the human body, to be enriched by the addition of other body parts. Older children may draw scenes like a ring of children holding hands. One way that many children portray this is by drawing a circle, with an array of children extending from it, feet to the border of the circle, heads outwards. If this were meant to be a drawing from a single point of view, it would be interpreted as children lying on the ground on the perimeter of a circle. But this is not what was intended, nor is it what is understood. Drawings such as these do not attempt to adopt a consistent point of view. Neither the Impressionists nor the Cubists invented mixed perspectives, nor is their use restricted to children. The tourist maps popular today that superimpose frontal views of landmarks onto aerial views of road networks have their ancient counterparts (e.g., Brown, 1949; Noble, 1981; Southworth and Southworth, 1982). Comics provide another common example of drawings that present conceptions of reality (McCloud, 1993); we have become so accustomed to conventions of conveying motion, excitement, and heat that we think we "see" them directly in the drawings. Drawings, then, are representations of reality, not presentations of reality. Drawings can omit things that are actually there, they can distort things that are there, they can add things that are not there. They need not have a consistent point of view or a point of view at all. As such, drawings are of even greater interest to art critics, designers, and psychologists alike. They can provide insights into conceptulizations not just imaginings.