Which words do children learn earliest, and why? These questions bear on how humans organize the world into semantic concepts, and how children acquire this parsing. A useful perspective is to think of how bits of experience are conflated into the same concept. One possibility is that children are born with the set of conceptual conflations that figures in human language. But assuming (as we will) that most semantic concepts are learned, not innate, there remain two possibilities. First, aspects of perceptual experience could form inevitable conflations that are conceptualized and lexicalized as unified concepts.

In this case, we would have cognitive dominance: concepts arise from the cognitive-perceptual sphere and are simply named by language. A second possibility is guistic dominancee world presents perceptual bits whose clumping is not pre-ordained, and language has a say in how the bits get conflated into concepts. We propose that both cognitive and linguistic dominance apply, but to different degrees for different kinds of words (Gentner 1981, 1982). Some bits of experience naturally form themselves into inevitable (preindividuated) concepts, while other bits are able to enter into several different possible combinations.

Relational relativity and the division of dominance

Embracing both cognitive and linguistic dominance may seem to be a vague middle-of-the-road position. But we can make the distinction sharper by asking which applies when. We suggest a larger pattern, a division of dominance (Gentner 1988). The Division of Dominance continuum is shown in figure 8.1. At one extreme, concrete nouns - terms for objects and animate beings - follow cognitive- perceptual dominance.

Analogy and metaphor are central to scientific thought. They figure in discovery, as in Rutherford's analogy of the solar system for the atom or Faraday's use of lines of magnetized iron filings to reason about electric fields (Nersessian, 1984; Tweney, 1983). They are also used in teaching: novices are told to think of electricity as analogous to water flowing through pipes (Gentner & Gentner, 1983) or of a chemical process as analogous to a ball rolling down a hill (Van Lehn & J. S. Brown, 1980). Yet for all its usefulness, analogical thinking is never formally taught to us. We seem to think of it as a natural human skill, and of its use in science as a straightforward extension of its use in commonsense reasoning. For example, William James believed that “men, taken historically, reason by analogy long before they have learned to reason by abstract characters” (James, 1890, vol. II, p. 363). All this points to an appealing intuition: that a faculty for analogical reasoning is an innate part of human cognition, and that the concept of a sound, inferentially useful analogy is universal.

In this essay we question this intuition. We analyze the way in which analogy and metaphor have been used at different points in the history of Western scientific thought, tracing their use backward from the present time. We begin by laying out the current framework for analogical reasoning, followed by two examples that conform to the modern aesthetic, those of Sadi Carnot (1796–1832) and Robert Boyle (1627–1691).

Similarity has been cast both as hero and as villain in theories of cognitive processing, and the same is true for cognitive development. On the positive side, Rosch and her colleagues have suggested that similarity is an initial organizing principle in the development of categorization (e.g., Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976), and Carey (1985) implicates a similarity mechanism in children's learning of the biological domain. It has also been suggested that similarity may play a role in word acquisition (Anglin, 1970; Bowerman, 1973, 1976; E. V. Clark, 1973; Davidson & Gelman, 1990; Gentner, 1982c). Others have taken a more pessimistic view, according to which similarity is either a misleading or at best an inferior strategy used as a last resort. Keil (1989), for example, posits that children begin with theories of the world and that similarity functions merely as a fallback strategy to be resorted to when theory fails.

A related issue is the course of development of similarity. Many researchers have suggested that children's use of similarity changes from an early and naiïve form to a later, more enlightened form.

It is widely accepted that similarity is a key determinant of transfer. In this chapter I suggest that both of these venerable terms – similarity and transfer – refer to complex notions that require further differentiation. I approach the problem by a double decomposition: decomposing similarity into finer subclasses and decomposing learning by similarity and analogy into a set of component subprocesses.

One thing reminds us of another. Mental experience is full of moments in which a current situation reminds us of some prior experience stored in memory. Sometimes such remindings lead to a change in the way we think about one or both of the situations. Here is an example reported by Dan Slobin (personal communication, April 1986). His daughter, Heida, had traveled quite a bit by the age of 3. One day in Turkey she heard a dog barking and remarked, “Dogs in Turkey make the same sound as dogs in America.… Maybe all dogs do. Do dogs in India sound the same?” Where did this question come from? According to Slobin's notebook, “She apparently noticed that while the people sounded different from country to country, the dogs did not.” The fact that only humans speak different languages may seem obvious to an adult, but for Heida to arrive at it by observation must have required a series of insights. She had to compare people from different countries and note that they typically sound different.

Analogy is widely considered to be an important mechanism of scientific thinking and a source of creative insight in theory development (e.g., Tweney, Chapter 13, this volume). No less an authority than Johannes Kepler stated: “And I cherish more than anything the Analogies, my most trustworthy masters. They know all the secrets of Nature, and they ought to be least neglected in Geometry” (quoted in Polya, 1954, p. 12). In addition to its uses in scientific discovery, analogy functions as part of the workaday tool kit of science. In instruction, novices are told to think of electricity as analogous to water or of addition as analogous to piling up blocks, and in problemsolving analogy is a standard tool among both experts and novices (e.g., see Clement, 1981; Collins & Gentner, 1987; Gentner & Gentner, 1983; Van Lehn & Brown, 1980). Finally analogy is also used in everyday reasoning, as when the stock market is said to “climb to dizzying heights” or when there is said to be a “balance of trade” (see Lakoff & Johnson, 1980).

Yet for all its usefulness, analogy is never formally taught to us. We seem to think of analogy as a natural human skill, and of the practice of analogy in science as a straightforward extension of its use in common-sense reasoning. For example, William James believed that “men, taken historically, reason by analogy long before they have learned to reason by abstract characters” (James, 1890, II, 363).

Analogies are powerful ways to understand how things work in a new domain. We think this is because analogies enable people to construct a structure–mapping that carries across the way the components in a system interact. This allows people to create new mental models that they can then run to generate predictions about what should happen in various situations in the real world. This paper shows how analogies can be used to construct models of evaporation and how two subjects used such models to reason about evaporation.

As Lakoff and Johnson (1980) have documented, our language is full of metaphor and analogy. People discuss conversation as a physical transfer: (e.g., “Let's see if I can get this across to you” (Reddy 1979). They analogize marriage to a manufactured object: (e.g., “They had a basic solid foundation in their marriages that could be shaped into something good” (Quinn this volume). They speak of anger as a hot liquid in a container (Lakoff & Kövecses this volume); and they describe their home thermostat as analogous to the accelerator on a car (Kempton this volume).

Why are analogies so common? What exactly are they doing for us? We believe people use them to create generative mental models, models they can use to arrive at new inferences.