3. Understanding practical cognition: The role of tacit knowledge

What distinguishes people who are more successful from those who are less successful in their everyday lives? Sternberg and his colleagues (Sternberg et al., 1993; Sternberg et al., 1995; Wagner and Sternberg, 1985; Wagner, 1987) have taken a knowledge-based approach to addressing this question. They have found in their research that much of the knowledge needed to succeed in real-world tasks is tacit. It is acquired while performing everyday activities, but typically without conscious awareness of what is being learned. And although people's actions may reflect their knowledge, they may find it difficult to articulate what they know. The notion that people acquire knowledge without awareness of what is being learned is reflected in the common language of the workplace as people speak of "learning by doing" and of "learning by osmosis." Terms like professional intuition and professional instinct further imply that the knowledge associated with successful performance has a tacit quality.

The term tacit knowledge, introduced by Polanyi (1966), has been used to characterize the knowledge gained from everyday experience that has an implicit, unarticulated quality (Neisser, 1976; Schön, 1983; Sternberg, 1985a, 1988, 1997a). Sternberg and his colleagues (Sternberg, 1997a, 1997b; Sternberg and Horvath, 1999; Wagner and Sternberg, 1985) view tacit knowledge as an aspect of practical cognition. It is knowledge that reflects the practical skill to learn from experience and to apply that knowledge in pursuit of personally valued goals. Tacit knowledge is needed to successfully adapt to, select, or shape real-world environments. Because tacit knowledge is an aspect of practical cognition, it provides insight into an important factor underlying the successful performance of real-world tasks. Research by Sternberg and his colleagues (see e.g., Sternberg et al., 1993; Sternberg et al., 1995), which we review in later sections of this report, has shown that tacit knowledge can be applied to understanding performance in a variety of job domains.

Support for the importance of the concept of tacit knowledge is found also in research on expertise and implicit learning. Research with experts in a variety of knowledge-intensive domains has shown that reasoning and problem solving in such domains depend upon proceduralized skills and schematicallyorganized knowledge, both of which may operate outside of focal awareness (see Chi, Glaser, and Farr, 1988). Furthermore, expert knowledge appears to reflect the structure of the operating environment or situation more closely than it does the structure of formal, disciplinary knowledge (Groen and Patel, 1988).

Research on implicit learning focuses on the phenomenon of learning without intention or awareness. Tacit knowledge may be, but need not be, acquired implicitly. Arthur Reber and his colleagues' work on the acquisition of stochastic grammars and of event sequences suggested that human beings are capable of acquiring knowledge of a very complex nature without conscious intention or awareness of learning (Reber, 1967, 1969; Reber and Millward, 1968). Researchers subsequently applied the paradigm to study learning of meaningful information (e.g., information about other people and information about the behavior of an economic system) and replicated the basic pattern of results (Broadbent and Aston, 1978; Broadbent, Fitzgerald, and Broadbent, 1986). The research on implicit learning suggests that knowledge can be acquired in the absence of awareness or intention to learn, and thus has a hidden or tacit quality.

In this section, we begin by discussing the type of theoretical concept we consider tacit knowledge to be. Next, we describe the characteristic features of tacit knowledge and how it is distinguished from related concepts. Then, we consider how tacit knowledge is represented at different levels of abstraction. We present a cognitive model that relates the key features of tacit knowledge to the acquisition, storage, and retrieval of knowledge in and from memory.