3.2.1 Tacit knowledge typically is acquired without environmental support

Tacit knowledge generally is acquired on one's own. That is, it is acquired under conditions of minimal environmental support. By environmental support, we mean either people or media that help the individual to acquire the knowledge. As such, tacit knowledge tends to be unspoken, underemphasized, and poorly conveyed relative to its importance for practical success.

When people or media support the acquisition of knowledge, they facilitate three knowledge-acquisition components: selective encoding, selective combination, and selective comparison (Sternberg, 1988). When an individual is helped to distinguish more from less important information (selective encoding), to combine elements of information in useful ways (selective combination), and to identify knowledge in memory that is relevant to the present situation (selective comparison), the individual has been supported in acquiring knowledge. In performing real-world tasks, individuals often must engage in these processes on their own in order to make sense of and respond to situations. The resulting knowledge may reflect the use of these processes, but the individual may not be able to express how the knowledge was acquired.

3.2.2 Tacit knowledge is procedural

The second feature of tacit knowledge is its close association with action. Tacit knowledge takes the form of "knowing how" rather than "knowing that." Anderson (1983) has characterized these two respective types of knowledge as procedural and declarative. More precisely, procedural knowledge is knowledge that is represented in a way that commits it to a particular use or set of uses. It is knowledge that guides behavior, usually without being readily available to conscious introspection. People may not know they possess and/or may find it difficult to articulate such knowledge. We view procedural knowledge as a superset of tacit knowledge. All tacit knowledge is procedural, although not all procedural knowledge is tacit.

The characterization of tacit knowledge as procedural derives from our research. We have found that when individuals are queried about the knowledge they have acquired through their experiences, they often begin by articulating general rules in roughly declarative form (e.g., "a good leader needs to know people"). When these general statements are probed, the statements often reveal themselves to be more abstract or summary representations of a family of complexly specified procedural rules (e.g., rules about how to judge people accurately for a variety of purposes and under a variety of circumstances). These procedural rules, we believe, represent the characteristic structure of tacit knowledge and serves as the basis for identifying and measuring tacit knowledge.

We can represent tacit knowledge in the form of condition-action pairings:

IF <antecedent condition> THEN <consequent action>

For example, the knowledge of how to respond to a red traffic light could be represented as:

IF <light is red> THEN <stop>