From David Bordwell, Making Meaning. Harvard University Press, 1989. pp. 136 - 138.
Despite differences in terminology and assumptive frameworks, cognitive theories from various disciplines have in recent years converged on a central fact about our ways of thinking. Human induction achieves its goals by using organized, selective, and simplified bodies of knowledge. For example, to understand an event as a purchase or a sale summons up a conceptual structure consisting of two agents, buyer and seller; a piece of property; and money.  These are taken to be the necessary components of the situation. The transaction is mentally represented as an exchange of the property for the money. In understanding that I sell a bike to Ben, you pick out the pertinent features of the empirical situation according to this structure and you assign them to the buyer/seller/property/money/exchange slots. You map, one to one, the conceptual structure onto the concrete case.
The "buy-sell" conceptual construct is internally organized: it consists of a set of relationships among tvpes of agents, objects, actions, and states of affairs. It is also made up of data, so that you can, in a concrete case, fill in slots that are left blank. For instance, if I say, "Vance came home from the showroom with a jeep," you will probably apply the buy-sell construct and will fill in the other agent slot (the salesperson) and Vance's payment of money. Yet the construct remains a regulative one, functioning not as an absolute guarantee but only as the best current candidate for understanding the situation. If I say, "Vance came home from the showroom with a jeep. The police arrested him ten minutes later," you will probably discard the buy-sell construct and opt for a less charitable one.
Although it contains data, the construct is quite schematic, or diagrammatically simplified. A great many cases of buying and selling do not exactly fit the schema: a third party may act as an intermediary, or corporations may transfer stock by computer. As a simplifying construct, the schema also relegates a lot of data, such as the weather or the cut of the seller's clothes, to a low point in the hierarchy of importance. Nevertheless, the schematic structure is "basic" in that one starts with it under default assumptions and then adapts it to the concrete situation (for example, the seller slot could be filled by a company, or the money slot could be filled by a credit card). However incomplete or in need of revision the structure may be, it remains a point of departure. Whatever we call such structuresframes, scripts, models, or, as I shall here, schematathey centrally mediate our cognitive activity." 
Of course, particular schemata are culturally variable. A society may lack the buy-sell schema; it may have only a "barter" schema or a "gift-giving" one or indeed nothing remotely similar. But in every society, human reasoning utilizes some schemata, and the principles undergirding their formation and use must be cross-cultural. This presupposes, in turn, that practical inductive reasoning is a fundamental feature of human thought, achieved by native endowment, cultural evolution, or a combination of both.
The concept of a "schema" runs back at least to Kant, who seems to have applied the term to both the knowledge structure itself (conceived, it would appear, primarily as a mental image) and the rule or procedure by which the mind produces and uses such structures.  Both usages can be found in the cognitive theory literature as well.
Schemata typically generate "prototype" effectsthe selection of one sort of instance as the clearest representative of the schema's essential features. The prototype of the buy/sell schema is that of a face-to-face transaction involving two individuals exchanging cash for a tangible piece of property. A televised auction in which buyers pledge to pay next year is comprehensible in terms of the schema, but it is not the "best" instance. As Lakoff indicates, prototype effects can arise from stereotypes, typical examples, ideals, and other sorts of samples. 
Schemata are retrieved, applied, adjusted, and rejected in the course of all perception and cognition. Within interpretive problem-solving, schemata are typically employed in what psychologists call a "top-down" manner: guided by more or less explicit goals, the critic tests abstract schemata against the empirical case. (By contrast, some aspects
of comprehension, such as perception of shape or movement or color, are "bottom-up," or data-driven. Still other aspects of comprehension, such as story construction, involve both top-down and bottom-up processing.) Thus it becomes necessary to consider how schemata are used in a cycle of interpretive action. The routines or procedures in question consist mostly of heuristics, rules of thumb that have proven useful in meeting the interpretive institution's demands for novelty and plausibility.
 My example is drawn from Ronald W. Casson, "Schemata in Cognitive Anthropology,"Annual Review of Anthropology (1983): 431-432.
 There are various conceptions of schemata in the cognitive theory literature. Good introductions can be found in John R. Anderson, Cognitive Psychology and Its Implications (New York: Freeman, 1985), pp. 124-133, and Neil A. Stillings et al., Cognitive Science: An Introduction (Cambridge: MIT Press, 1987), pp. 30-36, 65-73, 150-156. More advanced discussions pertinent to arguments in this book are in Mark Johnson, The Body in the Mind: The Bodily Basis of Meaning, Imagination, and Reason (Chicago: University of Chicago Press, 1987), pp.18-40, and George Lakoff, Women, Fire, and Dangerous Things (Cambridge: Harvard University Press, 1987), pp. 68 - 135, 269 - 303.
 The relevant argument is in Immanuel Kant, Critique of Pure Reason, trans. Norman Kemp Smith (London: Macmillan, 1983), A137-B176-A147-B187. Important discussions are Robert Paul Wolff, Kant's Theory of Mental Activity: A Commentary on the Transcendental Analytic of the "Critique of Pure Reason" (Cambridge: Harvard University Press, 1963), pp. 70, 206, 210-218; W. H. Walsh, "Schematism," in Kant:A Collection of Critical Essays, ed. Robert Paul Wolff (Garden City, N.Y.: Doubleday, 1967), pp. 71-87; Donald W. Crawford, "Kant's Theory of Creative Imagination," in Essays in Kant's Aesthetics, ed. Ted Cohen and Paul Guyer (Chicago: University of Chicago Press,1982), p.162; and Gordon Nagel, The Structure of Experience: Kant's System of Principles (Chicago: University of Chicago Press, 1983), pp. 67-81.
 Johnson, Body in the Mind, pp. 117-119; Lakoff, Women, Fire, p. 274.
 Lakoff, Women, Fire, pp. 79-90.