13 Script Theory

Script Theory (Roger Schank) 

The central focus of Schank's theory has been the structure of knowledge, especially in the context of language understanding. Schank (1975) outlined contextual dependency theory which deals with the representation of meaning in sentences. Building upon this framework, Schank & Abelson (1977) introduced the concepts of scripts, plans and themes to handle story-level understanding. Later work (e.g., Schank, 1982,1986) elaborated the theory to encompass other aspects of cognition.

The key element of conceptual dependency theory is the idea that all conceptualizations can be represented in terms of a small number of primative acts performed by an actor on an object. For example, the concept, "John read a book" could be represented as: John MTRANS (information) to LTM from book, where MTRANS is the primitive act of mental transfer. In Schank's theory, all memory is episodic, i.e., organized around personal experiences rather than semantic categories. Generalized episodes are called scripts -- specific memories are stored as pointers to scripts plus any unique events for a particular episode. Scripts allow individuals to make inferences needed for understanding by filling in missing information (i.e., schema).

Schank (1986) uses script theory as the basis for a dynamic model of memory. This model suggests that events are understood in terms of scripts, plans and other knowledge structures as well as relevant previous experiences. An important aspect of dynamic memory are explanatory processes (XPs) that represent stereotyped answers to events that involve anomalies or unusual events. Schank proposes that XPs are a critical mechanism of creativity.

Application 

Script theory is primarily intended to explain language processing and higher thinking skills. A variety of computer programs have been developed to demonstrate the theory. Schank (1991) applies his theoretical framework to storytelling and the development of intelligent tutors. Shank & Cleary (1995) describe the application of these ideas to educational software.

Example 

The classic example of Schank's theory is the restaurant script. The script has the following characteristics:

Scene 1: 

Entering 

S PTRANS S into restaurant, S ATTEND eyes to tables, S MBUILD< where to sit, S PTRANS S to table, S MOVE S to sitting position

Scene 2: 

Ordering 

S PTRANS< menu to S (menu already on table), S MBUILD< choice of food, S MTRANS< signal to waiter, waiter PTRANS to table, S MTRANS< 'I want food' to waiter, waiter PTRANS to cook

Scene 3: 

Eating 

Cook ATRANS food to waiter, waiter PTRANS food to S, S INGEST food

Scene 4: 

Exiting 

waiter MOVE write check, waiter PTRANS to S, waiter ATRANS check to S, S ATRANS money to waiter, S PTRANS out of restaurant

There are many variations possible on this general script having to do with different types of restaurants or procedures. For example, the script above assumes that the waiter takes the money; in some restaurants, the check is paid to a cashier. Such variations are opportunities for misunderstandings or incorrect inferences.

Principles 

1. Conceptualization is defined as an act or doing something to an object in a direction.

2. All conceptualizations can be analyzed in terms of a small number of primitive acts.

3. All memory is episodic and organized in terms of scripts.

4. Scripts allow individuals to make inferences and hence understand verbal/written discourse.

5. Higher level expectations are created by goals and plans.

References 

• Schank, R.C. (1975). Conceptual Information Processing. New York: Elsevier.
• Schank, R.C. (1982a). Dynamic Memory: A Theory of Reminding and Learning in Computers and People. Cambridge University Press.
• Schank, R.C. (1982b). Reading< and Understanding. Hillsdale , NJ: Erlbaum.
• Schank, R.C. (1986). Explanation Patterns: Understanding Mechanically and Creatively. Hillsdale , NJ: Erlbaum.
• Schank, R.C. (1991). Tell Me a Story: A New Look at Real and Artificial Intelligence. New York: Simon & Schuster.
• Schank, R.C. & Abelson, R. (1977). Scripts, Plans, Goals, and Understanding. Hillsdale , NJ: Earlbaum Assoc.
• Schank, R.C. & Cleary. C. (1995). Engines for education. Hillsdale , NJ: Erlbaum Assoc.