This article reviews research on the use of situation models in language comprehension and memory retrieval over the past 15 years. Situation models are integrated mental representations of a described state of affairs. Significant progress has been made in the scientific understanding of how situation models are involved in language comprehension and memory retrieval. Much of this research focuses on establishing the existence of situation models, often by using tasks that assess one dimension of a situation model. However, the authors argue that the time has now come for researchers to begin to take the multidimensionality of situation models seriously. The authors offer a theoretical framework and some methodological observations that may help researchers to tackle this issue. p. 1

In a discussion of situation models, it is important to distin- guish them from the better-known concept of schema (e.g., Alba & Hasher, 1983). Schemata are mental representations of~ stereotypical situations. A well-known example is Schank and Abelson's (1977) restaurant script. A script for a restaurant visit represents the actors, props, entry and exit conditions, and action sequence typically encountered during restaurant visits. In contrast, a situation model of a restaurant visit would be a mental representation of a specific restaurant visit (e.g., “Thurs- day, October 14, 1997, at Chez Pierre, lunch with K.”) p. 1

Language comprehension necessarily involves the construc- tion of a representation of the state of affairs described in a text. Furthermore, successful memory of what is comprehended would necessarily involve the retrieval of such representations. These claims may seem rather self-evident and therefore not worthy of scrutiny to many people. However, up until the early 1980s, many, if not most, cognitive psychologists viewed text comprehension as the construction and retrieval of a mental 1\representation of the text itself rather than of the situation de- scribed by the text. p. 1

schemata can be used as building blocks for the construction of situation models. p. 1

the mental rep- resentations of verbally described situations, which have become known as mental models (Johnson-Laird, 1983) or situation models (van Dijk & Kintsch, 1983). p. 1

Rather than treating language as information to analyze syntactically and semantically and then store in memory, !language is now seen as a set of processing instructions on how to construct a mental representation of the described situation (see also Gernsbacher, 1990). p. 1

The question “How do readers construct a coherent situation model?” presupposes that we know what a coherent situation model is. But do we? p. 2

according to Johnson-Laird, a situation model incorpo- rates at least temporal, spatial, causal, motivational, and person- and object-related information. p. 2

If we do indeed construct situation models during reading, listening, or viewing, then we might assume that we use modal- ity-independent cognitive procedures to construct these models. p. 3

Models are needed to explain the integration of verbal and visual information. Various text genres, such as scientific arti- cles, textbooks, brochures, and newspaper articles, are often accompanied by graphs and pictures intended to enhance com- prehension. Situation-model theorists argued that graphs and pictures aid comprehension by being jointly incorporated with information derived from the text into an integrated situation model. p. 3

Baggett (1979) found that students who saw a short film produced structurally similar recall protocols as stu- dents who heard a spoken version of the study that matched the movie in episodic structure. p. 3

In an interesting study, Schneider and Korkel (1989) compared the recall of soccer “experts” with novices p. 3

of a text about a soccer match. Soccer expertise was crossed with grade level ( 3rd, 5th, and 7th) . The most salient finding was that the 3rd grade soccer experts recalled more idea units from the text (54%) than did the 7th grade novices (42%). In other words, domain expertise more than offset the inherent difference in verbal skills between 3rd and 7th graders. p. 4

Situation Models Are Needed to Explain How People Learn About a Domain From Multiple Documents p. 4

This finding can be accounted for by asserting that the high-knowl(edge students had fewer problems constructing a situation model 1because they could assemble the model by retrieving relevant knowledge structures from their long-term memory (Ericsson & Kintsch, 1995), whereas low-knowledge readers had to con- struct the model essentially from scratch. There have been sev- eral other studies demonstrating how domain expertise may counteract verbal ability (e.g., Fincher-Kiefer, Post, Greene, & Voss, 1988; Yekovich, Walker, Ogle, & Thompson, 1990). p. 4

Much learning involves the integration of information from different documents. Perfetti, Britt, and Georgi ( 1995) provided a compelling example of how situation models are needed to account for text-based learning and reasoning about historical events, such as the events related to the construction of the Panama Canal. Multiple sources of information on the same topic overlap to varying degrees in terms of their referents and the relations among those referents. An efficient means of or- ganizing this information is to integrate knowledge from differ- ent sources into a common situation model. p. 4

As Perfetti and colleagues argued, people can construct a text base for each document they read, for example, a report on the ongoing prob- lems between Panama and the United States by the Center for Strategic Studies and a persuasive text against treaties between the United States and Panama written by a congressperson. How- ever, actual learning and reasoning (e.g., about whether the con- gressperson has a particular bias) takes place when people inte~ grate the information from the documents into a situation model.; p. 4

A General Processing Framework p. 4

3 models: the initial model when reading a clause or sentence, the integrated model, integrating one at a time models constructed while reading, and complete model - stored in long-term memory after all the textual input has been processed. p. 4

It should be noted that the complete model is not necessarily the final model. Comprehenders may ruminate over a story and generate additional inferences or develop en- tirely novel models. In fact, this is a quite common practice, as centuries of literary and religious hermeneutics demonstrate p. 5

However, this topic is beyond the scope of this article. To our knowledge, there exists no empirical research on it. We call the process of incorporating the current model into the integrated model updating. p. 5

Ericsson and Kintsch' s ( 1995) distinction between short-term and long-term working memory. In Ericsson and Kintsch's conceptualization, it is possible in highly prac- ticed and skilled activities, such as language comprehension, to extend the fixed capacity of the general short-term working memory (STWM) system by efficiently storing information in long-term memory and keeping this information accessible for further processing. This expansion of STWM is called long- term working memory (L TWM) and corresponds to the accessi- ble parts of a previously constructed mental representation in long-term memory. Because STWM contains retrieval cues to LTWM, people are able to efficiently retrieve previously en- coded information without engaging in extensive long-term memory searches. In the case of text comprehension, people achieve this by keeping relevant portions of the previously pro- cessed text accessible in LTWM and by maintaining retrieval cues to this information in STWM. This allows for the efficient integration of information across sentences. In line with this, we propose that readers keep the integrated situation model in LTWM while the current model is constructed in STWM. Dur- ing the construction process, there is transient activation in STWM to retrieval cues for parts of the integrated model. Up- dating occurs by forming links between the current model and the retrieved elements o f the integrated model. A t this point, the current model has been integrated and the integrated model has been updated, so that a new current model can be constructed in STWM. This process continues until the complete model is stored in long-term memory. p. 5

enting the same referent in STWM. Our discussion of the research on situation models is orga- nized in part in terms of whether they address (a) the fore- grounding of situational information, (b) the updating of the integrated model, or © the retrieval of the integrated model. p. 6

In our framework and in line with Ericsson and Kintsch' s ( 19~5) work, information is foregrounded by creating and maintaining a retrieval cue to this information in STWM. Sometimes, the reader foregrounds information on the basis of world knowledge because of what he or she knows about human goals and actions or about the narrative genre (see Zwaan, 1994, for a demonstration of the effects of genre knowledge on comprehension and retrieval processes). p. 6

causal inferences during on-line comprehension, even when it is also possible to form a connection between the current event and the information in working memory (Albrecht & Myers, 1995; Dopkins, 1996; Trabasso & Suh, 1993; van den Broek & Lorch, 1993). Theoretical arguments have also been advanced as to why readers monitor global causal coherence. Specifically, it is argued that readers form global causal connections in an “effort after meaning” (Graesser et al., 1994). p. 11

Consistent with the causal network model, various studies have demonstrated that explaining events, actions, and processes is an effective comprehension strategy (Chi, de Leeuw, Chiu, & LaVancher, 1994; Trabasso & Magliano, 1996; Zwaan & Brown, 1996). Chi et al. had two groups of high school students read an expository text about the blood circulation system. One group received no special instruction. However, the other group re- ceived the instruction to try to explain every process and event described in the text. The participants who received the explana- tion instruction increased their performance on a comprehension task by 10% over the control group. In addition, the better comprehenders, that is, students with higher college aptitude test scores, benefited as much from the instruction as less skilled comprehenders, that is, students with lower college aptitude test scores. There is also evidence that skilled comprehenders spontaneously generate more explanatory inferences than do less skilled comprehenders (Trabasso & Magliano, 1996; Zwaan & Brown, 1996). p. 11

Trabasso, van den Broek, and their colleagues have proposed a causal network model of compre- hension to capture this myriad of connections (Trabasso & Mag- liano, 1996; Trabasso & Sperry, 1985; Trabasso & Suh, 1993; Trabasso & van den Broek, 1985; van den Broek, 1994; van den Broek & Lorch, 1993) p. 11

According to the causal network model, text comprehension shares features with problem solv- ing. When a person reads about an event, he or she attempts to explain that event by using information from the previous sen- tence, from the mental representation of previously reported events-now in long-term memory-or from world knowledge. p. 11

One of the basic premises of the causal network model is that readers form causal connections between events in nonadjacent sentences in a text. This is an interesting claim because it suggests that readers look beyond the current contents of working memory (typically assumed to be one or two sentences) or to make causal connec- tions. Various studies suggest that readers do indeed make global p. 11

Furthermore, we need to learn more about the level of resolu- tion at which situations can be represented. Some have argued that it is unrealistic to assume that readers construct “lifelike” mental representations (e.g., “movies in the head”) of situa- tions during comprehension (McKoon & Ratcliff, 1992). Most situation model researchers would subscribe to this view. Situa- tion models are likely to be rather abstract representations in which, for example, tokens may represent protagonists or ob- jects (e.g., Johnson-Laird, 1983) . I t is known from the literature on mental imagery that people are capable of constructing rather detailed mental images from verbal descriptions. However, creat- ing a detailed mental image requires extensive and effortful processing. For example, it takes several exposures to a text to construct a spatial image (Denis & Cocude, 1992), and it takes participants at least 3 s to construct an elaborate image of, for example, a canary. Below the 3-s threshold, only rudimentary images may be formed (Marschark & Comoldi, 1991). Given that normal word reading times are at least 10 times faster, it seems unlikely that readers typically generate detailed visual images during comprehension. p. 17

Most researchers would claim, as do we, that the motivational and causal dimensions form the backbone of situations constructed during narrative comprehension. There are several reasons for this. At the level of task analysis, humans read texts to understand why events happened. Comprehension is an “effort after meaning” (Graes- ser et al., 1994).1t is not enough to know that TWA Flight 800 crashed or when or where it crashed. We want to know why it crashed. p. 17

Another prediction from the event-indexing model concerns the representation of stories in long-term memory. The end result of successful story comprehension is a coherent mental repre- sentation in long-term memory. According to the event-indexing model, the long-term memory representation of the situation model is a network of nodes that code the events described in and inferred from the story. Two event nodes may be connected through a given number of situational links. For example, if two events share a temporal or an agent index, they are connected through a temporal or agent link. The event-indexing model predicts that the strengths of the interconnections between mem- ory nodes coding for story events will vary with the number of shared event indexes between these events. p. 18

Zwaan, Langston, and Graesser (1995) have proposed an event-indexing model (events is taken generally and refers to both events and actions) of text comprehension. The event-in- dexing model makes general claims about both on-line compre- hension and about the resulting representation on the reader's long-term memory. During comprehension, each incoming event (as denoted by a verb) is decomposed into five indexes: time, space, causality, intentionality, and agent. These dimensions cor- respond to the dimensions listed by Chafe ( 1979; see also Gerns- bacher, 1990). There is empirical evidence that each of these variables individually plays a role in comprehension. However, we do not regard this set of indexes as exhaustive or fixed. Future research may demonstrate the importance of other situa- tion model dimensions. p. 18

Specifically, we distinguished three types of situation model: the current model, the integrated model, and the complete model. We also distinguished four classes of processes that operate on these models. Construction refers to the construction of a model of the situation described in the clause that is currently being read. Updating refers to the process of incorporating the current model into the integrated model of the situations described in previous clauses. Retrieval refers to the process of bringing parts of the integrated or final model back from long-term memory into LTWM and STWM. Finally, foregrounding refers to the process of maintaining re- trieval cues in STWM buffers to parts of the integrated model in LTWM. This process is different from, but often the result of, authors' and speakers' use offoregrounding devices in language. p. 19

the new model makes a distinction among (a) a situational framework, (b) situational relations, and © situational content. p. 19

Various connectionist type models of language comprehen- sion have been proposed, most notably Kintsch's (1988) con- struction-integration model and Just and Carpenter's (1992) capacity constrained READER model. Other examples are the landscape model (van den Broek, Risden, Fletcher, & Thurlow, 1996) and the capacity-constrained construction-integration model of Goldman, Varma, and Cote ( 1996) . p. 20

Anderson, J. R. (1974). Retrieval of propositional information from long-term memory. Cognitive Psychology, 6, 451-474. p. 20

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Chi, M. T. H., de Leeuw, N., Chiu, M., & LaVancher, C. ( 1994). Elic- iting self-explanations improves understanding. Cognitive Science, 18, 439-477. p. 20

Clark, H. H. ( 1972). Difficulties people have in answering the question “Where is it?” Journal ofVerbal Learning and Verbal Behavior, 11, 265-277. p. 20

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