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Situation Models
When people read a story, they construct mental representations of the words and sentences within the text, but also of the situations and events that are suggested by the text. A Situation Model is the mental representation of the events, people, places, etc., described within the text. Readers use their own previously acquired knowledge in order to add to information given to them in a text as a way to complete a coherent representation of the content in the text, and research has shown that the construction of clear and organized situation models is an important factor in understanding and remembering a text. Much of the research on situation models in narrative comprehension suggests that the readers behave as though they are inside the narrated situation and experience them vicariously (2). For example, when we read a newspaper article about some event we sometimes feel as though we had actually been present when the event occurred. Overtime, as narrative events evolve readers update their situation model (ex. moving characters to new places, or getting rid of old information no longer needed).

Situation models and schemas are often mistakenly used interchangeably, so it is important to make the distinction between the two. A Schema consists of a mental representation of stereotypical situations (ex. a script for a dentist checkup visit, where you know who you will talk to, what the dentist will do, etc.), versus a situation model which is a mental representation of a specific event or situation (ex. a specific dentist visit on September 12, 2011). Basically, schemata are more general representations and situation models are much more specific events/situations. Schemata can also be used as building blocks in the formation of situation models.



Three Levels of Reading Comprehension
Understanding a text requires representations on different levels of processing. There are at least 3 levels in which a text can be represented and these include, surface structure, text base, and the situation model. Each level is thought to be interconnected within the readers memory.

The surface structure is the lowest level of representation. It is a basic representation of the structure of the text, including the words and syntax that were used. The reader perceives the written words in front of them and understands word meanings, word ordering and any grammatical aspects. For example, if you read the sentence “the dog chased the cat,” the surface structure would be the actual sentence you are looking at on the screen. The textbase level is a propositional network which represents the meaning of the text (i.e. ideas present in the text that are not related to the specific structural form of the text). (5) At this level, the sentences entire meaning is understood and any actions or spatial aspects are inferred (ex. the physical motion of a dog chasing a cat). The highest level of representation is the situation model which is a mental representation of the situation, events, people, etc., being referred to in a text. (5) This is where the textual information the reader is provided with is combined with their own personal knowledge to create a mental representation of what they have just read.

Research suggests that each level the three levels are not equal in the degree to which they are used during memory retrieval. (6) It is believed that after the initial reading of a text each level is greatly available, but as time goes on the surface form is soon forgotten, followed by textbase level. At this point the situation model begins to take over processing because it remains at a much more constant level of availability then the others.

The type of text being read has also been said to have an effect on the strength of each level of representation. A study by Zwaan (1994) examined the strengths of each level of representation in relation to genre expectations. In each experiment subjects were divided into two groups reading the exact same texts, but were told they were reading them under two different perspectives. The first group read the text as a news story, while the second group would read the text as a literary story. News stories tend to force the reader to focus more on the events taking place in the text, while literary stories force the reader to focus on the text structure. The readers who believed they were reading a news story constructed much stronger situation models, while the readers who believed they were reading a literary story had much more activation in the textbase and surface structure levels. (5)

Structure Building Framework
In 1990, Gernsbacher proposed a structure building framework to explain the different dimensions of situational continuity. He believed that when reading a text, a person constructs mental structures and then proceeds to map out information onto the developing structure. Situational continuity was thought to be the guiding force behind this process.

Situational Continuity
Situational continuity occurs when previously established time frames, locations, or consequences of previously described events or actions are preserved during the comprehension of a text (7). Basically, when a text is continuous, information can be easily added to the current situation model because its events occur in chronological order. When there are discontinuities in a text the info is significantly harder to add to the situation model because it forces the reader to stop building one structure and begin construction on another (7). There are three basic types of situational variables which effect the construction of a situation model.

Temporal Continuity
Events in real life occur chronologically, however within texts characters and situations can easily jump from one time period to another. Temporal continuity is when a sentence in a story describes an event or action that is happening in the same time frame as the sentence before it. When there is a temporal discontinuity within a text, it may have a negative effect on text comprehension and reading time (7). Temporal discontinuities include any sort of time shift within a text, such as flashbacks or flash forwards. An example would be statements about events that will take place in the future, or phrases like “the next day” which cause the story to jump forward in time. The temporal information of a situation model has been identified as a very important portion in the formation of situation models, and readers have been shown to create time-based situation models in the absence of clear spatial information.

Spatial Continuity
Spatial continuity takes place when a text describes events and actions that occur in the same spatial setting (ex. the same room, scenario or area in a text). A spatial discontinuity occurs when the narrative changes locations. There is evidence that spatial discontinuities may have a negative effect the availability of information from previous spatial settings. (7)

Causal Continuity
Causal continuity occurs when the causation of the current sentence is related to previous information from the story. A sentence is said to have Causal discontinuity when the cause behind the current sentence cannot be established based on the previous sentences, and therefore forces the reader to infer a causal link between the two (7). An example of a causal discontinuity would be “Mackenzie tripped while he was running and his ice cream went flying. Robbie had to ask the teacher to go home to change his shirt.” The reader is forced to infer from this sentence that the ice cream landed on Robbie’s shirt, even though they are never explicitly told this is what happened.



Spatial Distance Effects
Spatial distance effect states that situation models preserve any spatial characteristics of the situation being described in the text. Representations in a text will preserve real life spatial features even though the representation is only mental. For example, in a study by Bower and Rinck (2001) it was discovered that while reading a text, the closer a target object in a building was to the area where the reader was focusing their attention, the faster the reader was able to answer questions about the object. It was also found that as a reader moves through a building, the activation of objects and places along their implied route increases. For example “Jenna walks from Room B into Room D” has an implied path through “Room C” (even though it was not physically mentioned in the text). The objects in Room B will be primed for retrieval at a level in between Room D (highest activation), Room B (lower activation) and everywhere else in the building the character is not walking through (i.e. Rooms A, E, F, G and the hallway would have the lowest activation) (10). This occurs because the characters location in the building is consistent with the reader’s mental representation of the text, which maintains spatial characteristics.

Updating Situation Models
Mental representations of events and situations are repeatedly updated as new information is introduced which allows situation models to continuously adapt over time. Two opposing views of this continuously revising process are the here-and-now view and the memory-based text processing view.

The here-and-now view believes that newly emerging information is compared against the current model (the here-and-now) and based on whether it conflicts with the current model or not, is integrated into the model. Incoming information will only interfere with the comprehension process if it is inconsistent with the here-and-now section of the model because outdated information will need to be reactivated and adjusted.

In contrast, the memory-based text processing view states information in long term memory is activated in response to current incoming information in working memory (11). The amount of activation is called the resonance, and it is determined by the amount that semantic features stored in a person’s long-term memory that overlap with features of the current text being read. The concepts in long term memory that resonate the most are combined into working memory and aid in updating the current situation model. In this view both new information and information already present in working memory serve as signals to information being stored in long term memory (11).

In Children
Children have been shown to experience difficulties forming situation models in certain types of situations. The difficulty is highest when cues (such as temporal subordinate conjunctions like before and after) are used to tell the child how to order events is placed in the center of a sentence, as opposed to the beginning or the end. For example “we went to the grocery store after we went to the pet store” would be more difficult for children to mentally represent then “after we went to the pet store, we went to the grocery store.” This suggests that children have difficulty revising mental representations of an event they are building a situation model around, because they are not able to organize the events correctly.

As We Age
It is widely known that as we age, our abilities to use various forms of cognitive processing declines. However, there are some areas of cognitive function that remain unchanged or even show improvement over time. While cognitive declines have been shown to occur in areas such as processing speed, smaller working memory capabilities, and inhibitory abilities, many studies have demonstrated that there appears to be no decline or deficits in processing at the situation model level in the elderly. As people age, they can update situation models by adding new information and taking out old information that is no longer necessary, however this process of constantly updating ones situation model has been observed to be unaffected by age. Situation models can therefore be understood to be a basic level of comprehension that is resilient to the effects of aging.