McKoon and Ratcliff (1992) contrast a minimalist theory of reading with a constructionist or mental-model theory "that readers automatically construct a full representation of the real-life situation described by a text." We take issue with three aspects of McKoon and Ratcliff's arguments. First, the contrast between the minimalist and the mental-model account is unwarranted: The minimalist account applies to automatic inferences, whereas mental models are not often constructed automatically. Second, mental models are not full representations of real-life situations. Last, we report the results of two experiments demonstrating problems with their "salience" account of phenomena previously attributed to mental models.
1.1 McKoon and Ratcliff (1992) have argued for a minimalist strategy in the investigation of automatic inferences during comprehension. Minimalism is intended to apply to reading in the absence of specific goals such as learning new information from a text. According to minimalism, when this condition is met, automatic inferences are made in two situations only. First, inferences are made automatically to preserve local coherence. Second, inferences are made automatically when the requisite information is highly available. McKoon and Ratcliff contrast minimalism with several other theories they interpret as positing that inferences are made under less restricted conditions. We agree with McKoon and Ratcliff that the minimalist position provides a sound (although not the only) research strategy, namely, assume the minimum until forced by the data to assume more. We do have three specific disagreements, however, each of them involving the concept of mental models. The first disagreement concerns the extent to which mental models are formed automatically, the second the extent to which mental models are "life-like," and the third has to do with McKoon and Ratcliff's interpretation of their Experiment 5, in which they purport to demonstrate that previous data supporting mental-model theory are best viewed as demonstrating the operation of "salience."
1.2 Virtually all pertinent theories postulate that comprehension results in the creation of some form of cognitive representation. Debate focuses on the processes used to derive the representation, the nature of the representation (e.g., propositional or imaginal), and the information that is represented. Among mental-model theories of comprehension, the greatest consensus concerns the last mentioned area. That is, a mental model is a representation of what the text is about, a representation of the events, objects, or processes described by the text, rather than of the words, sentences, or structure of the text itself. Thus, a mental model is likely to capture the spatial (Bryant, Tversky, and Franklin, 1992; Glenberg, Meyer, & Lindem, 1987; Morrow, Greenspan, & Bower, 1987) and temporal structure (Glenberg & Langston, 1992) of the events described in the text. Most mental-model theories do not deny the possibility of other levels of representation which may well be required for successful grammatical and referential processes. The basic intuition, however, is that these other levels alone do not fully capture the meaning of the term "comprehension."
2.1 McKoon and Ratcliff (1992) state that "The most important claim of many `mental model' theories of text comprehension is that the mental representation of a text automatically depicts the events described by the text in a `life-like' way," (p. 456) and "readers automatically construct a full representation of the real-life situation described by a text" (p. 458). To what extent are these statements correct? Note that there are really two components to be addressed: the extent to which mental models are formed automatically and the extent to which they should be considered a "full" representation of the situation described by the text.
2.2 We do not think most mental modelers would hold that mental models are constructed automatically (at least not all of the time). Although there is no universally accepted definition of automatic processing, some broadly agreed upon characteristics of automatic processing are that it is accomplished without intention, that it is unavoidable, and that it requires a minimum of effort. Because reading for deep comprehension is unlikely to be automatic in this sense, and because mental models are just what deep comprehension is all about, few mental modelers would propose that the construction of a mental model is automatic. Furthermore, many of the experimental demonstrations of mental-model-like effects have used procedures that engender nonautomatic processing. For example, Morrow et al.'s (1987) subjects were required to memorize a spatial layout before reading the test texts. Bryant et al.'s (1992) subjects were allowed to study the initial portions of a text "for as long as they wished." Radvansky and Zacks (1992) used a multi-trial study procedure. Glenberg and Langston (1992) demonstrated that for some texts, the construction of mental models seems to require that the text be accompanied by illustrations; thus, mental model construction was certainly not automatic for the unillustrated texts. Given this brief survey of methods for inducing mental models we can see that it is not "an important claim" of mental-model theory that mental models be constructed automatically.
2.3 In contrast to what McKoon and Ratcliff's have suggested, Glenberg, Kruley, and Langston (in press) have proposed several preconditions for the construction of mental models. For example, readers must be attending to the words and grammatical relations and must have the appropriate lexical and grammatical knowledge. They must also have some domain knowledge to be able to construct a representation of the events, for example, knowledge about the characteristics of the entities producing the event, the types of relations these entities can enter into, and how these relations can be represented. In highly familiar domains, this knowledge may be readily available, thereby facilitating the construction of mental models. This seems to have been the case in the experiments reported by Glenberg et al. (1987) and Sanford and Garrod (1981). When this knowledge is not readily available, however, constructing mental models may be cognitively laborious.
3.1 Some mental model theorists do claim that mental models are life-like, but in the particular sense that there are some analogical correspondences between mental models and the situations that are represented. The correspondences are between real-world numbers and numbers in the representation as well as between real-world spatial relations and spatial relations in the representation. Thus, when a text is about a single actor, the corresponding mental model will have an entity corresponding to that actor. In a text in which two actors are foregrounded (e.g., in a conversation), the mental model will have entities corresponding to both participants. At least some spatial relations between entities also appear to be represented analogically (see Bryant et al., 1992 and Morrow et al., 1987). These claims of limited analogical correspondence contrast with McKoon and Ratcliff's statement that mental models are "a full representation of the real-life situation described by a text."
3.2 Part, at least, of the difference between McKoon and Ratcliff's characterizations and what mental modelers actually propose may be traced to differences in representational assumptions and the language used to describe those assumptions. According to Palmer (1978), in a propositional representation, all relations must be explicitly encoded. For example, suppose that a text describes three sticks, A, B, and C, and that the text mentions that A is taller than B and B is taller than C. A propositional representation of the relations among the sticks may consist of the propositions "taller than (A, B)" and "taller than (B,C)." The fact that stick A is taller than stick C is not represented until it is explicitly encoded as "taller than (A,C)." In a representation in which number and the taller-than relation are represented analogically, the situation is different. That is, given that it is (analogically) represented that A is taller than B and that B is taller than C, the fact that A is taller than C is then also represented. Thus, the analogical representation is "life-like" in the limited sense that the analogical representation of "taller than" preserves the property of transitivity. The "inference" that A is taller than C is likewise made automatically, in that it is part of the representation. Nonetheless, there is no claim that other aspects of the situation need be represented fully or analogically. Thus, the exact heights of the sticks, their thicknesses, surface characteristics, densities, chemical compositions, etc., need not be represented to qualify the representation as a mental model.
3.3 In light of these distinctions, consider a prediction attributed by McKoon and Ratcliff to mental model theory: "[A] mental model for a text such as the actress fell from the fourteenth story should include the inference that she died. It would not be reasonable, from the mental model point of view, to leave her suspended in mid air" (p. 457). If mental models were indeed a complete representation of a real situation, it would perhaps be reasonable to infer from the representation that the actress would die. Mental models are not complete representations, however. Given the brief segment of text, a mental model would probably include one representation corresponding to the actress and one corresponding to the fourteenth floor. If the model represented spatial relations analogically then the actress would be (in the analogical representational medium) below the fourteenth floor. However, there is nothing in mental-model theory to suggest that readers will necessarily fill in the rest of the details and have the actress plunge to her death. The text could in fact continue in a variety of ways that would deny just that possibility (e.g., the actress is saved by falling into a swimming pool). Thus, McKoon, Ratcliff, and Seifert's (1989) data demonstrating that most people do not completely infer the actress's death is consistent with both the minimalist and the mental-model hypotheses.
3.4 If people do not automatically infer outcomes such as the death of the actress, why do they bother to construct mental models? Primarily because understanding a text consists of creating a representation of what the text is about, that is, a mental model. Also, mental models allow inferences (e.g., that the actress will die) if one is asked to infer what is likely to happen. Thus, if the text continues with "She died instantly," the mental model is useful in understanding how that could have come about. It is important to note that if the text continues with "A gust of wind blew her onto a ledge at the thirteenth floor," the mental model is also useful in understanding how this could have come about.
4.1 One piece of evidence consistent with a mental-model level of representation was provided by Glenberg, Meyer, and Lindem (1987). The subjects in their experiment read short texts describing ordinary situations. An important feature of the texts was that their propositional structure was quite different from that of the situation described by them. Consider as an example a text which describes a main actor, John, preparing for a marathon. The critical sentence in the associated version of the text is "After doing a few warm-up exercises, he put on his sweatshirt and went jogging." Note that the associated version of the text describes a situation in which the main actor, John, is associated spatially with a target object, the sweatshirt. The critical sentence in the dissociated version of the text describes a situation in which the main actor and the target object are spatially dissociated, "After doing a few warm-up exercises, he took off his sweatshirt and went jogging." If subjects are tracking the structure of the situation, that is, building a mental model from the text, then we would expect to find evidence of a stronger connection between the actor and the target object in the a condition than in the dissociated condition. Furthermore, Glenberg et al. assumed that subjects would keep the main actor foregrounded because the actor is referred to by a pronoun (see, for example, Sidner, 1982). Because the target object remains spatially close to the actor in the situation described by the associated condition, it too should remain foregrounded and easily accessible. In fact, after the last mention of the target object and a one-sentence delay, subjects were faster in making a recognition response to the name of the target object in the associated condition than in the dissociated condition. There was little difference in responding immediately after the last mention of the target object, presumably because the target object was foregrounded (due to recent mention) in both cases.
4.2 Note that these results are difficult to reconcile with the view that comprehension results in a propositional representation of the text. In the associated condition, the main actor and the target object are conjoined in a single proposition, something like, "on (John, sweatshirt)." In the dissociated condition, the two are also conjoined in a single proposition, something like, "off (John, sweatshirt)." Glenberg et al. reasoned that if these propositions formed the only representation then there would be no reason to predict differential speed of responding to the target object.
4.3 McKoon and Ratcliff (1992) proposed that the Glenberg et al. results do not reflect the construction of a mental model, but instead are due to "salience." That is, in the associated condition, the target object is viewed as more salient -- "more relevant to the topic of [the] discourse" (p. 460) -- than in the dissociated condition. According to McKoon and Ratcliff, it is this difference in salience that produces the differential speed of responding, not a difference in the structure of a mental model.
4.4 Before we introduce new data (PART II, see Sections 6 and 9, Experiments 1 and 2 for complete details), there are already two reasons to question the salience hypothesis. First, the very notion of salience may well derive from a mental model. That is, what make an object or event salient are its relations to the other objects and events and our knowledge about what those relations imply for further action. Yet for nonscript texts that knowledge may well be derived from constructing a mental model to ascertain the relations. Furthermore, once a model is constructed, it may be "run" (Gentner and Stevens, 1983) to determine future states or implications. Second, the salience account has difficulty addressing an interaction found by Glenberg et al. (1987). The associated/dissociated variable affected responding to the probe (e.g., sweatshirt) when the probe was delayed by one or two sentences. However, when the probe occurred immediately after the sentence in which the target object was introduced, there was no effect of the associated/dissociated variable. If differential salience of objects is conferred by propositional relations (rather than by mental models), differences in salience should be measurable immediately after reading the sentence introducing the object because the relevant propositions should be formed by this point. It should be noted, however, that the force of this second point is reduced by possible effects of verbatim representations.
4.5 These arguments notwithstanding, McKoon and Ratcliff conducted an experiment (their Experiment 5) to test the salience account. They modified the Glenberg, Meyer & Lindem (1987) texts so that each critical sentence introduced two objects, the original target object (which will be referred to as the GM&L target) and an initial location for the GM&L target (the initial location will be referred to as the M&R target). McKoon and Ratcliff write about the M&R target that, "[T]he location was something that could not move with the main character" (p. 460). An example of the initial portion of a modified text in the associated condition is: "John was preparing for a marathon in August. After doing a few warm-up exercises, he put on a sweatshirt from the laundry and went jogging." In this example, "laundry" is the M&R target
4.6 McKoon and Ratcliff reasoned that if subjects are building mental models, the associated/dissociated variable should affect responding to the GM&L target but not to the M&R target because the latter "could not move with the main character." However, suppose the associated/dissociated variable differentially confers salience on the propositions encoding the GM&L target. Remember that the M&R target is a location for the GM&L target; hence they are encoded in the same proposition. Thus, if the associated/dissociated variable confers salience on the proposition encoding the GM&L target, the salience of the M&R target should also be affected by the associated/dissociated variable. This is exactly what McKoon and Ratcliff found, supporting the salience interpretation of both their own data and the original Glenberg et al. data.
4.7 Although these data appear compelling, for the reasons mentioned previously we questioned the salience hypothesis and conducted two experiments to test it further. In the first experiment (see PART II, paragraphs l.0 to 8.4 for details), we asked people to judge the salience of the GM&L and the M&R targets. The judgments were reliable, but they were not strongly related to the associated/dissociated variable. In fact, for the M&R targets, subjects judged the target to be more salient in the dissociated condition than in the associated condition, just the opposite of what is predicted by the salience hypothesis.
4.8 If differential salience does not account for the results of McKoon and Ratcliff's Experiment 5, what does? In particular, why should recognition of the M&R target depend on the associated/dissociated status of the GM&L target? One hypothesis is derived from a simulation of mental models that we are developing (Glenberg, Kruley, & Langston, in press). In this simulation, mental models are constructed using pointers arrayed in a spatial working memory. Distances between pointers are representationally meaningful in that distance in the model has an analogical correspondence to distances in the situations being described (or to other salient dimensions in the text that are assigned to spatial dimensions for purposes of constructing a mental model). By manipulating the pointers, subjects can derive inferences that are not explicit in the text. Furthermore, pointers in the mental model activate corresponding propositions in memory. For example, as one continues to think about John's sweatshirt by keeping a pointer in the mental model, other information about the sweatshirt (encoded propositionally) remains active too.
4.9 Given this background, consider what happens when a subject keeps a GM&L target (such as sweatshirt) in the mental model in the associated condition. The representation of the GM&L target is activated, as is propositional information about the target. One such proposition is that the GM&L target has an initial location, namely, the M&R target. Thus, information about the M&R target is also activated by virtue of the GM&L target remaining in the mental model. Similarly, when the GM&L target is not in the mental model (in the dissociated condition), there is a reduction in activation of the GM&L target and of associated propositions, including the proposition encoding the M&R target. Thus, although the associated/dissociated variable is manipulated with reference to the GM&L target, it may well have a mediated effect on the accessibility of the M&R target.
4.10 One would expect any mediated effect to be rather small. However, those effects should be enhanced to the extent that other components of the mental model also have a mediating effect on the accessibility of the M&R target. One other source of mediating effects is the association of the M&R target and the main actor. McKoon and Ratcliff state that the M&R target was a location "that could not move with the main character"; thus, as the main actor moves, the M&R target should always be dissociated. However, in preparing the materials for Experiment 1, we noticed several instances in which this did not appear to be the case. For example, in one text about a fisherman in a rowboat, the critical dissociated sentence was, "He had just finished eating when the wind blew the empty bag out of his hand and into the water." The GM&L target is "bag," and the M&R target is "hand" (the original location of the bag). Clearly, the M&R target is a location that will move with the main actor. In a text about an athlete preparing to play racquetball, the dissociated sentence was, "He changed his shirt and took his watch off his wrist." The GM&L target is "watch," and the M&R target is "shirt." The intended referent for "shirt" was apparently the one the actor removed in the act of changing. However, when the word "shirt" is used as a recognition probe, it refers equally well (or better) to the new shirt that the main actor is wearing. A third example comes from a text about a businessman in a restaurant. The dissociated sentence is "Leaning back in his chair, he glanced at a woman from the next table who was walking out of the room." The GM&L target is "woman" and the M&R target is "table." Although the GM&L target is dissociated from the main actor by virtue of the woman leaving the room, the M&R target, "table," remains close to the main actor.
4.11 In all, we identified six texts in which the M&R target is not clearly dissociated from the main actor, so that the main actor can provide a type of mediated priming. Removing the six texts has a selective effect. In particular, for the M&R target, removing those texts greatly reduces the associated/dissociated effect (from 51 msec to 20 msec), while slightly enhancing the effect for the GM&L target (from 62 sec to 81 msec).
4.12 Given these data, an attempt to replicate McKoon and Ratcliff's Experiment 5 using rewritten texts was in order (see PART II, paragraphs 9.0 to 11.4 for details). We started with the texts used by McKoon and Ratcliff, but we rewrote freely to accomplish several goals. First, the M&R target was always a location for the GM&L target. Second, that location was always introduced in a prepositional phrase immediately following the GM&L target. Third, the combination of the critical sentence and the following sentence (the one immediately preceding the recognition probe) always dissociated the main actor and the M&R target. Of course, whether or not the main actor was dissociated from the GM&L target was the major variable in the experiment. Fourth, we ensured that there was only one main actor (in some of the texts used by McKoon and Ratcliff there were several actors referred to by pronouns, thus granting multiple actors "in focus" status).
4.13 Consider the predictions for the recognition times for the M&R and GM&L targets based on the mental-model account and the salience account. The mental-model account predicts a large effect of the associated/dissociated variable for the GM&L target (the one that is associated or dissociated from the main actor), but a much smaller (mediated) effect for the M&R target. The salience account is based on the assumption that the associated/dissociated variable confers salience on both the GM&L target and the M&R target, the original location of the GM&L target. Thus the associated/dissociated variable should affect both the GM&L target and the M&R target.
4.14 Although not all aspects of the data were as clean as one would like, the main result was clear. With the rewritten texts, the effect of the associated/dissociated variable (46 msec measured by texts) was significant for the GM&L target whereas the effect (0 msec, measured by texts) was not significant for the M&R target.
5.1 The salience account of the associated/dissociated effect appears to be incorrect in three respects. First, it cannot easily handle the absence of an effect immediately after the target is introduced (Glenberg et al., 1987). Second, reliable, direct judgments of salience do not conform to the associated/dissociated effect for the M&R targets (Experiment 1). Third, after the stimulus materials were vetted for inappropriate texts, the effect of the variable on the M&R target disappeared (Experiment 2 and reanalysis of McKoon and Ratcliff's data).
5.2 The data are consistent with the mental-model theory offered by Glenberg et al. (in press). While reading, subjects construct a mental model that may represent space analogically. Significantly, when the text describes central features (e.g., the main actor and a target object) as spatially close, they are related more strongly in the mental model than when the text describes the same features as farther apart. Thus, when the main actor is foregrounded by virtue of pronominal reference, the spatially close target object (in the associated condition) tends to remain highly accessible; when the target is described as spatially far from the target (in the dissociated condition), it is less accessible.
5.3 In concluding PART I, we note that we have few disagreements with McKoon and Ratcliff's proposals. The minimalist hypothesis is about the conditions under which inferences are made automatically. Although there is no universally accepted definition of automatic processing, we assume McKoon and Ratcliff mean that these inferences are drawn without intention, that they are unavoidable, and that they require a minimum of effort. As we have noted elsewhere (Glenberg et al., in press; Glenberg & Langston, 1992), we think the construction and maintenance of a mental model need not be automatic in these senses. Instead, forming mental models may well be strategic, and in unfamiliar domains, it may well be quite effortful. Also, some research demonstrating mental model effects during comprehension (Bryant et al., 1992; Morrow et al., 1987) involves extended learning procedures that would be difficult to view as automatic.
5.4 In addition, the minimalist hypothesis is meant to apply when reading "In the absence of specific, goal directed, strategic processes" (McKoon and Ratcliff, 1992, p. 440). Because the sort of reading for good comprehension that requires mental model construction is often goal directed and strategic, those situations that lead to mental models are just those of little concern to tests of the minimalist hypothesis.
5.5 Finally, we agree with McKoon and Ratcliff that readers generally do not construct a "full" representation of the situation described by the text. As we argued in the introduction, however, this does not exclude the possibility that readers are constructing mental models.
5.6 The one remaining disagreement seems to be settled by the findings reported in PART II of this article. McKoon and Ratcliff argue that the findings reported in Glenberg et al. (1987) reflect the operation of "salience." In contrast, the evidence is now strong that the effect of the associated/dissociated variable is due to the construction of a mental model. In fact, it may well be that representation in a mental model is one source of highly available information that supports the judgment of salience and the process of drawing minimal, automatic inferences.
6.1 How does one measure salience? McKoon and Ratcliff suggest that salience is related to topicality, and that an associated GM&L target may be "treated during comprehension as more relevant to the topic of its discourse" (p. 460) than a dissociated target. To measure salience, we asked subjects to make paired-comparison salience judgments. Each subject was presented with a pair of texts labeled Version A or Version B (see Table 1 for an example). One text in the pair consisted of a setting sentence and the associated sentence. The other consisted of the setting sentence and the dissociated sentence. In addition, a critical word (either the GM&L target or the M&R target) was identified. The subject's task was to determine the text in which the critical word was more salient. The subjects were instructed as follows. "You should decide if the critical word is more important in Version A or in Version B. That is, if the text continued, would the critical word play a more important role in Version A or Version B? Once you have decided, write the letter in the space provided."
Table 1 Example of Text Used in Experiment 1
Version A: John was preparing for a marathon in August. After doing a few warm-up exercises, he put on a sweatshirt from the laundry and went jogging.
Version B: John was preparing for a marathon in August. After doing a few warm-up exercises, he put his sweatshirt in the laundry and went jogging.
6.2 We will demonstrate that subjects can make these sorts of salience judgments reliably. The question of interest is then whether salience is affected by the associated/dissociated variable. If it is, we would expect the preponderance of choices to be of the associated version of the text. That is not the result we obtained, however.
7.1 SUBJECTS. A total of 48 students enrolled in introductory psychology classes at the University of Wisconsin-Madison participated in the research. They received extra credit points in payment for their participation.
7.2 MATERIALS AND DESIGN. Each subject received a booklet consisting of a consent form, two pairs of practice texts (on one page), and 24 pairs of experimental texts (on eight pages). Each pair of texts was laid out as in Table 1. For half of the experimental pairs in a booklet the associated text appeared on top and was labeled Version A; in the other half the associated text appeared on the bottom and was labeled Version B. There were four versions of the booklet. In two of them the 24 experimental pairs had the M&R target highlighted and in two the GM&L target was highlighted. Considering the two versions in which the M&R target was highlighted, in one version a given pair of texts was presented so that the associated text was on top and in the other version that pair was presented so that the associated text was on the bottom. This was also true for the two versions in which the GM&L target was highlighted.
7.3 Each subject received one of the four versions of the booklet. Thus, there were two between-subjects variables, whether the salience of the M&R target or the GM&L target was judged, and counterbalancing of the location (top or bottom) of the associated text in each pair.
7.4 PROCEDURE. Subjects were run in groups of up to 12. Within each group, the four versions of the booklets were randomly distributed among the subjects under the constraint that by the end of the experiment a total of 12 subjects received each version. After signing the consent form, the subjects worked on two practice texts and then completed the remaining texts at their own speed. Subjects also rated the difficulty of deciding on the text (in a pair) for which the critical target was most salient. These data were not analyzed, however.
8.1 The basic data consist of the frequencies of choosing the associated text as the one in which the critical word is most salient (important). After collecting the data we discovered that one text in one of the versions was mistyped. We did not score this text; responses to the other texts were converted to percentages before statistical analyses were performed.
8.2 Before answering the questions of interest, we need to demonstrate that our measure of salience is sensible. We believe it has face validity. Furthermore, we can demonstrate that the measure is reliable. Suppose the degree to which a particular term is salient varies with the text. That is, in some texts, associating the critical target with the actor may make it highly salient, whereas in other texts the salience may be enhanced little by association or it may even be enhanced by dissociating the target and the actor. If texts differ in fact in salience of the target items, and if subjects can reliably judge that salience, then we should observe significant correlations (computed across texts) between judgments of separate groups of subjects. To compute these correlations, we divided the subjects into four groups corresponding to the versions of the booklets they received. Thus, two of the groups had rated the GM&L target (one in each order of presentation of the associated and dissociated version) and two had rated the M&R target. For each group and for each of the 24 texts, we determined the proportion of times the subjects choose the associated version as most salient. We then computed the correlation between the two sets of proportions for the counterbalanced versions of the (24) M&R targets and the correlation between the two sets of proportions for the counterbalanced versions of the (24) GM&L targets. These correlations were .59 for the M&R target and .71 for the GM&L target, p<.01 for both. Clearly, subjects can reliably judge salience.
8.3 Now, is salience controlled by the associated/dissociated variable? Subjects judged the GM&L target to be more salient in the associated condition 57% of the time. This effect is reliably greater than 50% (the forced-choice neutral point) by subjects, t(23) = 2.26, but not by texts, t(22) = 1.63. Furthermore, subjects judged the M&R target to be more salient in the associated condition only 40% of the time. This effect is reliably less than 50% by both subjects, t(23) = -4.41, and by texts, t(23) = -3.34.
8.4 These data indicate that salience cannot explain faster responding (as found in McKoon and Ratcliff's Experiment 5) to the M&R target in the associated condition compared to the dissociated condition. The problem is that subjects find the M&R target to be more salient in the dissociated condition than in the associated condition. There is some evidence, however, that salience is positively correlated with the associated/dissociated variable for the GM&L target. One interpretation of this finding is that salience is indeed the controlling factor for the GM&L targets. Given the very strong evidence against salience playing a controlling role in responding to the M&R target, however, this seems unlikely. An alternative interpretation is that salience and association/dissociation are correlated, but that the causal direction is opposite to that supposed by McKoon and Ratcliff (1992). That is, when objects are represented in a mental model, they are more likely to be judged as salient than when the objects are absent from the mental model.
9.1 This experiment is a conceptual replication of McKoon and Ratcliff's (1992) Experiment 5, but using rewritten texts. The rational for the experiment was provided in PART I, paragraphs 4.8 - 4.13.
10.1 MATERIALS AND DESIGN. We wrote 84 texts. Four of these were used for practice, 40 were filler texts, and 40 were experimental texts. The 40 experimental texts had the following characteristics (see Table 2 for an example). The first sentence introduced a main actor and a situation. The second, critical, sentence could appear in one of two forms. In the associated condition, a target object (the GM&L target) was introduced and spatially associated with the main actor. In addition, an initial location for the GM&L target, the M&R target, was described in a prepositional phrase immediately after the GM&L target. In the dissociated condition, the GM&L target was spatially dissociated from the main actor. Otherwise, the associated and the dissociated sentences were very similar because we equated (almost exactly) the number of words, grammatical structures, and propositional structures of the two forms of the critical sentence. A third sentence reinforced implied movement of the main actor from the initial location (the M&R target). Thus, the third sentence forced a dissociation between the main actor and the M&R target and the third sentence reinforced any separation between the main actor and the GM&L target in the dissociated condition. The recognition probe (the M&R target or the GM&L target) always appeared after this third sentence. Finally, for each text we wrote a comprehension question, which could be answered with a yes or no.
Table 2 Example of a Text Used in Experiment 2
Setting sentence: Sonia spent the afternoon reading in her
Critical (associated): Realizing that it was such a nice day, she took
her book from the table and went outside.
Critical (dissociated): Realizing that it was such a nice day, she
left her book on the table and went outside.
Filler: She walked down to the lake to enjoy the
Comp. Question: Was Sonia going to walk to the park?
Note: The GM&L target is "book" and the M&R target is "table." Neither was highlighted in the texts read by subjects. ________________________________________________________________________
10.2 The 40 filler texts were designed to hide the nature of the critical texts. Although they had the same general format as the experimental texts (an introduction and additional sentences) they differed in several important respects. First, the correct answer to the recognition probe was "no" for 30 of the filler texts, whereas it was "yes" for all of the experimental texts. Second, the probe came after the first sentence (an average of) 16 times, after the second sentence (an average of) 16 times, and after the third sentence (an average of) 8 times, whereas the probe always followed the third sentence in the experimental texts. Finally, the probe word was a non- noun for half of the filler texts, whereas it was always a noun for the experimental texts.
10.3 The two variables of interest were manipulated within-subjects. These were whether the associated or the dissociated versions of the second sentence were presented and whether the recognition probe was the GM&L target or the M&R target. Ten texts were presented in each format. The assignment of the 40 experimental texts to the four conditions was randomized for each subject. Also, the order in which the 80 (filler and experimental) texts were presented was randomized for each subject within the following constraint: Each set of eight successive texts contained one example of each of the four experimental conditions and four filler texts.
10.4 PROCEDURE. Subjects participated individually. They were instructed on the use of the computer and given four practice texts. Each text was preceded by the word "Ready," which was dismissed by the simultaneous pressing of a microswitch labeled "yes" and another labeled "no." Each of the first three sentences followed in turn and each was dismissed in the same way. Upon the dismissal of the third sentence (in the experimental texts), a probe word appeared in a Macintosh "dialog" box and was underlined by asterisks. Subjects pressed the "yes" switch to indicate that the probe word had appeared in the text and the "no" switch to indicate otherwise. The "yes" label was always assigned to the switch pressed by subject's dominant hand. The response to the subject's probe word was followed by feedback, the comprehension question, the subject's response to the comprehension question, and feedback on that response.
10.5 SUBJECTS. The subjects were run in three waves. The first set consisted of 24 subjects who participated midway through the academic semester. Because the random assignment of texts to conditions resulted in some texts with very few observations in some conditions, we were unable to perform an analysis by texts at this point. We then collected data from another 23 subjects who participated near the end of the academic semester. To our chagrin, adding these new subjects greatly increased the variability and reduced the statistical significance of the results. Thus, we added a third set of 12 subjects during the summer session. The initial 47 subjects participated in exchange for extra credit in their introductory psychology courses. The remaining subjects were members of the University's summer community and were paid for their participation.
11.0 RESULTS AND DISCUSSION
11.1 We analyzed the probe recognition times when the responses to both the probe and the comprehension question were correct, calculating a median recognition time for each subject for each of the four conditions. The recognition time data that are presented are the means of the subjects' medians. As noted in the method section, adding the subjects who participated near the end of the academic semester increased the variability and reduced the significance of all of our effects. That these subjects were from a population different from that of the initial subjects is supported by a subsidiary analysis. In particular, the second wave of subjects was slower than the first wave by 126 msec, t(45) = 1.87, p=.07. Thus, we are presenting the data grouped by wave of subjects.
11.2 The means of the median correct recognition times for the first wave of subjects are presented in the top row of Table 3. Note that there is quite a large effect of the associated/dissociated variable (62 msec) for the GM&L target but a slight reversal for the M&R target (-6 msec). The only effect that was significant in an analysis of variance was the interaction between the associated/dissociated variable and type of target, F(1,23) = 6.54, MSE = 4387. The data from the second wave of 23 subjects are presented in the second line of Table 3. The only significant effect was for the type of target, F(1,22) = 7.83, MSE = 18108. Thus, the critical interaction did not replicate for these subjects. The data from the third wave of 12 subjects are presented in the third line of Table 3. As with the first wave of subjects, the only significant effect was for the interaction of type of target and the associated/dissociated variable, F (1,11) = 6.13, MSE = 4326. We also performed an analysis including all of the subjects, using wave as a between subjects variable. The type of target had a significant effect, F(1,56)=6.08, MSE=13072, indicating faster responding to the GM&L target than to the M&R target. The critical interaction between type of target and the associated/dissociated variable almost reached the standard level of significance, F(1, 56) = 3.52, MSE = 9231, p = .07. The last line of Table 3 reports the results from using the data from all 59 subjects to compute a median recognition time for each condition for each text. The means (over the 40 texts) of these medians are reported in Table 3. In the analysis of these data, the effect for type of target was significant, F(1, 39) = 8.119, MSE = 30158. The interaction was not significant; however, the effect of the associated/dissociated variable was significant for the GM&L target, F(1,39) = 4.36, MSE = 9520, but insignificant for the M&R target, F=0.
Table 3 Mean of Median Recognition Times for Experiment 2
M&R Target GM&L Target
Assoc Dissc D-A Assoc Dissc D-A
First 24 Subjects 938 932 -6 862 924 62
Second 23 Subjects 1080 1078 -2 1010 992 -18
Third 12 Subjects 982 913 -69 940 965 25
By Text (59 Subjects) 1003 1003 0 902 948 46
11.3 Two types of error rates are presented in Table 4. For the first type, a text was scored as an error if the subject responded incorrectly to either the recognition probe or the comprehension question. Errors of this sort were used to remove responses from the recognition time analysis. The second type of error rate (in parentheses) is the proportion of texts for which the subjects erred on the recognition probe regardless of the response to the comprehension question. This second type of error rate corresponds to those reported by McKoon and Ratcliff. For both types of error rate, for all three waves, and for the analysis by text, the only significant effect was for type of target: subjects made significantly fewer errors responding to the GM&L target than in responding to the M&R target. Significantly, these error data remove any concern for speed-accuracy tradeoffs in interpreting the interactions found for the recognition data.
Table 4 Mean Percentage Errors for Experiment 2
M&R Target GM&L Target Assoc Dissc D-A Assoc Dissc D-A
First 24 Ss 22(15) 26(14) 4(-1) 17(7) 21(8) 4(-1)
Second 23 Ss 26(18) 21(13) -5(-5) 16(7) 16(6) 0(-1)
Third 12 Ss 25(16) 24(11) -1(-5) 17(7) 14(5) -3(-2)
By Text (59 Ss) 24(15) 23(13) -1(-2) 17(7) 18(8) 1(1)
Note: The numbers in parentheses are the percentage errors in responding to the probe. The other numbers are the percentage of times the probe or the comprehension question was answered incorrectly.
11.4 It is of course a little disconcerting that the critical interaction (in the recognition times) was found for the first and third waves of subjects but not the second. Although we cannot be certain, it seems reasonable to attribute the failure to replicate to the oft-discussed problem of end-of-semester subjects. We can take some comfort in the following. First, the interaction of the associated/dissociated variable and type of target did replicate for two different populations (those populations sampled by the first and third waves). Second, for the M&R target, the associated/dissociated variable never had a positive effect. Third, the critical interaction was very close to conventional levels of significance in the analysis of all of the subjects. Fourth, in the analysis by text, the associated/dissociated variable was significant for the GM&L target but not for the M&R target. Overall, the case is fairly secure that the associated/dissociated variable has a positive effect for the GM&L target (to which the variable refers), but not for the M&R target. Thus the prediction derived from the salience account has been disconfirmed. Further discussion of these results may be found in PART I, Section 5.
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This research was funded in part by an Air Force Office of Scientific Research grant (89-0367) to Arthur Glenberg. We thank Will Langston for help in programming, and we thank Heather Rippl for help with preparation of the stimulus materials and data collection.