Pronoun assignment and semantic integration during reading: eye movements and immediacy of processing

JOURNAL OF VERBAL LEARNING AND VERBAL BEHAVIOR 22, 75--87 (1983)

Pronoun Assignment and Semantic Integration during Reading: Eye Movements and Immediacy of Processing K A T E EHRLICH AND K E I T H RAYNER

University of Massachusetts Subjects read passages of text in which the distance between a pronoun and its antecedent was varied. To complete pronoun assignment, a reader must access and integrate information from another portion of text in order to select an antecedent that matches the pronoun in number and gender. Our data suggest that although this process may be started when the pronoun is encoded, the assignment was not completed on the current fixation when the antecedent occurred some distance back in the text. The implications of the results for pronoun assignment are discussed as well as the implications for the immediacy of processing.

One of the most striking features of the pattern of eye movements of skilled readers is the extent to which the pattern varies (Rayner, 1978). Within a single reader and a single passage of text, the duration of a fixation may be as brief as 100 milliseconds or as long as 500 milliseconds. The distance between successive saccades can vary from 1 or 2 character spaces to over 20 character spaces. Most researchers agree that these variations in the locus and duration of fixations are not due to random fluctuations but rather reflect changes in the characteristics of the text and its content. The challenge is to explicate how and when the cognitive processing of the text is reflected in measures of processing, such as fixation duration and saccade length. A principal issue in this endeavor is whether cognitive processes are synchronous with fixations or This research was supported by Grant BNS79-17600 from the National Science Foundation and was conducted while the first author was the recipient of a Sloan Foundation Postdoctoral Fellowship in Cognitive Science at the University of Massachusetts. We wish to thank Patrick Carroll for his assistance in collecting the data and Chuck Clifton, Susan Ehrlich, Lyn Frazier, Marcel A. Just, Kevin O'Regan, and two anonymous reviewers for their comments on an earlier version of the article. Requests for reprints should be addressed to Kate Ehrlich, Department of Computer Science, Yale University, Box 2158, Yale Station, New Haven, Connecticut 06520.

whether there is a lag between fixating a word and completing processing of it. Varying theories have been advanced to account for the relation between the locus and duration of fixations during reading and comprehension. One class of theory holds that fixations are too rapid to account for the semantic processing necessary for comprehension in addition to the essential perceptual processing (e.g., Kolers, 1976; Bouma & deVoogd, 1974; Morton, 1964). According to this view, referred to as cognitive lag by Rayner (1977, 1978), there is an e y e - m i n d span in silent reading analogous to the e y e - v o i c e span in oral reading. Eye movements thus serve to bring information into the processing system via some kind of buffer. Hence, the semantic processing of a word will always lag behind its perceptual encoding, and, by implication, be carried out when the eyes have moved on to fixate a later portion of the text. Other theorists claim that there is no appreciable lag between fixating a word and processing it; both processes occur during the same fixation. According to this claim, referred to as the process monitoring hypothesis (Rayner, 1977, 1978), fixation durations should be longer for those words which require more processing to be understood. This claim is supported by a number of studies which show the fixation duration on

75 0022-5371/83/010075-13503.00/0 Copyright~) 1983by AcademicPress, Inc. AUrightsof reoroductionin any formreserved.

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a word to vary as a function of such features as the frequency of the word (Just & Carpenter, 1980; Rayner, 1977), its informativeness (Rayner, 1977; Wanat, 1971), its predictability (Ehrlich & Rayner, 1981), and the extent to which the word is constrained by context (Ehrlich & Rayner, 1981). An e x t r e m e v e r s i o n of the process monitoring hypothesis has recently been proposed by Just and Carpenter (1980). They presented a theory of reading in which they account for the amount of time people spend looking at the words in the text (gaze duration) in terms of the underlying cognitive processes. These processes range from encoding the word, through lexical access and assignment of case role relations, to interclause integration. There are two critical assumptions that serve to relate the model to the eye movement data they obtained. One assumption, the immediacy assumption, is that readers will try to interpret each word as fully as possible while the word is being fixated. Interpretation includes many of the processes listed above: encoding the word, choosing one meaning of it, assigning it to its referent, and determining its status in the discourse. The other assumption, the eye-mind assumption, is that readers will retain fixation on a word until processing is completed. An implication of this assumption is that there is no appreciable lag between fixating a word and completing processing of it. These assumptions are critical to the theory because Just and Carpenter want to claim that the time spent looking at a word primarily reflects processing of that word, rather than processes that overlap from previous words. Just and Carpenter's two critical assumptions differ from the process monitoring hypothesis in the extent to which various processes are completed on an individual fixation. Generally, the process monitoring hypothesis suggests that cognitive processes associated with lexical access will be reflected in the fixation dura-

tion on that word. With the immediacy assumption and the e y e - m i n d assumption, Just and Carpenter's theoretical analysis suggests that many higher level processes are initiated and completed on the individual fixation on which a word is encoded. The evidence that supports the idea that there is not an e y e - m i n d span in silent reading comes from studies that we have described above in which processing is closely related to the lexical features of a particular word. However, the process of retrieving the meaning of a word is but a small part of comprehension. Beyond lexical retrieval there are many levels at which the meanings of the words must be combined, integrated with other parts of the text, as well as integrated with stored general knowledge that relates the topic and domain of the text. The key issue is then whether there is also no e y e - m i n d span for these more complex processes. A strong version of the immediacy assumption would imply that there is no lag for these complex processes. However, there are some obvious limitations to such a version, many of which were pointed out by Just and Carpenter (1980). One limitation is that information later in the text can modify interpretation of the current word. The example given by Just and Carpenter is that the extensive meaning of an adjective such as large will be interpreted differently depending on the word it modifies. Since the adjective precedes the noun, some processing of the adjective will be delayed until after the noun is interpreted. Many other processes ranging from parsing to integrative processes are subject to this same limitation (see Frazier and Rayner (1982) for an analysis of the relation between parsing strategies and eye movements). These limitations modify the immediacy assumption by allowing that certain information may not be available to complete processing of a word, and hence some processing is deferred until later, usually to a clause or sentence boundary.

EYE MOVEMENTS AND PRONOUN ASSIGNMENT

Even though there may be limitations on how much processing can be completed immediately, the immediacy assumption still claims that processing to all levels is initiated as soon as possible, even at the risk of misinterpretation. An interesting application of this claim is pronoun assignment. According to the immediacy assumption, at least an attempt should be made to resolve the pronoun during the fixation on which it is first encountered. Some evidence to support this claim comes from a study done by Carpenter and Just (1977). They found that when readers encountered a pronoun in a text they initiated a regression about 50% of the time back to the antecedent, which was on the previous line. These regressions were initiated either immediately after encountering the pronoun or at the end of the line. Carpenter and Just interpreted these data as indicating that pronouns are resolved at two points: immediately when the pronoun is encountered or at the end of the clause. However, in their experiment, subjects were given the task of deciding, for each line of text, whether it was consistent or inconsistent with the previous discourse. This task is likely to encourage use of a particular kind of strategy which may not be representative of the way people read naturally. It seems unlikely that the main strategy that people use to resolve pronouns is to initiate regressions back to the antecedent phrase. Regressions are disruptive of the normal left to right pattern of reading and hence, hardly a good mechanism for the comprehension of pronouns. In a recent study, Erhlich (1983) found that regressions occur much less frequently than Carpenter and Just reported. In her study, subjects were asked to read short passages containing pronouns and be prepared to answer questions about the content of the text. It was found that regressions were initiated from the region of the pronoun in only 10% of the cases. There is some doubt, therefore, as to whether the Carpenter and Just study represents a good test of when

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decisions are ordinarily made about pronoun reference, and hence, of whether there is normally a lag between encoding a pronoun and resolving it. An alternative hypothesis concerning the relation between eye movements and cognitive processes is that readers will remain looking at a word only as long as it takes to complete lexical access and some syntactic parsing (Frazier & Rayner, 1982). The process monitoring hypothesis is an example of this kind of approach. Once the word is encoded, the reader can then move on to fixate the next word. The main distinction then between the process monitoring hypothesis and the immediacy assumption is how much semantic processing beyond lexical access takes place when a word is encountered. We have chosen to evaluate the implications of this distinction by examining the time course of pronoun assignment. Pronoun assignment provides a useful way to examine the assumption because the processes of assignment are more complex than lexical access and the process can be localized in a way that is directly c o m p a r a b l e to studies that have used nouns. In both cases, the noun or pronoun provides a distinct target area for taking measurements. Pronouns, however, have an advantage over nouns in that they differ very little in their perceptual and semantic characteristics: a single letter and a difference in gender is all that distinguishes she from he. Thus any variation in fixation durations in the region of the pronoun cannot be attributed to the perceptual and semantic characteristics of the pronoun. A second feature of pronouns is that assignment requires more complex processing than simply retrieving the meaning of the word from the mental lexicon. Minimally, pronoun assignment requires readers to access and integrate information from another portion of the text by selecting an antecedent that matches the number and gender of the pronoun. Maximally, pronoun assignment may involve the intervention of complex lin-

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guistic knowledge combined with sophisticated general knowledge. Moreover, at an intuitive level, pronouns are resolved almost instantaneously and automatically, and hence, may be considered a legitimate and normal part of reading. The studies reported in this article sought to examine whether processes of pronoun assignment are necessarily completed when the pronoun is encoded, or whether there may be a lag between encoding and completion of assignment. The main manipulation in the experiment was a variation in the distance between the pronoun and its antecedent. In all cases there was no ambiguity over the choice of referent and there was always sufficient information prior to the pronoun to complete assignment when the pronoun was encoded. Previous research has shown that the speed of pronoun assignment varies according to the distance between the pronoun and its antecedent (Clark & Sengul, 1979; Daneman & Carpenter, 1980; Garrod & Sanford, 1977). With respect to the theoretical positions under consideration, different predictions can be generated for the time-course of pronoun assignment in the experimental conditions. According to the e y e - m i n d assumption, readers should remain fixated on the pronoun until assignment is completed. Hence, any effect of the distance between the pronoun and its antecedent should be evident when the pronoun is encoded and only at that time. On the other hand, the immediacy assumption allows that some processing may spill over to later fixations, but that readers will, nevertheless, try to interpret each word as fully as possible when it is encountered. A pronoun is not fully interpreted until the referent has been recovered and assigned to the pronoun. If it takes longer to recover the referent when the antecedent is further back in the text, then the extra processing should be evident when the pronoun is encountered, according to the immediacy assumption. In particular, when there is only one possible antecedent in the text, assignment c a n take

place as soon as the pronoun is encountered. That is, the immediacy assumption would predict that people will spend longer looking at the pronoun when the antecedent is further back in the text than when the pronoun is nearby. 1 The process monitoring hypothesis makes a different prediction. It claims that readers will remain on a word until that word is encoded to the point of lexical access. In all cases, the word is a pronoun and hence there should be no difference in encoding time as a function of distance. Hence, the process monitoring hypothesis predicts that any effects due to the distance between the pronoun and the antecedent should be evident on a later portion of the text. Before describing the experiments, a few words are in order about the techniques that have been used to record the pattern of eye movements as people read texts. In the present experiments, our primary source of data are the locus and duration of the individual fixations that a person makes in the course of reading. These fixations occur on words as well as on the spaces between words. Moreover, the number of fixations on a word can vary from none, as is often the case for function words such as " a " or " t h e , " to several, when the word is very long and unusual. An alternative technique, used by Just and Carpenter (1980), is to aggregate across all fixations on a word to produce a measure of the total time spent looking at the word (gaze duration). Fixations that occur in the space between words are included in the reading time for the word to the right of the space. However, the technique of using gaze durations presents problems for examining the time course of pronoun assignment because pronouns are rarely fixated; Ehrlich (1983) re-

1 It should be noted that the immediacy assumption as described by Just and Carpenter (1980) does not make these specific predictions, although the predictions are consistent with the general claims of the assumption. If the assumption is to be testable, however, it is necessary that the claims be made specific.

EYE MOVEMENTS A N D PRONOUN ASSIGNMENT

ported that only 13% of the pronouns in her passages were fixated. This rate is comparable to that reported for function words (e.g., Rayner, 1977). Using gaze durations, only fixations that fell on the pronoun or on the space to the left of the pronoun would be included in the time taken to read the pronoun. If gaze durations rather than individual fixations are taken as the primary form of the data then there is no way of reliably and consistently knowing when the pronoun is encoded. In an attempt to increase the generalizability of our results, two separate experiments w e r e c o n d u c t e d using d i f f e r e n t stimuli and subjects. We will report the results of both experiments, but focus primarily on the second experiment. METHOD

Subjects. T h i r t y - o n e subjects participated in the experiments, 16 in Experiment 1 and 15 in Experiment 2. They were all members of the University of Massachusetts community and were paid for their participation in the e x p e r i m e n t s . All of the subjects were naive concerning the purposes of the experiment and they all had normal uncorrected vision. Materials and apparatus. The materials consisted of short passages of text in which the distance between a pronoun and its antecedent was varied. There were three conditions in the experiment. In the Near condition, the pronoun and its antecedent were adjacent to each other separated only by the standard conventions for ending one sentence and beginning another (the period and two spaces). In the Intermediate condition, the pronoun and its antecedent were on successive lines of text, and they were separated by a number of lexical items. Hence, the appropriate referent for she in the first passage in Table 1 was Susan. The appropriate referent for he in the second passage was Mark. In the Far condition, the pronoun (he) and its antecedent (Mark) were separated by at least three lines of text consisting of two intervening sentences.

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Table 1 shows a sample passage taken from Experiment 2. As seen in the table, the passage was very similar across the three conditions of the experiment except for (1) the presence or absence of a single letter (s for she or he) and (2) the name of one of the characters in the passage. In Experiment 1 there were six passages and in Experiment 2 there were nine passages. Whereas in Experiment 2 the exact lexical items were perfectly controlled, in Experiment 1 there were some slight differences in lexical items. Furthermore, in Experiment 2 the line containing the target p r o n o u n was identical (except for the presence or absence of the letter s) across conditions, whereas in Experiment 1 the line containing the target pronoun was not necessarily identical, although the pronoun was in the same spatial location on the line in all conditions, and the lexical items following the pronoun were always of the same form. Hence, Experiment 2 represents a more precisely controlled experimental situation. The e x p e r i m e n t a l p a s s a g e s w ere arranged in three different random orders so that within each experiment each passage appeared once for each order. The passages were read in conjunction with a number of other filler passages (9 fillers in Experiment 1 and 15 fdlers in Experiment 2). Each passage was arranged across the different orders so that e a c h c o n d i t i o n a p p e a r e d equally often. In this way, every subject received every condition. E y e m o v e m e n t s were r e c o r d e d by a Stanford Research Institute Dual Purkinje Eyetracker. Viewing was binocular with eye location recorded from the right eye. The eyetracking system was interfaced with a Hewlett-Packard 2100A computer that ran the experiment. The position of the s u b j e c t ' s eye was sam pl ed e v e r y millisecond by the computer and a determination of the location and duration of the fixation was made by comparing the position of the eye every 4 milliseconds with the prior 4-millisecond average. The eyetracker has a resolution of 10 rain of arc and the text was

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EHRLICH A N D RAYNER TABLE 1 SAMPLE OF MATERIAL FROM EXPERIMENT 2 SHOWING THE THREE LEVELS OF DISTANCE

Near

A GROUP OF PEOPLE WHO SHARED AN INTEREST IN PHOTOGRAPHY HAD R E C E N T L Y STARTED WRITING A N E W S L E T T E R OF THEIR ACTIVITIES. IN FACT, IN ONE ROOM MARK WAS MAILING A COPY OF THE PAPER TO SUSAN. SHE WAS VERY I N V O L V E D IN PHOTOGRAPHY AND SPENT EVERY W E E K E N D T A K I N G PICTURES.

Intermediate

A GROUP OF PEOPLE WHO SHARED AN INTEREST IN PHOTOGRAPHY HAD R E C E N T L Y STARTED WRITING A N E W S L E T T E R OF THEIR ACTIVITIES. IN FACT, IN ONE ROOM M A R K WAS MAILING A COPY OF THE PAPER TO SUSAN. HE WAS VERY INVOLVED IN PHOTOGRAPHY A N D SPENT EVERY W E E K E N D T A K I N G PICTURES.

Far

A GROUP OF PEOPLE WHO SHARED AN INTEREST IN PHOTOGRAPHY HAD R E C E N T L Y STARTED WRITING A N E W S L E T T E R OF THEIR ACTIVITIES. M A R K WROTE MOST OF T H E COPY BUT THE OTHER MEMBERS DID A LOT OF W O R K AS WELL. IN FACT, IN ONE ROOM CATHY WAS MAILING A COPY OF T H E PAPER TO SUSAN. HE WAS VERY I N V O L V E D IN PHOTOGRAPHY A N D SPENT EVERY W E E K E N D T A K I N G PICTURES.

Subjects were encouraged to read the presented in a region extending over 7 to 10 passages as they would normally do and not lines with up to 42 characters per line. The text was presented on a Hewlett- to try to memorize the passage. They were Packard 1300-A Cathode Ray Tube (CRT) told they were free to reread any segment of which was also interfaced with the com- the text if they desired. Prior to reading the puter. The subjects' eyes were 46 cm from experimental and filler passages, each subthe CRT and three characters equalled 1° of j ect read four warm-up passages. Upon visual angle. The characters were presented completion of each passage, the subject in upper case and were made up from a 5 x pushed a button that resulted in the passage 7 dot matrix. The CRT was covered with a disappearing from the CRT. The subject dark theatre gel so that the characters ap- then released the bite bar and the experimenter read the question associated with peared very clear to the subjects. Procedure. When a subject arrived for an that passage, and the subject gave his or her experiment, a bite bar was prepared which answer. The entire session lasted 3 0 - 4 5 served to eliminate head movements and minutes. the eyetracking system was calibrated for RESULTS the subject. The initial calibration process Across the two experiments, 12% of the took approximately 5 - 1 0 minutes. Then the purpose of the exper i m ent was ex- data from Experiment 1 and 7% of the data plained to the subject. They were told that from Experiment 2 were lost due to the the experiment dealt with where subjects eyetracking system failing to track the eye. look as they read text. They were told to For the most part, these track losses were read each passage for comprehension and due to blinks or pupillary constrictions. For that they would be required to answer a each subject the average fixation duration question following each passage. The com- was computed for the following sequence of prehension questions consisted of general fixations: (1) the fixation prior to encoding questions that often required the subjects to the target pronoun; (2) the fixation on make inferences based on the text they had which the pronoun was encoded; (3) the fixation following encoding of the pronoun; read.

EYE M O V E M E N T S A N D P R O N O U N A S S I G N M E N T

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gorithm was based on research dealing with the perceptual span in reading in which it has been shown that readers are able to obtain lexical information from words beginning 6 characters from fixation and in which it has been shown that the perceptual span C O P Y O F T H E PAPER TO SUSAN. H E WAS V E R Y is asymmetric to the right of fixation (cf., Rayner, 1975, 1978). COPY OF T H E PAPER TOoSUSAN.°HE WAS VERY Table 3 shows the average fixation duration COPY OF T H E PAPER TO SUSAN. H E WAS VERY values associated with each of the four critical fixations as a function of the distance between the pronoun and its antecedent. The results of both experiments were and (4) the fixation two after encoding the very consistent in showing the same pattern pronoun. In Experiment 1, 4% of the data of results; namely, that for the Near and cells had to be filled in with an average Intermediate distances the longest fixation value reflecting both the row and column duration was associated with the fixation on means. In Experiment 2, there were no which pronoun encoding occurred. ~ On the empty cells. The critical data scoring pro- other hand, while there was an increased cedure involved determining the fixation on fixation duration on the encoding fixation which pronoun encoding occurred. Table 2 in the F a r c o n d i t i o n , f i x a t i o n d u r a t i o n illustrates three typical examples of the increased on the two fixations following locus of fixation on the critical line of the pronoun encoding. In the Near and Interpassage. While pronouns represent ideal mediate conditions, there was no such cortargets for examining comprehension pro- responding increase on the fixations folcesses during reading, it is also the case that lowing pronoun encoding. In fact, the fixatwo and three letter words are only fixated tion two following encoding was somewhat approximately 2 0 - 30% of the time (Rayner shorter in both conditions than either the & McConkie, 1976). Furthermore, when fixation prior to or immediately after enshort words begin a sentence, the probabil- coding. This was due to the fact that this ity is even lower that they will be fixated. particular fixation generally represented the Given these constraints, we adopted an al- last fixation on the line in these two condigorithm in which we assumed that encoding tions and such fi xat i ons are g e n e r a l l y of the pronoun occurred on a fixation falling shorter than other fixations on a line (cf., in a region extending 6 characters to the left Rayner, 1978). The means from Experiment 1 were subof the beginning of the p r o n o u n and 1 jected to a 3 (Distance) x 4 (Serial Order of character to the right of the end of the proFixation) Analysis of Variance. Neither of noun. If there was more than one fixation the main effects were significant (p > . 15), within the r e g i o n / w e counted the fixation but the interaction was significant, F(6,90) closest to the pronoun as the fixation on = 2.70, p < .02. The means from Experiwhich encoding occurred. The other fixament 2 were s u b j e c t e d to an identical tion in the region was then categorized as analysis treating subjects as a random varithe fixation prior to encoding. For virtually able (F~) and an additional analysis treating 98% of the lines from which we had scorable data, this algorithm resulted in a fixa Although it is the case in Experiment 2 that many ation falling in the critical region. Our alTABLE 2 SAMPLE FIXATION LOCATIONS ON THE CRITICAL LINE. THE DOTS REPRESENT FIXATION LOCATION AND THE ARROWS INDICATE THE FIXATION ON WHICH PRONOUN ENCODING OCCURRED ACCORDING TO THE ALGORITHM WE USED

2 For 15% of the cases, two fixations fell within the critical area.

of the encoding fixations were on a proper noun, this was not the case in Experiment 1 or in a previous experiment reported by Ehrlich (the means from which are presented in Table 2).

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EHRLICH A N D RAYNER TABLE 3 MEAN FIXATION DURATION (MSEC) AS A FUNCTION OF THE DISTANCE BETWEEN THE PRONOUN AND ITS ANTECEDENT. DATA FROM THE REANALYSIS OF EHRLICH'S STUDY ARE BASED ON 8 SUBJECTS

Fixation Distance

Prior

Encoding

1 after

2 after

Experiment 1 Near Intermediate Far

212 208 205

230 222 222

213 228 233

200 194 243

214 213 223

208

225

225

212

217

224 230 220

248 253 242

224 234 269

207 206 296

226 231 257

225

248

243

236

238

217 201 197

247 228 253

197 234 261

191 191 216

213 214 232

205

243

231

199

220

:~ Experiment 2 Near Intermediate Far

Reanalysis of Ehrlich (1983) Near Intermediate Far

passages as a r a n d o m variable (F2) was carried out. The results of both A N O V A s were consistent with e a c h other in yielding a significant main effect of distance, F1(2,28) = 9.6,p < .001, F2(2,16) = 17.5,p < .001, and a significant interaction, F1(6,84) = 5.02, p < .001, F2(6,48) = 5.78, p < .001. A N e w m a n - K e u l s test on the main effect indicated that the N e a r and I n t e r m e d i a t e conditions did not differ f r o m each other, but they both differed f r o m the F a r condition. A t test comparing fixation duration on the fixation prior to encoding and the fixation on which encoding o c c u r r e d indicated that the duration was longer in the latter case, t(14) = 3.17, p < .01. In order to gain a m o r e c o m p l e t e analysis of the data, we c o m p u t e d the reading time p e r c h a r a c t e r on the line containing the target p r o n o u n in e a c h of the three conditions in E x p e r i m e n t 2 (where the lines were nearly identical across conditions). In this analysis, we included all fixations on the target line including any regressions b a c k to that line f r o m a following line. Again, there

was a highly significant effect of distance, F1(2,28) = 16.87,p < .001, F2(2,16) = 9.78, p < .01. A N e w m a n - K e u l s test again indicated that it t o o k longer to read the line in the F a r condition (2 = 38 milliseconds per character) than in either the I n t e r m e d i a t e (29 m i l l i s e c o n d s ) or t h e N e a r (26 milliseconds) conditions. T h e s e values corres p o n d to reading rates o f 277 w p m , 319 w p m , a n d 331 w p m in the F a r , I n t e r mediate, and N e a r conditions, respectively. The longer reading time for the line was reflected not only in the increased fixation durations discussed above, but also in the fact that saccades were shorter following p r o n o u n encoding in the F a r condition (2 = 7.0 characters) than in the other two conditions (8.2 characters for the a v e r a g e of the two; 8.4 for N e a r and 8.1 for Intermediate), t(14) = 5.34, p < .01, and this was further reflected in m o r e fixations on the line in the F a r condition than the o t h e r two conditions. Finally, we c o m p u t e d the probability of fixating on the target p r o n o u n as a function

EYE MOVEMENTS AND PRONOUN ASSIGNMENT

of experimental condition. For forward fixations (left-to-right), the probability of fixating the target pronoun was .21 across the three conditions. When regressive fixations were included, the probability of fixating the target pronoun was .31. There were no differences across the experimental conditions. As in the study reported by Ehrlich (1983), the probability of a regression back to the antecedent was close to zero (.02) in the Near and Intermediate conditions, and likewise, very infrequent (p = .04) in the Far condition. DISCUSSION

The primary purpose of the experiments was to test the e y e - m i n d and the immediacy assumptions (Just & Carpenter, 1980) and to examine the process monitoring hypothesis (Rayner, 1977, 1978) in the context o f p r o n o u n a s s i g n m e n t . All of t h e s e t h e o r e t i c a l claims address the issue of whether some processing of a word may lag behind its encoding. In addition, we were interested in providing further data concerning the effect of the distance between the pronoun and its antecedent on pronoun assignment (Clark & Sengul, 1979; Ehrlich, 1980; Garrod & Sanford, 1977). We found that people spent more time reading the text following a pronoun when the antecedent was far back in the text. Contrary to the e y e - m i n d as s um pt i on, the increase in reading time o c c u r r e d after people had moved on from the pronoun to fixate a later portion of the text. This result contradicts the e y e - m i n d claim that people will retain fixation on a word until all processing has been completed. Contrary to the immediacy assumption, we also failed to find an increase in the time spent looking at the pronoun as a function of the distance between the p r o n oun and the antecedent. Such an increase would be e x p e c t e d if people were trying to complete assignment while they were looking at the pronoun. Note that in all cases pronoun assignment c o u l d be completed as soon as readers encountered the pronoun.

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According to the immediacy assumption, processes associated with the difficulty in assigning a referent should occur when the pronoun is encoded. Although we failed to support this prediction, we did find that readers spent longer on the fixation on which the pronoun was encoded, relative to the fixation prior to encoding. The increase in fixation duration could be due to a number of factors. For example, the algorithm we used for pronoun encoding included a number of final fixations on a sentence. Thus, the increased fixation duration between the fixation prior to encoding and encoding could be rel at ed to s e n t e n c e wrap-up effects (Just & Carpenter, 1980). Alternatively, the increase could indicate that lexical encoding is completed and referent assignment is started, but not necessarily completed. In the Near and Intermediate conditions, pronoun assignment may have been completed on the encoding fixation resulting in longer fixations. In the Far condition, assignment may have been started, but not completed on the encoding fixation. This latter explanation is consistent with the process monitoring hypothesis which claims that readers will remain fixated on a word until that word has been encoded to the point of lexical access. In general, our results support the notion that there is not an e y e - m i n d span for lexical a c c e s s in silent reading (Just & Carpenter, 1980; Rayner, 1977, 1978); it seems that identification of a word to a level where its lexical features can be extracted occurs within the same fixation as perceptual encoding. Other evidence (Frazier & Rayner, 1982) suggests that syntactic parsing is initiated on the current fixation. For example, syntactic ambiguity is detected when a disambiguating word is encountered (Frazier & Rayner, 1982). Thus, evidence from current research indicates that perceptual encoding, lexical retrieval of a word, and some syntactic parsing occur while a reader has that word in fixation. However, in the case of pronouns, all that can be retrieved from an

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internal lexicon is information about the number and gender of the pronoun. To complete assignment, a reader must access and integrate information from another portion of the text in order to select an ant e c e d e n t that m a t c h e s the p r o n o u n in number and gender. Our data suggest that although this process may be started when the pronoun is within fixation, there is no evidence that assignment is necessarily completed within the same fixation, especially when the antecedent occurs some distance back in the text. Thus, more complex processes such as those involving integration are not necessarily completed during the fixation on which the process was initiated (see also Just & Carpenter, 1980; Carpenter & Just, 1983). Contrary to the e y e - m i n d assumption, when the antecedent was some distance back readers continued processing the text, that is, encoding and doing lexical access of the newly fixated words, while at the same time continuing the process of pronoun assignment. The extra load, however, was accompanied by a general slowdown in processing as reflected in the overall reading time, the average fixation duration, and the distance the eye moved (slightly shorter saccades on average). These results are consistent with a number of recent demonstrations that fixation duration is increased at very precise locations in the text where on some a priori ground extra processing load might be e x p e c t e d ( C a r p e n t e r & Daneman, 1981; Frazier & Rayner, 1982; Holmes & O'Regan, 1981; Just & Carpenter, 1980; Rayner, 1977). The results of the two experiments reported here are consistent with the results of an e x p e r i m e n t r e p o r t e d by Ehrlich (1983). She also varied the distance between the pronoun and its antecedent and found results like those reported here: namely, pronoun assignment occurred increasingly later as the distance between the pronoun and its antecedent increased. In Ehrlich (1983), there was always only one major protagonist in the passages. Distance

varied by changing the order of the sentences. Although the study by Ehrlich was carefully designed so that the sentence in which the pronoun occurred was the same over the different distances, the sentence prior to the pronoun was not the same. Hence, it is possible that the fixation duration on the pronoun in her study was affected by the perceptual and semantic characteristics of the immediately prior material. The experiment reported here provides an independent evaluation of the distance effect by controlling the material more carefully so that the lexical items preceding the target pronouns were identical in each condition. In the previous study, Ehrlich (1983) scored her data in terms of (1) the fixation nearest the pronoun, (2) the fixation before, and (3) the fixation after. Ambiguities over the nearest fixation were resolved by Ehrlich in favor of the fixation to the right of the pronoun, so long as that fixation was within 6 characters of the pronoun. Hence, the region of encoding for the pronoun extended from the beginning of the pronoun to 6 characters after the pronoun. She found that for an equivalent condition to our Near condition, fixation duration was longest on the fixation before encoding and that the longest fixation in the Far condition occurred on the fixation after encoding. On the basis of the results obtained in the present experiments, the data from Ehrlich (1983) were reanalyzed using the same algorithm as was used here. The reanalyzed fixation durations from Ehrlich (1983) are very similar to those obtained in the present experiment (see Table 3). The primary conclusion to be reached from Ehrlich's (1983) study is that pronoun assignment occurs later as the distance between the antecedent and the pronoun increases. This conclusion emerges independently of the characteristics of the particular algorithm used to categorize pronoun encoding. Hence, the general conclusion to be reached, that pronoun assignment occurred later as the distance between antecedent and pronoun increased, remains essentially the same.

EYE MOVEMENTS AND PRONOUN ASSIGNMENT

Results of our experiments are also consistent with those r e p o r t e d by Ehrlich (1983) in indicating that readers rarely made a r e g r e s s i o n back to the locus of the antecedent. In Ehrlich's study, the gender of the pronoun was varied in relation to a profession that r eader s might have exp e c t e d to be male (e.g., " p r e s i d e n t " ) . When the g e n d e r of the p r o n o u n was female, Ehrlich found that readers did not initiate regressions back to the antecedent. H o w e v e r , Ehrlich did find that readers made a high percentage of regressions when there was a major disruption in comprehension caused by an explicit conflict between the gender of the pronoun and that of the antecedent. Ehrlich was able to induce this disruption by, for example, presenting a passage about a character called T o m N o r m a n and referring to this character with the inappropriate pronoun, " s h e . " Hence, readers are able to resolve pronouns without making a regression back to the antecedent, e x c e p t in cases w he r e there is an explicit conflict between pronoun and antecedent (Ehrlich, 1983), or when the instructions encourage the reader to regress (Carpenter & Just, 1977). The results we obtained showing that the distance between a pronoun and its antecedent affects the locus and speed of assignment, supports previous research (Clark & Sengul, 1979; Ehrlich, 1983). The effect of distance on pronoun assignment has generally b een i n t e r p r e t e d as indicating that people examine potential antecedents serially, beginning with the candidate nearest the pronoun (Springston, Note 1). There are, however, a number of problems with this hypothesis as it stands. In particular, it is not clear whether the unit of search is the candidate or the clause. It is also not clear why antecedents far back in the text take longer to be assigned. It may be that if people examine each candidate in serial order, there are simply more candidates that have to be evaluated when the chosen referent is far back in the text or, it may be that the search is parallel but nearer an-

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tecedents are always retrieved faster than far ones. An alternative version of the parallel search claim is that the further antecedents are less accessible because they are no longer part of the current topic of the passage and hence are more difficult to retrieve from memory (Sanford & Garrod, 1981). For instance, there is some evidence that antecedents in the sentence immediately prior to the pronoun are part of the current topic (Hobbs, 1978). The data from the present experiments are consistent with the view that the antecedent in the Far condition was difficult to assign because it was no longer part of the current topic. In examining the implications of distance for the order in which readers search for antecedents, Clark and Sengul (1979) argued that the clause rather than the sentence was the critical unit. They found that an antecedent prior to the pronoun was assigned faster when it was in the nearer clause than when it was in the farther clause, irrespective of whether there was also a sentence boundary. These data indicate that clause boundaries rather than sentence boundaries are critical. In the present study we had conditions in which the antecedent could occur either at the beginning or at the end of a one-clause sentence prior to the pronoun. We found no difference in the locus or speed of assignment between these two conditions. However, both these antecedents were assigned faster than those that occurred further back in the text. Unlike the Clark and Sengul study, both our antecedents were in the same clause, but occupying different grammatical roles. Hence, our results suggest that insofar as there is any serial evaluation of candidates, potential antecedents are evaluated clause by clause rather than by individual candidates. Other research has also shown a similar lack of difference in assignment time when antecedents in the same clause are compared (Ehrlich, 1980; Chang, 1980). The main focus of this article has been to examine what kind of cognitive processes

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are synchronous with fixations. In examining this issue in the context of pronoun assignment we have chosen to evaluate the immediacy assumption against a process monitoring claim in which processing to the level of lexical access occurs during fixation. The main distinction between the two is that where the immediacy assumption is unclear about how much processing occurs when a reader is looking at a word, the alternative claim limits immediate processing to processes associated with lexical access and some syntactic parsing. Further research is needed to map out more precisely the range of immediate processing. In conclusion, the results of these experiments suggest that many processes associated with retrieving the meaning of a word are carried out while the word is within fixation. However, there is a limit to the range of processes that are carried out immediately; we suggest that only processes directly relevant to lexical access and syntactic parsing are carried out before the eyes move on to fixate the next word. As such our results are generally consistent with those of Rayner and Pollatsek (1981) who demonstrated that fixation duration is strongly influenced by the information available on the current fixation, but also that there are lag effects. Our experiments also indicate that, in the case of pronoun assignment, processes associated with retrieving the referent may be initiated when the pronoun is encoded. However, while assignment may be completed during the fixation on which encoding occurs, the process may often be completed on later fixations. One implication of this finding is that a variety of processes of text comprehension may be carried out in parallel. REFERENCES BOUMA, H., & DEVOOGD, A. H. On the control of eye saccades in reading. Vision Research, 1974, 14, 273-284. CARPENTER, P. A., & DANEMAN, M. Lexical retrieval and error recovery in reading: A model based on eye fixations. Journal of Verbal Learning and Verbal Behavior, 1981, 20, 137-160.

CARPENTER, P . A . , & JUST, M . A . Reading comprehension as eyes see it. In M. A. Just and P. A. Carpenter (Eds.), Cognitive processes in comprehension, Hillsdale, N.J.: Erlbaum, 1977. CARPENTER, P. A., 8£ JUST, M. A. What your eyes do while your mind is reading. In K. Rayner (Ed.),

Eye movements in reading: Perceptual and language processes. New York: Academic Press, 1983. CHANG, F. Active memory processes in visual sentence comprehension: Clause effects and pronominal reference. Memory and Cognition, 1980, 8, 58-64. CLARK, H. H., t% SENGUL, C. J. In search of referents for nouns and pronouns. Memory and Cognition, 1979, 7, 35-41. DANEMAN, M., • CARPENTER, P. A. Individual differences in working memory and reading. Journal of Verbal Learning and Verbal Behavior, 1980, 19, 450-466. EHRLICH, K. Comprehension of pronouns. Quarterly Journal of Experimental Psychology, 1980, 32, 247-255. EHRLICH, K. Eye movements in pronoun assignment: A studY of sentence integration. In K. Rayner (Ed.), Eye movements in reading: Perceptual and language processes. New York: Academic Press, 1983. EHRLICH, S. F., 8¢ RAYNER, K. Contextual effects on word p e r c e p t i o n and eye movements during reading. Journal of Verbal Learning and Verbal Behavior, 1981, 20, 641-655. FRAZIER, L., & RAYNER, K. Making and correcting errors during sentence comprehension: Eye movements in the analysis of structurally ambiguous sentences. Cognitive Psychology, 1982, 14, 178-210. GARROD, S., & SANFORD,A. J. Interpreting anaphoric relations: The integration of semantic information while reading. Journal of Verbal Learning and Verbal Behavior, 1977, 16, 77-90. HOBBS, J. R. Resolving pronoun references. Lingua, 1978, 44, 311-338. HOLMES, V. M., & O'REGAN, J. K. Eye fixation patterns during the reading of relative-clause sentences. Journal of Verbal Learning and Verbal Behavior, 1981, 20, 417-430. JUST, M. A., & CARPENTER, P. A. A theory of reading: F r o m eye fixations to c o m p r e h e n s i o n . Psychological Review, 1980, 87, 329-354. KOLERS, P. A. Buswell's discoveries. In R. A. Monty and J. W. Senders (Eds.), Eye movements and psychological processes. Hillsdale, N.J.: Erlbaum, 1976. MORTON, J. The effects of context upon speed of reading, eye movements, and the e y e - v o i c e span. Quarterly Journal of Experimental Psychology, 1964, 16, 340-354.

EYE MOVEMENTS AND PRONOUN ASSIGNMENT RAYNER, K. The perceptual span and peripheral cues in reading. Cognitive Psychology, 1975, 7, 65-81. RAYNER, K. Visual attention in reading: Eye movements reflect cognitive processes. Memory and Cognition, 1977, 4, 443-448. RAYNER, K. Eye movements in reading and information processing. Psychological Bulletin, 1978, 85, 618-660. RaYNER, K., & McCONKIE, G . W . What guides a reader's eye movements? Vision Research, 1976, 16, 829-837. RAYNER, K., & POLLATSEK, A. Eye movement control during reading: Evidence for direct control. Quarterly Journal of Experimental Psychology, 1981, 33A, 351-373.

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SANFORD, A. J., & GARROD,S. Understanding written language: Explorations in comprehension beyond the sentence. Chichester, England: Wiley & Sons, 1981. WANAT, S. Linguistic structure and visual attention in reading. Newark, Del.: International Reading Association, 1971. REFERENCE NOTES 1. SPRINGSTON,F. J. Some cognitive aspects of presupposed coreferential anaphora. Unpublished doctoral dissertation, Stanford University, 1975. (Received January 13, 1982)