Acta Psychologica 0 North-Holland
39 (1975), 271-282 Publishing Company.
PARAFOVEAL READING
IDENTIFICATION
DURING
A FIXATION
IN
Keith RAYNER* University of Rochester, Rochester, N. Y.14627, U.S.A.
Received
January
1975
This paper deals with the extent to which the perceptual span in reading differs as a function of grammatical categories. Stibjects read short passages of text and their eye movements were monitored as they did. Irregularities were entered into the text in the subject, verb, or object location of active sentences. Eye movement data were analyzed to determine how far from these various locations the readers were aware of the irregularities. Although there were no differences due to the different parts of speech employed, there was evidence that the perceptual span varied at different locations in text. It was found that readers seldom fixated between sentences and when they did, they were obtaining little information from parafoveal vision.
Reading is a complex skill involving perceptual, memorial, and linguistic capacities. Currently popular theories of reading (Smith 197 1; Mackworth 1972) assume that reading involves an initial perceptual input during an eye fixation that is subsequently coded into the memory system and transferred from a sensory store into short-term memory and finally stored away in long-term memory. Linguistic variables are important in that they make the text more predictable or redundant and, hence, easier to read. In this vein, studies utilizing the eye-voice span (the distance that the eye is ahead of the voice.in oral reading) have found the eye-voice span to be larger in more predictable areas of a sentence. For example, the eye-voice span is larger at the * This paper is based on part of a dissertation submitted to Cornell University in partial fulfillment of the Ph. D. requirements. The author would like to thank George W. McConkie, who was the thesis advisor, for his encouragement and support. The research was sponsored in part by Grant OEG-2-71-0531 from the U.S. Office of Education. Requests for reprints should be sent to the author at the Center for Development, Learning, and Instruction, University of Rochester, Rochester, N.Y. 14627.
212
K. Kayner/Parafoveal
identification in reading
end of passive sentences (which are more constrained and, hence, more predictable) than at the end of active sentences (Levin and Kaplan 1968). It is also larger in more predictable right-embedded sentences than in left-embedded sentences (Levin et al. 1973) and in agent included passive sentences than in agent deleted passives (Wanat and Levin 1970). In addition, other studies have found the eye-voice span is elastic and stretches or shrinks to phrase boundaries (Schlesinger 1968; Levin and Turner 1968; Resnick 1970). Eye movements are also affected by the redundancy and difficulty of textual material. More difficult material leads to more and longer fixations (Tinker 1965). Wanat (197 1) has reported that inspection time tends to be greater in the area of the main verb, and to decrease in areas of the sentence which are more highly predictable than other areas. Wanat’s finding that inspection times are longer in the area of the verb is paralleled by other non-reading studies. Recent studies have reported that tampering with the main verb of the sentence interferes with fluent processing (Gladney and Kralee 1967), that the main verb is the central element in sentence comprehension (Fodor et al. 1968), and that the main verb is most important in determining the meaning of the sentence (Healy and Miller 1970, 197 1). Linguists (Chafe 1970) have also speculated that the verb is the heart of the sentence. The present study dealt with the extent to which irregularities in key elements of the text could be detected in parafoveal (an area subtending from about 2” to 10” around fixation, according to Ditchburn 1973) and peripheral vision. Eye movements of skilIed readers were monitored as they read text and irregularities were entered into the text by mutilating various key words in the text, namely the subject, verb, and object of active sentences. It was assumed that if a reader detected an irregularity in the periphery, his eye movement pattern would be affected. Specifically, since the verb has been shown to be the key part of the sentence for obtaining the meaning of the sentence, it was expected that the reader might scan ahead to a greater extent when he was in the region of the main verb and thus an irregularity in the verb would be recognized further into the periphery than a corresponding irregularity in the subject or object. The present study also has implications for the nature of the perceptual span during reading. If the extent to which irregularities in the text can be detected varies, the variability would be evidence that the perceptual span varies at different locations in reading text.
K. RaynerjParafoveal
identification in reading
273
Method Subjects Ten undergraduate students, six male and four female, at the Massachusetts Institute of Technology were paid $2.00 an hour for their services. They were told that the purpose of the study was to determine what people look at when they read, and that their eye movements would be monitored and recorded by a computer. All of the Ss had normal, uncorrected vision and their reading speed was in the range of 200-400 words per min.
Materials Two hundred twenty five short paragraphs were prepared that were each 35-40 length. Within each paragraph, sentences were embedded which were of the following The subject
verbed
the object in the prepositional
words form:
in
phrase.
One word location within these sentences was identified as the critical word location (CWL) and alternative words or letter strings were prepared which could be inserted into that area. For example, if the critical sentence were: The children
the chemical
in the hall,
two of the alternatives were words (tasted, tested/ fitting into the sentence frame semantically and syntactically. The two word (W) alternatives always began and ended with the same letters and had the same overall word shape. The other three alternatives were non-word (N) letter strings (tcrted, tflmed, fcstcb/ which maintained or destroyed certain aspects of the two W alternatives. The specific characteristics of the five alternatives that could appear in the CWL are important for other data that will not be presented here. For the purpose of the present report, it is important that some of the alternatives were words and others were non-words. The words in the CWL were equally often five, six, or seven letters in length, and served as subject, verb, and object in their respective sentences equally often. The CWL also occurred equally often on the first, second, or third line of the paragraph. Table 1 shows some examples of the types of sentences used in the study. The 225 paragraphs were read in blocks of 15. After reading each block, the Ss were given a set of 12 sentences and asked to identify which of the sentences came from the passages they had just read. This task was included to insure that the subjects actually read the passages.
Apparatus The equipment used to record eye movements is described in detail by Rayner (1975) and consisted of a Biometrics Model SG Eye Movement Monitor interfaced with a PDP-6, thus providing the capability for on-line continuous monitoring of eye position. The eye movement monitor was modified by the addition of a biteboard and a forehead rest to prevent head movements. As the Ss read the text, the computer kept a complete record of fixation location, fixation duration, saccade duration, and saccade length. Pilot work with the eye movement apparatus indicated that it was highly accurate and seldom indicated that a reader was fixated
K. Rayrzer/Parafoveal identijicatiou in reading
214
Table 1 Examples
of sentences
used in the study
and the two word alternatives. Alternate word
Sentences 1. 2. 3.
The traitor brought his friends to the courtroom. The mayor picked the volunteer for the assignment. The writer broke the bottle on the floor.
teacher major waiter
Verb CWL:
4. 5. 6.
The captain granted the pass in the afternoon. The impact crushed the glass in the church. The employer hired the men in the office.
guarded cracked heard
Object
I. 8. 9.
The policeman carried the babies to the train. The guest heard the plane above the roar. The rebels guarded the palace with their guns.
bodies phone police
Subject
CWL:
CWL:
more than one or two character positions fixate. The paragraphs were displayed on a scope, which has a character generator phosphor. A dark theater gel was used to line of text that was displayed was around angle.
away from the character
he reported
Digital Equipment Corporation for both upper and lower case filter out the yellow afterglow of 72 characters long and occupied
he was trying
to
Model 340 display letters, and a P-7 the phosphor. Each 18 degrees of visual
Procedure Each S was tested individually. When a S arrived for the experiment, a bite bar was prepared for him. Then the eye tracking sensors, which were mounted on glasses’ frames and held securely by a head band, were placed on him. The glasses and sensors were adjusted for each S. The Ss were told that they would be required to read a series of passages to understand them. Each S then read three warm-up passages to become accustomed to the apparatus and become as comfortable as possible. Following the warm-up passages, each S read the 225 paragraphs. The paragraphs were read in blocks of 15, after which the S came off from the bite bar, answered and adjustments were made on the sensors if necessary. He then some recognition questions, went back on the bite bar and read another 15 passages. All of the Ss read the paragraphs in the same order. The paragraphs were displayed one at a time on the CathodeRay Tube. When each passage was initially displayed, the CWL could contain either a W or a N alternative. A boundary location was specified to the computer, and when the reader’s saccadc crossed that position the alternative that was initially displayed was replaced by one of the word alternatives. Thus, although either a W or a N alternative could be initially displayed in the CWL when the saccade began, by the time it ended or shortly thereafter (within 20 msec after the saccade ended), only one of the word alternatives was ever displayed. The boundary location was not visibly present in the text, but rather represented a character position on the line containing the CWL. Boundary locations were the fourth letter of the CWL, the first letter of the CWL, three character positions to the left of the CWL, six character positions to the left of the CWL, and nine character positions to the left of the CWL. Details of the display change are reported by Rayner (1975).
K. RaynerlParafoveal
identification in reading
215
Results Analyses of eye movement data consisted of two types: (1) fixation durations and (2) fixation locations. The analyses of fixation duration were carried out to determine how far into parafoveal and peripheral vision readers could make a distinction between words and non-words and to determine if irregularities in the verb could be detected further from the point of fixation than an irregularity in the subject or object. In carrying out the analyses on fixation durations, it was noticed that there were differences in fixation locations and further analyses were carried out regarding this aspect of the data.
Fixation
durations
Two analyses regarding fixation durations were carried out; the first involved the duration of the last fixation prior to crossing the boundary location and the second involved the duration of the first fixation after crossing the boundary. In the first duration analysis, six mean fixation durations were determined for each S at each of six locations with respect to the CWL. The six locations were the first three character positions of the CWL, or 1-3, 446, 7-9, 10-12, or 13-15 character positions prior to the CWL. The six mean scores were determined by the grammatical category of the CWL (subject, verb, or object) and whether the CWL contained a word or non-word. Thus, for example, all instances in which (1) the reader was fixated 7-9 character positions from the CWL on the last fixation prior to crossing the boundary, (2) the CWL was the subject of the sentence, and (3) the CWL was a non-word were grouped together and a mean score was calculated. Separate
450
t
+-----+ w-----o *---. *-- - o
Subject-W Sobiect - N Verb-W Verb-N Object-W Object-N
15-13
12-10
Area (No
Fig. 1. Mean duration location, grammatical a word or non-word.
to The
P
I
9-7 Left
of Character
6-4
3-l
of The
CWL
o-2
Positions!
of the last fixation prior to crossing the boundary as a function of its category of the CWL, and whether the initially displayed alternative was
K. RaynerlParafoveal
216
identification in reading
two-way analyses of variance were then carried out on these data at each of the six locations to determine differences between word and non-word conditions. The data are presented in fig. 1. As can be seen in fig. 1, fixation durations did not differ for words and non-words in the CWL when the reader fixated four or more character positions to the left of the CWL. However, when they fixated three to one character positions prior to the CWL or on the first three letters of the CWL itself, fixation durations were longer for non-words than for words (F(l, 9) = 8.30, p < 0.02, and F(1, 9) = 12.99, p < 0.006, respectively). There was also a significant grammatical category effect when they fixated three to one character positions prior to the CWL (F(2, 18) = 7.71, p < 0.004). A Newman-Keuls test indicated that the fixation durations were significantly longer (p < 0.01) when the CWL was a verb or object as opposed to being the subject of the sentence. Thus, there was evidence that parafoveal information was not picked up from the CWL when it was the subject of the sentence to the extent that information was picked up when it was the verb or the object of the sentence, In the second duration analysis, the duration of the first fixation after crossing the boundary location was examined. The rationale for this analysis was that if the reader gained information about the CWL when he was fixated at a certain area prior to the CWL and then found that when his eye landed on the CWL (following the display change) that a change had been made, there should be a longer fixation duration. Only fixations that landed on the CWL after crossing the boundary were included in this analysis and only conditions in which a non-word occurred initially in the CWL were analyzed. The reason for this latter limitation was that conditions in which a word was replaced by itself as a result of the display change comprised only one-fifth of the data. Hence, there were not < efficient data to provide comparisons between conditions in which the subject, verb, or o jzct of the sentence was replaced by itself and conditions in which the subject, verb, or object appeared initially as a non-word. Nevertheless, the results of the analysis which included only non-word conditions were supportive of the data presented previously regarding fixation durations prior to the display change. 325-
-Subject +----Verb 6 - --+ Object
iti E
II ,’ .’ 200 225 V’! 15-13 Area (No
L
9-7
12-10 to The
Left
of Character
1
1
6-4
of The
3-l CWL
Positions)
Fig. 2. Mean fixation durations on the CWL immediately after crossing the boundary as a function of grammatical category of the CWL and of the location of the prior fixation when the initially displayed alternative was a non-word.
X RaynerlParafoveal
271
identification in reading
An analysis of variance with factors being prior fixation location and grammatical category of the CWL yielded significant main effects of prior location (F(4, 36) = 2.88, p < 0.05) and of grammatical category (F(2, 18) = 3.55, p < 0.05). The interaction of these variables was not significant (F(8, 72) = 1.37, p < 0.20). Mean fixation durations according to grammatical category were as follows: subject, 236 msec; verb, 264 msec; and object, 260 msec. The display change caused less inflation of fixation durations when the CWL served as the subject of the sentence than when it served as verb or object. These data are shown in fig. 2. Here it can be seen that, in agreement with the data presented regarding the duration of the last fixation prior to crossing the boundary, when the reader fixated just left of the CWL, he was less likely to acquire visual information from the CWL region when it served the function of the subject of the sentence than when it served as verb or object. Interestingly, this was not true when he fixated further to the left of the CWL, between 7 and 15 character positions. This difference only occurred when the eye was within 6 character positions of that location. Roth of the analyses regarding fixation durations indicated that the reader did not acquire parafoveal information from the CWL when it served the syntactic function of the subject of the sentence. However, in carrying out these analyses it was noticed that there were substantial differences in the number of fixations found in the various locations with respect to the CWL. This discovery led to further analyses to determine the reason for the effects found with fixation duration data.
Location of fixations and saccade lengths Fig. 3 shows the frequency of fixations on different locations prior to the CWL. When the CWL was the subject of the sentence, there were fewer than normal fixations in the region l-6 character positions to the left of the CWL. When the CWL was the verb, there were fewer than normal fixations in the region IO-15 character positions orior to the CWL. A two-way analysis
18
-
Subiect
----- - - +
Verb Object
t I5
12 -
9.
6-
3-
I 15-13
12-10
9-7
6-4
3-l
Area to The Left of CWL ( No. Chorocter Positions) Fig. 3. Effect of grammatical category different areas to the left of the CWL.
of the CWL on the number
of fixations
which
fell in
K. Rauner/ParafoveaI
278
identification
irl reading
.-‘
IA- 260 Fig. 4. Relationship sentence containing
t of frequency the CWL.
of fixations
and durations
of fixations
in the area
of the
of variance on the number of fixations occurring in each category yielded a significant Grammatical Category X Location Interaction (F(8, 72) = 11.54, p < 0.001). The same pattern was present in the W and rhe N data. The basis of this data pattern can be seen in fig. 4, which shows the number of fixations occurring at each region of the sentence when the CWL occupied the position as subject, as verb, and as object. This figure also shows the durations of fixations at each arca of the sentence under the same conditions. The hatched lines between the two bar graphs indicate the three sets of five regions from which fixations were considered, depending on whether the CWL occupied the position of subject, verb or object. The bars are coded according to whether the data came from conditions when the CWL was subject, verb, or object. Bars with lines sloping down to the right indicate data from paragraphs in which the CWL served as subject; bars with no lines indicate data from paragraphs in which the CWL served as verb; and bars with lines sloping up to the right indicate data from paragraphs in which the CWL served as object. From this figure it can be Teen that the differences observed in number of fixations in different categories, shown in fig. 3, was due to a general tendency for Ss to make fewer fixations in the region occupied by the terminal character and period from the prior sentence, the spaces between the sentences, and the article at the beginning of the sentence containing the CWL. It can also be seen that when the S did fixate in that region, the duration of hit; fixation tended to bc substantially shorter than usual. Thus, it appears that when they fixated in this region, they tended not to acquire visual information from words as far from their fixation point as they did when they fixated at other regions in the sentence. Further evidence that the readers Feldom fixated this non-informative area was obtained by examining saccade lengths for cyc movements that landed in the area of the CWL. All saccades that began less than 16 character spaces and more than one character space to the left of the CWL and landed in the region of the CWL were examined for each S according to the gammatical category in the CWL. A one-way analysis of variance yielded a significant difference in saccade length depending on the grammatical category in the CWL (F(2, 27) = 30.74, p < 0.001). Although this analysis included both the N and W condition, a similar analysis for the different grammatical catcgorics when the CWL initially contained only a non-word yielded identical results. The mean vaccade lengths (in character spaces) were:
K. RaynerfParafoveal
identification in reading
219
subject, 12.04; verb, 8.31; and object, 8.65. A Newman-Keuls test indicated the subject differed from the verb and object (p < 0.01). Thus, the readers tended to move their eyes a greater distance when they were at the end of one sentence and ready to begin the processing of another than if they were in the middle of a sentence. The length of the saccade on the subject of the sentence was longer than for the verb or the object because the readers had to cross the uninformative areas containing the blank spaces between sentences and the function word beginning the new sentence. One final feature of the data which was noted was a tendency for Ss to fixate the left and right half of the CWL equally frequently when it served the function of subject, but for the left half to receive more fixations when it served as verb or object. For the verb and the object nearly 75% of all fixations on the CWL were on the left half of the word. A two-way analysis of variance found significant effects for fixation location (F(1, 9) = 20.53, p < 0.002) and for the Fixation Location X Grammatical Category Interaction (F(2, 18) = 20.29, p < 0.001). This may reflect a tendency for fixations to be more accurately located on the verb or object than on the subject in sentences of the syntactic construction used here, since saccades coming to the subject region originated either some distance from their target (at some location in the previous sentence) or from a nearer region (between the sentences) at which they tended not to acquire parafoveal visual information.
Discussion The results of this study indicate that the perceptual span in reading varies at different locations in the text. However, this variability does not seem to be tied to parts of speech; that is, there was no evidence that irregularities in the verb were detected any further into the periphery than irregularities in the object or subject. Since the verb has been shown to be the most important element for comprehending a sentence, it seemed reasonable to assume that the reader may scan ahead more when he approached the area of the main verb. The present results show that this assumption is not true. The evidence that the perceptual span may differ at various locations stems from the fact that readers in this study did not notice an irregularity in the CWL when they fixated on the non-informative area between two sentences and the function word beginning a new sentence. At times when they did not fixate on this non-informative area, the data suggest that the reader was obtaining semantic information for words beginning 6 or fewer character spaces from the fixation point. Since 4 character positions equaled 1” of visual angle in the present study, and since the average word length of the CWL was 6 character positions, the present data suggest that the reader semantically identifies words falling in an area subtending about 2” of visual angle to the right of his fixation point.
280
K. RaynerlParafoveal
identification in reading
The data regarding frequency of fixations in the non-informative area between sentences indicate that when a reader was approaching the end of a sentence his strategy was to cast his eye a greater distance than usual so that he could bypass this relatively uninformative area. It is of interest that when the reader fixated in the region l-6 character positions prior to the subject position he failed to obtain parafoveal visual information. This suggests that fixations made in the region between sentences play a special function. There are two possible explanations of the type of cognitive processes that might be occurring during these fixations, each of which would be harmonious with the notion that they are not used primarily for obtaining additional visual information for reading. The first possibility is that, as Woodworth (1938) has suggested, the understanding of the text lags somewhat behind the visual impressions. This may make it necessary occasionally to pause for an extra fixation at the end of a sentence to tiermit processing of the information obtained to be complete. The purpose of this fixation, then would not be for visual input, which may account for its reduced duration. A second possible explanation is that there is a certain amount of inaccuracy in the guidance of eye movements. Readers are capable of identifying regions in the text where there are no letters and are generally able to avoid them, as shown by Abrams and Zuber (1972). These investigators presented Ss with text modified to have a series of blank regions between words at random locations. They found that Ss made few fixations within these blank regions. Thus, it would seem likely that Ss identify the region between sentences, containing a to avoid locating punctuation mark and two spaces, and attempt fixations in these regions. However, oculomotor control is not complete, and the eye may inadvertently fall on this region. When this occurs, the reader quickly recognizes that he is fixating a retion of little visual information, and the next saccade is initiated. Thus, the fixation is shorter than normal and the S does no processing of parafoveal visual information. Which of these possibilities accurately account for the type of cognitive processing taking place during fixations between sentences, as well as other questions regarding the flexibility of the perceptual span, must be the subject of additional research.
K. RaynerlParafoveal
identification in reading
281
References Abrams, S. G., B. L. Zuber, 1972. Some temporal characteristics of information processing during reading. Reading Res. Quart. 8, 42-51. Chafe, W., 1970. Meaning and the structure of language. Chicago: Univ. of Chicago Press. Ditchburn, R. W., 1973. Eye-movements and visual perception. London: Oxford Univ. Press. Fodor, J. A., M. Garrett, T. G. Bever, 1968. Some syntactic determinants of sentential complexity, II: Verb structure. Perception and Psychophysics 3, 453-461. Gladney, T. A., G. K. Krulee, 1967. The influence of syntactic errors on sentence recognition. J. Verb. Learning Verb. Behav. 6, 692-698. Healy, A. F., G. A. Miller, 1970. The verb as the main determinant of sentence meaning. Psychonomic Sci. 20, 372. Healy, A. F., G. A. Miller, 1971. The relative contribution of nouns and verbs to sentence acceptability and comprehensibility. Psychonomic Sci. 24, 94-95. Levin, H., J. Grossman, E. Kaplan, R. Yang, 1972. Constraints and the eye-voice span in right and left embedded sentences. Language and Speech 15, 30-39. Levin, H., E. L. Kaplan, 1968. Eye-voice span (EVS) within active and passive sentences. Language and Speech 11, 25 1- 258. Levin, H., A. Turner, 1968. Sentence structure and the eye-voice span. In: H. Levin, E. J. Gibson, J. J. Gibson (eds.), The analysis of reading skill. Final Report to U.S.O.E., Project No. 5-1213. Mackworth, J. F., 1972. Some models of the reading process: learners and skilled readers. Reading Res. Quart. 7, 701-733. Rayner, K.. 1975. The perceptual span and peripheral cues in reading. Cognitive Psychol. 7, 65-81. Resnick, L., 1970. Relations between perceptual and syntactic control in oral reading. J. Educ. Psychol. 61, 382-385. Schlesinger, 1. M., 1968. Sentence structure and the reading process. The Hague: Mouton. Smith, F., 197 1. Understanding reading. New York: Holt, Rinehart and Winston. Tinker, M. A., 1965. Bases for effective reading. Minneapolis: Univ. of Minnesota Press. Wanat, S., 1971. Linguistic structure and visual attention in reading. Newark, Delaware: International Reading Ass. Wanat, S., H. Levin, 1970. Linguistic constraints in reader processing strategies. Paper presented at the Eastern Psychological Association meetings. Woodworth, R. S., 1938. Experimental psychology. New York: Henry Holt.
39 (1975), 271-282 Publishing Company.
PARAFOVEAL READING
IDENTIFICATION
DURING
A FIXATION
IN
Keith RAYNER* University of Rochester, Rochester, N. Y.14627, U.S.A.
Received
January
1975
This paper deals with the extent to which the perceptual span in reading differs as a function of grammatical categories. Stibjects read short passages of text and their eye movements were monitored as they did. Irregularities were entered into the text in the subject, verb, or object location of active sentences. Eye movement data were analyzed to determine how far from these various locations the readers were aware of the irregularities. Although there were no differences due to the different parts of speech employed, there was evidence that the perceptual span varied at different locations in text. It was found that readers seldom fixated between sentences and when they did, they were obtaining little information from parafoveal vision.
Reading is a complex skill involving perceptual, memorial, and linguistic capacities. Currently popular theories of reading (Smith 197 1; Mackworth 1972) assume that reading involves an initial perceptual input during an eye fixation that is subsequently coded into the memory system and transferred from a sensory store into short-term memory and finally stored away in long-term memory. Linguistic variables are important in that they make the text more predictable or redundant and, hence, easier to read. In this vein, studies utilizing the eye-voice span (the distance that the eye is ahead of the voice.in oral reading) have found the eye-voice span to be larger in more predictable areas of a sentence. For example, the eye-voice span is larger at the * This paper is based on part of a dissertation submitted to Cornell University in partial fulfillment of the Ph. D. requirements. The author would like to thank George W. McConkie, who was the thesis advisor, for his encouragement and support. The research was sponsored in part by Grant OEG-2-71-0531 from the U.S. Office of Education. Requests for reprints should be sent to the author at the Center for Development, Learning, and Instruction, University of Rochester, Rochester, N.Y. 14627.
212
K. Kayner/Parafoveal
identification in reading
end of passive sentences (which are more constrained and, hence, more predictable) than at the end of active sentences (Levin and Kaplan 1968). It is also larger in more predictable right-embedded sentences than in left-embedded sentences (Levin et al. 1973) and in agent included passive sentences than in agent deleted passives (Wanat and Levin 1970). In addition, other studies have found the eye-voice span is elastic and stretches or shrinks to phrase boundaries (Schlesinger 1968; Levin and Turner 1968; Resnick 1970). Eye movements are also affected by the redundancy and difficulty of textual material. More difficult material leads to more and longer fixations (Tinker 1965). Wanat (197 1) has reported that inspection time tends to be greater in the area of the main verb, and to decrease in areas of the sentence which are more highly predictable than other areas. Wanat’s finding that inspection times are longer in the area of the verb is paralleled by other non-reading studies. Recent studies have reported that tampering with the main verb of the sentence interferes with fluent processing (Gladney and Kralee 1967), that the main verb is the central element in sentence comprehension (Fodor et al. 1968), and that the main verb is most important in determining the meaning of the sentence (Healy and Miller 1970, 197 1). Linguists (Chafe 1970) have also speculated that the verb is the heart of the sentence. The present study dealt with the extent to which irregularities in key elements of the text could be detected in parafoveal (an area subtending from about 2” to 10” around fixation, according to Ditchburn 1973) and peripheral vision. Eye movements of skilIed readers were monitored as they read text and irregularities were entered into the text by mutilating various key words in the text, namely the subject, verb, and object of active sentences. It was assumed that if a reader detected an irregularity in the periphery, his eye movement pattern would be affected. Specifically, since the verb has been shown to be the key part of the sentence for obtaining the meaning of the sentence, it was expected that the reader might scan ahead to a greater extent when he was in the region of the main verb and thus an irregularity in the verb would be recognized further into the periphery than a corresponding irregularity in the subject or object. The present study also has implications for the nature of the perceptual span during reading. If the extent to which irregularities in the text can be detected varies, the variability would be evidence that the perceptual span varies at different locations in reading text.
K. RaynerjParafoveal
identification in reading
273
Method Subjects Ten undergraduate students, six male and four female, at the Massachusetts Institute of Technology were paid $2.00 an hour for their services. They were told that the purpose of the study was to determine what people look at when they read, and that their eye movements would be monitored and recorded by a computer. All of the Ss had normal, uncorrected vision and their reading speed was in the range of 200-400 words per min.
Materials Two hundred twenty five short paragraphs were prepared that were each 35-40 length. Within each paragraph, sentences were embedded which were of the following The subject
verbed
the object in the prepositional
words form:
in
phrase.
One word location within these sentences was identified as the critical word location (CWL) and alternative words or letter strings were prepared which could be inserted into that area. For example, if the critical sentence were: The children
the chemical
in the hall,
two of the alternatives were words (tasted, tested/ fitting into the sentence frame semantically and syntactically. The two word (W) alternatives always began and ended with the same letters and had the same overall word shape. The other three alternatives were non-word (N) letter strings (tcrted, tflmed, fcstcb/ which maintained or destroyed certain aspects of the two W alternatives. The specific characteristics of the five alternatives that could appear in the CWL are important for other data that will not be presented here. For the purpose of the present report, it is important that some of the alternatives were words and others were non-words. The words in the CWL were equally often five, six, or seven letters in length, and served as subject, verb, and object in their respective sentences equally often. The CWL also occurred equally often on the first, second, or third line of the paragraph. Table 1 shows some examples of the types of sentences used in the study. The 225 paragraphs were read in blocks of 15. After reading each block, the Ss were given a set of 12 sentences and asked to identify which of the sentences came from the passages they had just read. This task was included to insure that the subjects actually read the passages.
Apparatus The equipment used to record eye movements is described in detail by Rayner (1975) and consisted of a Biometrics Model SG Eye Movement Monitor interfaced with a PDP-6, thus providing the capability for on-line continuous monitoring of eye position. The eye movement monitor was modified by the addition of a biteboard and a forehead rest to prevent head movements. As the Ss read the text, the computer kept a complete record of fixation location, fixation duration, saccade duration, and saccade length. Pilot work with the eye movement apparatus indicated that it was highly accurate and seldom indicated that a reader was fixated
K. Rayrzer/Parafoveal identijicatiou in reading
214
Table 1 Examples
of sentences
used in the study
and the two word alternatives. Alternate word
Sentences 1. 2. 3.
The traitor brought his friends to the courtroom. The mayor picked the volunteer for the assignment. The writer broke the bottle on the floor.
teacher major waiter
Verb CWL:
4. 5. 6.
The captain granted the pass in the afternoon. The impact crushed the glass in the church. The employer hired the men in the office.
guarded cracked heard
Object
I. 8. 9.
The policeman carried the babies to the train. The guest heard the plane above the roar. The rebels guarded the palace with their guns.
bodies phone police
Subject
CWL:
CWL:
more than one or two character positions fixate. The paragraphs were displayed on a scope, which has a character generator phosphor. A dark theater gel was used to line of text that was displayed was around angle.
away from the character
he reported
Digital Equipment Corporation for both upper and lower case filter out the yellow afterglow of 72 characters long and occupied
he was trying
to
Model 340 display letters, and a P-7 the phosphor. Each 18 degrees of visual
Procedure Each S was tested individually. When a S arrived for the experiment, a bite bar was prepared for him. Then the eye tracking sensors, which were mounted on glasses’ frames and held securely by a head band, were placed on him. The glasses and sensors were adjusted for each S. The Ss were told that they would be required to read a series of passages to understand them. Each S then read three warm-up passages to become accustomed to the apparatus and become as comfortable as possible. Following the warm-up passages, each S read the 225 paragraphs. The paragraphs were read in blocks of 15, after which the S came off from the bite bar, answered and adjustments were made on the sensors if necessary. He then some recognition questions, went back on the bite bar and read another 15 passages. All of the Ss read the paragraphs in the same order. The paragraphs were displayed one at a time on the CathodeRay Tube. When each passage was initially displayed, the CWL could contain either a W or a N alternative. A boundary location was specified to the computer, and when the reader’s saccadc crossed that position the alternative that was initially displayed was replaced by one of the word alternatives. Thus, although either a W or a N alternative could be initially displayed in the CWL when the saccade began, by the time it ended or shortly thereafter (within 20 msec after the saccade ended), only one of the word alternatives was ever displayed. The boundary location was not visibly present in the text, but rather represented a character position on the line containing the CWL. Boundary locations were the fourth letter of the CWL, the first letter of the CWL, three character positions to the left of the CWL, six character positions to the left of the CWL, and nine character positions to the left of the CWL. Details of the display change are reported by Rayner (1975).
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Results Analyses of eye movement data consisted of two types: (1) fixation durations and (2) fixation locations. The analyses of fixation duration were carried out to determine how far into parafoveal and peripheral vision readers could make a distinction between words and non-words and to determine if irregularities in the verb could be detected further from the point of fixation than an irregularity in the subject or object. In carrying out the analyses on fixation durations, it was noticed that there were differences in fixation locations and further analyses were carried out regarding this aspect of the data.
Fixation
durations
Two analyses regarding fixation durations were carried out; the first involved the duration of the last fixation prior to crossing the boundary location and the second involved the duration of the first fixation after crossing the boundary. In the first duration analysis, six mean fixation durations were determined for each S at each of six locations with respect to the CWL. The six locations were the first three character positions of the CWL, or 1-3, 446, 7-9, 10-12, or 13-15 character positions prior to the CWL. The six mean scores were determined by the grammatical category of the CWL (subject, verb, or object) and whether the CWL contained a word or non-word. Thus, for example, all instances in which (1) the reader was fixated 7-9 character positions from the CWL on the last fixation prior to crossing the boundary, (2) the CWL was the subject of the sentence, and (3) the CWL was a non-word were grouped together and a mean score was calculated. Separate
450
t
+-----+ w-----o *---. *-- - o
Subject-W Sobiect - N Verb-W Verb-N Object-W Object-N
15-13
12-10
Area (No
Fig. 1. Mean duration location, grammatical a word or non-word.
to The
P
I
9-7 Left
of Character
6-4
3-l
of The
CWL
o-2
Positions!
of the last fixation prior to crossing the boundary as a function of its category of the CWL, and whether the initially displayed alternative was
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216
identification in reading
two-way analyses of variance were then carried out on these data at each of the six locations to determine differences between word and non-word conditions. The data are presented in fig. 1. As can be seen in fig. 1, fixation durations did not differ for words and non-words in the CWL when the reader fixated four or more character positions to the left of the CWL. However, when they fixated three to one character positions prior to the CWL or on the first three letters of the CWL itself, fixation durations were longer for non-words than for words (F(l, 9) = 8.30, p < 0.02, and F(1, 9) = 12.99, p < 0.006, respectively). There was also a significant grammatical category effect when they fixated three to one character positions prior to the CWL (F(2, 18) = 7.71, p < 0.004). A Newman-Keuls test indicated that the fixation durations were significantly longer (p < 0.01) when the CWL was a verb or object as opposed to being the subject of the sentence. Thus, there was evidence that parafoveal information was not picked up from the CWL when it was the subject of the sentence to the extent that information was picked up when it was the verb or the object of the sentence, In the second duration analysis, the duration of the first fixation after crossing the boundary location was examined. The rationale for this analysis was that if the reader gained information about the CWL when he was fixated at a certain area prior to the CWL and then found that when his eye landed on the CWL (following the display change) that a change had been made, there should be a longer fixation duration. Only fixations that landed on the CWL after crossing the boundary were included in this analysis and only conditions in which a non-word occurred initially in the CWL were analyzed. The reason for this latter limitation was that conditions in which a word was replaced by itself as a result of the display change comprised only one-fifth of the data. Hence, there were not < efficient data to provide comparisons between conditions in which the subject, verb, or o jzct of the sentence was replaced by itself and conditions in which the subject, verb, or object appeared initially as a non-word. Nevertheless, the results of the analysis which included only non-word conditions were supportive of the data presented previously regarding fixation durations prior to the display change. 325-
-Subject +----Verb 6 - --+ Object
iti E
II ,’ .’ 200 225 V’! 15-13 Area (No
L
9-7
12-10 to The
Left
of Character
1
1
6-4
of The
3-l CWL
Positions)
Fig. 2. Mean fixation durations on the CWL immediately after crossing the boundary as a function of grammatical category of the CWL and of the location of the prior fixation when the initially displayed alternative was a non-word.
X RaynerlParafoveal
271
identification in reading
An analysis of variance with factors being prior fixation location and grammatical category of the CWL yielded significant main effects of prior location (F(4, 36) = 2.88, p < 0.05) and of grammatical category (F(2, 18) = 3.55, p < 0.05). The interaction of these variables was not significant (F(8, 72) = 1.37, p < 0.20). Mean fixation durations according to grammatical category were as follows: subject, 236 msec; verb, 264 msec; and object, 260 msec. The display change caused less inflation of fixation durations when the CWL served as the subject of the sentence than when it served as verb or object. These data are shown in fig. 2. Here it can be seen that, in agreement with the data presented regarding the duration of the last fixation prior to crossing the boundary, when the reader fixated just left of the CWL, he was less likely to acquire visual information from the CWL region when it served the function of the subject of the sentence than when it served as verb or object. Interestingly, this was not true when he fixated further to the left of the CWL, between 7 and 15 character positions. This difference only occurred when the eye was within 6 character positions of that location. Roth of the analyses regarding fixation durations indicated that the reader did not acquire parafoveal information from the CWL when it served the syntactic function of the subject of the sentence. However, in carrying out these analyses it was noticed that there were substantial differences in the number of fixations found in the various locations with respect to the CWL. This discovery led to further analyses to determine the reason for the effects found with fixation duration data.
Location of fixations and saccade lengths Fig. 3 shows the frequency of fixations on different locations prior to the CWL. When the CWL was the subject of the sentence, there were fewer than normal fixations in the region l-6 character positions to the left of the CWL. When the CWL was the verb, there were fewer than normal fixations in the region IO-15 character positions orior to the CWL. A two-way analysis
18
-
Subiect
----- - - +
Verb Object
t I5
12 -
9.
6-
3-
I 15-13
12-10
9-7
6-4
3-l
Area to The Left of CWL ( No. Chorocter Positions) Fig. 3. Effect of grammatical category different areas to the left of the CWL.
of the CWL on the number
of fixations
which
fell in
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278
identification
irl reading
.-‘
IA- 260 Fig. 4. Relationship sentence containing
t of frequency the CWL.
of fixations
and durations
of fixations
in the area
of the
of variance on the number of fixations occurring in each category yielded a significant Grammatical Category X Location Interaction (F(8, 72) = 11.54, p < 0.001). The same pattern was present in the W and rhe N data. The basis of this data pattern can be seen in fig. 4, which shows the number of fixations occurring at each region of the sentence when the CWL occupied the position as subject, as verb, and as object. This figure also shows the durations of fixations at each arca of the sentence under the same conditions. The hatched lines between the two bar graphs indicate the three sets of five regions from which fixations were considered, depending on whether the CWL occupied the position of subject, verb or object. The bars are coded according to whether the data came from conditions when the CWL was subject, verb, or object. Bars with lines sloping down to the right indicate data from paragraphs in which the CWL served as subject; bars with no lines indicate data from paragraphs in which the CWL served as verb; and bars with lines sloping up to the right indicate data from paragraphs in which the CWL served as object. From this figure it can be Teen that the differences observed in number of fixations in different categories, shown in fig. 3, was due to a general tendency for Ss to make fewer fixations in the region occupied by the terminal character and period from the prior sentence, the spaces between the sentences, and the article at the beginning of the sentence containing the CWL. It can also be seen that when the S did fixate in that region, the duration of hit; fixation tended to bc substantially shorter than usual. Thus, it appears that when they fixated in this region, they tended not to acquire visual information from words as far from their fixation point as they did when they fixated at other regions in the sentence. Further evidence that the readers Feldom fixated this non-informative area was obtained by examining saccade lengths for cyc movements that landed in the area of the CWL. All saccades that began less than 16 character spaces and more than one character space to the left of the CWL and landed in the region of the CWL were examined for each S according to the gammatical category in the CWL. A one-way analysis of variance yielded a significant difference in saccade length depending on the grammatical category in the CWL (F(2, 27) = 30.74, p < 0.001). Although this analysis included both the N and W condition, a similar analysis for the different grammatical catcgorics when the CWL initially contained only a non-word yielded identical results. The mean vaccade lengths (in character spaces) were:
K. RaynerfParafoveal
identification in reading
219
subject, 12.04; verb, 8.31; and object, 8.65. A Newman-Keuls test indicated the subject differed from the verb and object (p < 0.01). Thus, the readers tended to move their eyes a greater distance when they were at the end of one sentence and ready to begin the processing of another than if they were in the middle of a sentence. The length of the saccade on the subject of the sentence was longer than for the verb or the object because the readers had to cross the uninformative areas containing the blank spaces between sentences and the function word beginning the new sentence. One final feature of the data which was noted was a tendency for Ss to fixate the left and right half of the CWL equally frequently when it served the function of subject, but for the left half to receive more fixations when it served as verb or object. For the verb and the object nearly 75% of all fixations on the CWL were on the left half of the word. A two-way analysis of variance found significant effects for fixation location (F(1, 9) = 20.53, p < 0.002) and for the Fixation Location X Grammatical Category Interaction (F(2, 18) = 20.29, p < 0.001). This may reflect a tendency for fixations to be more accurately located on the verb or object than on the subject in sentences of the syntactic construction used here, since saccades coming to the subject region originated either some distance from their target (at some location in the previous sentence) or from a nearer region (between the sentences) at which they tended not to acquire parafoveal visual information.
Discussion The results of this study indicate that the perceptual span in reading varies at different locations in the text. However, this variability does not seem to be tied to parts of speech; that is, there was no evidence that irregularities in the verb were detected any further into the periphery than irregularities in the object or subject. Since the verb has been shown to be the most important element for comprehending a sentence, it seemed reasonable to assume that the reader may scan ahead more when he approached the area of the main verb. The present results show that this assumption is not true. The evidence that the perceptual span may differ at various locations stems from the fact that readers in this study did not notice an irregularity in the CWL when they fixated on the non-informative area between two sentences and the function word beginning a new sentence. At times when they did not fixate on this non-informative area, the data suggest that the reader was obtaining semantic information for words beginning 6 or fewer character spaces from the fixation point. Since 4 character positions equaled 1” of visual angle in the present study, and since the average word length of the CWL was 6 character positions, the present data suggest that the reader semantically identifies words falling in an area subtending about 2” of visual angle to the right of his fixation point.
280
K. RaynerlParafoveal
identification in reading
The data regarding frequency of fixations in the non-informative area between sentences indicate that when a reader was approaching the end of a sentence his strategy was to cast his eye a greater distance than usual so that he could bypass this relatively uninformative area. It is of interest that when the reader fixated in the region l-6 character positions prior to the subject position he failed to obtain parafoveal visual information. This suggests that fixations made in the region between sentences play a special function. There are two possible explanations of the type of cognitive processes that might be occurring during these fixations, each of which would be harmonious with the notion that they are not used primarily for obtaining additional visual information for reading. The first possibility is that, as Woodworth (1938) has suggested, the understanding of the text lags somewhat behind the visual impressions. This may make it necessary occasionally to pause for an extra fixation at the end of a sentence to tiermit processing of the information obtained to be complete. The purpose of this fixation, then would not be for visual input, which may account for its reduced duration. A second possible explanation is that there is a certain amount of inaccuracy in the guidance of eye movements. Readers are capable of identifying regions in the text where there are no letters and are generally able to avoid them, as shown by Abrams and Zuber (1972). These investigators presented Ss with text modified to have a series of blank regions between words at random locations. They found that Ss made few fixations within these blank regions. Thus, it would seem likely that Ss identify the region between sentences, containing a to avoid locating punctuation mark and two spaces, and attempt fixations in these regions. However, oculomotor control is not complete, and the eye may inadvertently fall on this region. When this occurs, the reader quickly recognizes that he is fixating a retion of little visual information, and the next saccade is initiated. Thus, the fixation is shorter than normal and the S does no processing of parafoveal visual information. Which of these possibilities accurately account for the type of cognitive processing taking place during fixations between sentences, as well as other questions regarding the flexibility of the perceptual span, must be the subject of additional research.
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281
References Abrams, S. G., B. L. Zuber, 1972. Some temporal characteristics of information processing during reading. Reading Res. Quart. 8, 42-51. Chafe, W., 1970. Meaning and the structure of language. Chicago: Univ. of Chicago Press. Ditchburn, R. W., 1973. Eye-movements and visual perception. London: Oxford Univ. Press. Fodor, J. A., M. Garrett, T. G. Bever, 1968. Some syntactic determinants of sentential complexity, II: Verb structure. Perception and Psychophysics 3, 453-461. Gladney, T. A., G. K. Krulee, 1967. The influence of syntactic errors on sentence recognition. J. Verb. Learning Verb. Behav. 6, 692-698. Healy, A. F., G. A. Miller, 1970. The verb as the main determinant of sentence meaning. Psychonomic Sci. 20, 372. Healy, A. F., G. A. Miller, 1971. The relative contribution of nouns and verbs to sentence acceptability and comprehensibility. Psychonomic Sci. 24, 94-95. Levin, H., J. Grossman, E. Kaplan, R. Yang, 1972. Constraints and the eye-voice span in right and left embedded sentences. Language and Speech 15, 30-39. Levin, H., E. L. Kaplan, 1968. Eye-voice span (EVS) within active and passive sentences. Language and Speech 11, 25 1- 258. Levin, H., A. Turner, 1968. Sentence structure and the eye-voice span. In: H. Levin, E. J. Gibson, J. J. Gibson (eds.), The analysis of reading skill. Final Report to U.S.O.E., Project No. 5-1213. Mackworth, J. F., 1972. Some models of the reading process: learners and skilled readers. Reading Res. Quart. 7, 701-733. Rayner, K.. 1975. The perceptual span and peripheral cues in reading. Cognitive Psychol. 7, 65-81. Resnick, L., 1970. Relations between perceptual and syntactic control in oral reading. J. Educ. Psychol. 61, 382-385. Schlesinger, 1. M., 1968. Sentence structure and the reading process. The Hague: Mouton. Smith, F., 197 1. Understanding reading. New York: Holt, Rinehart and Winston. Tinker, M. A., 1965. Bases for effective reading. Minneapolis: Univ. of Minnesota Press. Wanat, S., 1971. Linguistic structure and visual attention in reading. Newark, Delaware: International Reading Ass. Wanat, S., H. Levin, 1970. Linguistic constraints in reader processing strategies. Paper presented at the Eastern Psychological Association meetings. Woodworth, R. S., 1938. Experimental psychology. New York: Henry Holt.
