Reading and listening to high and low imagery sentences

JOURNAL OF VERBAL LEARNING AND VERBAL BEHAVIOR20, 333-345 (1981)

Reading and Listening to High and Low Imagery Sentences JOHN K . E D D Y AND ARNOLD L . GLASS

Rutgers University Five reaction time experiments were performed to clarify the role that imagery plays in sentence understanding. In the first experiment, subjects had to decide whether visually presented sentences were true or false. Reading and verifying high-imagery sentences took longer than reading and verifying low-imagery sentences. This was true even though both types of sentences were equal in difficulty when auditorily presented. In Experiment 2, the words of each sentence were serially presented in order to make the reading presentation more like the listening presentation. Again, reading interfered more with the processing of high-imagery sentences than low-imagery sentences. Experiments 3 and 4 were identical to Experiments 1 and 2 except that a comprehension task was used instead of a verification task. Again, reading interfered more with the high- than the low-imagery sentences. However, in Experiment 5, when a grammatical judgment task was used, reading no longer interfered more with the high-imagery sentences. These results suggest that imagery plays a significant role in the comprehension of high-imagery sentences.

The role that imagery plays in many cognitive processes has been studied extensively in the past decade. Studies have shown that high-imagery words (Christian, Bickley, Tarka, & Clayton, 1978; Paivio, 1971; Postman, 1975) and sentences (Marschark & Paivio, 1977) are recalled better than low-imagery words and sentences. Other studies have shown that performing an imagery task can interfere with perception (Segal, 1971; Segal & Fusella, 1970) and, conversely, that performing a perceptual task can interfere with imagery (Brooks, 1967; 1968; Byrne, 1974). Ernest (1979) has shown that subjects with high imagery ability are able to recognize unfamiliar pictures more quickly and at a lower threshold than subjects with low imagery ability. Kosslyn (1975; 1976a; 1978) has performed numerous experiments atThis research was supported by National Institute of Mental Health grant, MH 29398 to Arnold L. Glass. We would like to thank Denise Williams for her help in collecting the data. The experiments described here were suggested independently by Allan Paivio while commenting on another report of ours. We would like to thank him for the encouragement his comments gave us. Reprint requests should be sent to Arnold L. Glass, Rutgers College, Department of Psychology, Busch Campus, Piscataway, N.J. 08903.

tempting to specify the qualities and limits of the imagery experience. Despite this research, indicating that imagery is a factor in many cognitive processes, it is still uncertain whether imagery plays a role in language comprehension. One approach has been to compare the verification times of high- versus lowimagery sentences, but these experiments have produced inconclusive or inconsistent results. F o r instance, J o r g e n s o n and Kintsch (1973) found that high-imagery sentences were verified faster than lowimagery sentences, but H o l y o a k (1974) raised doubts concerning this experiment by showing that imagery was confounded with the semantic relatedness of the subject and predicate. Holmes and Langford (1976) found that concrete sentences were comprehended faster than abstract sentences, but Glass, E d d y , and Schwanenflugel (1980) found that high-imagery sentences were verified slower than low-imagery sentences. So the influence of imagery on comprehension reaction time is unclear. In addition, there is a more general objection to drawing conclusions about the role of imagery from this type of experiment, in which responses to high- and low-imagery

333 0022-5371/81/030333-13502.00/0 Copyright© 1981by AcademicPress,Inc. All rtghts of reproductionin any formreserved

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E D D Y A N D GLASS

sentences are compared for some task. The high- and low-imagery sentences usually differ on other semantically relevant dimensions in addition to imagery. So it is not possible to attribute differences in the response measure directly to the effect of imagery. For example, consider again the studies of Holmes and Langford (1976) and of Glass et al. (1980). Holmes and Langford (1976) carefully matched high- and lowimagery sentences on other factors known to influence reaction time. They found that the high-imagery sentences were comprehended faster. Yet, when Glass et al. (1980) compared equally well matched highand low-imagery sentences in a verification task, it was the low-imagery sentences that were verified faster. What could have caused these contradictory findings? One hypothesis could be that the results were influenced by task differences, that highimagery sentences are comprehended more rapidly than low-imagery sentences but verified more slowly. However, the general conceptual similarity of comprehension and verification makes this ad hoc hypothesis seem very unlikely. Furthermore, the work of MacLeod, Hunt, and Mathews (1978) suggests j u s t the opposite, that highimagery sentences should take longer to comprehend and less time to verify than low-imagery sentences. Rather, it seems more likely that there are still unspecified factors that influence verification and comprehension that may be correlated with imagery in a particular item set and these factors were not controlled in the studies of Holmes and Langford (1976) and Glass et al. (1980). Another approach to the study of the role of imagery in language comprehension is to show that visual tasks interfere more with the processing of high-imagery sentences than low-imagery sentences. Glass et al. (1980) recently found that the verification of high-imagery sentences selectively interfered with the retention of a visual pattern. In their experiments, subjects were first given a visual pattern and told to construct and maintain a mental image of it. Next

they were auditorily presented with a sentence for verification. Finally, they were shown another visual pattern and asked if it was the same or different than the original pattern. Visual pattern recognition took longer and was less accurate following high-imagery sentences than following low-imagery sentences. The results of Glass et al. (1980) suggest that visual imagery plays a role in the verification of high-imagery sentences. However, the pattern retention task failed to interfere more with the verification of high-imagery sentences than with lowimagery sentences. If the high-imagery sentences interfered with the pattern recognition task because both tasks required a common process (i.e., imagery), then the retention of the visual pattern should have interfered also with the verification of the high-imagery s e n t e n c e s . Glass et al. suggested several hypotheses why the interference was asymmetrical. For example, perhaps subjects were unable to mentally maintain the visual pattern while verifying the high-imagery sentences. If so, sentence verification reaction time would be unaffected. However, if this explanation (or any other offered by Glass et al.) is correct, then there should be some way of demonstrating that a visual processing task interferes with the verification of highimagery sentences. A more general objection to concluding from the Glass et al. experiments that imagery is involved in comprehension is that the imagery that interfered with the retention of the visual pattern may have occurred subsequent to the comprehension of the sentence and may have been incidental to it. After all, few theorists would deny that the comprehension of certain sentences may lead, incidentally, to the experience of visual imagery. But that does not mean that the imagery was required for comprehension. In contrast, if a task requiring visual processing selectively interfered with the comprehension of high-imagery sentences, it would imply that imagery was a necessary part of the comprehension process for

READING IMAGERY SENTENCES

those sentences. The purpose o f this study was to provide such a demonstration. The rationale for the experiments was as follows. Sets o f high- and l o w - i m a g e r y sentences were selected whose mean auditory reaction times were equal. N e x t , a task was needed that would interfere with the u n d e r s t a n d i n g o f high-imagery sentences but not low-imagery sentences. Previous research (Brooks, 1967; 1968; Byrne, 1974) suggested that the most effective interference task involves visual perception and occurs simultaneously with the task. It was decided that reading, as opposed to listening, was the perfect task for selective interference. It was e x p e c t e d that in the reading condition, the high-imagery sentences would be verified more slowly and less accurately than the low-imagery sentences. Five experiments are reported. In Experiment 1, the subject's task was to verify whether a sentence was true or false. Half o f the sentences were presented visually and half o f the sentences were presented auditorily. Experiment 2 was identical to Experiment 1 except that it controlled for some of the temporal presentation differences between reading and listening. Experiment 3 replicated Experiment 1 using a comprehension task. Experiment 4 was the temporal control for E x p e r i m e n t 3. Experiment 5 replicated Experiment 4 using a grammatical judgment task. EXPERIMENT 1 The subject's task was sentence verification. Half o f the sentences were read from a video monitor and the other half were listened to over headphones. If imagery plays a r o l e in s e n t e n c e u n d e r s t a n d i n g t h e n reading should interfere more with the processing o f high- t h a n l o w - i m a g e r y sentences. T h e r e f o r e , the high-imagery sentences should have a longer reaction time and have more errors than the low-imagery sentences. Method Items. Thirty-six critical sentences were used in the e x p e r i m e n t . Most s e n t e n c e s

335

were selected from the items used by Glass et al. (1980). Eighteen sentences were high imagery and eighteen were low imagery. The imagery of the sentences was rated by 21 undergraduates from Rutgers University. A sentence was rated high in imagery if an image was r e q u i r e d to d e t e r m i n e whether the sentence was true or false. A sentence was rated low in imagery if the sentence did not require an image to determine its truth value. The raters were instructed to give a sentence a low imagery rating even if a sentence was accompanied by an image but it was felt that this image was not necessary to determine its truth. This method o f rating imagery was used because Glass et al. found that not all sentences having high-imagery nouns cause a selective interference effect. For example, w h e r e a s the s e n t e n c e , ~'A grapefruit is larger than an o r a n g e " might require imagery to determine its truth value, the sentence, " T h e sun is larger than an orange" probably does not. On a 7-point scale the mean imagery rating for high-imagery sentences, M = 5.22, was significantly different from the mean imagery rating for the low-imagery sentences, M = 1.40, t(34) = 4.63, p < .001. In addition to being selected on the basis o f their imagery, sentences were also selected for truth agreement. It is usually much easier to agree whether highimagery sentences are true or false than low i m a g e r y s e n t e n c e s (Glass et al., 1980). Therefore, it was important to equate sentences on truth agreement. Since each sentence was rated for a true and false version and there were 21 raters, 42 would represent perfect truth agreement. No difference in truth agreement was found between highimagery sentences, M = 41.0, and lowimagery sentences, M = 40.5, t(34) = .20. The sentences were also rated on a 7-point scale for comprehensibility, since Johnson, B r a n s f o r d , N y b e r g , a n d C l e a r y (1972) found that high-imagery sentences can be more c o m p r e h e n s i b l e than low-imagery sentences. The high-imagery sentences, M = 6.60, w e r e r a t e d similar to the lowimagery sentences, M = 6.67, t(34) = .19.

336

E D D Y A N D GLASS

Finally, the sentences were selected from described above and the other 18 were filler among those used by Glass et al. so that the items that received low or inconsistent rathigh- and low-imagery sentences did not ings (see the Appendix). The items were differ in their mean auditory verification block randomized so that the 36 sentences reaction times. Glass et al. had found that were in 9 blocks of 4 items each. Each when high- and low-imagery sentences block had one high-imagery true sentence, were matched on these criteria, the high- one low-imagery true sentence, one highimagery sentences took longer to verify i m a g e r y false s e n t e n c e , and one lowthan the low-imagery sentences, However, imagery false sentence. After these 36 senthere was enough overlap in the distribu- tences, the subjects were given a 2-minute tions of verification reaction time to match rest. Next they were given 10 practice senpairs of high- and low-imagery sentences on tences. Finally, they were given 36 more auditory verification reaction time. The en- sentences for verification. These 36 sentire set of high- and low-imagery sentences tences were block randomized in the same can be found in the Appendix. manner as the first 36. Apparatus. Each subject station conFor half of the subjects, the experimental sisted of a 23-cm diagonal video monitor, a sentences were true and the filler items response keyboard, and a pair of head- were false. For the other half of the subphones worn by the subject. The video jects, the reverse was true. Half the submonitor was used to present the sentence jects read the first 36 experimental senfor reading by the subject. The entire sen- tences and listened to the last 36 experitence appeared on the screen and the timer mental sentences. The opposite was true was started simultaneously. The response for the other half of the subjects. Half of the keyboard had two microswitches, on which subjects heard one set of sentences in the the subject rested one finger from his right first experimental block and half heard the and left hands. The keys were used to ter- other set first. Thus, each subject was asminate the timer with the right key being signed to one of eight treatment groups (2 × the true response and the left key being the 2 × 2). So all subjects heard each sentence false response. The headphones were con- only once. Subjects. The subjects were 64 undernected to a tape recorder that presented sentences auditorily to the subjects. The graduates at Rutgers University. Subjects reaction timer was started by a 1000-Hz were General Psychology students who pulse on a separate channel of the tape re- participated in the experiment as part of a corder. The pulse was set so that reaction course requirement. No subject had ever time was started at the onset of the last participated in any other aspect of the exword of each sentence. periment. These three devices were controlled by a PDP-II/40 computer which ran the entire Results The data in this and subsequent experiexperiment. The computer presented both ments were analyzed using the quasi-F prothe visual and auditory stimuli, recorded cedure recommended by Clark (1973) in the subject's response, and measured the which items and subjects are both treated subject's reaction time. The computer controlled seven stations, so that from one to as random effects. Both correct reaction s e v e n s u b j e c t s c o u l d be run simulta- times and errors were entered as dependent measures in analyses of variance in which neously. Design and procedure. Subjects verified the factors were (1) a grouping factor for 102 sentences. The first 20 sentences were order of presentation type and order of always practice sentences. The next 36 sentence sets, (2) truth of the sentences, (3) sentences were experimental sentences. presentation type, that is, reading or lisEighteen of these were selected from those tening, and (4) imagery of the sentence.

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READING IMAGERY SENTENCES

The results of the experiment are shown sible that the length of this word influenced in Table 1. The critical interaction between reaction time. However, the correlation presentation type and sentence type was between sentence verification reaction time significant, F'(1,174) = 22.72, p < .001, and the number of syllables in the last word MSe = 2766015. As can be seen from the of the sentence was -.005; between pertable, there was no difference in verifica- centage errors and the number of syllables tion reaction time when listening to the the correlation was .08. high- and low-imagery sentences for verification. However, when the same sentences Discussion were read, high-imagery sentences took The predicted results were obtained. As over 680 milliseconds longer to verify than Glass et al. (1980) had previously found, low-imagery sentences. Error rates were there was no difference in auditory verifipositively correlated with reaction time, cation reaction time for this particular set of however, the differences in error rate were high- and low-imagery sentences. Hownot significant. The overall error rate was ever, the high-imagery s e n t e n c e s t o o k 14%, which is typical for sentences like the longer to verify when the sentences were ones used here (see H o l y o a k & Glass, read. A visual processing task (i.e., read1975). ing) selectively interferes with the verificaReading reaction time was significantly tion of high-imagery sentences. This result, longer than listening reaction time, F'(1,186) along with the Glass et al. finding that = 593.7, p < .001, MSe = 3617937. This high-imagery sentences interfere with the difference was an artifact, reflecting the maintenance of a visual pattern, suggests fact that reading reaction time was timed that imagery plays a role in the verification from the onset of the entire sentence while of high-imagery sentences. The interaction listening reaction time was timed from the also suggests that various stages involved in onset of the last word of the sentence. the comprehension of written material are S e v e r a l a d d i t i o n a l a n a l y s e s w e r e per- not independent of each other. Rather, it formed to assess whether the mode of pre- appears that the early stage during which sentation significantly influenced verifica- written material is decoded may influence tion reaction time. Since each sentence subsequent stages during which the meanhad different numbers of words, syllables, ing of a sentence is verified. These points and letters, it was possible that one of these will be further discussed after the results of variables could influence the results of the all the experiments are presented. reading condition. However, the correlaEXPERIMENT 2 tions of each of these with sentence reaction time and errors was very low, ranging When listening to a sentence, one word is from .01 t o . 13, so their effect was minimal. heard at a time. In reading, the entire senSimilarly, in the listening condition, the tence is available at once. Perhaps the inreaction time was taken from the onset of teraction found in Experiment 1 was caused the last word of the sentence, so it was pos- by these different modes of presentation, TABLE 1 REACTION TIME (RT) AND PERCENTAGE ERRORS (E) FOR SENTENCES IN EXPERIMENT 1 Sentence

Listening

Reading

Mean

type

RT

E

RT

E

High imagery Low imagery Mean

1196 1207 1201

17 13 15

3385 2700 3043

16 10 14

Note. Data for RT are given in milliseconds.

RT

E

2291 1953 2122

16 12 14

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EDDY AND GLASS

r a t h e r than by the visual processing required in the reading condition. In particular, since the auditory sentences were presented one word at a time, their presentation rate probably influenced the rate at which they were decoded. H o w e v e r , since the printed sentences appeared all at once and remained on until the response was made, their decoding rate was totally under the subject's control. Therefore, in Experiment 2, the printed sentences were presented one word at a time, at approximately the same rate as in the listening condition. In addition, in the reading condition the timer was started immediately following the onset of the last word o f the sentence.

Method The sentences, apparatus, and design iri this experiment were identical to those of Experiment 1. Procedure. T h e p r o c e d u r e in this experiment was identical to Experiment 1 except that in the reading condition the sentences were presented word by word and the reaction time was begun immediately after the last w o r d was p r e s e n t e d . The sentence was presented by adding one word to the screen at a time, from left to right. Hence, the sentence was literally printed across the screen. The pause interval between the presentation of two successive words o f the sentence was equal to the number of letters in the first word × 75 milliseconds. Thus, after a five-letter word was presented, the next word would not appear until 375 milliseconds later. Subjects. Subjects were 56 Rutgers University General Psychology students who participated in the experiment as part of

course requirement. No subject had ever participated in any other aspect of the experiment.

Results The results are shown in Table 2. The critical presentation type x sentence type i n t e r a c t i o n was significant, F'(1,173) = 6.48, p < .05, MSe = 753713. In the listening condition, high-imagery sentences were verified 78 milliseconds faster than the low-imagery s e n t e n c e s . H o w e v e r , w h e n the same sentences were read, the highimagery sentences took 137 milliseconds longer to v e r i f y t h a n l o w - i m a g e r y sentences. Again, the error rate interaction was not significant. The overall error rate was 18%. Reaction time and errors were correlated less t h a n . 11 with the n u m b e r o f syllables in the last word and the n u m b e r of letters, syllables, and words in the sentence. Reading sentences was significantly s l o w e r t h a n l i s t e n i n g to s e n t e n c e s , F'(1,128) = 64.8,p < .001, MSe = 1187733.

Discussion The findings o f Experiment 1 were replicated. H o w e v e r , the results of the two experiments do not reveal the level of processing at which imagery influences verification reaction time. This led to Experiment 3. EXPERIMENT 3 At a minimum, sentence verification involves (1) understanding the sentence and (2) determining w h e t h e r the assertion is true. It is possible that in Experiments 1 and 2 all the sentences were c o m p r e h e n d e d in the same m a n n e r and the high- and low-imagery sentences differed only in the manner in which their assertions were ver-

TABLE 2 REACTION TIME (RT)AND PERCENTAGE ERRORS (E) FOR SENTENCES IN EXPERIMENT 2 Listening

Reading

Mean

Sentence type

RT

E

RT

E

RT

E

High imagery Low imagery Mean

1265 1344 1304

19 15 17

1620 1483 1552

24 16 20

1443 1413 1428

22 15 18

Note. Data for RT are given in milliseconds.

R E A D I N G IMAGERY S E N T E N C E S

ified. If this w e r e the case, t h e n t h e r e should be no difference between the reaction time to determine whether the highand low-imagery sentences used in the previous experiments were meaningful. However, if high- and low-imagery sentences are c o m p r e h e n d e d differently, then reaction time to determine whether they have meanings should again differ in the reading condition. To decide between these two hypotheses, a comprehension task was used (Holmes & Langford, 1976; Klee & Eysenck, 1973). In this experiment there are two sets of s e n t e n c e s , n o r m a l meaningful s e n t e n c e s and s e m a n t i c a l l y a n o m a l o u s s e n t e n c e s . T h e n o r m a l s e n t e n c e s w e r e the experimental sentences from the two previous experiments. An example of a semantically anomalous sentence is "Baseball is played with nine flavors." The subject's task was to decide whether a sentence made sense. That is, it was not required that they verify whether a sentence was true, merely whether it was plausible. If imagery plays a functional role only in verifying a sent e n c e then there should be no selective interference in this c o m p r e h e n s i o n task. H o w e v e r , if imagery plays a role at a lower level of processing, that is, at the level of comprehension, then high-imagery sentences should take longer to verify than low-imagery sentences in the reading condition but not the listening condition. Method

The e x p e r i m e n t a l items were the true versions of the 36 items used in the previous experiments. The filler items were the same 36 filler items e x c e p t that the last word in the sentence was changed to make the sentence semantically but not grammatically anomalous (see the Appendix). The same apparatus was used in this experiment as in the last two experiments. The design was the same except that there was no truth factor, therefore, only four treatment groups were required. The procedure was also identical except that subj e c t s were i n s t r u c t e d to press the right

339

switch if a sentence made sense or was plausible and the left switch if a sentence made little sense or was implausible. It was emphasized to the subjects that it was not necessary to determine whether a sentence was true or false. Subjects. Subjects were 32 Rutgers University General Psychology students who participated in the experiment as part o f a course requirement. No subject had ever participated in any other aspect o f the experiment. Results

Both c o r r e c t reaction time and errors were e n t e r e d as d e p e n d e n t m e a s u r e s in analyses of variance in which the factors were (1) a grouping factor for order of presentation type and order o f sentence sets, (2) presentation type, and (3) imagery of the sentences. The results are p r e s e n t e d in Table 3. Notice first, that the reaction times were lower than in the first experiment. This is exactly what would be expected since comprehension is a theoretically simpler task than verification. Again, there was a significant interaction o f presentation type by imagery, F ' ( 1 , 1 5 3 ) = 6.59, p < .05, MSe = 1013804. There was no difference between r e a c t i o n time to c o m p r e h e n d high- and low-imagery sentences in the listening condition. H o w e v e r , w h e n the s a m e sentences were read, it took 326 milliseconds longer to c o m p r e h e n d high- versus lowimagery sentences. Again, the error rates were positively correlated with the reaction times for each condition. The overall error rate was 5%. The reading reaction times were significantly longer than listening reaction times, F'(1,79) = 274.6, but as in Experiment 1, this was because reading was m e a s u r e d from the onset o f the sentence while listening reaction time was measured from the onset of the final word. The reaction time and error rates were correlated less t h a n . 12 with the n u m b e r o f syllables in the last word and the n u m b e r o f letters, syllables, and words in the sentence.

340

EDDY AND GLASS TABLE 3 REACTION TIME (RT) AND PERCENTAGE ERRORS (E) FOR SENTENCES IN EXPERIMENT 3 Listening

Reading

Mean

Sentence type

RT

E

RT

E

RT

E

High imagery Low imagery Mean

1035 1023 1029

4 8 6

2432 2106 2269

7 3 5

1734 1564 1649

6 5 5

Note. Data for RT are given in milliseconds.

Discussion

Reading selectively interfered with understanding the high-imagery sentences. The results suggest that imagery plays a role not only in the verification of sentences but also in the process of comprehension. As the lower error rate and reaction time suggest, a comprehension task is much simpler than a verification task. Yet, as can be seen, imagery is still a significant factor. EXPERIMENT 4 This experiment was identical to Experiment 3 except that the serial presentation of the printed words used in Experiment 2 was used in this experiment as well. Also, the timer was started immediately after the onset of the last word instead of at the onset of the entire sentence. Method

Subjects were 20 Rutgers University General Psychology students who participated in the experiment as part of a course requirement. No subject had ever participated in any other aspect of the experiment. Results

The same analyses of variance were performed in this experiment as in Experiment 3. The results of the presentation type by imagery interaction are shown in Table 4. The interaction was significant, F' (1,133) = 3.95, p < .05, MS~ = 205388. It took 32 milliseconds longer to comprehend highversus low-imagery sentences when they were auditorily presented. However, it

took 205 milliseconds longer to comprehend high- versus low-imagery sentences when they were read. Again, though positively correlated with reaction time across conditions, the error rates were not significantly different. The overall error rate was 6%. Reading reaction times were significantly longer than listening reaction times, F'(1,132) = 36.6, p < .001, MS~ = 936150. Discussion

These results support and replicate the findings of the three previous experiments. The reading task selectively interfered with the comprehension of high-imagery sentences but not with the comprehension of low-imagery sentences. EXPERIMENT 5

If the effect of imagery in Experiments 1 - 4 is specific to the level of comprehension or the levels of comprehension and verification, then reading should not interfere with high-imagery sentences in tasks that do not require comprehension. Therefore in this experiment, the last word of each filler was changed to make the sentence ungrammatical (e.g., A baseball team has nine pursue). Subjects were then asked whether the sentences were grammatical. Such a syntactic judgment does not require comprehension (as in the famous example, Colorless green ideas sleep furiously). Therefore, for this task, reading should not interfere more with decisions for highimagery sentences than for low-imagery sentences.

341

READING IMAGERY SENTENCES TABLE 4 REACTION TIME (RT) AND PERCENTAGE ERRORS (E) FOR SENTENCES IN EXPERIMENT 4 Listening

Reading

Mean

Sentence type

RT

E

RT

E

RT

E

High imagery Low imagery Mean

1068 1036 1052

7 7 7

1472 1267 1370

6 4 5

1270 1152 1211

6 6 6

Note. Data for RT are given in milliseconds.

In Experiments 1 and 2, and Experiments 3 and 4, simultaneous versus serial presentation of the printed words in the reading condition yielded virtually identical results. Therefore, it was decided to drop one of these redundant conditions. In this experiment, a Rapid Sequential Visual Presentation (or RSVP, Forster, 1970) procedure was used. In this procedure each successive word overwrites the previous word at the same position in the center of the screen. This presentation technique was used since it was very comparable to the listening condition. Method

The 36 experimental items were the same sentences used in the previous four experiments. The filler items were 36 sentences in which the last word was grammatically inappropriate (see the Appendix). The procedure and instructions were identical to Experiments 3 and 4 except that the RSVP technique was used. Subjects were 32 Rutgers University General Psychology students who participated in the experiment as part of a course requirement. No subject had ever participated in any other aspect of the experiment. Results

The same analyses of variance were performed in this experiment as in the previous experiments. The results of the experiment are shown in Table 5. There was no interaction between listening and reading for the high- and low-imagery sen-

tences, F'(1,155) = 1.44, p > .10, M S e = 216299. Grammatical judgments took no longer for low-imagery than high-imagery sentences, F ' < 1. Again, though positively correlated with reaction time across conditions, the error rates were not significantly different. The overall error rate was 6%. Discussion

These results strengthen the hypothesis that imagery plays a role in the comprehension of high-imagery sentences. If imagery had some general effect on sentence processing, not specificially related to comprehension, then reading should have selectively interfered with the grammaticality judgments for high-imagery sentences. However, imagery had no effect even though it had produced a robust interference effect in earlier experiments in which comprehension of the sentences was required. GENERAL DISCUSSION

The major finding of this study was that reading selectively interferes with the comprehension of high-imagery sentences. This finding is significant for several reasons. First, it is the first time that an effect of imagery on language comprehension has been found. The fact that a task requiring visual processing (i.e., reading) interfered with the comprehension of high-imagery sentences in Experiments 3 and 4 implies that imagery is a necessary part of the comprehension process for those sentences. Furthermore, since reading did not inter-

342

EDDY AND GLASS TABLE 5 REACTION TIME (RT) AND PERCENTAGE ERRORS (E) FOR SENTENCES IN EXPERIMENT 5 Listening

Reading

Mean

Sentence type

RT

E

RT

E

RT

E

High imagery Low imagery Mean

638 673 655

3 7 5

822 790 806

8 7 7

730 731 730

5 7 6

Note. Data for RT are given in milliseconds.

fere with grammatical judgments for those words and representing the meaning of a sentences, its effect can be isolated with high-imagery sentence both require visual some confidence at the levels of analysis representation. Therefore, these two tasks involving comprehension. interfered with each other. The results and Thus, the finding is a step t o w a r d conclusion here are consistent with those of clarifying the extent to which sentence Kosslyn (1976b). He found that children comprehension is the product of an auton- spontaneously used imagery much more omous linguistic processing system versus than adults did in a sentence verification the extent to which more general cognitive task. He concluded that this was because processes are involved. Specifically, the re- their abstract representations were more sult provides support for the dual code hy- impoverished and so they found it necespothesis (Paivio, 1971). According to this sary more often to consult their visual rephypothesis, human memory consists of two resentation. types of representations. One representaThe result is also significant because it tion is abstract and propositional and the demonstrates selective interference at a other is spatial, visual, or imagistic. The new level of abstractness. Previously, the fact that reading interfered only with the most robust demonstrations of selective verification and comprehension of high- interference have been between conscious imagery sentences suggests that the infor- mental imagery and a perceptual task inmation stored in the two kinds of repre- volving the same modality. For example, sentations is not completely redundant. If Brooks (1968) demonstrated selective inexactly the same information was encoded terference between visual imagery and a viin both the abstract representation and the sually controlled response. Similarly, Segal visual representation, then there would be and Fusella (1970) demonstrated selective no reason for reading to selectively inter- interference between auditory imagery and fere with the c o m p r e h e n s i o n o f high- auditory perception and between visual imimagery sentences since all the information agery and visual perception. In each case, necessary to comprehend both high- and the selective interference confirmed our low-imagery sentences could be obtained intuitions that imagery and perception infrom the abstract representation. Rather, it volve some of the same processes. Howappears that imagery plays a role in verifi- ever, it left intact a possible distinction cation and comprehension primarily for b e t w e e n peripheral p e r c e p t u a l reprethose sentences for which essential infor- sentations, used in recognizing faces, obmation is not a part of the abstract repre- jects, visual patterns, sounds, and words, sentation but is a part of the visual repre- and a central, abstract amodal representasentation. Presumably, reading interfered tion, used in representing the meanings of with the c o m p r e h e n s i o n of the high- words, the properties of numbers, and logiimagery sentences because reading the cal information. In the experiments re-

READING IMAGERY SENTENCES

ported here, subjects had clear intuitions that they used imagery in verifying sentences. However, when comprehending sentences, it should be obvious that it is much more difficult to introspect and have a clear intuition whether imagery is required. Nevertheless, a robust selective interference effect was found. Hence, the selective interference suggests that the representation or representations involved in comprehension are not completely amodal but overlap in some way with the representations involved in perception. Finally, the interaction between presentation mode and sentence type suggests that reading and listening place different demands on the process of language comprehension. Furthermore, it provides clear evidence that a logically earlier stage of processing may interfere with a later one. Whether a sentence is presented visually or auditorily an initial decoding stage must occur in which the meanings of the words are retrieved before the meaning of the entire sentence is constructed. Nevertheless, the interference between reading and high-imagery sentences demonstrates that sentence comprehension is not a process that is independent of the decoding stage, but is influenced by the modality in which the utterance was presented. Even though the subjects in these experiments were all highly skilled readers, and the sentences were not difficult, visual presentation still substantially slowed their comprehension of the highimagery material. Therefore, it seems possible that less skilled readers might have even more difficulty in reading highimagery materials. As far as we are able to tell there is no experimental literature on this particular issue. However, the case of S. (Luria, 1968), who had incredibly vivid mental imagery, may be relevant. S. reported that his imagery got in the way of his understanding the meaning of what he read. Since the results obtained have such general significance, a caveat about their definitiveness should be mentioned. The

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distinction between verification and comprehension, as operationally defined in Experiments 1-4 was murky. All the meaningful sentences in Experiments 3 and 4 were true, so the task in these experiments could have been interpreted as simply a very easy verification task. On the one hand it might be argued that the differences in reaction time among the verification, comprehension, and grammatical judgment tasks suggests that three different kinds of judgments were involved. On the other hand, it might be argued that task type and task difficulty were confounded. Perhaps reading only interferes with high-imagery sentences on difficult tasks but not on easy ones. So more empirical work is needed to more precisely define comprehension in order to accurately locate the effect of the interference. For example, if meaningfulness and truth are separate judgments, then it should be possible to design a future experiment in which true and false statements are identified as meaningful equally fast. Also, to distinguish task type and task difficulty, the grammatical task might be made more difficult. If no effect of imagery was found even when the grammatical judgment task and the comprehension task were of equal difficulty, it would be hard to argue that the same tasks were being performed in each experiment. In conclusion, the reading/listening interference paradigm provides a robust and easily reproducible demonstration that imagery plays a role in language comprehension. In the future, it should be possible to use this effect to discover the nature of the representation common to imagery and language. Does the representation contain all kinds of visual information including color, size, and shape, or is it restricted to spatial information? It should be possible to investigate this question by examining what kinds of sentences result in an interference effect. Exploitation of this paradigm should yield further information about semantic representation.

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EDDY AND GLASS

APPENDIX: EXPERIMENTAL AND F I L L E R SENTENCES USED IN EXPERIMENTS 1 - - 5

High-Imagery Sentences--True~False A Star of David has six/five points. Tractors have two very large wheels in the back/front. The hot water handle on a sink is on the left/right. The letter W is formed with four/three lines. The stars on the American flag are white/blue. Abraham Lincoln/George Washington had a beard. A stop sign has eight/seven sides. The number 8 can be constructed from two/a single circle(s). The accelorator on a car is the right/left pedal. A tic-tac-toe game is drawn with four/five lines.

A grapefruit is larger than an orange/canteloupe. The number 9 can be constructed from a circle and a single line/two circles. The dial on a telephone has ten/nine holes. A row boat comes to a point in the front/back. The symbol for degrees is a tiny circle/an apostrophe. The letter A is formed with three/four lines. Brown/yellow is darker than orange. A right handed hitter places his left/right side toward the pitcher.

Low-Imagery Sentences--True~False There are seven/six days in a week. Biology/Geology is the study of living matter. Middle age comes before/after old age. The best student is at the top/bottom of the class. A country has citizens/windows. There are two/three human sexes. Spring is a season/month. A novel is longer/shorter than a novelette. The introduction precedes/follows the story.

Salt is used more/less often than pepper. The prince will one day be king/queen. A pound is heavier than an ounce/a ton. Most watchdogs are German Shepherds/bulldogs. Animals are stuffed by a taxidermist/toxicologist. Geology studies the history of the earth/mankind. A father has/buys children. The US government functions under a two/three party system.

High-Imagery Sentences--Normal Fillers~Semantically Anomalous~Grammatically Anomalous The statue of liberty holds a torch in her right hand/ hair/meant. A book opens on the right side/whee//high. Every trapezoid has four sides/bills/were. George Washington wore a wig/mars/soon. To open a jar, you turn the lid clockwise~western~ frosty. Russia is east of Germany~Kennedy/consistent. The radiator of a car is in front of the engine/kitchen/ quickly. In a place setting, the spoon is on the right/fear/insure. A tomatoe has yellow seeds/cars/grows.

The bottom light on a traffic signal is green/hard/ should. The driver of a truck sits on the left/flood/lost. Negative ten is smaller than negative one/tag/forced. A house is larger than a cottage/fever/highly. On a map, north is usually at the top/flight/cried. A staple has two points/plants/does. The handle on a refrigerator is on the right/yard/saves. A person's hips are closer to the ground than his shoulders/trees/slows. A tadpole turns into a frog/face/prompts.

Low-Imagery Sentences---Normal Fillers/Semantically Anomalous~Grammatically Anomalous Light travels faster than sound/trust/per. The plot of a story is its theme/weed/more. Fairy tales end with the words " E v e r after/below/ infant". Weddings are held in chapels/baseballs/became. A conservative is considered on the political right/ short/new. The p r e s i d e n t is higher ranking than the vice president/leverage/correspond. Most people are right handed/worded/create. Human gestation takes nine months/piles/into. A planet has an orbit/grand-danghter/develops.

Sunday occurs about four times a month/roast/the. A piano is a string instrument/sofa/neither. Baseball is played with nine players/flavors/pursue. A marathon race is about 26 miles/wills/like. In Celsius degrees, water freezes at zero/register/ falsify. A penny is made of copper/feast/my. A combination lock is opened with three numbers/ bottles/ordered. Stereo speakers come in twos/cheers/canse. As you go north the weather tends to be cooler/taller/ teacher.

READING IMAGERY SENTENCES REFERENCES

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