BRAIN AND LANGUAGE 14, 174-180 (1981) Asymmetries in the Perceptual Span for Israeli Readers ALEXANDER POLLATSEK,SHMUELBOLOZKY, ARNOLDD. WELL, AND KEITH RAYNER University of Massachusetts Native Israelireadersread Hebrew and English text as their eye movements were monitored. A window of text moved in synchrony with their eye movements and the window was either symmetrical about the fixation point or offset to the left or right. When subjects were reading Hebrew, the perceptual span was asymmetric to the left and when they were reading English it was asymmetric to the right. The results point out the importance of attentional factors in reading. A great deal of research has confirmed that for right-handed subjects, individual words are processed more efficiently when presented in the right visual field (to the right of a central fixation location) than in the left visual field. Early explanations of this asymmetry centered oh scanning habits that result from experience with reading (Heron, 1957; Mishkin & Forgays, 1952). Inherent in much of the recent research on the topic, however, is the assumption that the processing differences are due to a functional asymmetry of the brain (Hecaen & Albert, 1978). According to this position, the left hemisphere is more specialized for verbal processing and the right hemisphere is more specialized for spatial processing, so that words are better recognized when presented in the right visual field and thus initially received by the left or language-specialized hemisphere. The scanning explanation predicts that native readers of Hebrew should show a left-visual-field superiority for words since the direction of reading is from right to left. However, readers of Hebrew, like readers of left-to-right languages, show a marked right-visual-field advantage for the recognition of individual words (Orbach, 1967; Barton, Goodglass, & Shai, 1956; Carmon, Nachson, & Starinsky, 1976; Silverberg, Bentin, This research was supported by Grant HD12727 from the National Institute of Child Health and Human Development (Keith Rayner, principal investigator). The authors thank Jim Bertera and Robert Morrison for their assistance in conducting the study. Requests for reprints should be addressed to Alexander Pollatsek, Department of Psychology, University of Massachusetts, Amherst, MA 01003. 174 0093-934Xl81/050174-07$02.00/O Copyright All rights 0 1981 by Academic Press. Inc. of reproduction in any form reserved. ASYMMETRIES IN PERCEPTUAL SPAN 175 Gaziel, Obler, & Albert, 1979). Thus, it has generally been concluded that although scanning habits may have some influence on perceptual asymmetries, there is an overriding effect of left-hemisphere superiority for reading tasks (Jonides, 1979). It is not clear, however, to what extent conclusions can be made about the reading of text from studies in which individual words are briefly displayed to the left or right visual field. Experiments (McConkie & Rayner, 1976; Rayner, Well, & Pollatsek, 1980) with readers of English text have confirmed that the perceptual span (the area of text from which useful information is extracted during a fixation) is asymmetric, with little information obtained from the left of the fixation point. In these experiments, eye movement information was monitored and fed into a computer controlling a cathode-ray tube (CRT) from which the subject was reading. Changes were made on the CRT on the basis of the location of the reader’s gaze. For example, a passage of mutilated text was initially presented on the CRT with every letter from the original text replaced by an X. However, whenever the reader fixated, a region around the fixation point changed into readable test. This “window” area moved in synchrony with the eye movement so that wherever the reader fixated, the real text was exposed, but everywhere outside the window area the mutilated text remained. By varying how far the window extends to the left and right of fixation, it has been possible to determine the extent to which the perceptual span in reading is asymmetric. The data suggest that English readers show no difference in performance between (a) a symmetric window extending 14 characters to the left of fixation and 14 characters to the right of fixation and (b) an asymmetric window extending 14 characters to the right of fixation but only 4 characters to the left. On the other hand, if the window extends 14 characters to the left of the fixation point but only 4 characters to the right, the reading performance of English readers was considerably disrupted. No experiments dealing with the characteristics of the perceptual span for readers of Hebrew text have been reported, although there have been suggestions that the direction of reading and hemispheric specialization may be important for Hebrew readers (Albert, 1975). If the perceptual span when reading text is determined by the same factors that are responsible for asymmetries when processing individual words (presumably hemispheric specialization), then the perceptual span should be asymmetric to the right. On the other hand, if the asymmetry of the perceptual span for readers of English text is due primarily to attentional considerations related to the pattern of eye movements, then the perceptual span for readers of Hebrew text should be asymmetric to the left. In the experiments reported here, the technique (Rayner et al., 1980) used previously to investigate the asymmetry of the perceptual span for English readers was employed to determine if the perceptual span of Israeli 176 POLLATSEK ET AL. readers is asymmetric to the left or right or is possibly symmetric due to the conflict between the direction of scanning and hemispheric specialization. Israeli readers who were also fluent in English were asked to read Hebrew sentences and English sentences presented on a CRT as their eye movements were monitored. The window area around a fixation point was either symmetric, extending 14 characters both left and right of fixation, or asymmetric so that it extended either 14 characters left and 4 right of fixation or 4 left and 14 right of fixation. METHOD Subjects Six native Israeli subjects participated of experience they had reading English instruction in reading English beginning subjects were right-handed and none of mean age of the subjects was 30 (range in the study. All were bilingual and the amount varied from 3 to 29 years. They had all received in at least the fifth year of school. All of the them required corrective lenses for reading. The = 15-39 years) and two of them were female. Apparatus and Procedure Eye movements were recorded with a dual Purkinje eye tracker (Stanford Research Institute) that was interfaced with a Hewlett-Packard 2100 computer. The eye tracker has a resolution of 10 arcmin, and the output is linear over the visual angle (14 deg) occupied by the sentences. Subjects’ heads were fixed by a bite bar. The subject’s eye was 46 cm from the CRT used to present the sentences; three characters equaled 1 deg of visual angle. Details of the apparatus have been described by Rayner et al. (1980). At the beginning of the experiment each subject read some warm-up sentences with the window offset either to the left or right of fixation. Following the warm-up sentences, each subject read 16 Hebrew sentences in each of the 3 experimental conditions. Sentences were read in blocks of 8 with the window either being symmetrical around the fixation point, asymmetric to the right or asymmetric to the left. Subjects returned to the laboratory on another day and read 48 English sentences, 16 in each of the conditions in the same manner as the Hebrew sentences had been read. The English sentences were similar in length and structure to English translations of the Hebrew sentences. For both Hebrew and English sentences, the order of the conditions and the sentences read were counterbalanced across subjects. Subjects were instructed to read each sentence and then report the sentence to the experimenter. They were instructed to report the sentence verbatim or to paraphrase it. RESULTS AND DISCUSSION With Hebrew text, reading performance (See Table 1 and Figure 1) did not differ between the symmetric condition and the asymmetric condition in which the window was shifted to the left. Conversely, when subjects read English text, their performance was similar to that of native English readers in that the symmetric condition did not differ from the asymmetric condition in which the window was shifted to the right. As can be seen in Table 1, the Israeli subjects read English (in the symmetric and asymmetric right conditions) at the rate of 230 wpm (words per ASYMMETRIES IN PERCEPTUAL TABLE EFFECTIVE HEBREW 1 READING RATES IN WORDS PER MINUTE FOR THE ISRAELI SUBJECTS READING SENTENCES AND ENGLISH SENTENCE< COMPARED TO AMERICAN SUBJECTS READING COMPARABLE ENGLISH SENTENCES Israeli subjects Window condition 14-14 14-4 4-14 177 SPAN Hebrew 286 282 185 English English speaking subjects 233 131 221 350 218 336 minute). Native English-speaking subjects’ typical reading rates are between 320 and 350 wpm on sentences of similar length and complexity. We assume that the slower reading rate for the Israeli subjects on English sentences is because English is not their native language. However, it is instructive to note that for all of the variables shown in Table 1 and Figure 1, the window offset had the same effect as it did for English readers reading English. For both types of text, the asymmetric condition in which the window was shifted in the direction opposite to that of reading resulted in marked decrements in reading behavior. -Hebrew .i‘%j :------r;,: 2 Asymmtrlc Left Symmetric Asymmatric Right FIG. 1. Mean saccade length, mean fixation duration, Hebrew and English text. and number of fixations for 178 POLLATSEK ET AL. When reading Hebrew, performance m the 14L-4R condition was superior to that in the 4L-14R condition for each of the six subjects with the exception of a reversal for a single subject on the fixation duration measure. For reading rate, mean saccade length and mean number of fixations per line, the results were highly significant, t(5) = 4.10, 7.45, and 4.61, respectively, p < .Ol, whereas for average fixation duration, the difference was not significant, t(5) = 1.26, p > .20. When reading English, performance in the 4L-14R condition was superior to that in the 14L-4R condition for each of the six subjects, with the exception of a reversal for a single subject on the fixation duration measure. For mean saccade length and mean number of fixations per line, the differences were highly significant, t(5) = 3.39 and 4.04, respectively, p < .02, while for reading rate and mean fixation duration the results failed to reach conventional levels of significance, t(5) = 2.39 and 2.52, respectively, .05 < p < .10. However, this reduced level of significance for reading rate was due to one subject who had a much larger difference than the others which inflated the error term. If this subject who showed the largest asymmetry (a difference of 292 wpm vs. an average difference of 57 wpm for the other five subjects) is removed from the analysis, then the difference in reading rate for the other five subjects is highly significant, t(4) = 5.16, p < .Ol. These results provide an unambiguous demonstration that during the reading of meaningful text, the direction of reading (and not hemispheric specialization) primarily determines the asymmetry of the perceptual span. For each of the six bilingual subjects, the perceptual span was asymmetric to the left when Hebrew was read and asymmetric to the right when English was read. It is interesting to note that Hebrew varies structurally and orthographically from English in some important ways that are relevant to our experiment. In Hebrew, many function words are clitic, i.e., are attached like prefixes or suffixes to content words. Furthermore, unlike English, not all vowels are represented in Hebrew orthography. The net effect of these differences is that Hebrew sentences normally contain fewer words than their English counterparts. In our case, for example, the Hebrew sentences were translations of English sentences, and the Hebrew sentences were shorter than the English versions by approximately 1.3 words per sentence. Thus while the Israeli readers reading Hebrew are markedly slower than American readers reading English (see Table l), when measured by words per minute, this may be accounted for by the above structural and orthographic differences. As a quick check that there was nothing abnormally slow about our Hebrew readers, we computed the reading rate in Hebrew based on the number of words contained in the English translations of the Hebrew sentences. Using this measure, the average reading rate for our native Israeli subjects reading Hebrew ASYMMETRIESINPERCEPTUALSPAN 179 in the 14-14 condition was 348 words per minute, a rate almost identical to that of a group of 9 native English speaking subjects reading similar English sentences under similar conditions (see Table 1). While the above analysis suggests that Hebrew readers acquire meaning from text in their native language about as rapidly as their American counterparts, a considerably more ambitious study would clearly be needed to compare the efficiency of the two languages in terms of information transmission. However, it is clear that Hebrew readers are reading their native language more slowly in terms of surface measures such as words per minute. Inasmuch as more information is condensed into less space in Hebrew because of the greater use of clitics and because of the omission of many vowels, it is not surprising that the average saccade length found for the readers of Hebrew in the 14-14 condition (5.5 characters) is smaller than the average saccade length (7-9 characters) typically found for readers of English (Rayner, 1978). In experiments similar to that described here, carried out with English speaking subjects, we have obtained average saccade lengths of approximately 7 characters and average fixation durations of about 220 msec (Rayner et al., 1980). The finding that the average saccade length varies as a function of the writing system is consistent with studies of Japanese and Chinese readers @hen, 1927; Ikeda & Saida, 1978; Stern, 1978). Our data also show that the average saccade length of Israeli subjects when reading English is much shorter than is the case for native English readers. While this might simply reflect the fact that Israeli subjects are not as fluent in reading English, a more intriguing possibility is that there is some carryover from their experience with Hebrew. It is also interesting to note that the Israeli readers’ average fixation duration while reading Hebrew in the 14-14 condition (265 msec) is about 45 msec longer than the average fixation duration we have obtained for English speaking readers in a number of studies in our laboratory. On the other hand, the 265-msec average does not differ markedly from the range of 200-250 msec that is typically described as the average fixation time in reading (Rayner, 1978). Our results suggest that languages can be characterized by their density (in terms of such measures as the ratio of morphemes to graphemes or syllables to graphemes) and as density increases, subjects will shorten their saccades and lengthen their fixations. Clearly this study is not definitive since it compares readers of different languages and texts in different languages that have not been equated in precise ways. We are pursuing these ideas using variations of text within a given language. In summary, we find clear and striking evidence that during the reading of Hebrew, the perceptual span of Israeli subjects is asymmetric to the left. Thus, while in experiments (Hecaen & Albert, 1978) in which stimuli are presented tachistoscopically to the left and right visual fields the 180 POLLATSEK ET AL. typical conclusion is that hemispheric specialization is the major factor underlying processing asymmetries, our experiments indicate that in an ongoing reading task, attentional factors and factors associated with the direction of eye movements are crucial. Finally, our results are consistent with a case study (Dessoff, 1957) of a Hebrew-English bilingual suffering from brain damage that resulted from right hemifield homonymous hemianopia. The subject could not read English as the fovea1 and parafoveal regions were affected by the damage. However, since the brain damage affected the right visual field only, he apparently could read Hebrew without difficulty. 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