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Numerical judgments with Kanji and Kana
Neuroprhologla. Vol. ?I. No Pnned I” Great Br11am.
0028-3932 8353.00+0.00 ? 1983 Pergamon Press Ltd.
3. pp. 259-263. 1983.
NUMERICAL
JUDGMENTS
WITH
KANJI
AND KANA
AKIKO TAKAHASHI and DAVID GREEN* Department
of Psychology.
University
College
London.
London
WClE
6BT. England
(Accepted 23 December 1982) Abstract-Native Japanese speakers were timed to judge the numerically larger of two numbers. written either in Kanji (an ideographic script) or in Kana (a syllabic script). For Kanji. irrelevant variations in the physical size of the numbers speeded reaction time in one condition and slowed it in another. Such variations only slowed processing for Kana, except when subjects had previously performed with Kanji. For both scripts, reaction time varied with the numerical difference between the two numbers but not in an identical manner. The implications of the findings are considered.
can be expressed using different scripts. Numbers, for instance, can be identified in English using either words (two; eight) or Arabic numerals (2; 8). The former alphabetic script is tied to the spoken form, whereas the latter, ideographic script is not. Neuropsychological observations of patients with alexia without agraphia suggest that these two scripts may be processed differently [4]. Evidence from normal subjects argues for the same conclusion [l]. When timed to judge which of two presented Arabic numerals is numerically the larger, subjects are influenced by their physical size. When the numerically larger number is also physically larger (Congruent condition), subjects are faster than when both numbers are the same physical size (Same condition). When the numerically larger number is physically smaller (Incongruent condition), subjects are slowest of all. Such Stroop-like effects do not seem to occur for judgments with number words. Reaction time (RT) is equal for the Congruent and Incongruent conditions. Whether there are any general effects of such mixed size stimuli is unknown since word stimuli of the same size were not included. We explored whether a similar set of results would arise for Japanese speakers comprehending numbers written in either the Japanese ideographic script, Kanji, or in Kana, a non-ideographic script whose elements map onto the syllables of speech. Both psychological [3] and clinical observations [7-93 suggest that these two scripts may be comprehended differently. A further feature of the number judgment task is that reaction time increases as the numerical distance between the two numbers decreases [ 1, 2, 51. This symbolic distance effect appears to be independent of whether words or pictures are used to identify the concept in question [6]. Since ideographs are similar to pictures in that neither specifies pronunciation although both stand for concepts, we expected to obtain such a function for both Kanji and Kana characters. Our task was identical to that used previously [l] but we made certain refinements in terms of design. For both scripts, we used identical number pairs in the same display format, CONCEPTS
*Author
to whom
all correspondence
should
be addressed 259
and included a same size control. In addition, \ve explored whether the nature of the script full) determines processing in this task. or Lvhether the manner of processing one script can affect processing of the alternate script. Accordingly. the experiment was conducted in two sessions in order to examine carry-over effects.
EXPERIMENT The stimuli were the numerals 1-9 inclusive which were written either in Kanji or in Kana. On each trial, two were presented, one above the other, using a projector fitted with a shutter. The inter-trial interval was four seconds. Subjects indicated which of the tM.0 numbers, the top or the bottom. was numerically larger by pressing one of two vertically-aligned microswitches. Subjects depressed the top switch with their dominant hand and the lower switch with their other hand. RT was recorded using a standard electronic msec timer and was noted, together with any errors, by the experimenter. The experiment consisted of two sessions. One group of subjects responded to the Kanji script in the first session and the other group to the Kana script. The alternate script was used in the second session. Within each session, Script was a between-subjects factor and Physical Size and Numerical Distance were within-subjects factors. Each of these two factors had three levels. For the variable of Physical Size these were: a Congruent condition in which the numerically larger number was also physically larger; an Incongruent condition where this number was physically smaller and a Same Size condition where both numerals were small. For the variable of Numerical Distance the three levels were: one (using the numeral pairs 23, 45, 67, 89); three (14, 25, 36, 58) and five (16, 27, 38, 49). The nine conditions occurred 16 times, yielding 144 trials for each Script. Within each condition, the numerically larger number appeared equally often at the top and at the bottom of the display. Before each session subjects were asked to write down the numbers one to ten in the script they were about to see. A short practice block was then presented and subjects were instructed to respond as fast and as accurately as possible. The second session was run after a break of 20 min. Seventeen Japanese women were recruited from two small groups attending part-time courses. All were right-handed with normal or corrected vision and had been living in London for 3 yr. The first group of 10 (mean age 17 yr) responded to Kanji in the first session and to Kana in the second. The second group of seven (mean age 26 yr) responded to the scripts in the converse order.
RESULTS Mean correct RT for the first session is plotted in Fig. IA and that for the second session in Fig. 1B. In session I, the standard error of the mean was 58 msec for the Kana condition (upper three curves) and 32 msec for the Kanji condition (lower three curves). Errors averaged 1.1 and 5.3 y, respectively. (The error pattern for Kanji was similar to that obtained previously for alphabetic stimuli [l] and showed no trade-off between speed and accuracy across conditions.) Subjects reacted more rapidly to Kanji than to Kana [F (1, 15)=45.48. P
K\SJI
.AVD K.4h.A
261
PROCESSISG
Y-Y--Y-w kmerical
difference
between
stimuli
FIG. I. Mean correct reaction time for each condition of session I (A) and sewon 2 (B). In each case, the upper three curves are the means for Kana and the lower three for Kanji.
“symbols” have to be processed compared to one in Kanji. Physical Size exerted a main effect [F (2, 30)=8.51, PP>O.O5, respectively], but there was no difference between these mixed size conditions [F< 11. As expected, RT was inversely related to Numerical Distance [F (2, 30)=51.97, P
XKIKO
262
TAKAHASHI and DAVIDGREES
implies a processing carry-over and indeed, for this group, the within-subjects interaction of Script and Physical Size was not reliable [F(2, 18)= 1.95, ns]. For the Kanji script, by contrast, the pattern obtained in session 1 reappeared. Subjects reacted faster to Congruent compared to Same Size stimuli [F (1, 12)= 5.39, P < O.OS]and more rapidly to the latter than to Incongruent stimuli [F (1, 12) = 22.90, PC O.OOl].Hence, for this group who had processed Kana in session 1, there was no carry-over of processing and the within-subjects interaction of Script and Physical size was highly reliable [F (2, 12)= 13.21, P
DISCUSSION The results for Kanji script, in both sessions, revealed the Stroop-like effects previously obtained for the processing of Arabic numerals by English speakers [l]. As with English number words, Kana script induced a different pattern, at least in session 1. There was no difference between Congruent and Incongruent stimuli. These findings confirm and extend the observations reported by BE~NER and COLTHEART [l]. Irrelevant variation in the Physical Size of the Kana stimuli did exert some effect in session 1. It slowed RT relative to the Same condition. Whether this outcome should be interpreted as a central or peripheral effect is uncertain. It may be central since subjects who reacted to Kanji stimuli in the first session showed a congruency effect for Kana stimuli in the second session, as though they were treating the script ideographically. However, similarity of outcome does not prove identity of process. An intriguing aspect of the study is that the RT function for numerical distance is somewhat different for the two scripts and this difference exists in both sessions. Such a result argues that Kana characters either access a different numerical representation from Kanji characters, or invoke different procedures for comparing the two numbers. Finally, we can begin to answer the question posed by Besner and Coltheart, of whether or not Arabic numerals and Kanji characters are read by the same mechanism. On the assumption that a given type of process is realised by a single cerebral device, our results argue that they are, and that therefore an aphasic Japanese patient who can read Arabic numerals should be able to read numerals written in Kanji [cf. S].
REFERENCES I. BESNER. D. and Neurops~~chologio
COLTHEART. M. Ideographx 17, 467--172.
and
alphabetic
processing
in skilled
reading
of English.
1979.
2. BUCKLEY. P. and GILLS~N. C. Comparisons
of digits and dot patterns. J. exp. Psycho!. 103, 1131-l 136, 1974. 3. HATTA. T. Recognition of Japanese Kanji in the left and right visual field. Neuropsychologia 15,655-688, 1977. 4: H~CAEN. H. and KREMIN, H. Neurolinguistic research on reading disorders resulting from left hemisphere lesions. In Sfudies in Neurolinguisfics. H. WHITAKER and H. A. WHITAKER (Editors), Vol. 2. Academic Press, New York, 1976. 5. MOYER, R. and LANDAUER. T. Time required for judgments of numerical inequality. ,Vo’ature, Land. 215, 1519-1520. 1967. 6. PAIVIO. A. Perceptual
comparisons
through
the mind’s eye. Mem. Cognic. 3, 635-647,
1975.
KANJI ASD K.4SA PRCN~SISG
263
7. SASASWIA. S. Acquired dyslexia in Japanese: clinical features and underlying mechanisms. In Deep Dyslexm. M. COLTHEART. K. PATTER~DNand J. MARSHALL (Editors). Routledge and Kegan Paul. 1980. 8. SASANL..W. S. and ,MOSOI, H. The syndrome of gogi (word meaning) aphasia. Neurolog,v 25, 627 -632. 1975. 9. YAMAWRI. A. Ideogram reading in alexia. Brain 98, 231-238, 1975.
Des syjets ayant le jaoonais comw langue maternelle ont iti chronodtres dans une tache 03 ils devaient estlmer le plus ilevi de deux nombres icrits soit en Kanji (une 6criture ideoqraphique). soft en Kana (une ecriture syllabiwe). Pour le Kanji, le fait de varier la taille des caracteres de facon noncorrel6e au notire, a provoque un raccourcissemnt du tenps de riactlon dans une condition et un allonqement dans une autre. De telles variations de taille ont seulement allong le temps de traitement pour le Kana, sauf pour les sujets qui avaient auparavant subi le test avec le Kanji. Pour les deux icrltures. le temps de rdactfon variaft avec la diffirence nudrique entre les deux nombres, mais pas de la m&se facon. Les imolications de ces Gsultats sont discutis.
Zusammenfassung
Japanische Sprecher wurden darauf trainiert, die numerisch grbi3ere von rwei Zahlen zu beurteilen, die entweder in Kanji oder in Kana geschrieben war. Fur Kanji beschleunioten unbedeutende Variationen in der physischen GrbOe der Zahlen die Reaktionszeiten bei einer Bedingung und verlangerten sie bei Derartige Variatlonen verlannsamten c'ie Verareiner anderen. heitung beim Kana ausschlieblich, sofern die Versuchspersonen nicht vorher in Kanji gearbeitet hatten. Fur beide Schriftarten variierte die Reaktionszeit mit dem nummerischen [Interschied zwischen den zwei Zahlen, aber nicht in einer identischen Art. Die Eedeutung dieser Befunde wird diskutiert.
0028-3932 8353.00+0.00 ? 1983 Pergamon Press Ltd.
3. pp. 259-263. 1983.
NUMERICAL
JUDGMENTS
WITH
KANJI
AND KANA
AKIKO TAKAHASHI and DAVID GREEN* Department
of Psychology.
University
College
London.
London
WClE
6BT. England
(Accepted 23 December 1982) Abstract-Native Japanese speakers were timed to judge the numerically larger of two numbers. written either in Kanji (an ideographic script) or in Kana (a syllabic script). For Kanji. irrelevant variations in the physical size of the numbers speeded reaction time in one condition and slowed it in another. Such variations only slowed processing for Kana, except when subjects had previously performed with Kanji. For both scripts, reaction time varied with the numerical difference between the two numbers but not in an identical manner. The implications of the findings are considered.
can be expressed using different scripts. Numbers, for instance, can be identified in English using either words (two; eight) or Arabic numerals (2; 8). The former alphabetic script is tied to the spoken form, whereas the latter, ideographic script is not. Neuropsychological observations of patients with alexia without agraphia suggest that these two scripts may be processed differently [4]. Evidence from normal subjects argues for the same conclusion [l]. When timed to judge which of two presented Arabic numerals is numerically the larger, subjects are influenced by their physical size. When the numerically larger number is also physically larger (Congruent condition), subjects are faster than when both numbers are the same physical size (Same condition). When the numerically larger number is physically smaller (Incongruent condition), subjects are slowest of all. Such Stroop-like effects do not seem to occur for judgments with number words. Reaction time (RT) is equal for the Congruent and Incongruent conditions. Whether there are any general effects of such mixed size stimuli is unknown since word stimuli of the same size were not included. We explored whether a similar set of results would arise for Japanese speakers comprehending numbers written in either the Japanese ideographic script, Kanji, or in Kana, a non-ideographic script whose elements map onto the syllables of speech. Both psychological [3] and clinical observations [7-93 suggest that these two scripts may be comprehended differently. A further feature of the number judgment task is that reaction time increases as the numerical distance between the two numbers decreases [ 1, 2, 51. This symbolic distance effect appears to be independent of whether words or pictures are used to identify the concept in question [6]. Since ideographs are similar to pictures in that neither specifies pronunciation although both stand for concepts, we expected to obtain such a function for both Kanji and Kana characters. Our task was identical to that used previously [l] but we made certain refinements in terms of design. For both scripts, we used identical number pairs in the same display format, CONCEPTS
*Author
to whom
all correspondence
should
be addressed 259
and included a same size control. In addition, \ve explored whether the nature of the script full) determines processing in this task. or Lvhether the manner of processing one script can affect processing of the alternate script. Accordingly. the experiment was conducted in two sessions in order to examine carry-over effects.
EXPERIMENT The stimuli were the numerals 1-9 inclusive which were written either in Kanji or in Kana. On each trial, two were presented, one above the other, using a projector fitted with a shutter. The inter-trial interval was four seconds. Subjects indicated which of the tM.0 numbers, the top or the bottom. was numerically larger by pressing one of two vertically-aligned microswitches. Subjects depressed the top switch with their dominant hand and the lower switch with their other hand. RT was recorded using a standard electronic msec timer and was noted, together with any errors, by the experimenter. The experiment consisted of two sessions. One group of subjects responded to the Kanji script in the first session and the other group to the Kana script. The alternate script was used in the second session. Within each session, Script was a between-subjects factor and Physical Size and Numerical Distance were within-subjects factors. Each of these two factors had three levels. For the variable of Physical Size these were: a Congruent condition in which the numerically larger number was also physically larger; an Incongruent condition where this number was physically smaller and a Same Size condition where both numerals were small. For the variable of Numerical Distance the three levels were: one (using the numeral pairs 23, 45, 67, 89); three (14, 25, 36, 58) and five (16, 27, 38, 49). The nine conditions occurred 16 times, yielding 144 trials for each Script. Within each condition, the numerically larger number appeared equally often at the top and at the bottom of the display. Before each session subjects were asked to write down the numbers one to ten in the script they were about to see. A short practice block was then presented and subjects were instructed to respond as fast and as accurately as possible. The second session was run after a break of 20 min. Seventeen Japanese women were recruited from two small groups attending part-time courses. All were right-handed with normal or corrected vision and had been living in London for 3 yr. The first group of 10 (mean age 17 yr) responded to Kanji in the first session and to Kana in the second. The second group of seven (mean age 26 yr) responded to the scripts in the converse order.
RESULTS Mean correct RT for the first session is plotted in Fig. IA and that for the second session in Fig. 1B. In session I, the standard error of the mean was 58 msec for the Kana condition (upper three curves) and 32 msec for the Kanji condition (lower three curves). Errors averaged 1.1 and 5.3 y, respectively. (The error pattern for Kanji was similar to that obtained previously for alphabetic stimuli [l] and showed no trade-off between speed and accuracy across conditions.) Subjects reacted more rapidly to Kanji than to Kana [F (1, 15)=45.48. P
K\SJI
.AVD K.4h.A
261
PROCESSISG
Y-Y--Y-w kmerical
difference
between
stimuli
FIG. I. Mean correct reaction time for each condition of session I (A) and sewon 2 (B). In each case, the upper three curves are the means for Kana and the lower three for Kanji.
“symbols” have to be processed compared to one in Kanji. Physical Size exerted a main effect [F (2, 30)=8.51, P
XKIKO
262
TAKAHASHI and DAVIDGREES
implies a processing carry-over and indeed, for this group, the within-subjects interaction of Script and Physical Size was not reliable [F(2, 18)= 1.95, ns]. For the Kanji script, by contrast, the pattern obtained in session 1 reappeared. Subjects reacted faster to Congruent compared to Same Size stimuli [F (1, 12)= 5.39, P < O.OS]and more rapidly to the latter than to Incongruent stimuli [F (1, 12) = 22.90, PC O.OOl].Hence, for this group who had processed Kana in session 1, there was no carry-over of processing and the within-subjects interaction of Script and Physical size was highly reliable [F (2, 12)= 13.21, P
DISCUSSION The results for Kanji script, in both sessions, revealed the Stroop-like effects previously obtained for the processing of Arabic numerals by English speakers [l]. As with English number words, Kana script induced a different pattern, at least in session 1. There was no difference between Congruent and Incongruent stimuli. These findings confirm and extend the observations reported by BE~NER and COLTHEART [l]. Irrelevant variation in the Physical Size of the Kana stimuli did exert some effect in session 1. It slowed RT relative to the Same condition. Whether this outcome should be interpreted as a central or peripheral effect is uncertain. It may be central since subjects who reacted to Kanji stimuli in the first session showed a congruency effect for Kana stimuli in the second session, as though they were treating the script ideographically. However, similarity of outcome does not prove identity of process. An intriguing aspect of the study is that the RT function for numerical distance is somewhat different for the two scripts and this difference exists in both sessions. Such a result argues that Kana characters either access a different numerical representation from Kanji characters, or invoke different procedures for comparing the two numbers. Finally, we can begin to answer the question posed by Besner and Coltheart, of whether or not Arabic numerals and Kanji characters are read by the same mechanism. On the assumption that a given type of process is realised by a single cerebral device, our results argue that they are, and that therefore an aphasic Japanese patient who can read Arabic numerals should be able to read numerals written in Kanji [cf. S].
REFERENCES I. BESNER. D. and Neurops~~chologio
COLTHEART. M. Ideographx 17, 467--172.
and
alphabetic
processing
in skilled
reading
of English.
1979.
2. BUCKLEY. P. and GILLS~N. C. Comparisons
of digits and dot patterns. J. exp. Psycho!. 103, 1131-l 136, 1974. 3. HATTA. T. Recognition of Japanese Kanji in the left and right visual field. Neuropsychologia 15,655-688, 1977. 4: H~CAEN. H. and KREMIN, H. Neurolinguistic research on reading disorders resulting from left hemisphere lesions. In Sfudies in Neurolinguisfics. H. WHITAKER and H. A. WHITAKER (Editors), Vol. 2. Academic Press, New York, 1976. 5. MOYER, R. and LANDAUER. T. Time required for judgments of numerical inequality. ,Vo’ature, Land. 215, 1519-1520. 1967. 6. PAIVIO. A. Perceptual
comparisons
through
the mind’s eye. Mem. Cognic. 3, 635-647,
1975.
KANJI ASD K.4SA PRCN~SISG
263
7. SASASWIA. S. Acquired dyslexia in Japanese: clinical features and underlying mechanisms. In Deep Dyslexm. M. COLTHEART. K. PATTER~DNand J. MARSHALL (Editors). Routledge and Kegan Paul. 1980. 8. SASANL..W. S. and ,MOSOI, H. The syndrome of gogi (word meaning) aphasia. Neurolog,v 25, 627 -632. 1975. 9. YAMAWRI. A. Ideogram reading in alexia. Brain 98, 231-238, 1975.
Des syjets ayant le jaoonais comw langue maternelle ont iti chronodtres dans une tache 03 ils devaient estlmer le plus ilevi de deux nombres icrits soit en Kanji (une 6criture ideoqraphique). soft en Kana (une ecriture syllabiwe). Pour le Kanji, le fait de varier la taille des caracteres de facon noncorrel6e au notire, a provoque un raccourcissemnt du tenps de riactlon dans une condition et un allonqement dans une autre. De telles variations de taille ont seulement allong le temps de traitement pour le Kana, sauf pour les sujets qui avaient auparavant subi le test avec le Kanji. Pour les deux icrltures. le temps de rdactfon variaft avec la diffirence nudrique entre les deux nombres, mais pas de la m&se facon. Les imolications de ces Gsultats sont discutis.
Zusammenfassung
Japanische Sprecher wurden darauf trainiert, die numerisch grbi3ere von rwei Zahlen zu beurteilen, die entweder in Kanji oder in Kana geschrieben war. Fur Kanji beschleunioten unbedeutende Variationen in der physischen GrbOe der Zahlen die Reaktionszeiten bei einer Bedingung und verlangerten sie bei Derartige Variatlonen verlannsamten c'ie Verareiner anderen. heitung beim Kana ausschlieblich, sofern die Versuchspersonen nicht vorher in Kanji gearbeitet hatten. Fur beide Schriftarten variierte die Reaktionszeit mit dem nummerischen [Interschied zwischen den zwei Zahlen, aber nicht in einer identischen Art. Die Eedeutung dieser Befunde wird diskutiert.