Across Hemispheres:
Comparing Interhemispheric Transfer Times of Japanese and Americans

Andrew J. Dimond and Aaron Tiesling-Rusch
Beloit College

Keywords: interhemispheric transfer time, cross-cultural comparison, Japanese, English, language


This study sought to determine whether hemispheric differences in language processing would lead to differences in interhemispheric transfer time (IHTT), the time it takes for information to be transmitted from one hemisphere of the brain to the other, between English speaking Americans and Japanese speakers in Japan. Compared to English, reading and writing Japanese requires more bilateral brain activity, and as a result may impact IHTT in a manner similar to previous findings regarding people that frequently play an instrument. We recruited participants from both the United States and Japan and used a manual response reaction time task to estimate the participants' IHTT. We found that there was no cross-cultural difference in the IHTT of American and Japanese participants, which indicates the possibility that the results from other IHTT studies, which only used Americans, may be generalizable to other national groups.


Interhemispheric transfer time (IHTT) is a measure of how long it takes for information to be sent from one hemisphere of the brain to the other across the corpus callosum (Marzi, Bisiacchi, & Nicoletti, 1991). Studies frequently use a technique known as the Poffenberger Paradigm to estimate IHTT (Bayer, Kessler, Güntürkün, & Hausmann, 2008; Bernard, 2011; Buse et al., 2012). The Poffenberger Paradigm involves a simple reaction time task in which participants give unimanual responses to stimuli that are presented separately to the participants' left- and right-visual fields (Poffenberger, 1912). The participants go through the task twice, once responding with their right-hands and a second time responding with their left-hands. The reaction times from the ipsilateral hand and visual field conditions are taken and subtracted from the contralateral conditions and the result is considered an estimate of the participants' IHTT. On average, previous studies have reported an IHTT estimate of 4-12ms and right-hemisphere to left-hemisphere transfer is usually faster than left-hemisphere to right-hemisphere transfer by approximately 2-3ms (Marzi, Bisiacchi, & Nicoletti, 1991).

The speed of IHTT matters for normal brain activity, because information often needs to be quickly shared and processed by both hemispheres. A number of studies have discovered IHTT abnormalities present in individuals diagnosed with certain mental illnesses, such as dyslexia (Davidson & Saron, 1992; Velay, Daffaure, Giraud, & Habib, 2002; Walker, 2001), ADHD (Rolfe, Kirk, & Waldie, 2007), and schizophrenia (Barnett & Kirk, 2005; Barnett, Kirk, & Corballis, 2005; Florio, Fossella, Maravita, Miniussi, & Marzi, 2002).

In English speaking populations, the mental and physical activities individuals participate in, such as playing an instrument, can lead to differences in IHTT patterns (Patston, Kirk, Rolfe, Corballis, & Tippett, 2007). In a study comparing EEG estimated IHTT between musicians and non-musicians, Patston et al. (2007) found that musicians were faster than non-musicians for left-hemisphere to right-hemisphere transfer, but not right-hemisphere to left-hemisphere transfer, and that the musicians overall had a higher level of bilateral neural connectivity. This raises the possibility that other differences in people's mental activities may lead to similar IHTT differences between groups of people.

One such difference between people may be the mental activity required for the processing of certain languages. There is evidence that the logographic, or symbol based, kanji system of the Japanese language is processed equilaterally by the hemispheres of the brain. It is currently not known why this difference exists, but it has been suggested that it could be due to the kanji characters' semantic information being accessible without first needing to access phonological information about the kanji characters (Hanavan & Coney, 2005). English speakers, on the other hand, do more language processing in the left-hemisphere of the brain than in the right-hemisphere (Chiarello, 1988).

In the present research, we explored whether the speed of communication between the hemispheres of the brain is different for Americans and Japanese. We collected IHTT estimates from participants in Japan and the United States. To our knowledge, this was the first time that IHTT has been measured in any non-English speaking population. We were curious, in particular, as to whether the special processing required by the logographic structure of the Japanese kanji system might lead to a difference in IHTT between Japanese and English speakers. We posited that hemispheric differences in the mental activity of language processing may lead to differences in IHTT in a similar fashion to the IHTT differences between musicians and non-musicians.



Participants were 21 college students in Japan (10 men and 11 women) and 21 college students in the United States (7 men and 14 women). All Japanese participants had studied the English language (M = 9.8 years, SD = 3.3) and 20 of the American participants had studied Japanese for at least 1 year (M = 1.9 years, SD = 1.0). Most of the participants in this study were recruited as part of another study that required people who had at least basic knowledge of both Japanese and English.

Materials and Procedure

Interhemispheric transfer time was measured via a computer program similar to that used by Savage and Thomas (1993). As participants stared at a central fixation point, squares would randomly appear on either the far right or far left side of the screen, and the participants would then quickly press a response button with one hand. After completing 200 trials, the participants then switched the hand with which they responded and completed an identical set of 200 additional trials. 


We estimated IHTT by subtracting the reaction times during ipsilateral hand plus visual field conditions from the reaction times during contralateral hand plus visual field conditions. For both cultural groups, there was a significant correlation between left-hemisphere to right-hemisphere and right-hemisphere to left-hemisphere transfer times, r = .536, n = 42, p < .001 (Figure 1.). As can be seen in Figure 2, Japanese and American participants did not differ with respect to their right-hemisphere to left-hemisphere (F(1, 40) = .066, p = .799) nor left-hemisphere to right-hemisphere (F(1, 40) = .091, p = .764) transfer times.


Limitations of this study included using a small sample from each population. The participant groups also had a great deal of skill in each other's native language, particularly the Japanese students, who began learning English as part of their primary school level education. It is possible that the bilingual nature of our participants confounded any IHTT differences caused by differences in the processing required by the participants' native languages. Different results may be found if a study is conducted using only monolingual participants.

Japanese and American participants exhibited very similar IHTT. This indicates that cultural, language, and language processing differences do not necessarily lead to differences in interhemispheric transfer. If the results of this study are supported by further research, results from other IHTT studies, such as those regarding mental illnesses, may be generalizable to various national groups. Thus, IHTT could possibly be used as a culture free way of testing for the presence of some mental disorders. This study provides a new finding that IHTT may be very similar across cultures, in spite of language and cultural differences.


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