Sound and the Brain

Is it true that the part of the brain that processes sounds entering the ear is different for Japanese people and Westerners?

It all started with a paper by Dr. Tsunoda, which was published over 30 years ago, but it became widely known after it was mentioned in a book called "The Japanese Brain."

What are the differences?

First, you probably know that the brain has a left and right hemisphere, right? Let me explain using this diagram (Figure 1, Reference 1) which shows the differences in how the brain responds to various sounds between Japanese and Westerners. The left hemisphere is said to be the language brain, and the right hemisphere is said to be the music brain and art brain, with the left hemisphere responsible for rational cognition and the right hemisphere for emotional cognition. However, it seems that the left hemisphere of Japanese people contains a mixture of rational and emotional cognition.

This diagram shows that Japanese people, compared to Westerners, process a wider range of sounds using the left hemisphere of their brain.

That's right. A distinctive feature is that vowels are being processed in the left hemisphere of the brain. Dr. Tsunoda's experiment was originally about determining which side of the brain—the left or right—is predominantly responsible for receiving language and non-language information. The test sounds used were a 1 kHz pure tone for non-language sounds, and the language sound was the sustained vowel "ah," representing human speech.

Did you play that test sound for people from different countries and investigate which part of their brain was being used to hear it?

That's right. Nowadays, to identify active areas of the brain, there's a technique called fMRI (functional magnetic resonance imaging) which measures changes in brain blood flow, but back then, it seems they were experimenting with analog devices to measure the switching mechanism of the brainstem system that determines which side of the brain is processing sound. Some researchers apparently questioned the reliability of these results, but other researchers conducted follow-up experiments using electroencephalography (EEG) and magnetoencephalography (MEG).

Were the results the same as Dr. Tsunoda's?

The results showed that Japanese people's left brains were more active in response to vowel stimuli, while Americans' right brains were more active, thus confirming Dr. Tsunoda's findings. (Reference 2) The same trend was observed with the sounds of insects such as crickets.

In this diagram (Figure 1), "Japanese instruments" refers to instruments from Japan, right? It's strange that even with the same instrument, Japanese people perceive the sound of Japanese instruments with their left brain and the sound of Western instruments with their right brain. The sound of the shamisen that we analyzed the other day was also perceived by Japanese people with their left brain, but by Westerners with their right brain.

That's right. That's a distinctive difference. Japanese people process all sounds with vowel-like structures, such as those from traditional Japanese musical instruments and natural sounds, in the left hemisphere of the brain, which is responsible for language. Even the "gong" of a temple bell might sound like a vowel in its lingering resonance.

What about people from other Asian countries, or Japanese people who grew up overseas?

Currently, it's said that the unique way Japanese people's brains process sound is entirely due to the Japanese language itself. That's why Koreans and Chinese people show the same tendencies as Westerners, and even among Japanese people, those whose native language isn't Japanese have the same left-right brain distribution as Westerners.

Japanese people perceive even the sounds of insects with the left hemisphere of their brain, the part that handles language.

Japanese people have a unique way of listening to the sounds of insects. I have some interesting stories about insect sounds, so I'll tell you about them all next time.

If Japanese people have a different perception of sound than people from other countries, does that cause any problems?

I don't think we can definitively say that our sensibilities are different, but especially when it comes to natural sounds like the sounds of insects or rain, we don't simply treat sounds as physical objects. Instead, we connect them to the seasons, to people's feelings, and find meaning in them. This is a big difference from people in other countries. This also influences Japanese culture, which embraces nature rather than confronting it, and perhaps Japanese people could be more conscious of this.