An American-Japanese team has found evidence that mother tongue influences the way people hear music rhythms and group non-language sounds into rhythms.

Exposure to certain patterns of speech can influence one's perception about the rhythm. People seem to hear rhythms based on the structures of their own languages. Traditionally, individuals were tested for the way they group rhythms by playing simple sequences of tones.

Listeners were presented with tones that alternated in loudness (...loud-soft-loud-soft...) or duration (...long-short-long-short...) and were asked to indicate their perceived grouping. For a century, studies have widely accepted: a louder sound usually points the beginning of a group, and a lengthened sound usually marks the end of a group. This principle has been thought as universal for perception, behind the rhythms of both speech and music.

However, the "universal" data has made analyzing a limited range of Western languages, such as English, Dutch and French, which all belong to the Indo-European language group, and which have very similar grammatical and phonetic structures. In the new experiments, native speakers of Japanese and native speakers of American English agreed on the principle that they heard repeating "loud-soft" groups. The researchers tested this principle in native speakers of Japanese and native speakers of American English.

The research revealed a sharp difference when it came to the duration principle. English speakers perceived alternating short and long tones as "short-long", while Japanese speakers were more likely to perceive the tones as "long-short". This surprising finding contradicting the previous theory was confirmed with people from different parts of Japan.

The researchers suspect behind the difference of rhythm feeling the phrase structure in the two languages. Most English phrases in songs start with a short-long pattern, and most phrases in Japanese music start with a long-short pattern, then the brain might be accustomed to associate sound groups according to the patterns in their maternal language.

Consequently, the researchers examined the beginning phrases in 50 American and 50 Japanese children's songs. For each phrase they computed the duration ratio of the first note to the second note and counted how often phrases started with a short-long pattern versus other possible patterns such as long-short, or equal duration.

American songs showed no bias to start phrases with a short-long pattern, but Japanese songs presented a bias to start phrases with a long-short pattern, consistent with their perceptual findings.

A basic difference between English and Japanese is word order. In English, short grammatical words such as "the," "a," and "to," come at the beginning of phrases and combine with longer "function" words like nouns or verbs. Function words are typically reduced in speech, duration and have low stress, resulting in frequent linguistic chunks that start with a short element and end with a long one, such as "to eat," and "a big desk." This language structure favored the common verse form, iambic pentameter, not only in English, but in most European languages.

Japanese, in contrast, puts function words at the ends of phrases. Common function words in Japanese include short "case markers," which indicate the grammatical function of the noun (subject, direct object, indirect object etc.) For example, in the sentence "John-san-ga Mari-san-ni hon-wo agemashita," ("John gave a book to Mari") the suffixes "ga," "ni" and "wo" are case markers, indicating that John is the subject, Mari is the indirect object and "hon" (book) is the direct object.

Function words at the end of phrases create frequent chunks that start with a long element and end with a short one, the opposite of the rhythm of short phrases in English and Indo-Europeans languages. And this grammatical structure may be found in more Asian languages and not only.

The study demonstrates the need for cross-cultural research when it comes to understanding general principles of auditory perception.