We study the acquisition of Japanese prosody, focusing on two main themes: the acquisition of prosody by Japanese infants, and the role of prosody in sentence comprehension.
The Japanese language is said to possess a moraic rhythm. A mora is a unit of length, corresponding to one beat in a line of haiku or tanka verse, typically represented with a single character in the kana syllabary. The moraic nature of Japanese is said to derive from the tendency of Japanese speakers to pronounce each mora with roughly equal length.
Research on European languages such as English and French has highlighted the importance of linguistic rhythm in the early stages of acquiring a language. Just how a moraic language is acquired, however, as well as the extent to which the moraic rhythm of Japanese influences the acquisition of other features of the language, such as vocabulary and grammar, are questions whose answers remain poorly understood.
Although understanding the speech of others is an everyday activity that we typically carry out unconsciously, comprehending language is in fact an extraordinarily complex feat of information processing. Listeners must divide the continuous speech stream they hear into syllables and words, retrieve the meaning of each word, group words together into phrases, and analyze how these phrases are related to each other syntactically. In our research on sentence comprehension, we endeavor to uncover the inner workings of this process - what information must be processed in what order, and how is this order determined?
Our focus is on the contribution of prosody to sentence comprehension. The speech that we encounter everyday is full of ambiguities that typically go unnoticed. For example, a phrase such as "red ribbons and boxes" can have two different meanings depending on how it is pronounced. If "ribbons" and "boxes" are placed in separate phrases ([red ribbons] and boxes), it means that only the ribbons are red, while if "ribbons and boxes" is pronounced as a single phrase (red [ribbons and boxes]), both ribbons and boxes are red.
Recent research has revealed that until the age of five or six, children understand such prosodic ambiguities somewhat differently than adults. In our lab, we have children listen to sentences containing ambiguities, and study how their comprehension is affected by prosody or other linguistic information. In some experiments,children are asked to choose the picture that matches the sentence from a group of pictures, while in others the children answer questions while looking at a picture book. We also use eye tracking technology which allows us to measure which part of a picture the child is looking at as they listen to a given sentence.