Holistic and combinatorial processing of Swedish tone accents in the brain: An MMN study

Abstract: All words in Swedish have a particular melody. There are two tonal patterns that are observed in different prosodic and morphological contexts – accent 1 and accent 2. The tone of accent 1 is the default melody in Swedish and is said to be of intonational nature. The melody of accent 2, on the other hand, only occurs in presence of certain suffixes in the word, hence, accent 2 is claimed to be a property of suffixes. This thesis investigated how these accents are processed in the native speakers’ brain. A hypothesis was raised suggesting that accent 1 is post-lexical and accent 2 is morphological. Two test implications were derived: 1) the melody of accent 1 is processed together with the word itself and in the brain they have a common, holistic representation, a so-called whole-word memory trace, and 2) accent 2 words are a feature of the suffix rather than of the entire word, so combinatorial processing is said to be involved when listeners hear accent 2 words. These test implications were investigated by conducting an electroencephalographic experiment designed to elicit a type of brain response that is called mismatch negativity. To elicit a mismatch response, a series of identical words was played to the study participants but every now and then a different, deviant word was inserted into the series. Four such pairs of standard and deviant words were used in the experiment, each pair probing into the neurophysiological responses to a particular combination of accent and suffix. The results corroborated the hypothesis and an additional discovery was made – there might be a difference not only in the way the tone accents are stored in the memory, but also in the way the suffixes are integrated into word representations in the memory, depending on the type of suffix. The accent-neutral suffix, also analysed as a clitic morpheme, elicited responses that pointed towards whole-word storage, whereas the accent 2-inducing suffix elicited responses indicative of combinatorial processing.