Doctoral Dissertation Research: Units of orthographic complexity and their influence in speech production

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How does literacy impact speech? There is evidence that the number of symbols in the written form of a sound can influence how long that sound is produced, even when a written form is not explicitly present. For example, the final /k/ sounds in the English words "tic", "click", and "clique" are represented by 1, 2, and 3 letters, respectively. When people produce these words, the final /k/ of "click" is produced longer than than the final /k/ of "tic". And the final /k/ of "clique" is produced longer still. Therefore, it has been hypothesized that as the complexity of a written form increases, so too does the speech duration of the associated sound, all else being equal. This phenomenon is inconsistent with some models of language production which argue that written information should not influence speech, especially when written information is not explicitly present. Additionally, it remains unclear exactly which types of written information can influence speech duration as there is disagreement about the mechanisms that drive this effect. Some argue the relationship between sounds and written symbols underlie this effect. Others argue the amount of visual information itself regardless of any connection to sounds is driving these duration differences. This study examines the relationship between sounds, symbols, and speech duration to develop our understanding of what types of written information can alter speech patterns. Addressing this question will inform theoretical models of human speech production. Additionally, data collected through this research can be incorporated into computational speech synthesis and speech recognition systems for more accurate, robust, and natural models of human speech. A challenge of previous research in this area was that it relied upon natural speech data which includes many external factors across individuals that can influence speech duration outside of written forms (e.g. word frequency). To gain greater control of these variables, the current study will employ a three-day novel-word-learning experiment in which participants learn sets of novel non-word homophones along with one of several novel writing systems. Novel homophones in a set are learned as the same word phonologically but are written distinctly. Written complexity for homophones may vary by: a) number of whole characters; b) number of pen strokes; c) number of components with phonological associations; d) number of components without phonological associations. Participants will produce learned words in a picture-naming task without written forms explicitly present. Participants' production will be recorded and speech duration will be measured. Duration among homophones in a set and across writing systems will be compared to determine: a) if increased written complexity influences duration even when written forms are not explicitly present; b) which types of written information may influence duration and whether written complexity must have a phonological association to influence speech; and c) at which point in the training process speech patterns change and whether these patterns persist through the end of the experimental period. This data will comprise a portion of the doctoral dissertation. An earlier portion of the dissertation investigated similar durational phenomenon in Japanese speakers in regards to written character complexity. To remain consistent with previous data set, retain the ability to compare results from the current study with earlier data in the dissertation, and provide the opportunity to replicate previous findings in the current study, participants for the current study will be native Japanese speakers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.