Does morphology affect phonetic characteristics?

Yes, is the short answer. The long answer: it depends on how well you learned the connection between a morphological function and  the word, the sound and the context in which the word is located.

Long story short: the better you learned this connection, and consequently the more sure you are the message you want to convey, the longer you make the phonetic signal.

Together with my colleagues Mirjam Ernestus, Ingo Plag and Harald Baayen we were able to show this relation in word-final [s] or [z] in American English and the morphological function it expresses, e.g. plural in ‘dogs’ or third person singular in ‘takes’.

To simulate learning with a computer, we used Naive Discriminative Learning (NDL), a computational formalization of Discriminative Learning. Discriminative learning assumes that speakers learn to discriminate their environment by language. Listeners on the other hand learn to use the perceived signal to predict the message the speaker intended. The theory predicts that the amount of experience speakers and listeners have with the relation between message and signal will affect their behavior. In speakers, it is the behavior is the production of the speech signal which encodes the message; in listeners, the behavior is how they respond to the signal. Here, we studied the speakers.

We operationalized the intended message as the morphological function a word has to convey and the cues as the intended acoustic signal. NDL thus learned to discriminate the morphological function on the basis of the acoustic cues. Crucially, our model used cues from the target word such as ‘dogs’ or ‘takes’, but also from words in the context of those words. The reason for this is that we assume that a word’s morphological function is not only encoded by the acoustics of the word itself, but by the acoustics of the words surrounding it.

NDL further allows to calculate measures about 1) how well the morphological function is supported by a set of cues and 2) how uncertain the model is about the lexical information. Take a driving on the highway as an example. Let’s say, you are waiting for an exit to leave the highway and finally a sign occurs. The larger an exit sign on the street, the more support you have that an exit will occur. However, the size of the sign does not say anything about how certain (or uncertain) you actually are that it is actually the exit you should take. Both will affect how you will behave on the street.

To sum it up, NDL allows you to simulate how morphological function and the phonetic signal are connected and therefore to investigate how the processes guiding speech production affect the phonetic signal

Interaction_Adiv_Act_LastDiphone.png
The Figure shows how [s] duration is affected by the interaction between bottom-up support (x-axis) and uncertainty (y-axis) about a word’s morphological function. Blue regions represent short durations, yellow regions represent long durations.

The entire study will be published under the title:

Phonetic effects of morphology and context: Modeling the duration of word-final S in English with NaÏve Discriminative Learning

It has been accepted for publication by the “Journal of Linguistics” and is being prepared for publication. A pre-publication version can be downloaded from psyarxive here.

The paper also provides a very good introduction to Discriminative Learning, how it is performed and how it can be used for predicting phonetic characteristics. If you want to perform an NDL learning simulation on your own, you can find an introduction to this technique in my R introduction here.

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