The /k/s, the /t/s, and the inbetweens : Novel approaches to examining the perceptual consequences of misarticulated speech

Abstract: This thesis comprises investigations of the perceptual consequences of children’s misarticulated speech – as perceived by clinicians, by everyday listeners, and by the children themselves. By inviting methods from other areas to the study of speech disorders, this work demonstrates some successful cases of cross-fertilization. The population in focus is children with a phonological disorder (PD), who misarticulate /t/ and /k/. A theoretical assumption underlying this work is that errors in speech production are often paralleled in perception, e.g. that children base their decision on whether a speech sound is a /t/ or a /k/ on other acoustic-phonetic criteria than those employed by proficient language users. This assumption, together with an aim at stimulating self-monitoring in these children, motivated two of the included studies. Through these studies, new insights into children’s perception of their own speech were achieved – insights entailing both clinical and psycholinguistic implications. For example, the finding that children with PD generally recognize themselves as the speaker in recordings of their own utterances lends support to the use of recordings in therapy, to attract children’s attention to their own speech production. Furthermore, through the introduction of a novel method for automatic correction of children’s speech errors, these findings were extended with the observation that children with PD tend to evaluate misarticulated utterances as correct when just having produced them, and to perceive inaccuracies better when time has passed. Another theme in this thesis is the gradual nature of speech perception related to phonological categories, and a concern that perceptual sensitivity is obscured in descriptions based solely on discrete categorical labels. This concern is substantiated by the finding that listeners rate “substitutions” of [t] for /k/ as less /t/-like than correct productions of [t] for intended /t/. Finally, a novel method of registering listener reactions during the continuous playback of misarticulated speech is introduced, demonstrating a viable approach to exploring how different speech errors influence intelligibility and/or acceptability. By integrating such information in the prioritizing of therapeutic targets, intervention may be better directed at those patterns that cause the most problems for the child in his or her everyday life.