Separating the effects of acoustic and phonetic factors in linguistic processing with impoverished signals by adults and children

Post written by Susan Nittrouer based on an article from Applied Psycholinguistics

Separating the effects of acoustic and phonetic factors in linguistic processing with impoverished signals by adults and children

Traditional models of psycholinguistic processing postulate that listeners recover phonemic structure from the acoustic speech signal and use it for further linguistic processing, largely discarding acoustic detail at the time that phonemes are accessed. An example of that perspective involves a commonly accepted model of verbal working memory in which a component of the memory system extracts phonemic elements and uses them as the ingredients for storing items in a short-term buffer.

Significant challenges for deaf individuals who use cochlear implants (CIs) are implicated by the traditional model. Although CIs can restore auditory sensitivity to normal levels, the acoustic structure of those signals remains highly degraded. The signal processing algorithms of the devices preserve little in the way of spectral detail, the kind of structure commonly shown to define phonemic categories. Physiological anomalies within the impaired auditory system further diminish signal quality, rendering the signal that is available to CI users bereft of the kind of structure needed to recover phonemic elements. In spite of this significant constraint, however, CI users are able to perform linguistic processes, albeit with some deficit and great effort.

In an interesting twist on the usual translation of basic-science findings to clinical application, the success of CI users raises the theoretical question of whether phonemic segments are recovered and utilized in linguistic processing to the exclusive extent that traditional models suggest. Alternatively, is it possible other kinds of acoustic structure serve as the stuff of linguistic processing? That question was addressed in the paper Separating the effects of acoustic and phonetic factors in linguistic processing with impoverished signals by adults and children.

A secondary question addressed by the study concerned the direction of effect. Traditional models suggest that listeners recover phonemic segments from acoustic structure, in a bottom-up manner. But is it possible that language users can access phonemes through a more indirect route, by recognizing whole words and using top-down knowledge of word structure to recover the phonemic elements shaping those words? That possibility was also addressed in this study.

To test these questions, adults and 8-year-old children were tested on verbal working memory and phonemic awareness tasks using unprocessed and two kinds of degraded signals. Results showed that listeners of both ages were able to perform the working memory task, even when signals were degraded such that access to phonemic structure was impaired. Furthermore, adults, but not 8-year-olds, seemed able to recover phonemic structure through the indirect route. These findings suggest that acoustic structure in the speech signal that is extraneous to phonemic categorization provides important information for linguistic processing.

Read the full article until June 30, 2014: “Separating the effects of acoustic and phonetic factors in linguistic processing with impoverished signals by adults and children” by Susan Nittrouer and Joanna Lowenstein

Leave a Reply

 

 

 

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>