Specific language impairment
Bob McMurray, J. Bruce Tomblin, Cheyenne Munson, and W. Dan McEchron
SLI is a language disorder that affects approximately 8% of the children in Iowa. (For comparison, both autism
and down's syndrome affect less than 1%.) SLI is characterized by poor language use in the absence of any obvious cause:
SLI children have normal non-verbal intelligence, no developmental disorders, no neurological disorders,
good articulation (pronunciation), and good hearing. Nonetheless they struggle with many different aspects of
language. With this project, in collaboration with the Child Language
Research Center, we have been investigating how children with SLI understand and process spoken words.
We've been using eye-tracking tasks with these children as we do with normal adults, comparing performance between
SLI adolescents and their age-matched peers.
In the sample display shown above, study participants were asked to click on a critical target picture like the peach while we varied the VOT along a continuum, such as peach to beach. You can click below to hear the beach-peach continuum, although participants only heard one word (not a whole continuum) on each trial.
While subjects listened to the target word (e.g. peach) we examined how often they looked at the competitor object, beach. We found that language impaired participants made more looks to the competitor overall, but they were not any more sensistive to small changes in VOT than were their typically-developing peers—the slopes of the lines below do not differ by group on either side of the VOT continuum.
In addition to our behavioral data collection, we are able to use models of word recognition like TRACE to understand the mechanisms behind these impairments at a deeper level. With these models we can selectively impair certain core processes. For example, we might slow the rate that activation flows from phonemes to words, damage its ability to retain the input over time, or decrease the competition between lexical items. We can then match the predictions of TRACE to our eye-tracking data and pinpoint what part of the system may not be working properly.
Presentations:
Munson, C., McEchron, W. D., McMurray, B., & Tomblin, J. B. (2008, November).
Perceptual sensitivity to within-category acoustic variation by language impaired and typically developing adolescents.
Poster presented at the 156th Meeting of the Acoustical Society of America. Miami, FL.
poster
Munson, C., McEchron, W. D., McMurray, B., & Tomblin, J. B. (2008, June).
Gradient perception of within-category acoustic detail by normal and language impaired listeners.
Poster presented at the Symposium on Research in Child Language Disorders. Madison, WI.
poster