title: Refining Stimulus Parameters in Assessing Infant Speech Perception Using Visual Reinforcement Infant Speech Discrimination: Sensation Level.
abstract: BACKGROUND
  Speech perception measures have long been considered an integral piece of the audiological assessment battery. Currently, a prelinguistic, standardized measure of speech perception is missing in the clinical assessment battery for infants and young toddlers. Such a measure would allow systematic assessment of speech perception abilities of infants as well as the potential to investigate the impact early identification of hearing loss and early fitting of amplification have on the auditory pathways.
  
  
  OBJECTIVE
  To investigate the impact of sensation level (SL) on the ability of infants with normal hearing (NH) to discriminate /a-i/ and /ba-da/ and to determine if performance on the two contrasts are significantly different in predicting the discrimination criterion.
  
  
  METHODS
  The design was based on a survival analysis model for event occurrence and a repeated measures logistic model for binary outcomes. The outcome for survival analysis was the minimum SL for criterion and the outcome for the logistic regression model was the presence/absence of achieving the criterion. Criterion achievement was designated when an infant's proportion correct score was >0.75 on the discrimination performance task.
  
  
  METHODS
  Twenty-two infants with NH sensitivity participated in this study. There were 9 males and 13 females, aged 6-14 mo.
  
  
  METHODS
  Testing took place over two to three sessions. The first session consisted of a hearing test, threshold assessment of the two speech sounds (/a/ and /i/), and if time and attention allowed, visual reinforcement infant speech discrimination (VRISD). The second session consisted of VRISD assessment for the two test contrasts (/a-i/ and /ba-da/). The presentation level started at 50 dBA. If the infant was unable to successfully achieve criterion (>0.75) at 50 dBA, the presentation level was increased to 70 dBA followed by 60 dBA. Data examination included an event analysis, which provided the probability of criterion distribution across SL. The second stage of the analysis was a repeated measures logistic regression where SL and contrast were used to predict the likelihood of speech discrimination criterion.
  
  
  RESULTS
  Infants were able to reach criterion for the /a-i/ contrast at statistically lower SLs when compared to /ba-da/. There were six infants who never reached criterion for /ba-da/ and one never reached criterion for /a-i/. The conditional probability of not reaching criterion by 70 dB SL was 0% for /a-i/ and 21% for /ba-da/. The predictive logistic regression model showed that children were more likely to discriminate the /a-i/ even when controlling for SL.
  
  
  CONCLUSIONS
  Nearly all normal-hearing infants can demonstrate discrimination criterion of a vowel contrast at 60 dB SL, while a level of ≥70 dB SL may be needed to allow all infants to demonstrate discrimination criterion of a difficult consonant contrast.
authors.affiliation: University of Colorado Denver School of Medicine, Aurora, CO.
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Uhler
authors.affiliation: University of Colorado Boulder, Boulder, CO.
authors.forename: Rosalinda
authors.initials: R
authors.lastname: Baca
authors.affiliation: University of Colorado Boulder, Boulder, CO.
authors.forename: Emily
authors.initials: E
authors.lastname: Dudas
authors.affiliation: University of Colorado Boulder, Boulder, CO.
authors.forename: Tammy
authors.initials: T
authors.lastname: Fredrickson
mesh_terms: D000161:Acoustic Stimulation; D005260:Female; D006309:Hearing / Q000502:physiology; D006801:Humans; D007223:Infant; D008297:Male; D010700:Phonetics; D010775:Photic Stimulation; D012054:Reinforcement, Psychology; D012677:Sensation / Q000502:physiology; D013067:Speech Perception / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology