When exposed to speech, children with normal hearing learn to listen, begin to babble, start imitating speech, develop an understanding of speech and language, and produce words. Children with hearing loss who are not fit with technology will not move on from babbling through the typical development of speech and language. However, if these children are fit early on with suitable technology and receive appropriate therapy, they will develop spoken language similar to that of their typically hearing peers. Having a systematic approach to differentiating auditory perception from speech production is vital to better management of a child with performance problems.
Children who can't hear soft speech will have significantly reduced language exposure. This can lead to critical problems in listening development since 85 percent of what children learn is incidentally overheard. If a child has limited auditory access to specific frequency ranges, then his or her errors will reflect such poor access. Poor access to high-frequency sounds will result in difficulties in producing fricative sounds and other high-frequency speech features. Inability to hear low-frequency sounds will result in issues that impact vowel perception and prosody. This limited access will negatively impact a child's language exposure and auditory brain development. Data from the Hart and Risley study clearly demonstrated that the amount of language to which children are exposed daily affects both their IQ and vocabulary at 3 years of age (See Table 1; Hart & Risley. Brooks Publishing, 1995).
PRODUCTION VS. PERCEPTION
Auditory perception refers to what one hears without visual cues, while speech production refers to the sound one makes. Production is generally the best indicator of perception because children typically produce phonemes the way they hear them. However, this is not always the case. Perception needs to be assessed when production is absent, disordered, or unintelligible. It is essential to determine whether an articulation error stems from poor perception or poor production because perception and production errors have different solutions.
CLINICIAN KNOWLEDGE BASE
Managing children with hearing loss involves multiple clinicians—all critical members of a team but each with different skills and knowledge base. Audiologists test hearing in children, assess speech perception, and program hearing technology. However, they might have limited knowledge of speech development. Listening and Spoken Language Specialists (LSLSs) are trained in managing speech perception and production through audition, but may have limited skills in managing speech production through motor, visual, or tactile means, which is the domain of expertise of speech-language pathologists (SLPs). Teachers of the Deaf who do not have LSLS training may not have the skills or experience to evaluate perception and production issues. Perception errors are generally the responsibility of the audiologist, who controls and adjusts technology settings. Production errors are generally the responsibility of LSLSs and SLPs, who work to develop a child's essential auditory skills, including perception.
FACTORS AFFECTING SPEECH PERCEPTION
Clinicians must address multiple factors and consider if the child can detect sound. We can determine if all the phonemes are audible by checking the aided audiogram. It is important to know how long the child has been listening to determine if this duration is sufficient to expect the child to be able to produce age-appropriate phonemes. A child with limited listening experience may not have adequate exposure to develop good perception or production. Children whose hearing loss is identified late or who are older when they start using appropriately fitted technology will have issues related to their limited listening experience.
We need to know that a child is hearing well enough in each ear and both ears together. Decreased audibility in one ear can result in decreased binaural perception. If auditory access is appropriate in both ears as identified by aided thresholds but speech perception is not as good in one of the ears, targeted therapy and dedicated listening time each day with the poorer ear alone may be necessary.
FACTORS AFFECTING SPEECH PRODUCTION
The primary factor that affects speech production is auditory access. To quote auditory-verbal education pioneer Daniel Ling, PhD: “What they hear is what they say.” If a child can't hear the /s/ sound, it will be very difficult for him or her to accurately articulate words with that phoneme. Thus, the first step is to assess a child's auditory access to determine if he or she can accurately perceive the entire speech spectrum and all speech phonemes using hearing technology.
Next, clinicians should be aware of the child's exposure to speech sounds that he or she may be struggling to produce. For example, people who speak Japanese do not have exposure to /l/ or /r/, so we cannot expect them to have those phonemes in their speech. Additionally, some children have oral motor problems and may have difficulty producing specific phonemes or speech features. However, caution is needed when evaluating an oral motor disorder. If a child can chew food with varied textures, close his or her lips when drinking from a cup or straw, or lick a lollipop, then oral motor problems are not likely to be the main source of the production problem. Other relevant disorders can include craniofacial disorders and feeding disorders. Children who eat through a gastrointestinal tube will have limited experience with specific mouth movements that may affect speech production. Overuse of pacifiers may alter the resting tongue position and promote atypical patterns of articulation. Children who are identified late may have poor articulation because of poor, long-standing production habits.
EVALUATION AND DIFFERENTIATION STRATEGIES
The audiologist, LSLS, and SLP all have a responsibility to distinguish detection, discrimination, identification, and production errors. To start, evaluate errors and seek answers to questions. For example, does the child know what phoneme he or she is listening for? If yes, then move on. Next, look for error patterns. Does the child make the same error and substitution every time and in all word positions? Does it matter what sounds surround the phoneme? Does the child make it in syllables at the phonetic level and/or in words at the phonologic level? Is it an auditory error pattern or specific to one phoneme?
Various tasks can be incorporated into therapy activities to assess the child. Visual cues must be eliminated when testing. The most appropriate test(s) must be used, which could be a combination of formal and informal tests, as well as open and closed set tests. The use of finger-point discrimination or identification tasks independent of production can help determine if a child can correctly perceive th difference between two phonemes. Word identification tools can also be used such as pictures, objects, or written words (book/cook; pat/mat/cat). Nonsense syllables are very useful as they don't require comprehension of specific vocabulary used. Same/different tasks are useful and can also be done with nonsense syllables.
Initial evaluations start with perception and progress to production. The Screening Auditory Discriminations test screens for discrimination and identification based on the Ling speech hierarchy using a neutral vowel and discriminating between consonant manner, voice, and place features. For example, if a child misses /f/ but produces frication, we know that he hears the fricative quality, but we do not know if he is hearing the specific phoneme. Table 2 shows an assessment grid for manner discrimination with different vowels’ contexts.
Formal perception tasks may include the Compass Test of Auditory Discrimination that analyzes errors by vowel and consonant features in different word positions. The Medial Consonant Test is beneficial in assessing perception using different vowel-consonant-vowel combinations (e.g., aba, ama, afa, ata, etc.). Recording the child's errors (e.g., producing /ada/ for /aba/) can also help illuminate the perception pattern errors. When testing infants, we can use the Visual Reinforcement of Infant Speech Discrimination, which uses a conditioned head turn to identify perception of specific phonemes (e.g., aashshaaa or ssshshshssss).
Selecting appropriate speech perception tests for audiologic evaluation can also assist in evaluating errors. Tests must be appropriate for the child's level. It is not suitable to use a speech perception test designed for preschool children on a child in third grade since it will not measure the performance required for listening at the child's grade level. When testing speech perception, it is very useful to record individual errors to identify perception error patterns and use this information to adjust technology settings.
Finally, all identified perception errors must be addressed through the audiologist's adjustments or changes to the child's hearing technology before commencing any targeted production therapy. However, once formal and informal assessments indicate that the child can accurately perceive the targeted phoneme and has had auditory exposure but cannot produce it, initiating articulation therapy would be appropriate.
ADDRESSING SPECIFIC CONCERNS
If concerns regarding speech perception and/or production errors are identified, clinicians must revisit the child's hearing and auditory access when using technology. When those issues are addressed, clinicians can then differentiate between the perception and production as discussed. Note the following steps to systematically address a child's condition:
- Check if the technology has been appropriately set and provides sufficient gain throughout the frequency range.
- Provide better access to any information the child is missing.
- Evaluate the device being used for possible distortion. Each device needs to be evaluated separately and in combination to ensure clear output.
- Ensure that the speech perception tests are appropriate for the child's age and language level. Facilitate children's full-time use of technology. If a child only wears the device for four hours a day, it will take him or her six years to hear what a child with normal hearing hears within one year. Not wearing technology full-time will lead to significant delays in speech and language development.
- Determine if the child is receiving sufficient language exposure. Is the child exposed to rich language models?
- Provide the child with therapy that builds listening and spoken language development.
Through careful analysis of perception and production, clinicians and hearing care teams can identify why a child is struggling. Data must be collected by everyone involved, including the child's parents and caregivers. Through this approach, the three main areas of focus—auditory access, auditory perception, and speech production—can be assessed comprehensively. Errors found during data collection and/or assessment should be addressed by the appropriate professional skilled in the area of concern. If auditory access is found to be inadequate, adjustments must be made. If perception pattern errors are identified, then the technology must be modified to optimize perception. If production is not deemed appropriate, then speech perception and auditory abilities must be improved through therapy.
We cannot stress it enough: “OK,” “adequate,” and “good enough” are not sufficient. With today's available technology and therapy, virtually all children with hearing loss can successfully learn to listen and speak. So if a child is not doing well, clinicians can and need to find out why—and fix it.