Testing Hypotheses About Language Disorders
by The intent of this section is to operationalize variation in language impairments as testable hypotheses that shape the assessment process. The tests, tasks, and measures used by the diagnostician are chosen specifically to allow a hypothesis to be confirmed (or not).The process described is shaped by my own work setting—a hospital-based outpatient clinic, where norm-referenced tests and criterion-referenced tasks are the most commonly used tools, but there is no question that the process would be enriched by direct observations of classroom performance and other models, including curriculum-based assessment and dynamic assessment.
Drawing from the previous discussion, I present three hypotheses as examples of the types of hypotheses that could be formulated. Each one is also restated as one or more questions to clarify the intended meaning. This is followed by a discussion of applicable assessment tools and decision pathways. The hypothetical child (or adolescent) in each hypothesis is Matthew. An important caveat to consider before starting this discussion is that norm-referenced tests seldom have enough items of any one type to allow examiners to draw absolute conclusions about a linguistic trait. The tools are used to test our working hypotheses. The fact that clinical hypotheses (in many medical and psychological practices) are working hypotheses that gather strength with time and accumulating evidence is not new. In the numbered points that follow, working hypotheses are listed, followed by related questions that will be used to test the hypotheses.
1. Matthew has a primary language impairment.
Is this a primary language impairment, isolated to language, or are there additional cognitive, social–emotional, medical/neurological factors that play a significant role?
This very basic question seems obvious but is nevertheless important to confirm (note that the hypothesis could have been stated in its dichotomous form—Matthew has a secondary language impairment). A careful developmental, medical, and educational history from the parent/caregiver usually provides the answer to this question. Obtaining copies of all relevant documents (e.g., medical records,psychoeducational evaluations, individualized educational plan documents) is critical. It is particularly important to verify cognitive status. Although researchers studying children with SLI typically invoke the criterion that participants score within 1 SD on a test of nonverbal intelligence, there is a literature on the longitudinal course of oral and written primary language impairment that has used a criterion of ±2 SDs (e.g., Ellis-Weismer et al., 2000; Rice, Tomblin, Hoffman, Richman, & Marquis, 2004). In these investigations, participants with a cognitive standard score of 85 or more are grouped separately from those whose scores fall between70 and 85. Not uncommonly, children in the latter group (termed nonspecific language impairment, or NLI) post lower scores on a variety of oral and written language tests and tasks. If cognitive test scores are not available in accessible records or historical information, a nonverbal cognitive measure, such as the Test of Nonverbal Intelligence, third edition (TONI-3) (Brown, Sherbenau, & Johnsen, 1997), can be administered. Determination of primary versus secondary status of a language impairment has implications not only for the linguistic phenotype (pattern of language strengths and weaknesses), as discussed previously, but also for prognosis because factors in addition to language per se can affect a child’s ability to learn.
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