One essential feature of specific learning disorder is persistent difficulties learning key- stone academic skills (Criterion A), with onset during the years of formal schooling (i.e., the de- velopmental period). Key academic skills include reading of single words accurately and ﬂuently, reading comprehension, written expression and spelling, arithmetic calculation, and mathematical reasoning (solving mathematical problems). In contrast to talking or walking, which are acquired developmental milestones that emerge with brain maturation, academic skills (e.g., reading, spelling, writing, mathematics) have to be taught and learned explicitly.
Specific learning disorder disrupts the normal pattern of learning academic skills; it is not sirn- ply a consequence of lack of opportunity of learning or inadequate instruction. Difficulties mastering these key academic skills may also impede learning in other academic subjects (e.g., history, science, social studies), but those problems are attributable to difficulties learning the underlying academic skills. Difficulties learning to map letters with the sounds of one’s lan- guage—to read printed words (often called dyslexia)—is one of the most common manifesta- tions of specific learning disorder. The learning difficulties manifest as a range of observable, descriptive behaviors or symptoms (as listed in Criteria A1—A6). These clinical symptoms may be observed, probed by means of the clinical interview, or ascertained from school reports, rat- ing scales, or descriptions in previous educational or psychological assessments. The learning difficulties are persistent, not transitory. In children and adolescents, persistence is defined as restricted progress in learning (i.e., no evidence that the individual is catching up with class- mates) for at least 6 months despite the provision of extra help at home or school. For example, difficulties learning to read single words that do not fully or rapidly remit with the provision of learning disorder. Evidence of persistent learning difficulties may be derived from cumulative school reports, portfolios of the child’s evaluated work, curriculum—based measures, or clinical interview. In adults, persistent difficulty refers to ongoing difficulties in literacy or numeracy skills that manifest during childhood or adolescence, as indicated by cumulative evidence from school reports, evaluated portfolios of work, or previous assessments.
A second key feature is that the individual’s performance of the affected academic skills is well below average for age (Criterion B). One robust clinical indicator of difficulties learning academic skills is low academic achievement for age or average achievement that is sustain- able only by extraordinarily high levels of effort or support. In children, the low academic skills teacher’s grades or ratings). Another clinical indicator, particularly in adults, is avoidance of activities that require the academic skills. Also in adulthood, low academic skills interfere with port or report by others). However, this criterion also requires psychometric evidence from an individually administered, psychometrically sound and culturally appropriate test of aca- demic achievement that is norm-referenced or criterion-referenced. Academic skills are dis- tributed along a continuum, so there is no natural cutpoint that can be used to differentiate individuals with and without specific learning disorder. Thus, any threshold used to specify what constitutes significantly low academic achievement (e.g., academic skills well below age expectation) is to a large extent arbitrary. Low achievement scores on one or more standard- ized tests or subtests within an academic domain (i.e., at least 1.5 standard deviations [SD] be- low the population mean for age, which translates to a standard score of 78 or less, which is below the 7th percentile) are needed for the greatest diagnostic certainty. However, precise scores will vary according to the particular standardized tests that are used. On the basis of clinical judgment, a more lenient threshold may be used (e.g., 1.0—2.5 SD below the pop- ulation mean for age), when learning difficulties are supported by converging evidence from clinical assessment, academic history, school reports, or test scores. Moreover, since standardized tests are not available in all languages, the diagnosis may then be based in part on clinical judgment of scores on available test measures.