low the population mean for age, which translates to a standard score of 78 or less, which is
below the 7th percentile) are need ed 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 leni ent threshold may be used (e.g., 1.0–2.5 SD below the pop-
ulation mean for age), when learning diffic ulties 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 sc ores on available test measures.
A third core feature is that the learning di fficulties are readily apparent in the early
school years in most individuals (Criterion C) . However, in others, the learning difficulties
may not manifest fully until later school year s, by which time learning demands have in-
creased and exceed the individual’s limited capacities.
Another key diagnostic feature is that the learning difficulties  are considered “spe-
cific,” for four reasons. First, they are not attr ibutable to intellectual disabilities (intellec-
tual disability [intellectual developmenta l disorder]); global developmental delay;
hearing or vision disorders, or neurological or motor disorders) (Criterion D). Specific
learning disorder affects lear ning in individuals who othe rwise demonstrate normal lev-
els of intellectual functioning (generally estima ted by an IQ score of greater than about 70
[±5 points allowing for measurement error ]). The phrase “unexpected academic under-
achievement” is often cited as the defining ch aracteristic of specific learning disorder in
that the specific learning disabilities are not part of a more general learning difficulty as