Abstract
A case study of a16 year-old male with a history of truancy issues that began in the first weeks of
grade nine, at age 14 years. “John” permanently left school in the first term of grade ten,
receiving credit for only two grade 10 classes. The behavior was uncharacteristic, given John’s
elementary school history of average school achievement, stable family support, good peer
relations, and lack of attentional or behavioral issues. At 16 years, John was given a
comprehensive psycho-educational assessment. Despite placing in the Above Average range on
the General Ability Index, WISC-V subtests of cognitive ability revealed significantly divergent
scores. In particular, any subtest involving numerals notably skewed scores downward. To tease
out a suspected learning disability of dyscalculia, domain specific subtests incorporating only
numerals were administered and compared to same-domain subtest scores utilizing only
vocabulary. Thus, “numerical” subtests could be segregated to identify a LD of dyscalculia,
whereas “non-numerical” subtests revealed a more accurate representation of John’s true
cognitive ability beyond dyscalculia. Results demonstrated that subtests entailing numerical
processing resulted in scores as low as the 1st percentile. What distinguishes dyscalculia from a
“lack of opportunity” for learning basic math facts is exceptionally poor performance in
subitizing tasks and retention/recall for numerals, both of which do not require mental
manipulation of digits or basic arithmetic skills. The segregated method of cognitive testing
uncovered extensive difficulties in mastering a sense of numbers, grasping and understanding the
size or quantity of numbers, learning number facts, and performing basic arithmetic calculations,
all characteristic of developmental dyscalculia.