This study evaluated college adults (N = 138) referred for learning problems using a Cattell-Horn-Carroll based intelligence measure (Woodcock Johnson-Revised: WJ-R) and spatial and executive function neuropsychological measures to determine processing abilities underlying math skills. Auditory and visual perceptual (WJ-R Ga and Gv), long- and short-memory (WJ-R Glr and Gsm), crystallized and fluid intellectual (WJ-R Gc and Gf), and spatial and executive function (Judgment of Line Orientation [JLO] and Category Test) measures differentiated those with and without math deficits. Multiple regression revealed selective processing abilities (Gf, JLO, and Category) predicting about 16% of the variance in math skills after variance associated with general intelligence (also about 16%) was removed. Cluster analysis found evidence for a selective spatial deficit group, a selective executive function deficit group and a double deficit (spatial and executive function) group. Results were discussed in relation to a double deficit hypothesis associated with developmental dyscalculia.

The Word Reading Test (WRT) was designed to detect effort problems specific to a learning disability sample. The WRT and the Word Memory Test (WMT) were administered to two simulator and normal control groups. The WRT showed excellent receiver operating characteristics (e.g., 90% sensitivity and 100% positive predictive power) and outperformed the WMT in detecting both reading and mental speed simulators. This finding and a double dissociation between reading and speed simulators on WRT errors and reaction time suggested specific effort effects while poor effort of simulators on the WMT suggested general effort effects. Results are supportive of the WRT as a potential effort indicator in learning disability.

Measures of orthographic and phonologic skills were related to co-normed Woodcock Johnson-Revised (WJ-R) cognitive measures in 138 college age, learning problem adults. Only orthographic deficits were associated with a processing disorder (p<.001). Selective processing abilities were associated with phonologic (p<.001, Delta adj R(2)=.053) and orthographic (p<.001, Delta adj R(2)=.047) skills after removal of variance associated with general intelligence. Analyses found common processing abilities across both phonologic and orthographic skills for WJ-R visual processing (-Gv) and short-term memory processing factors (Gsm) (p<.001). Cluster analysis established a phonologic deficit and a double deficit (phonologic and orthographic) group. Discussion relates results to the differences between adult and child reading decoding deficits, the lack of a selective orthographically impaired subtype of dyslexia, and the evidence of visual processing compensation for reading problems.