Two forms of implicit learning in young adults with dyslexia

Abstract

Implicit learning is thought to underlie the acquisition of many skills including reading. Previous research has shown that some forms of implicit learning are reduced in individuals with dyslexia (e.g., sequence learning), whereas other forms are spared (e.g., spatial context learning). However, it has been proposed that dyslexia-related motor dysfunction may have contributed to the implicit sequence learning deficits reported earlier. To assess implicit sequence learning in the absence of a motor sequence, 16 young adults diagnosed with dyslexia (20.6 +/- 1.5 years) and 18 healthy controls (20.8 +/- 2.0 years) completed a triplet frequency learning task (TRIP) that involved learning a sequential regularity in which the location of certain events followed a repeating pattern, but motor responses did not. Participants also completed the spatial contextual cueing task (SCCT), which involved learning a spatial regularity in which the location of distractors in some visual arrays predicted the target location. In addition, neuropsychological tests of real-word and pseudo-word reading were administered. TRIP task analyses revealed no between-group differences in pattern learning, but a positive correlation between individual learning scores and reading ability indicated that poor readers learned less well than did good readers. Thus, earlier reports of reduced implicit sequence learning in dyslexics cannot be entirely accounted for by motor sequencing deficits. No significant correlations or group differences in learning were found for SCCT. These findings offer additional evidence for a link between poor reading and impaired implicit sequence learning.

Figure 1

For the TRIP task, responses to high frequency (circle) and low frequency (square) triplets for the control (closed) and dyslexic (open) groups on mean of median reaction time (ms) and mean accuracy (proportion correct) measures.

Figure 2

For the SCCT, responses to familiar (circle) and novel (square) arrays for the control (closed) and dyslexic (open) groups on mean of median reaction time (sec) and mean accuracy (proportion correct) measures.

Figure 3

Scatter plots separately comparing learning scores for the TRIP task (accuracy) and SCCT (reaction time) to the measure of pseudo-word reading (age-scaled score) for the control (closed circle) and dyslexic (open circle) groups.