Evidencing the developmental shift from reactive to proactive control in early childhood and its relationship to working memory.

As they age, children tend to get more effective at regulating their behavior in complex situations; this improvement in cognitive control is often interpreted as a shift from predominantly reactive control to proactive control. There are three issues with this interpretation. First, hard evidence is lacking that younger children actually rely on reactive control. Second, the precise age range when such a shift would occur is still unclear. Third, the reasons for this shift have not been explored. In the current study, we tested the hypothesis that children under 5 years of age do rely on reactive control, that they progressively shift to proactive control with age, and that this shift is related to increases in working memory capacity (which is necessary for proactive control). Children aged 4 to 7 years performed a cognitive control task, the AX-CPT (AX-Continuous Performance Task), as well as verbal and visuospatial working memory tasks. Using the paradigmatic AX-CPT in this age range allowed us to observe, for the first time, an actual reactive pattern in children under 5 years of age. There was a progressive shift from reactive control to proactive control, with an estimated turning point between 5 and 6 years of age. The effect of age on proactive control was essentially shared with working memory capacity, confirming that these two cognitive processes develop in tandem.

Vocabulary skills are well developed in university students with dyslexia: Evidence from multiple case studies.

Most studies in adults with developmental dyslexia have focused on identifying the deficits responsible for their persistent reading difficulties, but little is known on how these readers manage the intensive exposure to written language required to obtain a university degree. The main objective of this study was to identify certain skills, and specifically vocabulary skills, that French university students with dyslexia have developed and that may contribute to their literacy skills. We tested 20 university students with dyslexia and 20 normal readers (matched on chronological age, gender, nonverbal IQ, and level of education) in reading, phonological, vocabulary breadth (number of known words), and vocabulary depth (accuracy and precision) tasks. In comparing vocabulary measures, we used both Rasch model and single case study methodologies. Results on reading and phonological tasks confirmed the persistence of deficits in written word recognition and phonological skills. However, using the Rasch model we found that the two groups performed at the same level in the vocabulary breadth task, whereas dyslexics systematically outperformed their chronological age controls in the vocabulary depth task. These results are supplemented by multiple case studies. The vocabulary skills of French university students with dyslexia are well developed. Possible interpretations of these results are discussed.