This article introduces this special issue of "Frontline Learning Research." The first paper offers a methodological guide using Ericsson & Smith's (1991) "expert performance approach." This is followed by three papers that analyze the use of eye tracking in visual expertise models, and a paper reviewing the use of methods…

In the present study we examined whether children with Developmental Dyscalculia (DD) exhibit a deficit in the so-called "Approximate Number System" (ANS). To do so, we examined a group of elementary school children who demonstrated persistent low math achievement over 4 years and compared them to typically developing (TD), aged-matched…