The effect of orthographic depth on letter string processing: the case of visual attention span and rapid automatized naming

The present study investigated whether orthographic depth can increase the bias towards multi-letter processing in two reading-related skills: visual attention span (VAS) and rapid automatized naming (RAN). VAS (i.e., the number of visual elements that can be processed at once in a multi-element array) was tested with a visual 1-back task and RAN was measured in a serial letter naming task that introduced a novel manipulation (some letter sequences formed frequent words). Spanish-Basque and French-Basque bilingual children were tested at early (30 children in 1st and 2nd grade), and more advanced (24 children in 3rd, 4th and 5th grade) stages of reading acquisition to investigate whether they would be differently biased towards multi-letter processing due to reading in two shallow (Spanish, Basque), or a deep and a shallow (French, Basque) orthography. The French-Basque bilinguals, who read in a deep orthography, were expected to rely on larger orthographic units in reading and thus to be more biased towards multi-letter processing in both tasks. This was expected to be reflected by: (a) a uniform distribution of attention across letter strings in the VAS task, and (b) a greater interference of the embedded words on letter-by-letter naming in RAN, leading to longer naming times. The expected group differences were observed in the more advanced readers, with French-Basque bilinguals showing a wider distribution of VAS across letter strings and longer naming times in RAN.