Cross-linguistic transfer in bilingual reading is item specific

The grain size of orthographic representations prompted by a consistent orthography (like Spanish or Basque) increases if reading is simultaneously learned in another language with an inconsistent orthography (like French). Here, we aimed to identify item properties that trigger this grain-size accommodation in bilingual reading. Twenty-five French-Basque and 25 Spanish-Basque bilingual children attending Grade 3 read Basque words and pseudowords containing "complex" letter clusters mapping to one sound in French but several sounds in Basque or Spanish, and "simple" letter clusters mapping to the same sound structure in all three languages. Only French speaking children read "complex" Basque words faster than "simple" ones, suggesting that they accessed multi-letter "French" units to boost lexical processing. A negative complexity effect was found for pseudowords across groups. We discuss the existence of flexible cross-linguistic transfer in bilingual reading, proposing that the grain size of orthographic representations adjusts to item-specific characteristics during reading.