Recent masked priming studies investigating the recognition of letters with diacritics with native readers of the script have consistently yielded an asymmetric pattern of priming such that a base-letter prime without the diacritic speeds up the recognition of the letter with a diacritic almost as much as an identity prime, but not vice versa (e.g., á-Á ≦ a-Á, but a-A ≪á-A). Here we tested English readers unfamiliar with diacritics in a letter match task using Japanese kana and the vowel letters of the Latin alphabet, and found the asymmetry was reduced to a negligible level (á-Á ≦ a-Á, and a-A ≦ á-A) (Experiments 1 and 2). However, the diacritic novices showed the asymmetric pattern of priming like the diacritic experts when the task condition explicitly required the letters with and without diacritics to be distinguished (Experiments 3 and 4). These results are explained in terms of how expertise moderates an early letter identification process in interpreting a visual feature as noise, or a signal diagnostic of letter identity. (PsycInfo Database Record (c) 2023 APA, all rights reserved).