On the age of acquisition effects in word naming and orthographic transparency: mapping specific or universal?

One account for age-of-acquisition (AoA) effects in word naming is the arbitrary mapping hypothesis proposed by Ellis and Lambon Ralph (2000), who argue that these should be stronger when arbitrary rather than consistent mappings between representations are involved. The arbitrary mapping hypothesis predicts that AoA effects should be reduced when reading words in languages with transparent orthography-to-phonology mappings. This prediction was put to the test in the transparent orthography of Turkish. Early and late acquired Turkish words matched on frequency, imageability, initial phoneme, and length were presented for naming. Early acquired words were read aloud reliably faster than late acquired words, thus failing to support the claims of the arbitrary mapping hypothesis. The implications of this finding are discussed within current theoretical frameworks accounting for AoA effects and orthographic transparency.