Estimating when and how words are acquired: A natural experiment on the development of the mental lexicon

Purpose: Sensitivity of subjective estimates of age of acquisition (AOA) and acquisition channel (AC; printed, spoken, signed) to differences in word exposure within and between populations that differ dramatically in perceptual experience was examined. Methods: Fifty participants with early-onset deafness and 50 participants with normal hearing rated 175 words in terms of subjective AOA and AC. Additional data were collected using a standardized test of reading and vocabulary. Results: Participants with early-onset deafness rated words as learned later (M = 10 years) than did participants with normal hearing (M = 8.5 years), F (1, 99) = 28.59, p < .01. Group-averaged item ratings of AOA were highly correlated across the groups (r = .971) and with normative order of acquisition (deaf: r = .950, hearing: r = .946). The groups differed in their ratings of AC (hearing: printed = 30%, spoken = 70%, signed = 0%; deaf: printed = 45%, spoken = 38%, signed = 17%). Conclusions: Subjective AOA and AC measures are sensitive to between- and within-group differences in word experience. The results demonstrate that these subjective measures can be applied as proxies for direct measures of lexical development in studies of lexical knowledge in adults with prelingual onset deafness.