Re-evaluating age-of-acquisition effects: are they simply cumulative-frequency effects?

The time it takes to read or produce a word is influenced by the word's age of acquisition (AoA) and its frequency (e.g. Quarterly Journal of Experime ntal Psychology 12 (1973) 85). Lewis (Cognition 71 (1999) B23) suggested th at a parsimonious explanation would he that it is the total number of times a word has been encountered that predicts reaction times. Such a cumulativ e-frequency hypothesis. however, has always been rejected because the stati stical effects of AoA and frequency are additive. Here, it is demonstrated mathematically that the cumulative-frequency hypothesis actually predicts s uch results when applied to curvilinear learning. Further, the data from fo ur influential studies (two of which claim support for independent effects of AoA and frequency) are re-analyzed to reveal that, in fact, they are con sistent with a cumulative-frequency hypothesis. The conclusion drawn is tha t there is no evidence with which to refute the most parsimonious of explan ations, i.e, cumulative frequency can account for both frequency and AoA ef fects. (C) 2001 Elsevier Science B.V. All rights reserved.