Acta Psychologica 50 (1982) 21-34 North-Holland Publishing Company 21 zyxwvutsrqp WORD AGE-OF-ACQUISITION AND LEXICAL DECISION MAKING * K.J. GILHOOLY and R.H. LOGIE zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO University of Aberdeen, Scotland, UK Accepted March 1981 This paper reports two experiments concerning the effects of word age-of-acquisition and other word attributes on speed of lexical decision. Analyses of group average data indicated that word length, frequency and familiarity were the major determinants of decision speed. Previous reports of age-of-acquisition effects on lexical decision are attributed to failures to control for word familiarity. A number of recent studies have reported effects of word age-of-acqui- sition on adult performance in a range of verbal tasks. In particular, age effects have been reported for tasks involving retrieval from lexical memory, such as picture naming (Carroll and White 1973a), category instance naming (Loftus and Suppes 1972) and word completion (Gil- hooly and Gilhooly 1979). In these tasks, earlier acquired words have generally been retrieved more readily than later acquisitions. It should be mentioned at this point that age-of-acquisition has usually been mea- sured by having adults rate words in terms of when they think that they learned the words. Although this procedure may seem implausible, such ratings (e.g. Carroll and White 1973b; Gilhooly and Hay 1977; Gilhooly and Logie 1980) have been found to be reliable. Furthermore, the valid- ity of the ratings has been checked with favourable results, (a) by making comparisons between adults’ ratings and the average age at * This research was supported by grant HR 5957 from the (United Kingdom) S.S.R.C. Thanks are due to A. Thomassen, A. de Groot and two anonymous referees for helpful comments on an earlier version of this paper. Requests for reprints should be sent to K.J. Gilhooly, Dept. of Psychology, University of Aberdeen, King’s College, Old Aberdeen AB9 2UB, Scotland, UK. 0001-69 18/82/0000-0000/$02.75 0 1982 North-Holland