This study investigated a method used to determine whether children were using implicit phonology in making a choice between phonologically legal and illegal nonwords. An additional aspect was also investigated, this being the role of association value in making a choice. In Experiment 1, which used the original pairings found in Messer (1967), it was found that adults prefered the legal nonwords over the illegal nonwords. These are the same results which were found by Messer using children as subjects. An additional analysis was done, and it was found that subjects used association values in making a judgment only when the stimuli were phonologically legal. In Experiment 2, when both members of the pair were either legal or illegal and one had a high associative value and one had a low associative value, it was found that subjects used association values in making a judgment only when both members of the pair were legal. In Experiment 3 the legal member of the pair had a low associative value while the illegal member had a high associative value. It was found that there was not a preference for either member of the pair. In Experiment 4, the legal and illegal members of each pair had approximately the same associative value, and the legal member of the pair was prefered over the illegal member. The results of these four experiments were related to the internal lexicon and hypotheses made about it by Rubenstein, Lewis and Rubenstein (1971). / Master of Science