First language researchers have proposed dozens of explanations why infants across cultures seem to acquire more nouns than verbs among their earliest words. No such finding has been documented among adult foreign language learners. I wished to determine whether adults have greater difficulty learning verbs than nouns, and if so, why that could be.

To investigate whether adult college students might learn concrete nouns or verbs better, I constructed and measured a list of noun and verb concepts, images, and auditory stimuli. I measured these stimuli on many dimensions with a mind to statistically control these extraneous factors when testing for differences in noun and verb learning (Study 1). In Studies 2 and 3 I trained participants with these words and tested their recognition of targets with multiple-choice tests. I then statistically controlled and measured the effects of measured and manipulated factors to see what confluence of factors affected word learning. While there was generally a noun bias effect, I found that methods of learning and delay qualified this effect (removing the noun bias at inferential learning, and reversing the word bias at one week), image media quality is of likely help to the learner, and cross-situational learning is greatly helpful. This dissertation concludes with a summary of findings and accounts of them. Although it remained partly unclear why nouns were generally learned better than verbs, Gleitman et al.'s (2006) surface variability hypothesis was taken as the most likely account for the noun bias observed among this sample of young adults.