How easily people are able to initially learn foreign language vocabulary depends on a number of different factors including effective variables such as motivation, anxiety, the cognitive processes involved in utilizing different strategies, and most relevant to the present study, linguistic features of the words themselves which is also known as mental lexicon. Thus, one of the major problems learners face in language learning either in EFL or ESL settings is the issue of vocabulary or the mental lexicon that has been changing constantly over time. Therefore, the current study aimed to find out if EFL learners’ crystallized intelligence can significantly correlate with their mental lexicon. To this aim, 80 EFL learners were asked to fill out a C-test which is a reliable instrument to measure crystallized intelligence, and the Lex30 word association test to measure their mental lexicon. Moreover, the study aimed at finding any significant differences between male and female EFL learners concerning their mental lexicon and crystallized intelligence. To analyze the data, Pearson Correlation and Independent sample T-Test were run. The results showed that there is a significant positive relationship between crystallized intelligence and mental lexicon with no significant differences between males and females. This research has some implications for teachers, supervisors, as well as syllabus designers in a way to achieve better language acquisition.
