Mohammad Reza Khodadust - Assistant Professor, English Department, Farhangian University, Tehran, Iran
Parviz Jalili - MA in TEFL, English Department, Payame Noor University, Tabriz, Iran

Learning English, as the global lingua franca of the century, as well as its skills, subskills, and components including vocabulary, has recently gained prime importance. Moreover, learning words is a serious challenge for some L2 learners today, and many scholars have exercised their utmost efforts to locate efficient techniques of teaching/learning L2 vocabulary. On the other hand, educators have attempted to facilitate the process of L2 vocabular acquisition by means of newly-developed software. In this line, the present quantitative study was an attempt to examine the effect of Narcis-based teaching of ‗504 Absolutely Essential Words‘ to Iranian introvert/extrovert EFL Learners' lexical knowledge. To this end, 120 intermediate EFL learners were randomly selected and their homogeneity was checked using Nelson test. After administering Vocabulary Knowledge Knowledge (VKS) to identify the learners‘ vocabulary knowledge prior to the treatment and Eysenck Personality Test to identify the introvert and extrovert learners, they were randomly categorized into two experimental and two control groups. The treatment was offered in the form of Narcis-based teaching of 504 words, in a span of one month. Meanwhile, control groups were taught by using the regular 504 book. Comparison and SPSS analysis of post-test scores and VKS scores in the groups showed that there was no significant difference between mean posttest scores of the learners in the experimental and control groups indicating that the use of Narcis-based 504 teaching had no significant effect on vocabulary acquisition of Iranian introvert/extrovert EFL learners. This has implications for language policy makers, educators, and material developers.