This study was conducted to combine the scientific findings of the human brain, especially Reticular Activating System (RAS), or attention center in the brain, to an explicit approach of vocabulary instruction. The purpose of the present study is to examine the effects of a RAS-based instruction (RASBI) on learning vocabulary of EFL elementary students and then to compare it with translation based instruction (TBI). Sixty male participants were chosen from among 92 elementary EFL learners whose levels of proficiency were determined by Michigan test. The learners under study were randomly divided into two groups: the first group, consisting of 30 students, received a RAS-based vocabulary instruction (RASBVI). The other group, consisting of 30 students, received a translation based vocabulary instruction. Data analysis and statistical calculations of pre-tests and post-tests indicated that those participants who received RAS-based vocabulary instruction outperformed their counterparts in the second group that received translation based vocabulary instruction.