This study investigated the effect of two different types of offline planning, namely cooperative and individual, on the oral proficiency of impulsive and reflective EFL learners. Accordingly, 114 intermediate learners studying at a private language school in Tehran were chosen nonrandomly through their performance on a Preliminary English Test (PET). The participants also filled out the Eysenck and Eysenck’s (1991) Impulsiveness Questionnaire (EIQ) through which they were categorized into two subgroups within each offline planning setting consisting of impulsive and reflective learners. All in all, there were four subgroups: 28 impulsive and 28 reflective learners undergoing the cooperative offline planning treatment, and 32 impulsive and 26 reflective learners experiencing the individual offline planning treatment. Following the 14-session treatment, the mean scores of all four groups on the speaking posttest were computed and a two-way ANOVA was run to test all the four hypotheses raised in the study. The results revealed that the effect of offline planning to a great degree depends on the cognitive learning style of the learners: while impulsive learners benefit more from cooperative offline planning, reflective ones prefer to perform the task individually.
