Analyzing the effectiveness of incidental and intentional vocabulary learning in SLA

Abstract

This research synthesis examines the effectiveness of incidental and intentional vocabulary learning strategies in second language acquisition, aiming to give an answer to what approach fosters better lexical retention among students. While incidental learning occurs unconsciously through exposure to the target language, intentional learning requires conscious and structured efforts. This research synthesis is a systematic review of 20 empirical studies published in the last 15 years. Studies which employed quantitative, qualitative or mixed methods were selected, as well as research focused on vocabulary development of L2 learners. The present study aims to compare the usage of intentional and incidental approaches across proficiency and educational levels. Based on the analysis of the literature, it can be concluded that intentional learning stands out among beginners, providing faster vocabulary gains by explicit instruction, meanwhile incidental learning showed more benefits for those who already possess an intermediate to advanced level. Nevertheless, a mixed approach was confirmed to be the most effective strategy, providing balance with the strengths of each method. Additionally, this synthesis highlights the lack of research analyzing the impact of incidental learning at the beginner stage, as well as the relatively limited investigation conducted in non-Asian countries. Finally, tailored instruction based on proficiency, extensive input activities, and vocabulary recycling are recommended as practical strategies.