This study investigated the effects of processing three types of texts, namely expository texts, narrative texts, and a combination of both known as twin texts, on incidental vocabulary acquisition and retention in L2 learners. College freshmen (N = 109), who were lower to upper intermediate learners of English, were assigned into a control group and three experimental groups representing different reading conditions. Over a period of seven weeks, the experimental groups engaged in two reading sessions to read their assigned texts accompanied by output tasks and input enhancement. The participants’ receptive and productive vocabulary gains were measured with an immediate posttest and a delayed posttest to assess retention. Results revealed significant impacts of text genres on L2 incidental vocabulary learning and retention. Processing twin texts and expository texts yielded significantly greater vocabulary gains than processing narrative texts alone. These effects might be due to different processing mechanisms required for texts structured in distinct ways. Expository texts are informative and explanatory in nature, providing explicit and contextually rich information for word comprehension and retention.

This study examines the claim that vocabulary learning and retention are dependent on a task's involvement load (i.e., need, search, evaluation), as proposed by Hulstijn and Laufer (2001a). The study aims at comparing the effects of task types and task involvement load on vocabulary retention for Korean EFL university students. More specifically, this study was designed to test whether differential levels of task involvement loads lead to equally effective results to vocabulary retention when the total involvement index being equal. Three types of productive word-focused tasks (gap-filling using a dictionary, writing original sentences, and gap-filling through word transformation) were used to examine the interplay of involvement index and task types. The result indicated that there were significant main effects of task types, test types, and proficiency levels. The results also indicated that there were significant interaction effects of task types on the retention tests, proficiency levels on the retention tests, and task types×proficiency levels on the retentions. The pedagogical implications and further research directions are discussed.