This study introduced first language metalinguistic comments as an explicit focus on forms option and probed to investigate its effects on the accuracy and durability of Iranian EFL learners’ recognition of third person /s/ as measured by their performance on a grammaticality judgment test. To this purpose, two intact university classes including 63 participants, were randomly selected and assigned to experimental and comparison groups. Both groups were homogenized in terms of language and grammar proficiency. Based on their scores on the proficiency test, participants in groups were classified as lower-intermediates. Both groups received 6 hours of grammar instruction. The experimental group was instructed through first language metalinguistic comments and the comparison group through second language metalinguistic comments. The data analysis showed both groups improved their mean scores of accuracy on the immediate posttest. However, the results of the delayed posttest showed the superiority of the experimental group. It can be concluded that in situations where English is used as a foreign language, first language metalinguistic comments may have more durable effects than second language metalinguistic comments. The findings imply that the use of first language comments may help learners to become more cognitively conscious and linguistically aware of instructed grammar features.
