comparison of linguistic categories usage and distribution in blind and sighted students

langacker provided new schema-based descriptions of linguistic categories when he was questioning traditional theories of categorization. langecker's model of grammar deals with the reflection of grammatical subsystems of concepts related to space and time in language. also he explains how phenomena such as attention and point of view are encoded in language. the present research aimed to explore the differences of the three groups of sighted, semi-blind and blind students in terms of usage and distribution of linguistic categories. method: sampling method in this research was matched sampling method. so the sighted student group matched with visually impaired group in socialfactors. the research instrument was a researcher-made questionnaire revised after validity and reliability analysis. the new revised questionnaire was applied on three groups. participants were 160 students being educated at a primary school.  data were analyzed quantitatively and qualitatively. the results showed a higher mean rank for sighted groups in most of the linguistic categories on the questionnaire. in longacker's terms, the three groups' differences of mean rank were more considerable in questions asked about relational categories rather than nominal categories. also in line with previous research, the present study shows that semi-blind students acquire abstract words at older ages compared to their sighted and blind groups. the results of this study highlight that visually impaired students have a lower mean rank in both relational and nominal categories. it can be concluded that the visual perceptual impairments can cause serious damages partly to nominal categories and more widely to relational categories.