Obligatory grammatical categories and the expression of temporal events

Thai has imperfective aspectual morphemes that are not obligatory inusage, whereas English has obligatory grammaticized imperfectiveaspectual marking on the verb. Furthermore, Thai has verb finaldeictic-path verbs that form a closed class set. The current studyinvestigated if obligatoriness of these grammatical categories in Thaiand English affects the expression of co-occurring temporal events andactions depicted in three different short animations. Ten children agedfour years, five years, six years and seven years, and ten adults as acomparison group from each of the two languages participated. Englishspeakers explicitly expressed the ongoingness of the events more thanThai speakers, whereas Thai speakers expressed the entrance and exitof protagonists depicted in the animations significantly more thanEnglish speakers. These results support the notion that obligatorygrammatical categories shape how Thai and English speakers expresstemporal events or actions.