AN ERP STUDY ON THE SEMANTIC PROCESSING OF UNAMBIGUOUS NOUN, UNAMBIGUOUS VERB AND VERB-NOUN AMBIGUOUS WORD IN MANDARIN CHINESE

This paper is intended to explore the semantic processing of unambiguous noun, unambiguous verb and verb-noun ambiguous word in Mandarin Chinese by using event-related potentials (ERP). The experiment, which was conducted in the lexical decision task, contained four sets of stimuli: disyllabic unambiguous nouns (UN), unambiguous verbs (UV), verb-biased (V-VN) and noun-biased (N-VN) verb-noun ambiguous words. The results showed that the amplitude values of P2 and N400 corresponding to the semantic processing were greater for UN and UV than for V-VN and N-VN and UN elicited greater P2 and N400 than UV. Furthermore, the results indicated that the N400 component included a frontal "imagistically sensitive N400" and a posterior "linguistically sensitive N400". The amplitudes of N400 activated by UN and UV were more negative than those of V-VN and N-VN on the frontal electrodes because UN and UV were more concrete than V-VN and N-VN. Meanwhile, N400 on the posterior scalp sites was related to semantic features. UN that designated men and things elicited higher N400 than UV, V-VN and N-VN; UV that referred to action and behaviors elicited higher N400 than V-VN and N-VN; V-VN and N-VN that referred to behaviors and designated event elicited smaller N400 values. Besides, N-VN elicited a LPC component that was the reflection of confidence in the decision-making process, with more positive magnitude than UN, UV and V-VN. It indicated that the decision confidence of N-VN was greater than that of UN, UV and V-VN because N-VN was more notable in semantic activation. V-VN that had multiple meanings elicited higher LPC than UN and UV on some electrodes, indicating that the decision confidence was higher for V-VN than for UN and UV. Since both UN and VN had a single meaning, they were less notable in semantic activation, which resulted in less decision confidence and lower LPC amplitudes. The results of LPC reflected the continuum of grammatical classes as "UV-V-VN-N-VN-UN', which provided the supporting evidence for the conformance of syntax level and semantic level.