How the time reference of a sentence is processed based on the grammatical marking of the verb has already been explored in several languages with grammatical tense and aspect. It can also be grammatically expressed according to the reality status of the event (whether the event exists in time, realis mood, or not, irrealis). This study reports results from an acceptability judgment experiment in Paiwan, a Formosan language which exhibits a realis-perfective/irrealis distinction. By placing realis-perfective and irrealis markers after deictic past or future time adverbs and manipulating the grammaticality of the sentences, we asked which temporal concord violation (i.e., realis-perfective or irrealis) was harder to detect. The temporal concord violation of the realis-perfective marker induced greater processing difficulties (interactions between time reference and mood marking revealed lower accuracy rates and longer reaction time), but not the irrealis marker, in line with previous hypotheses. These processing difficulties may be partly due to the Paiwan realis mood marker which also encodes perfective aspect meaning. The reanalysis of the design of previous studies indicates that the interaction with perfective aspect also led to additional processing cost, suggesting that perfective aspect marking plays a crucial role in the processing of time reference.

This study investigates whether the perceptual salience of grammatical morphemes influences the online processing of temporarily ambiguous sentences during adult first-language (L1) comprehension. In a bidirectional self-paced reading task, adult L1 English participants (N = 44) read sentences with time adjuncts that were in a structural position in which they could attach either to the most recent verb phrase (VP) or to a VP in a higher clause. Consistent with previous findings, the reading times on these sentences indicated processing difficulty when this adjunct allowed only for high attachment. Crucially, this effect was modulated by the perceptual salience of the grammatical morphemes used to indicate time reference in these clauses. Specifically, the processing cost for high attachment was larger when time in the lower clause was indicated by the auxiliary verb will compared to when it was indicated by the relatively less salient past -ed morpheme. These findings were taken to indicate that the influence of perceptual salience extends beyond the acquisition of and sensitivity to grammatical morphemes during L1 and L2 development. Rather, the perceptual salience of these forms also appears to affect online structural processing during adult L1 sentence comprehension.

In the current study, we examined how adult heritage and monolingual speakers of Turkish process evidentiality (the linguistic expression of information source) through finite verb inflections and time reference, expressed on non-finite participles. A sentence-verification task was used to measure participants’ sensitivity to evidentiality and time-reference violations in Turkish. Our findings showed that the heritage speakers were less accurate and slower than the monolinguals in responding to both evidentiality and time-reference violations. Also, the heritage speakers made more errors and had longer RTs when responding to evidentiality violations as compared to time-reference violations. The monolinguals had longer RTs (and more accurate responses) to time reference than to evidentiality violations. This study shows that evidentiality is susceptible to incomplete acquisition in Turkish heritage speakers. It is suggested that the requirement for simultaneous processing at different linguistic levels makes the evidentiality markers vulnerable.