Research paperProcessing past time reference in a tenseless language: An ERP study on the Mandarin aspectual morphemes -le and -guo
Introduction
Time reference (or temporal reference), the perception of an event that occurred in the past, is happening right now, or is about to occur in the future, is generally considered a common function of human cognition. However, the expression of time reference in language exhibits a great number of crosslinguistic differences since it can be encoded using different devices, including categories of tense and aspect. Tense is “grammaticalized expression of location in time” and can be further distinguished between absolute tense (taking the time of speech as its exclusive reference time) and relative tense (when any time interval can be taken as its reference time as long as it is contextually available (Comrie, 1985). Aspect is “different ways of viewing the internal constituency of a situation” (Comrie, 1976) and can be categorized into viewpoint aspect and situation aspect (Smith, 1997). Specifically, viewpoint aspect is related to the subjective focus of a situation, such as perfective (taking the whole situation as its focus--beginning and ending times included) and imperfective (paying attention to the internal part of a situation--beginning and ending times excluded), while situation aspect is related to the objective aspectual features of a lexical verb, such as stative/dynamic (e.g., stative: ‘to love someone’; dynamic: ‘to run’), telic/atelic (e.g., telic: ‘to run to the park’ (with a spatial goal as an endpoint); atelic: ‘to run in the park’ (without an endpoint)), and punctual/durative (e.g., punctual: ‘to win a race’; durative: ‘to build a house’; Smith, 1997).1 Not all languages give an equal importance to tense and aspect—“tense-prominent” languages tend to place events in time using tense (e.g., English, German), while “aspect-prominent” ones refer to such time perception through aspect (e.g., Mandarin)--which makes the crosslinguistic differences even more diverse (Bhat, 1999).
Compared with the abundant literature in linguistics on the expression of time, only a few event-related brain potential (ERP) studies have been conducted regarding this topic. So far, most of the ERP studies on time expression were conducted in tense-prominent languages using a temporal mismatch paradigm. The first study of this kind was conducted in Dutch, in which a mismatch was created by placing a present tensed verb after a past time adverb (e.g., ‘*Last Sunday Vincent paints the window frames of his country house’; Baggio, 2008). This agreement violation elicited a left anterior negativity (or LAN, 200–400 ms) followed by a marginal P600 (400–700 ms) at the verb. Baggio (2008) interpreted the LAN as reflecting a failure of applying agreement rules between the time adverb and the tense morpheme, but the author did not discuss the marginal P600. In a follow-up study, Dragoy, Stowe, Bos, & Bastiaanse, 2012 also found that ERP response was sensitive to temporal mismatch between a time adverb and a verb; however, the pattern differed according to whether the verb was flexed for past or present tense: a P600 was observed when a past time adverb co-occurred with a present tensed verb, while no effect was found when a present time adverb was placed with a past tensed verb. Interestingly, Dragoy, Stowe, Bos, & Bastiaanse, 2012 found similarities between their discovery in temporal computations and prior findings of pronominal in the literature: a P600 was elicited when an agreement violation by a pronoun was judged as occurring within a sentence, while an early anterior negativity or no local effect occurred when the antecedent referred to by the pronoun was outside the sentence (e.g., The aunti heard that shei/hej/*i had won the lottery; Osterhout and Mobley, 1995). The authors thus explained the different patterns in their study with the “Past Discourse Linking Hypothesis (PADILIH)”: processing past tense needs to retrieve/link its antecedent in the discourse (just as processing pronouns taking their referents outside the sentence), while processing present tense requires local binding at the sentence level (just as processing pronouns taking their referents inside the sentence). These results were later replicated and extended to Dutch periphrastic forms (i.e., an auxiliary plus a lexical verb; Bos, Dragoy, Stowe, & Bastiaanse, 2013). The ‘auxiliarypresent tense + verb’ structure in Dutch can refer to either past time reference (as ‘havepresent tense + verb’ in English) or future time reference (as ‘willpresent tense + verb’ in English). With a tense conflict, such forms elicited similar patterns as their counterparts involving a simple form, showing that the effects are due to a mismatch of time reference, not tense per se.
The findings discussed so far only show part of the picture of the neural processing of time in language, i.e., reference to the concept of time via tensed verbs. To have a more complete understanding of such processing, we also need to explore non-tense-prominent languages, and Mandarin Chinese is a good candidate.
Mandarin Chinese is generally seen as an aspect-prominent/tenseless language—there is a great variety of aspectual viewpoint markers, including perfective and imperfective, but no dedicated morpheme whose primary function is to locate a situation in time as in a tense language (Li & Thompson, 1981; Klein et al., 2000; Xiao & McEnery, 2004, among others).2 Two main verbal perfective morphemes are often considered in Mandarin: (1) -le, indicating (among others) termination/completion of an event with consequences of this event still visible at the reference time, or indicating a sequence of events, and (2) -guo, marking an experiential aspect (or discontinuity with the present or other reference time; Smith, 1997). Specifically, the experiential meaning of -guo can be punctual, implying a completion of an event with no consequences visible at the reference time, or implying a sequence of events. Also, the experiential meaning of -guo can be extended to the lifetime, indicating that the event occurred at least once. Note that when a time adverb is found in the sentence, the termination/completion meaning of -guo is easily derived and that -guo can be interchangeable with -le in such cases (Xiao & McEnery, 2004). Although -le and -guo are often analyzed as marking perfective aspect, their meanings are slightly different. The example sentences in Table 1 (i.e., ‘Lisi broke his left leg’) can illustrate this point: when -le is attached to the verb, the interpretation of the sentence is that Lisi's left leg is still recovering. Contrastively, when -guo is used, the sentence is interpreted such that Lisi's leg has already healed. As for imperfectives, two types are often mentioned in the literature: (i) the postverbal durative -zhe, indicating that a state is perduring in time, and (ii) the preverbal progressive free morpheme zai, expressing an on-going dynamic event (See Table 1 for a summary of aspect makers in Mandarin).
Even though aspect markers in tenseless languages are generally not considered as tense markers, there are still temporal restrictions on their use (Li & Thompson, 1981, Tai, 1985). For example, a simple sentence with the occurrence of -le or -guo in Mandarin obtains a past time interpretation by default, and thus the use of a future time adverb is prohibited when only one event is mentioned (e.g., *Lisi xiageyue die-duan-le zuotui ‘*Lisi broke his left leg next month’, where xiageyue means ‘next month’). Linguists provided two types of views to capture this default past interpretation phenomenon. The first type of view intended to offer a unified explanation for both -le and -guo. For example, Smith and Erbaugh (2005) proposed two pragmatic principles to explain the default past time interpretation: the “bounded event constraint” and the “simplicity principle interpretation”. The bounded event constraint states that bounded events (i.e., an event that has a clearly defined temporal endpoint) are not located in the present and thus entails that -le and -guo do not place an event in the present time. The simplicity principle interpretation argues that speakers/comprehenders choose the interpretation that requires the least additional information. Therefore, since past events already happened and are cognitively available, while future events are only hypothesized, the principle entails that -le and -guo place the event in the past, not in the future. Another unified explanation for the default past interpretation was offered by Lin (2006), who argued that both -le and -guo introduce an “anteriority relation” (i.e., one event happens before another event) with a contextually given reference time, such that they are seen as relative past tense markers in addition to their aspectual meaning (e.g., the two examples in Table 1: zuotian wo chi-le wanfan yihou qu zhao ni ‘I went to see you after I had supper yesterday’; zuotian wo chi-guo wanfan yihou zhao-guo ni ‘I went to see you after I had supper yesterday’). In contrast to the first type of view, which treats both -le and -guo similarly, the second type of view explains the default past time interpretation by treating these two morphemes differentially regarding their aspectual meanings. Klein et al. (2000) proposed that -le implies two distinct times while -guo only implies one. The two distinct times implied by -le are (i) the assertion of the whole event included in a reference time (i.e., the perfective aspect), and (ii) the anaphoric assertion of the result state of the event (i.e., the interpretation of something depends upon another expression in context). Therefore, -le puts an event in the past since asserting the result state of an event at the speech time would automatically place that particular event before the speech time, while only one time point is introduced by -guo: the (not anaphoric, pragmatic) assertion of the time after the event (hence a perfective experiential aspect). These two types of assertions are schematically summarized in Table 2, abstracting the meaning of -le and -guo as exemplified in Table 1.
As illustrated in Table 2, due to the discontinuity between the posttime of the event and the actual event, -guo implies an “anteriority” meaning and the event is seen retrospectively. Specifically, when a sentence with -guo is uttered, the posttime of the event is by default placed at the time of speech, which in turn places the event before the time of speech. Note that the anteriority meaning implied by -le and -guo are different, and hence their indirect relation with the time of speech: (i) the event itself is considered with -le (including the result implied by the event), while -guo only asserts the posttime of the event, and (ii) -le asserts an anaphoric time in addition to another reference time (i.e., two time points), while -guo only asserts a (non-anaphoric) reference time (i.e., one time point). In sum, the second type of view states that -le links to past time reference by anaphoric assertion, searching for its antecedent in the available discourse, while -guo does so by pragmatic assertion.
From the above discussion, we can see that the linguistic debate over whether -le and -guo should be treated similarly when expressing past time reference is still far from being settled, and that is why the present study aimed to contribute to the literature by providing evidence from a cognitive science perspective.
Several ERP studies involving the aspectual viewpoint markers in Mandarin have been conducted. Although none of them directly addressed how -le and -guo should be considered, findings in two of these studies were relevant to the current discussion. Zhang and Zhang (2008) investigated agreement violations of Chinese grammatical aspect by placing both a perfective (-le) and a mismatched imperfective (zhengzai) marker in a sentence (see Table 3). While no difference was found at the verb, the perfective morpheme -le (presented in a different frame from the verb) in the violation condition induced a left-central and posterior negativity (at the 200–400 ms time window, different from a N400 and a LAN) followed by a P600 (450–800 ms time window). The authors interpreted the negativity as a failure to bind a perfective marker with a progressive marker, and the P600 as indexing syntactic repair or monitoring and resolving the conflict caused by the aspectual disagreement.
Qiu and Zhou (2012) used disagreement between a time adverb (e.g., 'next month') and the perfective -guo as one condition to investigate temporal processing in Mandarin (see Table 3; note that the primary focus of this study was to inspect the neural processing of time adverbs, not the abovementioned mismatch pattern). The occurrence of -guo (presented with the verb in the same frame) after a mismatched future time adverb resulted in a P600 effect (at the 600–1000 ms time window), when compared with its occurrence after a past time adverb. The P600 here was taken as reflecting a failure of checking the temporal agreement between the time adverb and -guo at the morphosyntactic level.
While both studies provide important insights into the neural processing of -le and -guo, there are still some limitations. First, the above two studies cannot be directly compared because Zhang and Zhang (2008) relied on the mismatch between two aspect markers (imperfective preverbal marker zhengzai + perfective postverbal marker -le), while Qiu and Zhou (2012) relied on the incongruity between a future time adverb and -guo (similar to previous designs in tense languages discussed above). Moreover, the use of zhengzai in Zhang and Zhang (2008) might be controversial because zhengzai can be further decomposed into two parts: the temporal adverb zheng ‘just, sharp’ and the progressive morpheme zai (Lin & Liu, 2004, pp. 169–175). Thus, the design in Zhang and Zhang (2008) might be confounded by violations of both temporal (zheng) and aspectual (zai) constraints, which might explain the observation of the rarely seen early posterior negativity in language processing (instead of an N400 or a LAN). As for Qiu and Zhou (2012), as pointed out by the authors, due to the diversity of the kinds of time adverbs used in their study, the attention of the participants might have been guided to the grammatical properties of the sentences rather than the semantic features of the markers, enhancing a P600 and thus reducing an N400 effect at the same time.
To directly address the question regarding whether -le and -guo are different or similar perfective aspect markers when it comes to time reference, the present study aimed to use the ERP technique to investigate how these two makers were processed by looking into their relationships with time adverbs. Specifically, based on the theoretical considerations of the Mandarin aspectual system and previous ERP findings reviewed above, we planned to examine first whether there was indeed a default past time interpretation with the use of perfective morphemes and, if so, whether such interpretation was obtained through similar or different mechanisms for these two morphemes. To this end, we adopted the general experimental designs from tense-prominent languages (e.g., Baggio, 2008; Dragoy, Stowe, Bos, & Bastiaanse, 2012; Bos et al., 2013) and aspect-prominent languages (e.g., Qiu and Zhou (2012)), in which a temporal concord or mismatch between a time adverb (setting the time frame of a sentence) and a particular morpheme attached to the verb was manipulated. Our hypothesis was straightforward: If processing -le and -guo involves a general strategy (based on the default deictic pattern; Smith & Erbaugh, 2005), the temporal incongruency of both markers should elicit a qualitatively similar component, which could be an early anterior negativity or an absence of local effect (as the findings of Dutch past tense in Baggio (2008), Dragoy, Stowe, Bos, & Bastiaanse, 2012 and Bos, Dragoy, Stowe, & Bastiaanse, 2013) or a P600 (as the finding of Mandarin in Qiu and Zhou (2012)). On the other hand, if the perfective markers are related to past time reference on different bases (i.e., -le asserts an anaphoric time in addition to another reference time (i.e., two time points), while -guo only asserts a (non-anaphoric) reference time (i.e., one time point)), then different ERP components should be observed. Specifically, a P600 should be found for -guo, if the finding in Qiu and Zhou (2012) is replicated, and a different component should be observed for -le, which could possibly be an early anterior negativity or an absence of local effect, as reported in previous research on tense-prominent languages (as in Baggio, 2008; Dragoy, Stowe, Bos, & Bastiaanse, 2012; Bos, Dragoy, Stowe, & Bastiaanse, 2013).
Section snippets
Participants
Twenty-six naïve participants (19 females, age 20–35 years old, mean: 23.1) took part in the ERP experiment. They were all native speakers of Mandarin Chinese in Taiwan, with normal or corrected-to-normal vision. They were right-handed as assessed by a simplified version of the Edinburgh Handedness Inventory (Oldfield, 1971) and had no history of neurological surgery or disorder. A written consent form approved by the Research Ethics Office of National Taiwan University, in which the whole
Behavioral results
The behavioral data from one participant were lost during data collection. Overall, the behavioral results were similar to the online sentence acceptability survey before the ERP experiment, in which sentences with a past time reference were accepted, whereas future time reference sentences were judged unacceptable. Therefore, the accuracy rate rather than the acceptability judgment is reported for the task performed during the ERP experiment. The accuracy rates for the two markers with a past
Discussion
The aim of this paper was to determine whether there was a default past time interpretation with the use of perfective morphemes, -le and -guo, in Mandarin, and if so, whether their access to past time reference was similar or different. To address this, a temporal violation of the two morphemes with a future time adverb was checked against a congruent counterpart with a past time adverb using the ERP technique. The results clearly showed that -le and -guo were incompatible with a future time
Conclusion
The findings from this experiment expand the knowledge of the neural processing of time reference in tense languages and provide new insights from the perspective of a tenseless language—Mandarin Chinese. The present study reveals that not all the references to past time through aspect in an aspect-prominent language are processed in the same way. Importantly, the results further show that the distinction between anaphoric and non-anaphoric references to time, as respectively demonstrated in -le
Funding
This research was supported by grants from the Ministry of Science and Technology (formerly National Science Council) of Taiwan (MOST 106-2410-H-003-137-MY2 and MOST 108-2410-H-003-020-MY3).
CRediT authorship contribution statement
Aymeric Collart: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing - original draft, Writing - review & editing, Visualization. Shiao-hui Chan: Conceptualization, Methodology, Formal analysis, Resources, Writing - original draft, Writing - review & editing, Supervision, Project administration, Funding acquisition.
Declaration of competing interest
None.
Acknowledgments
The authors are thankful for the valuable comments of two anonymous reviewers on an earlier draft of this manuscript, as well as for the constructive comments and discussion on previous interpretations of the results from the 32nd and 33rd Annual CUNY Human Sentence Processing Conferences (2019: University of Colorado, Boulder, Colorado, USA; 2020: UMass Amherst, Amherst, Massachusetts, USA (online sessions). The authors also thank the research assistants of the Neurolinguistics Lab at National
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