Journal of Experimental Psychology: Learning, Memory, and Cognition 2015, Vol. 41, No. 2, 482-500

© 2014 American Psychological Association 0278-7393/15/$ 12.00 http://dx.doi.org/10.1037/a0038389

Predicting the Unbeaten Path Through Syntactic Priming Manabu Arai

Chie Nakamura

The University of Tokyo and RIKEN Brain Science Institute, Japan

The University of Tokyo, RIKEN Brain Science Institute, and Japan Society for the Promotion of Science, Japan

Reiko Mazuka RIKEN Brain Science Institute, Japan, and Duke University A number of previous studies showed that comprehenders make use of lexically based constraints such as subcategorization frequency in processing structurally ambiguous sentences. One piece of such evidence is lexically specific syntactic priming in comprehension; following the costly processing of a temporarily ambiguous sentence, comprehenders experience less processing difficulty with the same structure with the same verb in subsequent processing. In previous studies using a reading paradigm, however, the effect was observed at or following disambiguating information and it is not known whether a priming effect affects only the process of resolving structural ambiguity following disambiguating input or it also affects the process before ambiguity is resolved. Using a visual world paradigm, the current study addressed this issue with Japanese relative clause sentences. Our results demonstrated that after experiencing the relative clause structure, comprehenders were more likely to predict the usually dispreferred structure immediately upon hearing the same verb. No compatible effect, in contrast, was observed on hearing a different verb. Our results are consistent with the constraint-based lexicalist view, which assumes the parallel activation of possible structural analyses at the verb. Our study demonstrated that an experience of a dispreferred structure activates the structural information in a lexically specific manner, leading comprehenders to predict another instance of the same structure on encountering the same verb. Keywords: syntactic priming, prediction, garden-path sentence, anticipatory eye movements, visualworld paradigm

There is a large body of research investigating how language users process temporarily ambiguous syntactic structures during sentence comprehension. In particular, many previous studies fo­ cused on whether and how lexically based constraints such as verb frequency information influence syntactic analysis that compre­ henders make as they process each unit of linguistic information. This issue is crucial for the notion of modularity of grammar (Fodor, 1983) and bears direct relevance to the question about the grain size of the information that the human language processor is sensitive to during online processing (Mitchell, Cuetos, Corley, & Brysbaert, 1995). Although many previous studies demonstrated an influence of lexically specific syntactic information of the verb

during online processing of ambiguous sentences, such an effect was typically observed as facilitation of the processes after the structure was disambiguated. Therefore, it still remains to be seen whether lexically specific constraints affect syntactic analysis im­ mediately on encountering the verb, crucially before any disam­ biguating information arrives. The current study addressed this issue by examining anticipatory eye movements in two visualworld eye-tracking experiments using the Japanese relative clause structure. It is widely accepted that comprehenders can access lexically specific syntactic information in processing temporarily ambigu­ ous structures. For example, Trueswell, Tanenhaus, and Kello (1993) investigated an influence of verb specific structural bias in comprehending sentences such as (1) using an eye-tracking read­ ing methodology.

This article was published Online First December 22, 2014. Manabu Arai, Department of Language and Information Sciences, The University of Tokyo and Laboratory for Language Development, RIKEN Brain Science Institute, Japan; Chie Nakamura, Department of Language and Information Sciences, The University of Tokyo; Laboratory for Lan­ guage Development, RIKEN Brain Science Institute; and Japan Society for the Promotion of Science, Japan; Reiko Mazuka, Laboratory for Language Development, RIKEN Brain Science Institute, and Department of Psychol­ ogy and Neuroscience, Duke University. Correspondence concerning this article should be addressed to Manabu Arai, Department of Language and Information Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan. E-mail: [email protected]

(la) The student hoped the solution was in the back of the book. (lb) The student forgot the solution was in the back of the book.

The sentences contained either the verb that occurs more fre­ quently with a sentence complement than with a direct object (e.g., hope in [la]) or the verb that occurs more frequently with a direct object than with a sentence complement (forget in [lb]). Their results showed that readers experienced greater processing diffi­ culty at the disambiguating second verb (i.e., was) for the verb forget than for hope, confirming that comprehenders immediately 482

PREDICTING THE UNBEATEN PATH

use lexically specific frequency information in processing these ambiguous structures (e.g., Garnsey, Pearlmutter, Myers, & Lotocky, 1997). Another line of research showed that processing difficulty as­ sociated with sentences such as (lb) is reduced if a reader expe­ riences the same type of structure in an immediately preceding trial, demonstrating that language users keep track of the type of structures in recently processed sentences. This phenomenon is generally referred to as syntactic priming. Although it was origi­ nally found in production (Bock, 1986), there is now sufficient evidence that suggests it also occurs in comprehension (Arai, van Gompel, & Scheepers, 2007; Branigan, Pickering, & McLean, 2005; Ledoux, Traxler & Swaab, 2007; Luka & Barsalou, 2005; Kim, Carbary, & Tanenhaus, 2014; Noppeney & Price, 2004; Thothathiri & Snedeker, 2008; Tooley & Bock, 2011; Tooley, Traxler, & Swaab, 2009; Traxler & Pickering, 2005; Traxler & Tooley, 2008). Among these previous studies on comprehension, many studies reported an effect of syntactic priming as facilitation, that is, the reduction of cost due to structural ambiguity. For instance, Ledoux et al. (2007) used event-related potentials (ERPs) to measure electrophysiological changes in the comprehension of reduced relative clause sentences such as (2). (2) The manager proposed by the directors was a bitter old man.

They observed that the P600, the ERP response that reflects structural ambiguity cost, was smaller when readers previously read another reduced relative clause sentence (e.g., The speaker proposed by the group would work perfectly for the program) than when they previously did a main clause sentence (e.g., The speaker proposed the solution to the group at the space program). Their finding cannot be reduced to the presence of the overlapping verb between the prime and target sentences as the verb was repeated for all the conditions. It instead suggests that the activation of the relevant structural representation during a prime trial persisted at least for a short time so that comprehenders experienced less difficulty in accessing the same syntactic representation in the subsequent trial. Similar findings of facilitation due to syntactic priming have been reported in quite a few other studies using other methodologies such as an eye-tracking technique. For example, Tooley et al. (2009) reported a compatible effect of priming with the same relative clause structure using both ERP and eye-tracking techniques. Their study demonstrated a priming effect at the post­ verbal by-phrase for the target sentences of the same structure with the same verb as in prime sentences but not for those with synon­ ymous verbs, demonstrating that the effect is indeed lexically specific and is not due to the overlap of the verb’s semantic information. It should be noted, however, that the results in most of the previous studies are based on the measures of behavioral responses after the sentence was disambiguated, that is, following the encounter of disambiguating information (i.e., directors in (2) in Ledoux et al. (2007) and the by-phrase in Tooley et al., 2009). Since the priming effect in previous comprehension studies was observed at or following a disambiguating region, it is still un­ known whether priming influences the processing of syntactic structures before the point of disambiguation. This is the question addressed by the current study; does syntactic priming affect only the processes after encountering the disambiguating information or does it also affect the processes prior to it? This issue is theoret­

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ically important as it directly relates to how structural ambiguity is resolved in real time. If syntactic priming affects only the pro­ cesses after a sentence is disambiguated, it would suggest that previous syntactic context only affects the process of integrating the disambiguating information, possibly without any influence on the parsing decision made before the point of disambiguation. This is compatible with deterministic sentence processing models such as the garden-path account (Frazier, 1987) and its modified ver­ sion called the construal hypothesis (Frazier & Clifton, 1996). In the face of the structural ambiguity between a main clause and a relative clause at the initial verb, both accounts predict that readers would adopt the main clause analysis because, according to the construal hypothesis, the main clause represents a primary syntac­ tic relation and a context-free principle called minimal attachment is applied in determining the initial parsing decision (See also Clifton, Speer, & Abney, 1991). Other types of information such as verb subcategorization knowledge or thematic fit are expected to take effect later after the sentence is disambiguated (See McElree & Griffith, 1995 for differential processing for subcategory and thematic information). One study demonstrated an immediate influence of verb subcategorization information by reporting the elimination of processing cost by fast priming (Trueswell & Kim, 1998). However, the absence of difficulty at disambiguating input is not direct evidence of an effect on the syntactic processing that takes place at the verb. It is interesting to note that the view of a priming effect as attenuation of reanalysis cost hints at certain relevance to studies that examined the role of domain-general cognitive control in resolving a conflict (or conflict adaptation) between syntactic representations (e.g., Kan et al., 2013; Kuperberg, Lau, & Clegg, 2011; Novick, Trueswell, & Thompson-Schill, 2005). Using an event-related potential (ERP) technique, Kuperberg et al. (2011) reported the P600 response evoked by syntactic anomalies was attenuated if a sentence with syntactic violation was preceded by another sentence with the same type of violation. This implies that the phenomenon of syntactic priming in comprehension may, at least partly, be accounted for by the prolonged engagement of cognitive control across successive trials and the results from previous research are largely compatible with this account. This account, however, assumes that the cognitive control is necessary when comprehenders need to rerank the initial structural analysis and the alternative correct analysis after a sentence is disambigu­ ated (Novick et al., 2005, pp. 269-270), and therefore does not predict an influence of past experience on the prediction, namely, prior to detecting any incompatible input. The evidence of such an influence would require the conflict adaptation account to be modified in such a way that the cognitive control is involved in the process of boosting the activation of the primed structure and suppressing that of the alternative structure at the ambiguous verb. On the other hand, it is possible that syntactic priming affects the processes that take place prior to the disambiguating informa­ tion. This is consistent with the idea that parsing operates in a probabilistic manner; previous syntactic context influences the probabilities that are estimated for possible structural options at the verb. Since probabilistic information or structural bias is seen as specific to individual verbs (Ford, Bresnan, & Kaplan, 1982; Gorrell, 1987; MacDonald, Pearlmutter, & Seidenberg, 1994; Pritchett, 1992; cf. Chomsky, 1965), the influence of priming is likely to be lexically specific too. In other words, this possibility

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suggests that a priming effect at the verb would be triggered only by encountering the same verb as in a preceding sentence but not by a different verb. This possibility also fits well with the constraint-based lexicalist account, which assumes that structural information is associated with individual lexical entries and that comprehenders keep track of the frequency of different structures that occurred with a particular verb (e.g., MacDonald et al., 1994). Such lexically specific exposure-based information has been im­ plemented in computational models by McRae, Spivey-Knowlton, and Tanenhaus (1998) and Spivey and Tanenhaus (1998). Further­ more, this is also consistent with recent processing models which assume that comprehenders make predictions by computing prob­ abilities over possible analyses at each word such as surprisal- and expectation-based models (Hale, 2001; Levy, 2008). According to these models, any changes to the likelihood of structures associ­ ated with the verb should be reflected in the processing cost of a following word in proportion to the size of the changes (e.g., Fine, Jaeger, Farmer, & Qian, 2013). In fact, there is some evidence that suggests a priming effect at the verb. Arai et al. (2007) reported that comprehenders predicted the same structure (either prepositional object or double objects structure) as in the prime as soon as they heard the verb. The prediction was observed immediately after hearing the verb and before hearing any postverbal information. However, such an effect has not been demonstrated for garden path sentences like (2). One possibility is that the bias for the dominant reading was so strong that it overrides a relatively weak priming effect. Indeed, Tooley et al. (2009) suggested that in processing relatively infre­ quent structures such as a reduced relative clause, the parser should still strongly prefer and adopt the main clause analysis as an initial structural choice before ambiguity is resolved. Traxler and Tooley (2008) also suggested that the effect of syntactic priming in com­ prehension is generally weak so that it is unlikely to affect the initial structural preference in a way that comprehenders immedi­ ately access a dispreferred structure before a sentence is disam­ biguated. This raises an important point concerning different ex­ perimental paradigms. Tooley et al.’s (2009)study, as well as other studies that observed a priming effect after disambiguating infor­ mation was encountered, used the reading paradigm, in which researchers usually focus on processing difficulty (or reduction of difficulty) that is reflected in various measures of reading times across regions. Increased reading time due to processing difficulty in processing garden-path sentences is expected to be observed precisely at a disambiguating region because the disambiguating information is inconsistent with the structural choice that was adopted initially or most highly ranked earlier. The reading time at the ambiguous verb, however, would not reflect the process at the verb because the verb itself is not expected to cause any difficulty. Therefore, even if an experience of a prime sentence influences subsequent processing in estimating the probabilities of possible structural options on encountering the same verb, the reading time measure may not be sensitive to the effect. This is perhaps most explicitly illustrated by surprisal-based models, according to which the processing cost is correlated with the size of a change in the probability distribution over possible syntactic analyses from one word to the next. A large change occurs when new input is incompatible with the analysis that was previously assigned the highest probability and univocally supports an alternative lowprobability analysis. Crucially, such a change should not occur

while the sentence is still ambiguous and thus these models predict no processing cost at the ambiguous verb. This also implies that reading times may not be an appropriate measure for investigating the processing of the verb. In contrast, the visual world paradigm enables one to measure anticipatory eye movements that would reflect listeners’ linguistic prediction before the structure is dis­ ambiguated. This suggests that the results from the two different experimental paradigms are not contradictory but rather comple­ mentary, in a sense that they examine two important aspects of syntactic processing (postdisambiguation cost or predisambigua­ tion anticipation). As mentioned above, if a previous experience of a specific structure affects the lexically specific representations of the structure, we expect to find a priming effect when compre­ henders experience the same verb as in the preceding sentence but not when they did a different verb. In fact, the majority of previous studies on syntactic priming during comprehension observed an effect only when the verb was repeated between prime and target sentences (e.g., Arai et al., 2007; Branigan et al., 2005; Ledoux et al., 2007; Pickering & Traxler, 2004; Tooley et al., 2009; Traxler & Pickering, 2005; Traxler & Tooley, 2008). This contrasts with the effect of structural priming in production, where an effect has been typically observed both when the verb was repeated and when it is not, even though an effect tends to be stronger in the former than in the latter situation (e.g., Pickering & Branigan, 1998). The lexical dependence of a priming effect in comprehen­ sion prompted some researchers to suggest that the influence of recent linguistic exposure is entirely lexically dependent (Picker­ ing & Traxler, 2004) and that lexical constraints have a stronger influence in comprehension than in production due to the incre­ mental and bottom-up characteristic of the comprehension process (Arai et al., 2007; Kim et al., 2014; see Tooley & Traxler, 2010 for a review). Alternatively, it is also possible that a priming effect in comprehension is in general weak and it is overridden by the strong general structural bias of a dominant analysis unless the effect is boosted by lexical overlap. The view that syntactic priming in comprehension is lexically driven is, however, challenged by the observation of a lexically independent priming effect in several previous studies (Kim et al., 2014; Scheepers & Crocker, 2004; Tooley & Bock, 2011; Traxler, 2008; Thothathiri & Snedeker, 2008). One possibility for these mixed results is the type of structures that were tested. Some researchers claimed that the structural information about argument structures is lexicalized or stored as a part of lexical information but the information about adjunct structures is not (Boland & Blodgett, 2006; Boland & Boehm-Jemigan, 1998; Jackendoff, 2002; Traxler & Tooley, 2007), in contrast with those who take a strongly lexicalist view that all the structural information is stored for individual lexical items (MacDonald et al., 1994; Vosse & Kempen, 2000; Vosse & Kempen, 2009). This argument structure account predicts that priming of argument relations is lexically specific whereas that of adjunct relations is lexically independent. Consistent with this account, Traxler (2008) demonstrated an effect of lexically independent priming with the adjunct structure of prepositional phrase modifiers. Another important factor that may influence the way a priming effect occurs is a typological difference across languages. In headinitial languages such as English, the verb arrives prior to its complements and poses constraints on postverbal constituents, reflecting its important role in incremental parsing process. In

PREDICTING THE UNBEATEN PATH contrast, the verb arrives follow ing its com plem ents in head-final languages like Japanese and other sources o f inform ation such as case provide inform ative cue fo r the syntactic processing that takes place p rio r to and independently o f the verb (e.g., M iyam oto, 2002; K am ide, A ltm ann, & H ayw ood, 2003; Y am ashita, 1997).

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cost or garden-path effect has been reported w ith the R C structure, particularly w hen prehead constituents strongly bias tow ard the M C analysis (e.g., Keikan-ga hannin-o tsukamaeta Kobayashi-ni rei-o itta, P olicem an-nom [crim inal-acc caught]RC K obayashi-dat thanked, ‘T he policem an thanked K obayashi w ho caught the crim ­

T his suggests the possibility th at the repetition o f the verb across

inal,” Inoue, 2006). U sing the visual w orld paradigm , how ever,

prim e-target sentences m ay m atter less in Japanese than in E nglish and th at p rim ing m ay be observed in the absence o f lexical overlap as w ell as in its presence.

N akam ura, A rai, and M azuka (2012) show ed that a prosodic cue, w hen p rovided in an appropriate context, led listeners to predict an RC structure as soon as they heard the em bedded verb in sim ilar

T he observation o f syntactic prim ing w ithout verb repetition

R C sentences in Japanese. G iven their results, it is possible that an effect o f syntactic prim ing could also lead to the p rediction o f the R C structure at the verb.

w ould indicate that the phenom enon tapped into the abstract syn­ tactic know ledge o f a relevant structure. Im portantly, several re­ searchers argue that lexically independent prim ing is a form o f im plicit learning (B ock & G riffin, 2000; C hang, Dell, & Bock,

W e adopted the visual-w orld paradigm , w hich p rovides an ideal environm ent to investigate predictive processes. A n um ber o f

2006). T here is som e em pirical evidence that supports this claim . F o r exam ple, H artsuiker, B em olet, Schoonbaert, Speybroeck, and

previous studies w ith this paradigm show ed the influence o f var­ ious sources o f inform ation such as verb sem antics (A ltm ann &

V anderelst (2008) dem onstrated in their production study that

an error-based learning m echanism in th eir SR N -based com puta­ tional m odel and successfully sim ulated the results from various studies on syntactic prim ing. A lthough the original claim concerns

K am ide, 1999), case m arkers (K am ide et al., 2003), prosody (N akam ura et al., 2012; W eber, G rice, & C rocker, 2006), and verb-specific frequency inform ation (A rai & K eller, 2013). A s in these previous studies, w e focused on listen ers’ anticipatory eye m ovem ents w hile listening to auditorily presented sentences w ithin visual scenes such as F igure 1. E ach picture depicted four objects in a scene, three corresponding to the referents m entioned

the language production system , recent research show ed that a com parable error-based learning m echanism is at w ork fo r com ­

in the sentence (i.e., actress, cham pagne, and rock star) and one distractor (toddler).

prehension prim ing (Fine & Jaeger, 2013) and also suggested that a com m on learning m echanism is operative at m ultiple levels o f language processing and possibly nonlinguistic dom ains as well. T hese studies dem onstrate evidence fo r a cum ulative effect o f

candidate for R C -head (i.e., toddler in the above exam ple as a to d d ler cannot drink cham pagne). T herefore, the anticipatory looks

lexically abstract prim ing p ersisted fo r a relatively long period w hereas lexically specific prim ing w aned quickly, suggesting that only the formfer reflects learning. C hang et al. (2006) im plem ented

syntactic adaptation to local distributional inform ation; initially unexpected structures quickly becom e less unexpected through

T he visual scene contained a distractor that is an im plausible

toward the plausible RC-head candidate but not to the implausible can­ didate would reflect the p rediction o f the R C structure. O n the other hand, if a listener predicted the M C structure instead, there should

repeated exposures and reduces the cost associated w ith those

not be such a bias because the R C -head entity and the distractor are

originally costly structures, w hich consequently leads to gradual attenuation o f the m agnitude o f a prim ing effect (Fine et al., 2013; Fine, Q ian, Jaeger, & Jacobs, 2 0 1 0 ).1

b oth perfectly plausible as a continuation follow ing the conjunc­ tion toki “w hen” (e.g., Joyuu-ga shanpan-o nondeiru toki, otokonoko ha hon-o yondeita, “W hen the actress w as drinking cham ­

T he current study tested locally am biguous relative clause sen­ tences in Japanese such as (3). Japanese is a head-final language and unlike E nglish, the gram m atical head appears follow ing its relative clause, w hich can provide an ideal setting to investigate an

pagne, the boy w as reading the book”). It is p ossible that listeners w ould predict only the gram m atical category o f the R C - head, not acting on the them atic fit betw een the gram m atical head and the

im m ediate effect o f syntactic prim ing p rio r to the disam biguation o f sentence structure. (3) Joyuu-ga shanpan-o nondeiru rokkusutaa-to ikitougoushita. actress-nom [champagne-acc drinking]ro rock star-acc clicked. “The actress clicked with the rock star who was drinking champagne.” In Japanese, relative clauses b ear no overt com plem entizer or any gram m atical m arking on the verb w ithin the relative clause (RC verb, henceforth). T his creates a local syntactic am biguity; on hearing the R C verb, the sentence is am biguous betw een the m ain clause (M C, henceforth) and R C structure. It is know n that people ten d to consider the V P (shanpan-o nondeiru, “drinking cham ­ pagne”) as a p art o f the M C structure, resulting in the strong activation o f the M C structure and the w eak or little activation o f the RC structure. T hey are later forced to reverse the activation p attern fo r the tw o structures on encountering the RC head noun (rokkusutaa, “rock star” in [3]), causing processing difficulty (Inoue & Fodor, 1995; M azuka & Itoh, 1995). Such an am biguity

relative clause. I f this is the case, w e should n o t observe any difference in looks betw een the plausible and im plausible candi­ dates even i f listeners anticipated a relative clause head. W e exam ined the looks to the im plausible candidate entity (i.e., d is­ tractor) to ch eck this possibility. O ur prim ary question is w hether an im m ediately preceding experience o f reading a sentence w ith the dispreferred structure w ould influence the type o f structure that com prehenders predict on hearing the am biguous verb in a follow ing trial. Such crossm odal prim ing has been reported in previous studies (A rai et al., 2007; Scheepers & C rocker, 2004) and reflects the fact that an effect taps into the com m on structural representations regardless o f processing m odalities (See also P ickering & G arrod, 2004 fo r the

1 It is generally agreed that a strong priming effect with repetition of the verb in production reflects the activation of lexically abstract syntax as well as the boost from a direct lexico-syntactic link for the repeated verb (cf. Pickering & Branigan, 1998). However, it is still unclear whether lexically dependent priming in comprehension partly reflects implicit learning of abstract syntactic structures or it only reflects transient activation of lexi­ cally specific syntactic representations.

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ARAI, NAKAMURA, AND MAZUKA The results showed that participants completed the fragments in the MC structure for 97.8% and in the RC structure for 2.2% (15 out o f 672 completions) with no completion in other structures or ungrammatical responses, confirming a strong preference for the MC over the RC structure. Among the 15 RC completions, 10 were those that relativized the second NP and the verb and five were those that relativized the whole fragment.

E xperim ent 1 Experiment 1 investigated syntactic priming in the comprehen­ sion o f the Japanese MC and RC structures where the initial verb was always repeated across the pairs o f prime and target sentences.

M ethod

Figure 1.

An example target picture.

further claim o f shared syntax for production and comprehension and Tooley & Bock, 2011 for its evidence). It is also important for competing sentence processing accounts to examine whether an effect of priming of this structure is lexically specific or not. We conducted two experiments; first, the first verb was always re­ peated between prime and target sentences (Experiment 1) and second, it was not repeated (Experiment 2).

Participants. Twenty-eight participants, recruited from the student community at the University of Tokyo, took part in the experiment for monetary compensation. All the participants were native speakers o f Japanese with normal or corrected-to-normal vision. Materials. W e prepared 28 experimental items, each consist­ ing of a pair o f a prime and target stimuli. The prime was a written sentence and the target was a prerecorded auditory sentence com ­ bined with a visual scene. Prime and target sentences were either the MC structure (5a, 6a) or the RC structure (5b, 6b), resulting in a fully crossed 2 X 2 design. (5a) MC Prime

Pretest Oosama-ga osake-o nondeiru toki, joousama-ni hanashikaketa. W e conducted a sentence completion test to examine the pref­ erence for the main clause over the relative clause structure. Participants were asked to produce continuations to sentence frag­ ments such as (4). These fragments were taken from the experi­ mental items used as target sentences in the main experiments and consisted of a nominative NP, an NP with an accusative marker o, and a verb (See Appendix). (4) Joyuu-ga shanpan-o nondei . . . Actress-nom champagne-acc drink

king-nom alcohol-acc drinking when queen-dat talked “When the king was drinking alcohol, he talked to the queen.” (5b) RC Prime Oosama-ga osake-o nondeiru joousama-ni hanashikaketa. king-nom [alcohol-acc drinking]rc queen-dat talked “The king talked to the queen who was drinking alcohol.” (6a) MC Target

The verb was presented in an incomplete form to allow contin­ uations with various verb endings such as nondeiru ( ‘is drinking’) or nondeita ( ‘was drinking’). This forced participants to produce continuations and prevented them from simply adding a period following the verb. The fragments can be completed with contin­ uations with a relative clause, with a main clause, or a subordinate clause with a conjunction. For possible continuations using relative clauses, one can in theory relativize only the verb (e.g., Joyuu-ga shanpan-o nondeiru otokoni ageta, “The actress gave the cham­ pagne to the man who was drinking”), the second noun and the verb (e.g., Joyuu-ga shanpan-o nondeiru otokoni hanashikaketa, “The actress talked to the man who was drinking champagne”), or all the three phrases (e.g., Joyuu-ga shanpan-o nondeiru shashin-o mita, “One saw the picture in which the actress was drinking champagne”). We created two lists in Latin square design with 28 experimental items. Each list included 46 fillers and was presented in pseudorandom order. The session started with two practice trials. Twenty-four participants took part in this test.

Joyuu-ga shanpan-o nondeiru toki, rokkusutaa-to ikitougoushita. actress-nom champagne-acc drinking when rock star with clicked “When the actress was drinking the champagne, she clicked with the rock star.” (6b) RC Target Joyuu-ga shanpan-o nondeiru rokkusutaa-to ikitougoushita. actress-nom [champagne-acc drinking] rc rock star with clicked “The actress clicked with the rock star who was drinking the champagne.” The two versions o f prime and target sentences are identical up to the first verb (nondeiru, “was drinking”) and thus structurally ambiguous between the MC or RC structure before the following element is encountered. The target sentences in the MC structure

PREDICTING THE UNBEATEN PATH

were necessary to counterbalance the number of the MC and RC structures that appeared in each experimental session so that ex­ perimental items did not bias participants to anticipate the RC structure over the course of experiments (although 50% chance of occurrences of the RC structure is expected to be unusually high compared to the probability of its occurrences in natural context). The finding of a priming effect of the RC structure with the MC target sentences would ensure that the effect cannot be an artifact due to potential prosodic information unique to the RC structure. We adopted target sentences in the RC structure from Nakamura et al. (2012) and created the MC version by simply adding a conjunction following the first verb while prime sentences were newly created. The conjunction used for the RC sentences was one of the following: toki (when), ato (after), node (because), or saichuu-ni (while). We used 18 verbs, eight of which were re­ peated twice across items. As shown in (5, 6), there was no lexical overlap between prime and target sentences except the initial verb for all conditions. The target sentences were recorded by a female speaker with a standard Tokyo accent. The recordings were saved as wav format at 44 kHz and presented through speakers. The visual scenes were created using commercially available clipart images and graphic software, which were saved as 16-bit color bitmap in 1024 X 768 pixels resolution. Each picture contained four entities, arranged in a rhombus fashion. The four entities were easily recognizable and corresponded to the sentence initial subject noun, direct object noun, RC-head noun (in RC targets) or noun following the conjunction (in MC targets), and a distractor. Across items, all the entities appeared equally often in each of the four positions, thus counterbalancing potential effects due to scanning preferences. Design and procedure. Our design combined the syntactic priming methodology with the visual-world paradigm (Arai et al., 2007; Scheepers & Crocker, 2004). Participants first read a prime sentence silently and next listened to a target sentence while seeing a corresponding target picture. Besides the 28 experimental items, participants also saw 70 fillers, none of which was in the RC structure. Fourteen fillers were written sentences and 56 fillers were spoken sentences accompanying visual scenes. Using a Latin square design, we created four lists in which each item appeared only once in one of the four conditions and the equal number of items appeared in each condition. The items and fillers were presented in a quasirandom order, in which at least one filler always intervened between experimental items. Participant’s eye movements were recorded during both prime and target trials with EyeLink Arm Remote (SR Research) at the sampling rate of 500 Hz with the spatial resolution of less than 0.01°. In the experimental session, participants were first asked to read a brief instruction form and next sat approximately 70 cm away

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from the 17” computer monitor. Next, they went through a brief calibration procedure, which typically took less than 1 minute. The calibration procedure was repeated during an experimental session if the recording appeared inaccurate but it was never performed between prime and target trials. Before each reading trial, for both experimental items and fillers, participants saw a small circle at the center of the screen, which performed an automatic drift correc­ tion. When participants finished reading a sentence, they pressed a space bar to proceed to the next trial. In target trials, visual scenes were presented immediately following previous trials without the fixation cross. Auditory sentences were presented with a delay of 2,500 ms to ensure that participants fully apprehended the visual scene. To keep participants focused, we included 12 comprehen­ sion questions following filler reading items. Each experimental session typically took approximately 30 minutes to complete.

Results Reading times in prime trials. We first examined reading times for prime sentences to see whether participants experienced processing difficulty with the structurally ambiguous RC sen­ tences. Such a finding would demonstrate that comprehenders consider the MC analysis most likely before the disambiguating RC head and later experience the cost for resolving the structural ambiguity on encountering the head. It would also suggest that the Japanese RC structure is similar to the type of temporarily ambig­ uous structures that have been tested in English. The prime sen­ tences were divided into regions for the purpose of analysis, shown in Table 1. For the analysis of fixation data in each region, we removed fixations that were either extremely long (1.200 ms or over) or extremely short (80 ms or under). This resulted in the exclusion of 6.0% of the reading data. Here we focus on first-pass reading time, which is the sum of fixation durations in a particular region following the first entry in the region until the first fixation outside the region (either to the left or the right). We analyzed the firstpass time in the object NP/RC-head NP region (joousama-ni, “to the queen”). Since the MC sentences contain the disambiguating conjuction toki immediately preceding this region, readers should show a structural ambiguity effect only for the RC sentences. However, previous research demonstrates that an ambiguity effect with garden path sentences is somewhat late and better captured by late measures such as second pass and total times (see Farmer, Fine, Yan, Cheimariou, & Jaeger, 2014 for an adaptation effect in late measures). Therefore, we also analyzed the first pass time in the sentence-final verb region (hanashikaketa, “talked”), which would reflect a late spill-over effect of structural ambiguity. The late measures in the predisambiguation as well as postdisambigu-

Table 1 Prime Sentences Divided Into Regions MC primes

RC primes

Subject NP Ousama-ga king-nom Subject NP Ousama-ga king-nom

SC = subordinate clause.

SC accusative NP osake-o alcohol-acc RC accusative NP osake-o alcohol-acc

SC verb + Conjunction nondeiru toki drinking when RC verb nondeiru drinking

Object NP joousama-ni queen-dat RC-head NP joousama-ni queen-dat

MC verb hanashikaketa talked MC verb hanashikaketa talked

ARAI, NAKAMURA, AND MAZUKA

488

ation regions did not show any effect of structural ambiguity (ps > 0.10) and they are not reported here. Table 2 shows the mean first-pass reading times for the two regions. We conducted statistical analyses on log-transformed first-pass times using Linear Mixed-Effects (LME) models (e.g., Baayen, Davidson, & Bates, 2008). We included Structure Type (MC or RC) as a single fixed factor and Number of Characters as a covariate. Participants and items were included as random factors. The fixed factors were centered with deviation coding. We se­ lected the best-fit model with an optimal random slope structure using a backward selection approach. We report coefficients (p), standard errors (SE), Lvalues, and their p values from the best-fit model.2 Fixed factors’ p values were computed based on the posterior distribution computed using Monte Carlo Markov chain sampling. Where the optimal model included more than one ran­ dom slope, we computed the p value for each factor using likeli­ hood ratio (LR) tests. The analysis of the object NP (MC)/RC-head NP (RC) region showed a marginally significant effect of Structure Type; partici­ pants tended to read this region more slowly in the MC condition than in the RC condition (p = —0.04, SE = 0.02, t = 1.95, p = .053). This pattern of results is opposite from what was predicted by expected processing cost at the disambiguating region with the RC structure. We thus examined regression-out rates (the rate of regressive eye movements crossing the left boundary of the region) in this region to see whether the shorter first pass times in the RC condition may be due to the greater probability of looking back at earlier regions to revise the incorrect MC interpretation. The analysis indeed revealed that there occurred more regressions in the RC condition than in the MC condition (M = 30.6% for MC and M = 38.6% forRC; p = 0.20, SE = 0.09, z = 2 .\2 ,p = .034). The analysis in the sentence-final verb region showed a significant effect of Structure Type; participants took longer to read this region in the RC condition than in the MC condition (P = 0.10, SE = 0.03, f = 3.79, p < .001). This spill-over effect most likely reflects the cost of structural ambiguity with the RC sentences. The results together suggest that comprehenders initially activated the MC analysis strongly relative to the RC analysis so that they experienced processing difficulty on encountering the RC head in the RC sentences. Eye movements in target trials. The spatial coordinates of fixations were automatically mapped onto one of the four objects in the scene or background. The area for the four objects was manually defined while allowing approximately 30 pixels around the contour of each object. These fixations were then converted to gazes. A gaze was defined as the accumulation of all consecutive fixations on one object until another object (or the background) was fixated. To analyze the gazes with reference to linguistic input, we manually marked the onset and offset of the RC verb (nondeiru, “drinking”) and the onset of the RC head noun for RC

targets and that of the noun following the conjunction for MC targets (rokkusutaa, “rock star”) in each target sentence. We are interested to see whether the participant’s structural prediction at the initial verb would be influenced by the structure of an immediately preceding prime sentence. As illustrated earlier in our experimental setting, the prediction of the RC structure would be reflected in increased looks toward the RC-head entity but not to the distractor. Figure 2 shows the proportion of looks to the RC-head entity (i.e., bijinesuman “businessman”) for the 1,800-ms interval starting from the initial verb onset. The three vertical lines correspond to the mean offset of the first verb (702 ms, SD = 129, min = 496 ms), the mean onset of the RC head noun in the RC target (1,105 ms, SD = 132, min = 870 ms), and the mean onset of the noun following the conjunction in the MC target (1,596 ms, SD = 145, min = 1,312 ms), respectively. The point of disambiguation was immediately following the offset of the first verb for the MC targets whereas it was at the onset of the RC head noun for the RC targets. Figure 2 indicated that there were few looks to the RC head entity before the verb offset and the looks increased following it, suggesting that participants launched anticipatory eye movements after hearing the verb. Across our items, the minimum duration between the verb offset and the RC head noun onset was 288 ms (M = 362 ms, SD = 47). In order to analyze only truly anticipatory eye movements, we analyzed the looks toward the target object for the minimum duration plus 100-ms (= 388-ms) interval following the offset of the initial verb. The 100-ms stretch was selected to secure the maximally conservative duration that fixations cannot possibly reflect auditory linguistic information. This ensures that the eye movements analyzed are not in any way affected by the disambiguating RC-head information for the both types of target sentences. We calculated the empirical logit of the looks to the RC-head entity out of the looks to all other objects in a scene, including background following the function below.

Table 2 Mean First-Pass Reading Times (and Standard Errors) in Prime Trials

2 To determine the best-fit model, we started from the full model with the maximum random effect structure (i.e., including prime type and target type as well as their interaction as random slopes for both participants and items) and simplified the model by reducing the number of the random slopes using a backward selection approach. This is because the full model often failed to converge with our data and it is still under debate what approach should be adopted in dealing with the convergence problem for the experimental design with more than one fixed predictor (cf. Barr, Levy, Scheepers, & Tily, 2013).

Object NP/RC-head NP region Sentence-final verb region

Main clause

Relative clause

438 (13) 586(24)

393 (17) 699 (27)

, , (y + 0.5) m = I n ---------------(n — y + 0.5) Where y is the total duration (ms) of the gazes to the RC-head entity and n is the total duration of the gazes to all the objects in a scene including background. We conducted an analysis on these values using LME models. The models included Prime Type (MC prime or RC prime) and Target Type (MC target or RC target), allowing the interaction between Prime Type and Target Type. Our prediction is as follows: If priming of the RC structure occurs immediately at the verb, participants would immediately predict the RC structure at the verb following the RC prime and the eye-movement pattern should reflect the structural prediction in the way that there will be more looks toward the RC-head entity in the visual scene following a RC prime than following a MC prime.

PREDICTING THE UNBEATEN PATH

Offset of

-^ M C Prime + MC Target

Onset of

489 Onset of

“° “MC Prime + RC Target

~*~RC Prime + MC Target________~*~RC Prime + RC Target Figure 2.

Proportion of looks to the RC-head entity for 1,800 ms following the onset of the first verb.

We included Target Type as a factor because the two types of target sentences differed following the first verb, that is, partici­ pants heard the conjunction for the MC targets but not for the RC targets. It is thus possible that the effect of priming interacts with the type of the target structure. As in the earlier analysis on reading times for prime sentences, we included participants and items as random factors and explored the best-fit model with an optimal random effect structure using a backward selection approach. Table 3 showed the summary of the results from the best-fit model. The results from the best-fit model showed a fully significant main effect of Prime Type, demonstrating clear evidence for syntactic priming with this structure; participants looked more at the RC-head entity following RC primes than following MC primes, reflecting the immediate analysis of the RC structure on hearing the first verb. Importantly, the effect occurred prior to the processing of any disambiguating information. There was neither an effect of Target Type nor that of an interaction between Prime Type and Target Type. This suggests that both the MC and RC target sentences were indeed ambiguous up to the first verb and the prediction based on the initial structural analysis was influenced by the type of the sentence that the participants previously read. One potential concern is the potential influence of the conjunction, which was heard immediately following the initial verb only in the MC target condition (no input was given during this period in the Table 3 Analysis o f the Looks to the RC-Head Entity During the 388-ms Interval Following the Offset o f the First Verb Factor

Coefficient

SE

t

P

(Intercept) Prime type Target type Prime type X Target type

89.29 19.34 0.75 -7.69

11.81 8.23 8.23 8.24

7.56 2.35 0.09 -0.93

* .* >

/iM.

‘The president reproached the employee who took off the necktie.’

Kagakusha-ga furasuko-o tsukatteiru (saichuu-ni) ashisutanto-o chuuishita.

15a.

ISUiOMt/Co

chemist-nom [flask-acc using]RC assistant-acc warned Repootaa-ga nyuusu-o yondeiru (toki) anaunsaa-ni hanashikaketa. “The chemist warned his assistant who was using the flask.”

reporter-nom [news-acc reading]RC announcer-acc talked “The reporter talked to the announcer who was reading the news.”

19a. » T # * * » * * < t Buka-ga siryou-o otoshita (toki) joushi-no kao-o ukagatta.

15b.

subordinate-nom [document-acc dropped]RC boss-acc tried to read mood

Roujin-ga shinbun-o yondeiru (toki) bijinesuman-ni hanashikaketa. oldman-nom [newspaper-acc reading]RC businessman-acc talked

“The subordinate tried to read the mood of the boss who dropped the document.”

“The old man talked to the businessman who was reading a newspaper.”

19b.

U fc(& )£ lcS S UiO'ltfco Teiin-ga supuun-o otoshita (ato) kyaku-ni hanashikaketa.

-d Tz o Shefu-ga oobun-o tsukatteiru (toki) minarai-ni kogoto-o itta.

clerk-nom [spoon-acc dropped]RC customer-acc talked

chef-nom [oven-acc using]RC trainee-acc made a complaint

“The clerk talked to the customer who dropped the spoon.”

“The chef made a complaint to the trainee who was using the oven.”

16b.

20a.

U T£ £ (« )* ¥ £ » !& Kantoku-ga kaiken-o shitekita (ato) senshu-o gekireishita.

Bengoshi-ga pasokon-o tsukatteiru (toki) hisho-ni tanomigoto-o shita.

coach-nom [interview-acc did]RC player-acc encouraged

lawyer-nom [computer-acc using]RC secretary-acc asked a favor

“The coach encouraged the player who did an interview.”

(Appendix continues)

PREDICTING THE UNBEATEN PATH

“The teacher complimented the student who was reading the textbook.”

20b. t ' v * 7 Y > # ' d V I / 7 £ U T # £ ( & ) 0 L l C f S £ | l B ( , '

Tzo Bijinesuman-ga gorufu-o shitekita (ato) ooeru-ni hanashi-o kiita.

499

24a.

businessman-nom [golf-acc did]RC businesswoman-acc heard story

Otokonoko-ga tetsubou-de asondeiru (toki) doukyuusei-ni hanashika­ keta.

“The businessman heard a story from the businesswoman who did golf.”

boy-nom [bars-acc playing]RC classmate-acc talked “The boy talked to his classmate who was playing on the bars.”

21a. Hoteruman-ga nimotsu-o motteiru (toki) kyaku-o annaishita.

24b.

hotelkeeper-nom [baggage-acc holding]80 guest-acc guide

Onnanoko-ga omocha-de asondeiru (toki) akachan-o sewashita.

“The hotelkeeper guided the guest who was holing the baggage.”

girl-nom [toy-acc playing]RC baby-acc looked after “The girl looked after the baby who was playing with the toy.”

2 lb . 25a. Joshikousei-ga keitai-o motteita (toki) bijinesuman-ni hanashikaketa.

Oujisama-ga basha-ni notteita (toki) ohimesama-ni kyuukonshita.

high school girl-nom [cell phone-acc holding]RC businessman-acc talked “The high school girl talked to the businessman who was holding the cell phone.” 22a.

a

prince-nom [carriage-acc riding]RC princess-acc proposed to “The prince proposed to the princess who was riding in the carriage.” 25b.

X 's V Z

Keisatsukan-ga jitensha-ni nottekita (ato) dansei-o oikaketa.

Dansei-ga jogingu-o shitekita (ato) rinjin-ni aisatsushita.

policeman-nom [bicycle-acc riding]RC man-acc chased

man-nom [jogging-acc did]RC neighbor-acc said hello

“The policeman chased the man who was riding the bicycle.”

“The man said hello to the neighbor who did jogging.” 22b. &

26a.

( £ ' £ > 2 htf-;U£UT££(&)*3D(,\2Ar