Processing events: Behavioral and neuromagnetic correlates of Aspectual Coercion

Brain & Language 106 (2008) 132–143

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Processing events: Behavioral and neuromagnetic correlates of Aspectual Coercion Jonathan Brennan a,*, Liina Pylkkänen a,b a b

Department of Linguistics, New York University, 726 Broadway, 7th Floor, New York, NY 10003, USA Department of Psychology, New York University, 6 Washington Place, New York, NY 10003, USA

a r t i c l e

i n f o

Article history: Accepted 25 April 2008 Available online 17 June 2008 Keywords: Semantic composition Aspectual Coercion MEG AMF

a b s t r a c t Much recent psycho- and neuro-linguistic work has aimed to elucidate the mechanisms by which sentence meanings are composed by investigating the processing of semantic mismatch. One controversial case for theories of semantic composition is expressions such as the clown jumped for ten minutes, in which the aspectual properties of a punctual verb clash with those of a durative modifier. Such sentences have been proposed to involve a coercion operation which shifts the punctual meaning of the verb to an iterative one. However, processing studies addressing this hypothesis have yielded mixed results. In this study, we tested four hypotheses of how aspectual mismatch is resolved with self-paced reading and magnetoencephalography. Using a set of verbs normed for punctuality, we identified an immediate behavioral cost of mismatch. The neural correlates of this processing were found to match effects in midline prefrontal regions previously implicated in the resolution of complement coercion. We also identified earlier effects in right-lateral frontal and temporal sites. We suggest that of the representational hypotheses currently in the literature, these data are most consistent with an account where aspectual mismatch initially involves the composition of an anomalous meaning that is later repaired via coercion. Ó 2008 Elsevier Inc. All rights reserved.

1. Introduction Humans’ ability to understand and produce previously unencountered expressions tells us that semantic interpretation must be by and large compositional, that is, the meanings of expressions are a function of their parts and the way the parts are syntactically combined. While the general idea of compositionality is largely uncontroversial, the computational mechanisms by which it is achieved remain poorly understood for a number of constructions. One particularly controversial case involves expressions such as the clown jumped for ten minutes, where there is no word which encodes the information, obvious to any healthy native speaker, that the clown jumped several times (Talmy, 1978). In this work, we used a combination of behavioral and neuromagnetic measures to elucidate the representation and processing of this type of expression. At least four different hypotheses have been proposed about the representation of expressions such as the clown jumped for ten minutes. One common approach is to introduce an unpronounced rule, corresponding to no overt syntactic element, which encodes the repetitive aspect of the verb’s meaning. The rule is invoked in response to the aspectual mismatch between the temporal modifier for ten minutes, which describes duration of time, and the verb jumped, which appears to describe a near-instantaneous, punctual event. Pustejovsky (1991) dubbed the resolution of this

* Corresponding author. E-mail address: [email protected] (J. Brennan). 0093-934X/$ - see front matter Ó 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.bandl.2008.04.003

mismatch Aspectual Coercion, adopting terminology introduced by Moens and Steedman (1988). The general idea of Aspectual Coercion can be implemented in several ways. In some theories it is a semantic operation which applies within the compositional system in order to resolve the aspectual mismatch between the punctual verb and the durative adverb (De Swart, 1998; Jackendoff, 1997; Pustejovsky, 1991, 1995; Smith, 1991). In these theories the aspectual properties of the verb and the adverb are encoded in the lexical meanings of these elements in such as way that composition is impossible without some type of meaning shift. This type of analysis can be contrasted with a pragmatic approach, where the verb and the adverb successfully compose in the semantics but create an anomalous meaning (such as ‘the clown performed a ten-minute long jump’). This anomalous meaning is then shifted to a repetitive meaning pragmatically (cf., Dölling, 1995, 1997, 2003a, 2003b). A core property of both of these approaches is that the punctual meaning of the verb is primitive and the iterative meaning derived. A third proposal of aspectual mismatch resolution has coercion applying in the opposite direction. In this account, verbs such as jump are represented as repetitive activities which coerce into punctual events in punctual contexts (e.g., at 3 o’clock, the clown jumped) (Rothstein, 2004). We will call this approach Punctual Coercion, to be distinguished from the approach described above, henceforth Iterative Coercion. Finally, all of these three coercion theories contrast with an approach that essentially denies the existence of Aspectual Coercion as any type of interpretive operation. Instead, verbs like jump are

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semantically underspecified with respect to their duration: they are equally capable of describing both punctual and durative events (Moens & Steedman, 1988). In other words, in this approach there is no representational difference between verbs such as jump and verbs such as run; whatever differences there are in the temporal properties of the events that these verbs describe plays no role in the linguistic representation of the verbs. In this work, we used self-paced reading and magnetoencephalography (MEG) to investigate the processing of Aspectual Coercion in light of these four hypotheses. For clarity, the hypotheses and their logical relationships to each other are depicted in Fig. 1. A major division is drawn between Underspecification and Coercion, the latter further subdividing into Punctual Coercion and Iterative Coercion. Finally, Iterative Coercion splits into the semantic and pragmatic varieties discussed above. Fig. 2 shows informal, and Appendix A more formal, tree representations of same four hypotheses. Several previous psycholinguistic studies have aimed to distinguish between Underspecification and Iterative Coercion. These studies have investigated whether expressions such as (1a), involving a punctual verb and a durative adverb, are more costly to process than expressions such as (1b), where both the verb and the adverb are durative (Husband, Beretta, & Stockall, 2006; Husband, Stockall, & Beretta, 2008; Pickering, McElree, Frisson, Chen, & Traxler, 2006; Piñango, Winnick, Ullah, & Zurif, 2006; Piñango, Zurif, & Jackendoff, 1999; Todorova, Straub, Badecker, & Frank, 2000; see also Piñango, 2003). Iterative Coercion predicts the mismatching (1a) to engender longer processing times than the aspectually matching (1b), whereas on Underspecification no such difference should be observed. The literature has thus far not directly addressed the possibility that coercion may, in fact, proceed in the opposite direction (Punctual Coercion; Rothstein, 2004), nor has there been any attempt to separate semantic from pragmatic effects in interpretation. 1. a. Susan jumped until dawn. (punctual verb, durative adverb) b. Susan slept until dawn. (durative verb, durative adverb) So far, the results on contrasts such as (1a) vs. (1b) are somewhat mixed. Piñango et al. (1999), (2006) have reported that reaction times in a secondary lexical decision task are increased for expressions involving punctual verbs and durative adverbs, consistent with Iterative Coercion. In these experiments, subjects listened to pairs of sentences such as those in (2). At the position in the sentence notated with an asterisk, a set of letters was flashed onto a screen and the subject decided if they represented an English word or not. Longer reaction times on the secondary task for the mismatch condition (2b), in comparison to controls (2a) were taken to indicate added processing effort associated with coercion. 2. a. The man examined the little bundle of fur for a long time * to see if it was alive. b. The man kicked the little bundle of fur for a long time * to see if it was alive.

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Todorova et al. (2000) replicated these results in a self-paced stopmaking-sense task and further concluded, by presenting sentence triples such as those in (3), that the cost is not associated with a simple delay associated with interpreting iterated events. The added control sentence, (3b), describes an iterated event without mismatch. Results showed longer reading times at the temporal modifier in the coercion condition (3a) in comparison to the two control conditions (3b and c). Lastly, Husband et al. (2006), (2008), using the same stimuli as Todorova et al., reported a replication of these results using a moving-window self-paced reading paradigm. 3. a. Even though Howard sent a large check to his daughter for many years, she refused to accept his money. b. Even though Howard sent large checks to his daughter for many years, she refused to accept his money. c. Even though Howard sent a large check to his daughter last year, she refused to accept his money. In contrast to the above findings, Pickering et al. (2006) found no cost associated with coercion in a series of four experiments in which subjects viewed the same stimuli used by Piñango et al. (1999) and Todorova et al. (2000). Pickering and colleagues used self-paced reading and eye-tracking, which they argued to reflect more natural reading than the previous dual-task paradigm (Piñango et al., 1999) or the stop-making-sense task (Todorova et al., 2000). In two of the four experiments, the stimuli were altered such that the temporal modifier preceded the target verb. This had the advantage of placing the hypothetical burden of coercion on the interpretation of a single word, the verb, rather than on a temporal modifier, which is a complex phrase. Pickering and colleagues took the absence of effects to support the Underspecification hypothesis of the representation of jump-type verbs and to show that aspectual mismatch is not costly in natural reading. In summary, while several studies suggest that aspectual mismatch is costly to process, consistent with the hypothesis that the interpretation of such sentences requires Iterative Coercion, conflicting results make it hard to draw firm conclusions. An added challenge for research in this area is that the notion of ‘‘punctuality” is quite difficult to define. Some punctual verbs describe events that are short-lasting but naturally repeating. For example, most knocking events involve multiple knocks. In contrast, a burping event is much more likely to involve only a single burp. It is quite possible that our knowledge about the likelihood of event repetition may shape our representations: perhaps knock is represented as a repeating activity and burp as a punctual point-action event. This possibility has not been taken into account in previous research, which may be a contributing factor to the currently somewhat confusing psycholinguistic profile of aspectual mismatch. In our research, we aimed to construct the strongest possible test for Aspectual Coercion. In order to achieve this, a large number of potentially punctual verbs were first rated for their likelihood of describing single or repeating events. On the basis of this pretest, we constructed stimuli such as (4a and b), which involved either a durative or a punctual adverb, followed by a (strongly) punctual target verb. 4. a. Coercion: Throughout the day the student sneezed in the back of the classroom. b. Control: After twenty minutes the student sneezed in the back of the classroom.

Fig. 1. Four hypotheses about the representation of aspectual mismatch and their relationships to each other (see text).

Experiment 1 investigated the processing of these stimuli in selfpaced reading. If the target verbs are underspecified with respect to event type (Moens & Steedman, 1988), the processing times of (4a) and (4b) should not differ. In contrast, if punctuality is specified

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Fig. 2. Informal tree representations for the four hypotheses depicted in Fig. 1. (a) Verbs are semantically distinguished into different types depending on event type, and the aspectual mismatch is resolved by a semantic coercion operation (Jackendoff, 1997; Pustejovsky, 1995). (b) The compositional system successfully composes the punctual verb with the durative adverb, but the representation is anomalous. A second, pragmatic, stage of interpretation resolves the mismatch (Dölling, 2003a). (c) Verbs like jump are represented as iterated events which can be coerced into punctual events in the appropriate context (Rothstein, 2004). (d) Verbs like jump are underspecified with respect to the duration of the events they describe and thus do not mismatch either with punctual or durative adverbs (Moens & Steedman, 1988).

as a part of the verb’s meaning (e.g., Jackendoff, 1997; Pustejovsky, 1995) and the mismatch is resolved by Iterative Coercion, there should be delayed reading times (RTs) at the verb in the coercion condition. Finally, under Punctual Coercion, where the iterated interpretation is basic and the punctual interpretation derived, RTs should be delayed at the verb in the control condition. In Experiment 2, we used MEG to investigate the neuromagnetic correlates of aspectual mismatch. We will outline potential candidate regions associated with aspectual mismatch in the introduction to Experiment 2, once we have established the behavioral processing profile of these expressions. Our main aim, however, was to assess to what extent aspectual mismatch affects the anterior midline field (AMF), which has recently been reported to be sensitive to so-called Complement Coercion (Pylkkänen & McElree, 2007). Complement Coercion refers to a meaning shift that occurs in expression such as the author began the book, where the entity-denoting noun phrase, the book, shifts to an event interpretation (e.g., reading or writing the book). So far Complement Coercion is the only construction that has been reported to affect the AMF, although only one previous study has explicitly investi-

gated the generality of the AMF effect. Harris, Pylkkänen, McElree, and Frisson (2007) tested so-called Concealed Question expressions, exemplified by sentences such as the announcer guessed the winner, where the winner shifts to a question-like meaning (i.e., ‘who the winner was’). The AMF was not modulated by questionconcealment, leaving open the possibility that the AMF effect may be rather specific to Complement Coercion. Harris et al. (2007), however, speculated that the relevant contrast between Complement Coercion and Concealed Questions may be that Complement Coercion is clearly meaning-adding, whereas the type-shifting that occurs in Concealed Questions is of a more purely logical nature. Abstracting away from the formal details of this, perhaps one way to make the contrast intuitive is by observing that the noun phrase the winner describes a relationship between an individual and a contest but does not name either the individual or the contest. The question complement who the winner was includes a syntactic argument (who) standing for the (winning) individual, but like the noun phrase, it says nothing about the identity of that individual. Thus, although the question complement differs in semantic type from the noun phrase, it does not

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communicate more than the noun phrase by itself. In Complement Coercion though, shifting from an entity to an activity involving that entity is a rather robust semantic change. Thus Harris et al.’s suggestion was that the AMF may be modulated by shifts that change the semantic content and not simply the semantic type of a constituent. If aspectual mismatch is resolved by coercion, whether punctual or iterative, then the coercion operation should introduce additional meaning concerning the nature of the event (see Appendix A). Consequently, if a change in meaning is what drove the AMF effect of Complement Coercion, then aspectual mismatch should also affect the AMF. Experiment 2 tested this prediction. 2. Experiment 1: self-paced reading 2.1. Methods 2.1.1. Participants Sixty right-handed native speakers of English participated in the study (ages 18–35, 42 females). 2.1.2. Stimuli As discussed above, a large number of verbs were first normed with respect to whether they were naturally interpreted as describing single or multiple events. Sixty-four subject–verb pairs (e.g., the clown jumped) were presented on a computer screen to 15 right-handed native English speakers who did not participate in the main reading time experiment. Participants were asked to judge as to what degree the verb of a particular sentence most naturally describes a single event or multiple events. As an example, they were given the sentence the marine waved and were instructed that although ‘‘one can imagine what a single wave would look like, the most natural interpretation of this sentence would involve a succession of repeated waves.” With this instruction, we aimed to assess to what extent the default interpretations of particular subject–verb combinations were punctual, as opposed to iterative. Participants judged each sentence on a seven-point scale where 1 corresponded to ‘‘single event”, and 7 corresponded to ‘‘multiple events”. Each sentence was presented in the middle of the screen immediately above the labeled seven-point scale; responses were entered using the computer keyboard. Twentysix subject–verb pairs which received a mean judgment of less than three were chosen for our study (M = 1.78, SD = .54). For the final stimuli, subject–verb pairs were combined with a durative modifier in the coercion condition and a punctual modifier in the control condition. Four of the verbs were repeated with different subjects and temporal modifiers to ensure an adequate number of stimuli. Temporal modifiers were matched for orthographic length (t(29) = .485, p = .63). Following Pickering et al. (2006), the modifiers were presented at the beginning of each sentence so that any potential cost of coercion could be assessed at a single word, i.e., the verb. This yielded 30 sentence pairs like the example given in (4) above. To ensure that the sentences were highly plausible, 33 subjects rated the coerced and control sentences on a seven-point plausibility scale (7 = highly plausible). Sentences were presented one by one on a computer screen and raters were instructed to indicate how ‘‘natural” each seemed. The sentence pairs were mixed with an equal number of anomalous fillers (see below) to form triplets which shared the same verb and sentence frames and were distributed across three lists such that no subject saw more then one member of a triplet. The three lists were randomized and each was presented to 11 raters. Mean plausibility ratings were 5.02 (SD = .95) for the coerced sentences and 5.03 (SD = .95) for the control sentences. Importantly, there was no statistical difference between the plausibility ratings for the two conditions (t(32) = .11, p = .9).

Sixty filler sentences were constructed using the same sentence frames and temporal modifiers as in the target sentences but replacing the verb with a durative predicate (e.g., walked). These fillers ensured that the presence of a durative modifier was not predictive of aspectual mismatch. Sixty anomalous fillers were also constructed which used the same sentence frames, adverbials, and verbs but included an inanimate sentential subject which was infelicitous with the verb. In total, all 30 sentence frames were used six times. The thirty target pairs were combined with these 120 fillers (50% anomalous), along with 260 sentences from a separate experiment that were similar in syntactic structure (33% anomalous) and 544 sentences from with a variety of different structures testing unrelated hypotheses (50% anomalous). The stimuli and fillers were then distributed across six different lists in order to ensure that no subject saw the same sentence frame more than once. Each target item was seen by ten subjects. 2.1.3. Procedure Each subject was seated in front of a Dell 1700 computer LCD. Sentences were presented in a black courier font, size 18, on a light grey background using E-Prime software (PST Inc., PA). Subjects were instructed to read at a natural pace such that they could answer whether the sentence made sense or not within 4 s at the end of each trial. Twelve practice trials were presented prior to the beginning of the experiment to familiarize each subject with the task. Subjects were required to achieve an 80% accuracy rate on the practice trials in order to move on to the main experiment. Each trial began with a fixation cross presented in the middle of the screen. After 300 ms, a series of dashes corresponding to the words in the sentence appeared. Using the computer’s spacebar, subjects advanced wordby-word through each sentence at their own pace. After the final word of each sentence, a question mark appeared and the subject entered a judgment on the computer’s keypad as to whether the sentence made sense or not. 2.2. Results Four subjects showing an overall accuracy rate of less than 80% were removed from the analysis. The data for the target sentences were cleaned first by removing all trials which were judged as nonsensical, eliminating approximately 7.7% of the data. Mean reaction time and accuracy for the end-of-sentence sensicality judgments are shown in Table 1. There was no difference in reaction time between conditions, though judgments were marginally more accurate for coerced sentences than for controls (t(55) = 1.89, p < .1). Reading times that were greater than three standard deviations from each subject’s mean RT for a given phrase were removed as outliers. According to this criterion, another 15% of the total number of word-by-word reading times were removed from both conditions. Mean word-by-word reading times are shown in Fig. 3. A regression equation was used to generate predicted reading times for each subject based on the length (in characters) of each word and observed reading times were subtracted from estimated reading times to create residual reading times (Ferreira & Clifton, 1986). Residual reading times were not normally distributed, as assessed by the Shapiro–Wilk test for normality (W = .78, p < .001), and, accordingly, statistical comparison was carried out using a Table 1 Behavioral sensicality judgment data for Experiment 1

% Sensical Mean response time (ms)

Coercion

Control

93.6 491

88.9 506

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Fig. 3. Moving-window self-paced reading time data for Experiment 1 (n = 56). Reading times in the coercion condition (solid line) were significantly slower at the verb than in the control condition (dashed line). The asterisk indicates a significant difference in residual reading times by participants and by items following baseline correction (see text).

non-parametric Wilcoxon signed-rank test using residual reading times that were averaged across participants (T1) and across items (T2). Planned comparisons were conducted comparing reading times on the verb and on the three words immediately following. At the verb, coerced sentences were read more slowly (M = 37) than controls (M = 60) (T1 = 532, p < .05), though this difference was not significant in the items analysis (T2 = 185, p = .34). There were no significant differences in the three words following the verb. Visual inspection of the data suggested that control sentences were read more slowly than coercion sentences prior to the verb, potentially reflecting the different lexical material used in the adverbial modifiers. Further tests confirmed a significant difference in RTs on the sentential subject such that coercion sentences were read faster than controls (T1 = 1073, p < .05; T2 = 380, p < .005). Turning to the three words of the sentence initial temporal modifier, control modifiers were read marginally faster than coercion modifiers at the second word (T1 = 969, p < .1; T2 = 315, p < .1) and the reading time difference at the first word reached significance in the items, but not participants, analysis (T2 = 337, p < .05; T1 = 956, p = .12). Thus the effect of mismatch at the verb may have been obscured in the items analysis by the opposite effect of the preceding durative modifier. To examine this, we normalized the baseline between conditions by taking the average residual RT at the temporal modifier (i.e., the first three words) for each condition and subtracting this value from the residual RT of each word in the sentence. With this correction, the difference between coerced verbs and control verbs was reliable both by participants (T1 = 1151, p < .005) and by items (T2 = 327, p = .05). 2.3. Discussion Consistent with the predictions of Iterative Coercion, reading times revealed a processing cost on punctual verbs when they appeared in a mismatching durative context. This is in line with the findings of Piñango et al. (1999), (2006), Todorova et al. (2000), and Husband et al. (2006), (2008). The effect was obtained even though immediately prior to the verb, control sentences were read more slowly than coerced sentences. Thus our findings suggest that when verbs are normed to ensure that they described a single event, aspectual mismatch is costly even in self-paced reading, contra Pickering et al. (2006). Concerning the reading time differences found on the temporal modifiers, Zwaan (1996) observed that temporal modifiers which

shift a narrative in time (e.g., after an hour) are more difficult to process than modifiers that do not do so (e.g., after a moment). Though our sentences were presented in isolation and not as parts of longer narratives, a subset of punctual modifiers in the control condition could be associated with a narrative shift (e.g., after twenty minutes). Thus, the RT differences between the modifiers are consistent with Zwaan’s (1996) finding that narrative time shifts engendered a processing cost. In summary, our reading time data suggest that the interpretation of punctual predicates in durative contexts is more difficult to compute than such predicates in a punctual context. These results, thus, provide evidence that the aspectual representation of at least strongly punctual verbs is not underspecified and that their iterative readings are derived. In Experiment 2, we used MEG to elucidate the neural bases of this process. 3. Experiment 2: MEG What brain regions might plausibly show an effect of Iterative Coercion? Although there have not been previous functional imaging or EEG/MEG studies on aspectual mismatch, we identify three previous results that help narrow down the hypothesis space. First, as already outlined in the introduction, the MEG correlates of meaning shift have been previously investigated for a different construction, so-called Complement Coercion (Pylkkänen & McElree, 2007). Complement Coercion refers to a semantic type-shift that converts the meaning of an entity-denoting NP, such as the book, to an event-meaning when the NP occurs as the complement of an event-selecting verb. For example, an expression such as the author began the book is intuitively interpreted as ‘the author began some activity (e.g., reading or writing) involving the book’. Complement Coercion has been reported as behaviorally costly in numerous studies (McElree, Frisson, & Pickering, 2006; McElree, Pylkkänen, Pickering, & Traxler, 2006; McElree, Traxler, Pickering, Seely, & Jackendoff, 2001; Pickering, McElree, & Traxler, 2005; Traxler, McElree, Williams, & Pickering, 2005; Traxler, Pickering, & McElree, 2002). In an MEG study aimed at localizing the neural generators of the coercion effect, Pylkkänen and McElree (2007) found that coerced sentences elicited increased activity in an MEG component dubbed the anterior midline field (AMF), generated in ventromedial prefrontal regions at approximately 400 ms after the onset of the target noun book. Thus the AMF constitutes an obvious component of interest for the present study: an AMF effect of Iterative Coercion would demonstrate that the AMF is

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not only modulated by entity-to-event shifts in Complement Coercion, but also by more subtle shifts involving the temporal properties of events. Further, as outlined in the Introduction, an AMF effect of aspectual mismatch would conform to Harris et al.’s (2007) suggestion that the AMF might be sensitive only to meaning-changing shifts, and not to purely logical type-shifts. A second prediction can be formulated on the basis of the pragmatic account of Iterative Coercion. If aspectual mismatch resolution indeed involves two computational stages, i.e., an initial composition of an implausible meaning followed by a subsequent meaning shift (Fig. 2b), an effect of anomaly detection should precede any effect associated with shifting. In ERP studies, violations of semantic plausibility classically elicit a negative-going deflection peaking at around 400 ms, the so-called N400, as originally reported by Kutas and Hillyard (1980) and subsequently replicated in numerous studies. Unfortunately, however, evaluating whether coercion elicits an N400-like effect is highly non-trivial, given that the N400 has been reported to involve a large number of generators, spanning the temporal lobes bilaterally as well as various regions of the frontal lobes (Halgren et al., 2002; Helenius, Salmelin, Service, & Connolly, 1999; Maess, Herrmann, Hahne, Nakamura, & Friederici, 2006; Service, Helenius, Maury, & Salmelin, 2007). Nevertheless, we aimed to at least tentatively examine this prediction by conducting a comprehensive review of MEG localizations of the N400 in studies using techniques maximally similar to ours (see Section 2.3.), in order to assess the extent to which our effects overlap with the areas implicated by these studies. Finally, another potential region of interest is suggested by a deficit/lesion study by Piñango and Zurif (2001), who found that left posterior temporal damage correlated with problems in comprehending Aspectual Coercion in a group of three Wernicke’s aphasics. An MEG finding corroborating this result would suggest that left temporal cortex indeed computes some part of Aspectual Coercion, as opposed to simply providing input for the operation. 3.1. Methods 3.1.1. Participants Participants were 15 right-handed native speakers of English (8 female) ranging in age from 19 to 39. All were students or employees at New York University. 3.1.2. Stimuli Target stimuli were the same as in Experiment 1. In addition to the 30 coerced and 30 control sentences, an additional 120 sentences with a similar form were also presented (50% anomalous; see discussion of fillers in Experiment 1). We also included 240 sentences of varying syntactic structures testing unrelated hypotheses (50% anomalous). Each of the subjects viewed all of the stimuli. The materials were presented in a pseudorandom order such that the effect of repetition was counterbalanced across conditions.

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whether the sentence made sense or not within 4 s. Neuromagnetic fields were recorded from 300 ms before the presentation of the target verb to 1000 ms after. 3.1.4. MEG data analysis Prior to statistical analysis, trials with erroneous responses were removed, and the data were cleaned of artifacts by rejecting trials for which the difference between the minimum and maximum amplitudes exceeded a threshold which varied between 2500 and 3500 fT depending on the amplitude range of each subject. MEG data from each subject were averaged by condition; approximately 90% of all trials were retained for each subject per condition. Data were then low-pass filtered at 40 Hz and a highpass band filtered at 1 Hz. In order to obtain a maximally simple initial evaluation of the contribution of the AMF in aspectual mismatch resolution, the MEG data were first analyzed by using a spatial filter defined by the mean localization and orientation of the AMF effect reported by Pylkkänen and McElree (2007) for Complement Coercion. The prediction was that if processing aspectual mismatch is associated with increased amplitude in the AMF source, the AMF spatial filter should show an effect of aspectual mismatch. The AMF spatial filter, a single equivalent current dipole, was placed in each subject’s data using BESA 5.1 software (Megis, DE) with the location and orientation fixed (Talairach coordinates: x = 4.8, y = 36.8, z = 5; x-ori = 0.14, y-ori = 0.13, z-ori = 0.98). As a second, more fine-grained, analysis, we carried out a distributed source analysis using minimum norm estimates (MNEs; Hämäläinen & Ilmoniemi, 1984). Unlike discrete source models, MNEs require little user intervention, such as assumptions about the number of sources involved in a solution. MNEs are also are suitable for representing both focal and distributed sources (Uutela, Hämäläinen, & Somersalo, 1999). Accordingly, MNEs allowed us to independently assess the spatial distribution of any activity differences identified with the spatial filter. The MNEs were calculated in BESA 5.1., assuming a minimum L2-norm. 1426 regional sources were evenly distributed at depths of approximately 10% and 30% below a smoothed standard brain surface. Regional sources in MEG can be regarded as sources with two orthogonally oriented dipoles in the same location, the RMS of each pair of dipoles providing the activation of the regional source. Pairs of sources at different depths were then averaged to create 713 non-directional sources for which activation could be compared across subjects and conditions. Finally, we assessed the extent to which the effects obtained in the source models were also observable in sensor-space. In order to test our hypothesis regarding the AMF, we calculated the RMS (root-mean-square) amplitudes of a region of anterior sensors. RMS analysis was also performed over a group of left temporal sensors as well as over a group of right temporal sensors. 3.2. Results

3.1.3. Procedure During the experiment, subjects lay in a dimly lit magnetically shielded room and viewed the stimuli on fiberglass goggles (Avotec, FL), while neuromagnetic fields were recorded with a wholehead 148-chanel magnetometer (4-D Neuroimaging Magnes WH 2500, San Diego CA), sampling at 678 Hz in a band between .1 and 200 Hz. Each trial began with a fixation cross presented in the middle of the screen. Subjects then initiated the presentation of each sentence themselves by pressing a button. Sentences were presented word-by-word in white Courier font, size 90, against a black background. Each word was presented for 300 ms with a 300 ms blank screen between words. At the end of each sentence, a question mark was displayed and the subject was instructed to judge

3.2.1. Behavioral data Data from the end-of-sentence sensicality judgments were analyzed for accuracy and response times; a summary is shown in Table 2. All subjects showed a high degree of accuracy. Importantly, coerced and control sentences did not differ in the degree to which they were judged as sensical. Response times were, however, significantly slower for coerced sentences, t(14) = 2.35, p < .05. 3.2.2. AMF spatial filter The mean time-course of the single-dipole spatial filter for both of the conditions across all subjects is shown in Fig. 4. Significant amplitude divergence between the waves was assessed with the cluster-mass statistic (Maris & Oostenveld, 2007) using the R

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Table 2 Behavioral sensicality judgment data for Experiment 2

% Sensical Mean response time (ms)

Coercion

Control

88.7 560

86 494

statistical software package (R Development Core Team, 2006). First, pairwise t-tests were conducted for each time sample between 0 and 600 ms after stimulus onset. Then, samples that differed at p < .05 (uncorrected) were grouped into clusters according to temporal adjacency. This step yielded three distinct temporal clusters at 45–50 ms, 354–360 ms, and 448–459 ms post stimulus onset. Next, a ‘‘cluster-level” t-statistic was derived by summing the absolute value of the t-statistics within each cluster. The last cluster showed the largest cluster-level t, and the probability distribution of this cluster’s t-statistic was determined using a permutation test in which conditions labels were shuffled and the statistic was computed 10,000 times for this time window. The resulting distribution was used to determine the p-value of the cluster-level t-statistic associated with each of the three clusters. Only the final cluster (ranging between 448 and 459 ms) reached significance according to this procedure (Monte Carlo p < .05, corrected). These results suggest that aspectual mismatch does lead to increased activity at the AMF. 3.2.3. Minimum norm estimates The minimum norm estimates allowed us to assess whether the effect revealed by the spatial filter, in fact, localized into midline frontal regions. Models were constructed for each subject, and statistical comparison proceeded by pairwise t-tests between each source at each time point from 300 to 500 ms post stimulus onset. For statistical reliability, we required at least 5 adjacent sources to show a significant difference for a continuous period of 12 ms (8 temporal samples), alpha = .05. Significant results from this comparison are shown in Fig. 5 where regions showing greater activity in the coerced condition are plotted in red. This analysis revealed two stages of reliably increased activity for the coerced verbs. In the first stage, beginning approximately 340 ms after verb onset, aspectually mismatching verbs elicited increased amplitudes in right-lateral middle frontal as well as in anterior and posterior temporal regions. The second effect, about a hundred milliseconds later, localized in anterior midline regions. These results suggest that the AMF spatial filter used in our first analysis was an appropriate model for the later effect at 450 ms but not for the earlier one.

Fig. 5. Areas showing reliably increased activity for the Coercion condition in the distributed source analysis. Two distinct effects are revealed, an earlier right-lateral frontal, anterior temporal and posterior temporal/cerebellar effect at 340–380 ms, and a later anterior midline effect at 440–460 ms.

3.2.4. Sensor-space RMS The RMS analysis allowed us to determine the extent to which the effects observed in the source models were also apparent in sensor-space. The mean time-course of the RMS for both conditions in each of the three regions of interest is shown in Fig. 6. As with the AMF spatial filter analysis, significant divergence between the waves was assessed using the cluster-mass statistic (Maris & Oostenveld, 2007). Pairwise t-tests were conducted for each time sample between 300 and 500 ms for each quadrant. Within each quadrant, samples that differed at p < .05 (uncorrected) were clustered according to temporal adjacency. This step yielded two clusters across all regions with one at 435–452 ms in the anterior quadrant, and one at 473–474 ms in the left-lateral quadrant. The frontal cluster showed the largest cluster-level t

Fig. 4. Grandaveraged source waveforms for the AMF spatial filter applied to the MEG data of Experiment 2. Activity in the coerced condition (solid line) was significantly greater between 448 and 459 ms as assessed using the cluster-mass test (Maris & Oostenveld, 2007).

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Fig. 6. Grandaveraged RMS waveforms over sensors for three regions of interest (shown at bottom). Waves in the anterior quadrant, between 437 and 452 ms, evidenced significantly larger amplitudes in the Coercion condition (solid), as compared to Control (dotted), confirming that the effect at the AMF was apparent in sensor-space.

and the distribution of the statistic was determined using a permutation test with 10,000 iterations. The p-value of each of the two cluster-level t-statistics was determined in comparison to this cluster’s distribution. Only the cluster in the anterior quadrant (435–452 ms) reached significance (Monte Carlo p < .05, corrected). The effect in the frontal quadrant between 400 and 500 ms matched the AMF effect in location and time-course identified in the AMF spatial filter and Minimum norm analyses. However, the right hemisphere effect noted in the Minimum norm analysis was not apparent in sensor-space. 3.3. Discussion Experiment 2 investigated the neural correlates associated with processing aspectual mismatch. In particular, we tested whether aspectual mismatch engages the AMF, which has been reported as sensitive to meaning mismatch in Complement Coercion. Aspectual Coercion elicited an AMF effect suggesting a contribution of the AMF in semantic interpretation that goes beyond Complement Coercion. We also aimed to assess whether the neural correlates of coercion occurred in one or two stages. The AMF effect was preceded by a distributed right hemispheric effect beginning around 340 and lasting about 40 ms. In order to evaluate whether this earlier RH effect might be associated with anomaly recognition, we investigated the degree to which this effect overlapped with previously reported generators of the N400 effect. Unfortunately, direct comparison with activity elicited by our anomalous fillers was not possible as they involved thematic violations (e.g., . . .the saucepan sneezed. . .), which in recent electrophysiological studies have elicited P600 instead of N400-like effects (Hoeks, Stowe, & Doedens,

2004; Kuperberg, Caplan, Sitnikova, Eddy, & Holcomb, 2006; Kuperberg, Kreher, Sitnikova, Caplan, & Holcomb, 2007; Kuperberg, Sitnikova, Capland, & Holcomb, 2003; but cf. Kim & Osterhout, 2005). Thus we compared our RH effect to previous MEG N400 studies, instead. MEG studies aiming to localize the N400 have used both discrete dipole modeling (Helenius et al., 1999; Service et al., 2007) as well as distributed source analysis (Halgren et al., 2002; Maess et al., 2006). Since our RH effect was obtained via distributed source analysis (and was clearly distributed), we limited our comparison to studies that were methodologically parallel. In a classic auditory semantic anomaly paradigm where German sentences ended with a semantically implausible final word (e.g., Die Melodi/Mülleimer wurde gepfiffen ‘The melody/trash bin was whistled’), Maess et al. (2006) reported 6 regions of interest as showing significantly greater activity in the anomalous condition at 300–550 ms: bilateral inferior temporal gyri, the left superior temporal gyrus, Broca’s area left-laterally (BA 44/45) and the inferior frontal gyri (BA 47) bilaterally. In the visual modality, Halgren et al. (2002) employed a similar manipulation and reported a widespread effect of anomaly in bilateral anterior temporal and orbital regions as well as in left-lateral perisylvian, orbital, frontopolar, dorsolateral and prefrontal areas. Fig. 7 plots the regions of activity reported in these two studies. Effects found in both studies involve three regions: the anterior temporal lobe bilaterally and left inferior frontal areas. A comparison between our right-lateral effect and the N400-related regions found by both Maess et al. (2006) and Halgren et al. (2002) indicated one common region: the right anterior temporal lobe. Thus our RH effect did overlap with previously reported anomaly effects, but only very partially.

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Fig. 7. Brain regions sensitive to semantic anomaly, as reported by two MEG studies employing distributed source analysis. Data are plotted on an inflated average MR image. Results from Halgren et al. (2002) are shaded in blue, those form Maess et al. (2006) are shaded in orange and regions reported active in both studies are shaded in purple.

Finally, with respect to the previous aphasic study on Aspectual Coercion by Piñango and Zurif (2001), our lack of left-lateral effects suggests that their findings on Wernicke’s aphasics with posterior left-lateral lesions and problems in interpreting Aspectual Coercion should not be taken as implicating a direct involvement of left hemisphere regions in aspectual mismatch resolution. Rather, these areas may provide input for the operation. For example, the role of posterior left temporal regions in lexical access is rather uncontroversial (e.g., Hickok & Poeppel, 2007; Salmelin, 2007). 4. General discussion This research examined the processing of Aspectual Coercion, for which four distinct representational hypotheses have been proposed. Reading time results from Experiment 1 ruled out two hypotheses: underspecification, whereby verbs like jump are not specified for event type, and Punctual Coercion, where the basic representation of such verbs is iterative. Instead, our results were consistent with the predictions of Iterative Coercion, where verbs like jump are represented as punctual, with iterative interpretations being derived either by semantic or pragmatic means. Thus, we found behavioral evidence that Aspectual Coercion does engender a processing cost, clarifying a controversy in previous literature. Experiment 2 aimed to localize the neural correlates of the processing cost. In particular, we were interested in assessing whether the AMF, previously shown to be sensitive to Complement Coercion, would also be modulated by Aspectual Coercion. We indeed obtained an effect in the AMF, suggesting that ventromedial prefrontal cortex participates in semantic interpretation in a way that spans the two different constructions. Thus, we can reject the hypothesis that the AMF reflects processing unique to Complement Coercion. This of course still leaves open many different interpretations of the AMF effect; for example, future studies will hopefully elucidate whether the AMF is involved in semantic composition in general or whether its function is limited to meaning mismatch. Interestingly, ventromedial prefrontal cortex (VMF) has been identified as a network node in a recent MEG study investigating long-range connectivity between brain areas involved in the comprehension of a written story (Kujala et al., 2007). Further, recent fMRI studies have shown the medial prefrontal cortex to be involved in processing coherent discourse (Ferstl & von Cramon, 2001, 2002; Kuperberg, Lakshmanan, Caplan, & Holcomb, 2006). These findings are at least compatible with the hypothesis that the VMF plays some rather central role in language comprehension, even though it does not figure in most extant neurocognitive models of language. Instead of language, the VMF has been implicated for many types of non-linguistic higher cognition, including theory-of-mind (Amodio & Frith, 2006; Gallagher & Frith, 2003;

Rowe, Bullock, Polkey, & Morris, 2001), emotion (Bechara, Damasio, & Damasio, 2000; Damasio, 1994), and decision making (Bechara et al., 2000; Fellows & Farah, 2007; see Wallis, 2007 for a recent review). Thus it is possible that the operations performed by the VMF in language processing are not computations unique to language. In addition to the contribution of the AMF in Aspectual Coercion, we also aimed to assess whether Aspectual Coercion engages neural generators of the N400 response associated with semantic anomaly. This was of interest because pragmatic accounts of Aspectual Coercion would predict it to involve a stage of processing where an anomalous meaning is computed. Our AMF effect was indeed preceded by a distributed right-lateral effect that partially overlapped with previous MEG localizations of the N400. Thus, although our data cannot rule out hypotheses in which Aspectual Coercion is resolved semantically in the type-system, our twostage effect is most easily interpreted as reflecting a right-lateral detection of anomaly which is followed by a prefrontal meaning shift. 5. Conclusion In this research, we used a combination of behavioral and neuromagnetic measures to investigate different representational hypotheses of aspectual mismatch. Our results suggest that aspectual mismatch elicits a processing cost, consistent with theories where the mismatch is resolved via some type of coercion. Our MEG data revealed that the mismatch is associated with increased amplitudes of the AMF, localized in ventromedial prefrontal cortex. In combination with the previous finding that the AMF is affected by Complement Coercion, these data suggest that the ventromedial prefrontal cortex participates in semantic interpretation in some rather central, non-construction-specific, way. Acknowledgments This research was supported by the National Science Foundation Grant BCS-0545186 and the New York University Challenge Fund Award (to L.P.). We also thank Martin Gevonden and Garrick Yu for help in the materials creation and data collection of Experiment 1, Jesse Harris and Andrew Smart for assistance running subjects, and Rodolfo Llinás for generously allowing us to perform the MEG recordings in his facility. Appendix A A.1. Formal hypotheses See Fig. 8.

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Fig. 8. A formal representation of the four hypotheses sketched out in Fig. 2. In the lambda notation, d is a variable ranging over durative events, p a variable ranging over punctual events, and e a variable ranging over eventualities in general. In (b), the subscripted terms stand for aspectual information that is part of world knowledge but not part of the type-driven compositional system. For a basic introduction for to the typed lambda formula used here, see Pylkkänen and McElree (2006).

Appendix B B.1. Stimuli 1. a. (coercion) All morning long the cart banged in the cramped store aisle. b. (control) Just after ten the cart banged in the cramped store aisle. 2. a. For 45 seconds the computer beeped in the busy lab. b. After 45 seconds the computer beeped in the busy lab. 3. a. For ten minutes the tailor belched on the empty sidewalk. b. At three o’clock the tailor belched on the empty sidewalk. 4. a. Throughout the day the cannon blasted on top of the castle. b. At one o’clock the cannon blasted on top of the castle. 5. a. For five minutes the fireman blinked in the dark stairwell. b. After a minute the fireman blinked in the dark stairwell.

6. a. Throughout the morning the manager burped in the corner office. b. After a while the manager burped in the corner office. 7. a. For ten minutes the professor called from the cluttered office. b. After an hour the professor called from the cluttered office. 8. a. All day long the instructor coughed in front of the classroom. b. After several minutes the instructor coughed in front of the classroom. 9. a. Throughout the evening the princess curtseyed in front of the guests. b. At nine o’clock the princess curtseyed in front of the guests. 10. a. All afternoon long the dog dived in the olympic-sized pool. b. Exactly at noon the dog dived in the olympic-sized pool. 11. a. For several seconds the explorer fired beside the big blue lake. b. After a minute the explorer fired beside the big blue lake.

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12. a. For twenty minutes the father glanced out of the small window. b. Right at midnight the father glanced out of the small window. 13. a. For many hours the janitor jumped in the empty hallway. b. At seven o’clock the janitor jumped in the empty hallway. 14. a. For several minutes the acrobat leapt on the bouncy trampoline. b. Right at two the acrobat leapt on the bouncy trampoline. 15. a. Throughout the day the student sneezed in the back of the classroom. b. After twenty minutes the student sneezed in the back of the classroom. 16. a. During the morning the designer sniffed in the freshly painted studio. b. Right at noon the designer sniffed in the freshly painted studio. 17. a. All night long the elephant snorted in the grassy savannah. b. After five minutes the elephant snorted in the grassy savannah. 18. a. All day long the alloy sparked atop the hot anvil. b. After ten minutes the alloy sparked atop the hot anvil. 19. a. For an hour the mouse squeaked in the cramped living room. b. After four hours the mouse squeaked in the cramped living room. 20. a. During the night the writer stumbled in the crowded apartment. b. Right at midnight the writer stumbled in the crowded apartment. 21. a. For some time the mosquito stung over the muddy riverbank. b. After a moment the mosquito stung over the muddy riverbank. 22. a. For several seconds the car swerved on the windy mountaintop. b. After a minute the car swerved on the windy mountaintop. 23. a. For thirty minutes the player swung in the practice cage. b. After thirty minutes the player swung in the practice cage. 24. a. Throughout the afternoon the girl tripped in the snowy field. b. After an hour the girl tripped in the snowy field. 25. a. All afternoon long the politician winked in front of the audience. b. At the end the politician winked in front of the audience. 26. a. For two hours the frog leapt across the shallow pond. b. After several seconds the frog leapt across the shallow pond. 27. a. For fifteen minutes the performer jumped in the practice studio. b. After two minutes the performer jumped in the practice studio. 28. a. For two minutes the lawyer glanced at the police officer. b. After fifteen minutes the lawyer glanced at the police officer. 29. a. For twenty minutes the patient sneezed in the waiting room. b. After several moments the patient sneezed in the waiting room. 30. a. For a minute the toddler burped in the back seat. b. After one minutes the toddler burped in the back seat. References Amodio, D. M., & Frith, C. D. (2006). Meeting of minds: The medial frontal cortex and social cognition. Nature Reviews Neuroscience, 7(4), 268–277. Bechara, A., Damasio, H., & Damasio, A. R. (2000). Emotion, decision making and the orbitofrontal cortex. Cerebral Cortex, 10, 295–307. Damasio, A. (1994). Descartes’ error: Emotion, reason, and the human brain. New York: Putnam. de Swart, H. (1998). Aspect shift and coercion. Natural Language & Linguistic Theory, 16, 347–385.

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