Second Language Research

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The influence of lexical familiarity on ERP responses during sentence comprehension in language learners Jutta L. Mueller Second Language Research 2009; 25; 43 DOI: 10.1177/0267658308098996 The online version of this article can be found at: http://slr.sagepub.com/cgi/content/abstract/25/1/43

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Second Language Research 25,1 (2009); pp. 43–76

The influence of lexical familiarity on ERP responses during sentence comprehension in language learners Jutta L. Mueller Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig Received April 2007; revised January 2008; accepted January 2008

Previous research on event-related potentials (ERPs) on second language processing has revealed a great degree of plasticity in brain mechanisms of adult language learners. Studies with natural and artificial languages show that the N400 as well as the P600 component appear in learners after sufficient training. The present experiment tests if and which ERP components in response to syntactic and thematic processes generalize to unfamiliar lexical material in adult language learners. Learners of a miniature version of Japanese were presented with correct and incorrect sentences, half of which contained an unfamiliar word in the crucial sentence position. Incorrect sentences were either case-marking violations or word category violations. When all words were familiar, case-marking violations elicited a biphasic N400–P600 pattern and word category violations led to an early negativity that was followed by a P600. When the case violation occurred on an unfamiliar noun, only a P600 was seen. Word category violations that involved unknown verbs led to an early negativity and only to a reduced P600. The results suggest a high degree of nativelikeness for the learners during processing of familiar sentences. Unfamiliar words seem to entail additional processing costs and specifically lead to difficulties in the domain of case processing. Keywords: ERPs in SLA, N400–P600 patterns in SLA, L2 lexical processing, L2 sentence comprehension, micro-language learning

Address for correspondence: Jutta L. Mueller, Stephanstr. 1a, 04103 Leipzig, Germany; email: [email protected] © The author(s), 2009. 10.1177/0267658308098996 Reprints and permissions: http://www.sagepub.co.nk/journals permission.nav Downloaded from http://slr.sagepub.com at Shanghai Jiaotong University on March 7, 2009

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The influence of lexical familiarity on ERP

I Introduction Although the present article deals with comprehension processes at the sentential level, I would like to start with a few words about words. While the exact definition of the unit ‘word’ is complicated by the diversity of linguistic elements within and across languages, most people would probably agree that words are linguistic symbols that are combined by (morpho)syntactic rules to form more complex linguistic units such as phrases and sentences. Thus, they are the basic building blocks of sentences. While native speakers normally know the words they have to process in a given sentence, this is clearly not true for the special group of language learners, e.g. children, or second language learners. Conservative estimates of vocabulary sizes are around 17 000 words for educated native English speakers (Goulden et al., 1990). Although the number of words needed for the comprehension of normal texts and conversations is a lot smaller, it is clear that lexical difficulties are a very common experience for language learners. With the above situation in mind our present study deals with L2 sentence comprehension mechanisms in adult listeners and their possible disruption by lexical difficulties. A lot of research has been concerned with the assessment of characteristic differences between native and non-native language processing in various linguistic domains, such as phonology, syntax and semantics (for reviews, see Epstein et al., 1996; Piske et al., 2001; Kroll and Sunderman, 2003; Clahsen and Felser, 2006; Slabakova, 2006). How nativelike non-native language processing can become at ultimate levels of proficiency is still a matter of debate although a couple of recent studies provided evidence that there are almost no differences between phonological, grammatical and lexical processes of native speakers and highly proficient non-native L2 speakers (White and Genesee, 1996; Frenck-Mestre and Prince, 1997; Flege and MacKay, 2004; Ylinen et al., 2005; Hopp, 2006). While behavioural measures provide direct information about the cognitive outcome of language comprehension mechanisms, neurophysiological measures, such as event-related potentials (ERPs), provide temporal and spatial information about neural correlates accompanying the respective cognitive operations. This is of special interest to research on differences between native and non-native speakers, as neurophysiological measures might be more sensitive with


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respect to qualitative differences compared to behavioural measures. For example, language comprehension mechanisms that look similar at the level of behaviour could be supported by different neural processes. For the purpose of the present study we take a closer look at studies using ERPs to test syntactic and semantic sentence comprehension mechanisms in non-native speakers of a language. To start with, a brief review of relevant ERP components in native speakers is given. In a seminal study, Kutas and Hillyard (1980) found that semantic violations in sentences such as ‘He spread the warm bread with socks’ yield a negative waveform peaking at around 400 ms after stimulus onset, which has been termed N400. A large number of subsequent studies have shown that the N400 can be elicited in a variety of contexts, ranging from wordlists (Holcomb, 1988) to world knowledge (Hagoort et al., 2004; Chwilla and Kolk, 2005). Therefore, it is usually seen as an indicator of semantic processing at the stage of lexical–semantic integration (for review, see Kutas and Federmeier, 2000). Some recent studies, in which the N400 was elicited in response to incorrect repetitions of case markers, suggested that the range of processes captured by the N400 may have to be extended beyond lexical–semantic processes to processes of thematic hierarchization, i.e. the ordering of sentential arguments according to their thematic roles (e.g. agent, patient; Frisch and Schlesewsky, 2001; Schlesewsky and Bornkessel, 2004). However, it is not very clear yet if the N400 in this case is physiologically identical with the classical lexical–semantic N400 (Roehm et al., 2004) and, thus, in this article we refer to the N400 in response to case violations as ‘thematic N400’. In contrast, syntactic processes have not been associated with a single ERP response, but rather with a family of components consisting of left anterior negativities (E/LANs) and posterior positivities (P600s). Outright syntactic violations frequently elicit anterior negativities (Neville et al., 1991; Friederici et al., 1993; Coulson et al., 1998; Gunter et al., 2000; Deutsch and Bentin, 2001), which are sometimes subdivided into several components, namely into the ELAN and LAN components (Friederici, 2002). LAN components occur between 300 ms and 500 ms after stimulus onset and were reported for different types of morphosyntactic agreement errors, such as gender, number and case violations (Coulson et al., 1998; Deutsch and Bentin, 2001; Gunter


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et al., 2000). ELAN components occur even earlier (100–300 ms after stimulus onset) and were mainly reported for local phrase structure violations (Neville et al., 1991; Friederici et al., 1993). While anterior negativities have been consistently reported for syntactic violations their exact functional interpretation is subject to continuing debate. Friederici (2002) suggested that the LAN can be seen as an index of morphosyntactic processing, while the ELAN reflects earlier and automatic phrase structure building processes which are based solely on word category information. Other studies, however, have challenged this notion. Some studies, for example, reported LAN effects with a very early timing (Kubota et al., 2003; 2004; Hasting and Kotz, 2008) or showed that syntactic constraints can modify the ELAN response (Lau et al., 2006). Even seemingly non-syntactic processes at the lexical level seem to elicit LAN effects in certain circumstances (e.g. Krott et al., 2006). Thus, the conditions under which the potentially different types of anterior negativities occur – and their specificity to syntactic processes – remain subject to further research. The P600 component – a positive deflection between 300 ms and 900 ms after stimulus onset – occurs for syntactic violations as well as for processing of syntactically ambiguous or complex structures (Osterhout and Holcomb, 1992; Osterhout et al., 1994). Similar to anterior negativities it is still debated how specific to syntactic processes the P600 is in fact as it has been shown that it also occurs for violation conditions that are rather semantic in nature (van Herten et al., 2005; van Herten, Chwilla, and Kolk, 2006). The P600 can vary in dependence on task demands (Coulson et al., 1998; Gunter and Friederici, 1999). Depending on the focus of research, the P600 has been seen as indicating more controlled syntactic mechanisms of reanalysis and repair (Friederici, 2002), processing of syntactic complexity (Kaan et al., 2000), or more general (non-syntactic) monitoring processes (van Herten et al., 2005; 2006). When it comes to the occurrence of these ERP components in L2 speakers, recently reported studies have provided a relatively consistent pattern of results, which is still in the process to be extended. Electrophysiological processes involved in the comsputation of semantic meaning seem to be relatively nativelike in L2 speakers. The N400 component, as seen in sentence comprehension studies, has been frequently reported for L2 speakers, even though it was delayed or reduced in some


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cases (Ardal et al., 1990; Weber-Fox and Neville, 1996; Hahne, 2001; Hahne and Friederici, 2001; Sanders and Neville, 2003; Moreno and Kutas, 2005; Ojima et al., 2005). In contrast to the N400, ERP components related to syntactic processes were not always found for L2 speakers to be similar as in native speakers. The first studies testing syntactic processing mechanisms in L2 using syntactic violations reported the absence of left anterior negativities and a reduction or delay of the P600 component (Weber-Fox and Neville, 1996; Hahne, 2001). However, high proficiency seems to enable the development of a P600 effect for syntactic violations (Hahne and Friederici, 2001). While these observations led to the conclusion that syntactic processes may be more vulnerable to age-of-acquisition effects compared to semantic processes (Weber-Fox and Neville, 1996), subsequent studies have shown that the development of a nativelike ERP pattern including anterior negativities is not totally out of reach for L2 speakers provided they are proficient enough. Several studies yielded P600 effects that were similar in native and non-native speakers (Hahne and Friederici, 2001; Mueller et al., 2005; Osterhout et al., 2006; Mueller et al., 2007). Moreover, Rossi et al. (2006) reported an ELAN component for highly proficient German as well as Italian speakers. Similarly, Hahne et al. (2006) reported a LAN component in native Russian learners of German in response to a violation of German verb inflection. It seems to be the case that high proficiency leads to the convergence of native and non-native language processing mechanisms as far as they are measurable in ERP components. One further result supporting this conclusion stems from longitudinal data reported by Osterhout et al. (2006). In this study it was shown that native English speakers learning French showed an N400 response for morphosyntactic errors in initial stages of learning, which developed into a P600 pattern at later, more advanced stages of learning. The authors interpreted this as indicative of a transition from lexically based processes to the application of grammatical knowledge with increasing proficiency. Most importantly, they show how dramatically ERP components can change during language learning before a nativelike pattern might eventually be reached. The possibility of nativelike ERP patterns in adult language learners is further supported by a series of studies using very restricted miniature


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and artificial languages to test if native-language-like syntactic and semantic ERP components would emerge even after short periods of training (Hoen and Dominey, 2000; 2004; Friederici, 2002; LelekovBoissard and Dominey, 2002). Thus, the hypothesis that there are necessary and insurmountable differences between native and non-native language comprehension mechanisms seems to stand on shaky grounds. What about the efficiency of the syntactic operations reflected in these ERP components in the light of possible lexical difficulties resulting from above described restrictions of the vocabulary size? Two possible scenarios are conceivable, namely independence of the syntactic processing system from the lexical–semantic system and interaction of the two systems. If both systems are independent from each other, then syntactic processing mechanisms should be applicable to every lexical item, be it familiar or not to the comprehender. However, if both systems interact to some degree, then syntactic processing mechanisms may be not very stable and easily disrupted if a difficulty is encountered in the lexical domain. This means that good vocabulary knowledge would be very important for L2 speakers not only in order to understand the concepts transmitted by the words but also to ensure trouble-free syntactic processing. There is some indication from research on native speakers’ sentence processing mechanisms in Jabberwocky sentences which may or may not be generalizable to second language learners’ processes (Hahne and Jescheniak, 2001). In this ERP study syntactic processing was investigated in sentences in which words were replaced by pseudowords while grammatical morphemes were still present. Hahne and Jescheniak presented word category violations in both sentence types and observed an ELAN effect as well as a P600 in both cases. Additionally, words in ‘semantic’ sentences yielded an N400 effect when compared to words in Jabberwocky sentences. This study suggests that, even in the absence of meaning, syntactic structure is computed in native speakers and, thus, that syntactic processes can function independently from semantic processes. We do not know whether such an independence of syntactic function could be found in L2 speakers. Sanders and Neville (2003) investigated lexical processes in Jabberwocky sentences in native and non-native speakers and reported an N400 effect for words compared to pseudowords. However, the


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N400 effect was smaller in the non-native speakers due to an increased N400 amplitude for pseudowords. This was taken to suggest that L2 speakers were engaged in lexical search to a greater degree compared to natives, possibly because non-natives experienced a greater uncertainty about the lexical status of words in Jabberwocky sentences (Sanders and Neville, 2003). As the sentences used by Sanders and Neville contained only pseudowords, it is difficult to predict how L2 speakers would deal with an unknown word in an otherwise semantically and syntactically normal sentence. II The present study In our present study we tested syntactic and thematic sentence comprehension processes in a group of participants that was highly trained in a subset of Japanese, which was termed Mini-Nihongo. The very same group of participants had already taken part in earlier experiments conducted within the Mini-Nihongo framework (see Mueller et al., 2005; 2007). For these as well as for the present study we used an ERP violation paradigm, in which sentence processing mechanisms were tested by assessing differences between ERP components measured while listening to correct and syntactically and thematically incorrect elements, respectively. The previous Mini-Nihongo studies revealed that, after a short period of training, P600 responses as well as earlier negativities appeared for word category and case violation conditions.1 The results were seen as indicating that controlled syntactic processes, as reflected in the P600, can be established after just a small amount of training. The early negativity in response to word category violations (100–300 ms after stimulus onset) observed for the learners showed a more posterior scalp distribution compared to the one observed for Japanese native speakers. This was seen as an indication of a greater reliance on prosodic cues for the learners, whereas the native speakers’ ELAN-like anterior focus indicated greater recruitment of syntactic processing mechanisms. For 1 The stimuli in the previous experiments were identical to those described as ‘familiar’ in Table 1. Note that the second noun is missing in word category violation, which leads to the disruption of the syntactic as well as the prosodic structure of the sentence, because noun phrase prosody is expected in a place in which verb phrase prosody occurs.


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the non-natives, the N400 in response to case violations was missing in the first Mini-Nihongo study; this was taken to suggest that thematic processes were not identical in native and non-native speakers (Mueller et al., 2005). In the second Mini-Nihongo study, case violations yielded a negativity even for non-natives, which was, however, differently distributed compared to the one in native speakers (Mueller et al., 2007). In the current experiment these highly trained participants were presented with sentences of the kind they were familiar with as well as sentences that contained new and unfamiliar words in the positions that were critical for the detection of possible violations. The sentences could either be correct or contain word category or case violations. Thus, we directly compared the cognitive brain mechanisms involved in the computation of syntactic difficulties when they were carried either by familiar words or by unfamiliar words within sentences. Generally speaking, we wanted to test if the processing mechanisms they had acquired in the miniature language would generalize to lexically new material. Table 1 shows examples of the stimulus material. Based on the previous Mini-Nihongo studies – and based on research on pseudoword processing – we made the following hypotheses: For the case and the word category violation with familiar words we expected to replicate previous results. Thus, for the case violation we expected a biphasic pattern of an N400 and a P600 (Mueller et al., 2007), and for the word category violation a pattern consisting of an early, broadly distributed negativity and a subsequent P600 (Mueller et al., 2005). With respect to case violations on unfamiliar nouns it was difficult to make predictions. Thematic processing as reflected in the N400 component of Frisch and Schlesewsky (2001) depends on both morphological case-marking and specific semantic information (such as animacy). There is no study with native speakers that tests thematic processing with Jabberwocky sentences. However, as the study by Frisch and Schlesewsky (2001) shows, thematic hierarchies can be built based on morphological case information alone (in the absence of informative animacy information). Thus, we expected that, in principle, the thematic N400 could also be found for case-marked pseudowords. However, in previous studies, the negativity in response to case violations is vulnerable compared to the P600 (Mueller et al., 2005; 2007), so we considered the possibility that it could be disrupted by lexical difficulties. For the


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Table 1 Examples of the stimuli used in the experiment

Correct condition: familiar Ichi wa no kamo ga ni hiki no nezumi o 1 [bird][gen.] duck 2 [small-animal][gen.] mouse [nom.] Correct condition: unfamiliar verb Ichi wa no hato ga ni hiki no neko o 1 [bird][gen.] pigeon 2 [small-animal][gen.] [nom.] cat [acc.]

tobikoeru tokoro desu. [acc] jump over take place. kizutsukeru tokoro desu. injure take place.

Correct condition: unfamiliar noun Ichi wa no hato ga ni hiki no kitsune o 1 [bird][gen.] pigeon 2 [small-animal][gen.] [nom.] fox [acc.]

tobikoeru tokoro desu. jump over take place.

Word category violation: familiar verb Ichi wa no kamo ga ni hiki no 1 [bird][gen.] duck [nom.] 2 [small-animal][gen.]


Word category violation: unfamiliar verb Ichi wa no kamo ga ni hiki no 1 [bird][gen.] duck [nom.] 2 [small-animal][gen.]

kizutsukeru tokoro desu. injure take place.

Case violation: familiar noun Ichi wa no kamo ga ni hiki no nezumi ga 1 [bird][gen.] duck [nom.] 2 [small-animal][gen.] mouse [nom.]


Case violation: unfamiliar noun Ichi wa no hato ga ni hiki no kitsune ga 1 [bird][gen.] pigeon [nom.] 2 [small-animal][gen.] fox [nom.]


Notes: gen. = genitive, nom. = nominative, acc. = accusative; incorrect elements are underlined; unfamiliar elements in boldface.

P600, we expected it to be present if behavioural results suggested a high level of performance. For word category violations on unfamiliar verbs we predicted relative stability. As the early negativity was attributed to processes of prosodic phrasing – i.e. the identification of prosodic phrase boundaries (c.f. Mueller et al., 2005) – we expected it to also be present for the case of unfamiliar verbs. Depending on the level of error detection rate we expected a P600 component to be present if the behavioural performance was good enough. III Method 1 Participants Twenty-one German native speakers (10 female, 11 male) participated in the experiment. All participants had taken part in the two previous


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Mini-Nihongo studies (Mueller et al., 2005; 2007), which took place some months before. All participants were right-handed and were aged between 20 and 26 years (mean: 23.9 years). Participants with an error rate > 40% in one condition were excluded from the analysis of that condition in the behavioural and in the ERP data. In the case violation condition only 14 participants reached the required criterion, whereas in the word category violation condition 19 participants could be included in the analyses. 2 Stimulus material The Mini-Nihongo grammar comprises four nouns (hato ‘pigeon’, kamo ‘duck’, neko ‘cat’, nezumi ‘mouse’), four verbs (oikakeru ‘walk behind’, oiharau ‘chase away’, tobikoeru ‘jump over’, tsukitobasu ‘push away’), three case-marking postpositions (ga ‘nominative’, o ‘accusative’, no ‘genitive’), two numeral classifiers (wa ‘bird class’, hiki ‘small animal class’), two numerals (ichi ‘one’, ni ‘two’), one adjective (akai ‘red’) and one temporal adverb (tokoro desu ‘take place’). The sentences for the training game comprised 640 different canonical (Subject–Object–Verb) and non-canonical (Object–Subject–Verb) sentences containing the above lexical and functional elements. They were recorded by a female native speaker of Japanese at a sampling rate of 44 kHz; the sentences were spoken at a natural speed. For the experiment only sentences that did not occur in the training phase were used. Only canonical sentence structures occurred in the experiment. The manipulation of lexical familiarity was achieved by adding either a new noun or a new verb to half of the sentences. Although these items were repeated many times within the experiment we could assume that no lexical meaning could be learned due to the absence of any referential cues. Nonetheless, a certain familiarity with the lexical form could of course emerge. Altogether there were four new animate nouns that fitted in the predefined classifier categories (taka ‘hawk’, tombi ‘buzzard’, kitsune ‘fox’, saru ‘monkey’), and four new verbs (oshitaosu ‘throw down’, kizutsukeru ‘injure’, syugekisuru ‘attack’, ikakusuru ‘menace’). The new words were matched to the familiar words with respect to the number of syllables. Case and word category violations could be created in such a way that the violation element was either


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familiar or unfamiliar, resulting in six experimental conditions; these are listed in Table 1. The stimulus materials comprised 64 sentences of each of the six experimental conditions and 128 correct filler sentences. In total the stimuli comprised 512 sentences, half of which were incorrect. Each numeral, classifier, noun and verb occurred with equal frequency and half of the sentences contained the adjective akai in the first NP. Correct and incorrect sentences differed only with respect to the violation and were otherwise identical. All sentences were spoken by the same female Japanese native speaker who recorded the stimulus material for the training phase and the previous experiments. 3 Mini-Nihongo training game The participants had to refresh their abilities in Mini-Nihongo by playing a computer game until they reached the same proficiency criterion (75% correct responses in a comprehension task and 100% correct in a production task) that they had reached some months earlier. Individual training times needed to reach the criterion ranged from 1 to 2.5 hours (average: 1.6 hours). 4 Data acquisition and analysis All participants received written instruction before the ERP measurement in which they were informed about the occurrence of unfamiliar words. They were not informed about any aspect of the novel words such as word category or animacy. Participants were asked to listen attentively and to provide a grammaticality judgement after the presentation of each sentence. During the ERP measurement participants sat in a comfortable chair in a sound-attenuated booth 1.3 m in front of a computer screen. The sentences were presented via loudspeakers. Participants were asked to fixate a cross which appeared in each trial in the middle of the screen from 500 ms before to 1500 ms after stimulus presentation. The cross was then replaced for up to 2000 ms by two face-like icons appearing on the left and on the right side of the screen which symbolized, which button had to be pressed for the ‘correct’ and ‘incorrect’ judgement. Between trials there was a time interval of 1500 ms. After each block of 64 sentences there was a short pause. To ensure an artifact-free electroencephalography (EEG)


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recording participants were instructed to avoid eye movements during the time they could see the fixation cross on the screen. During the experiment accuracy rates and the continuous EEG were registered. As responses were temporally delayed, reaction times are not reported here. The EEG was recorded from 59 Ag/AgCl electrodes mounted in an elastic cap (Electro Cap International). The vertical electro-oculogram (EOG) was recorded from two electrodes placed above and below the right eye. The horizontal EOG was measured by electrodes placed at the outer canthus of each eye. The EEG recording was referenced to the left mastoid and later re-referenced to the linked mastoids. Electrode impedances were kept below 5 kΩ and sampling rate was 250 Hz. Trials containing artifacts due to eye movements, muscular activity or amplifier saturation were excluded from averaging. ERPs were averaged in the time window from –200 to 1500 ms post stimulus onset for the case violation condition, starting from the onset of the second noun, and from 0 to 1500 ms for the word category violation condition, starting from the onset of the verb. For the case violation condition the first 200 ms of the average served as amplitude baseline, for the word category violation the first 100 ms were chosen as post-stimulus baseline due to different sentential constituents before the violation point (for similar procedure, see Hahne and Friederici, 1999). An 8 Hz low-pass filter was used for the graphic illustrations only. All statistical evaluations were carried out on unfiltered ERP data. For statistical evaluation the SAS 8.2 Software package was used. Behavioural data were evaluated using two separate repeated measures ANOVAs on percentage of correct answers. ERP data were analysed using repeated measures ANOVAs on mean amplitude values during two time windows for each condition, which were selected to be comparable to previously published data (case violation: 350–500 ms and 600–900 ms; word category violation: 100–300 ms and 500–800 ms) (Mueller et al., 2005; 2007) and by visual inspection of the data (familiar vs. unfamiliar correct items: 200–600 ms). To assess regional distribution of ERP effects electrodes were subsumed in four regions of interests (ROIs): ● ● ● ●

left-anterior: FP1, AF7, AF3, F7, F5, F3, FT7, FC5, FC3; right-anterior: FP2, AF8, AF4, F8, F6, F4, FT8, FC6, FC4; left-posterior: TP7, CP5, CP3, P7, P5, P3, PO7, PO3, O1; right-posterior: TP8, CP6, CP4, P8, P6, P4, PO8, PO4, O2.


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The overall statistical analyses included the repeated factors Cond (condition: familiar vs. unfamiliar), Reg (region: anterior vs. posterior) and Hemi (hemisphere: left vs. right). Whenever an interaction including the factor Cond was significant further analyses on the lower levels were calculated. IV Results 1 Behavioural results Table 2 shows the accuracy rates for each condition. For the case violation condition and for the word category violation condition separate ANOVAS were calculated with correctness (CORR) and familiarity (FAM) as repeated measures factors. In both tests only the factor FAM reached significance (case: F(1,13) 23.84, p < .001; word category: F(1,18) 32.26, p < .001), showing that participants made more errors while judging sentences including unknown words. 2 ERP Results a Familiarity of words: Figure 1 illustrates ERPs in which familiar and unfamiliar items are contrasted with each other for each correct condition separately. There seems to be a classical N400 effect for correct nouns and verbs. For correct verbs there seems to be an additional positivity after the N400. To assess both components two time windows were chosen, one from 200–600 ms after stimulus onset and one from 600–1000 ms after stimulus onset. For both correct nouns and correct verbs separate ANOVAS were calculated in the two time windows with the factors Cond (condition: familiar vs. unfamiliar), Reg (region: anterior vs. posterior) and Hemi (hemisphere: left vs. right). For nouns there was a significant effect of the factor Cond (F(1,13) 16.09, p .01, MSe = 4.82) between 200 ms and 600 ms and a marginally significant effect of Cond Reg (F(1,13) 4.37, p .06, MSe 1.48) between 600 ms and 1000 ms, which did not, however, prove to be reliable in further analyses of the factor Cond in each level of Reg. Thus, the only reliable effect was a broadly distributed N400 effect for unfamiliar compared to familiar nouns.


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For verbs there was also a main effect of Cond (F(1,18) 12.10, p .01, MSe 3.95) and an additional interaction of Cond Hemi (F(1,18) 4.33, p .05, MSe 0.47) in the first time window. The interaction was due to a right lateralization of the negativity for verbs (left: F(1,18) 6.17, p .01, MSe 2.44; right: F(1,18) 17.58, p .001, MSe 1.98). Between 600 ms and 1000 ms there was a significant main effect of Cond (F(1,18) 10.61, p < .01, MSe 7.6), an interaction of Cond Reg (F(1,18) 19.24, p < .001, MSe 2.26) and an interaction of Cond Hemi (F(1,18) 5.95, p .05, MSe 0.93). The significant interaction of Cond Reg was due to a posterior distribution of the positivity (anterior: ns; posterior: F(1,18) 23.04, p .0001, MSe 5.26). The interaction of Cond Hemi reflects the left hemispheric maximum of the positivity (left: F(1,18) 12.73, p .01, MSe 5.04; right: F(1,18) 6.31, p .05, MSe 3.49). Thus, the statistical analysis confirmed a broadly distributed N400 followed by a P600. b Case violation condition: The averaged ERPs and isovoltage difference maps of the case violation conditions in sentences including either familiar of unfamiliar nouns are plotted in the Figures 2 and 3. Case violations in familiar sentences evoke a biphasic ERP pattern with a negativity followed by a later positivity (Figure 2). In sentences containing an unfamiliar noun only a small, posteriorly distributed positivity is visible (Figure 3). The results of the omnibus ANOVA are illustrated in Table 3. From 350 ms to 500 ms there was an interaction of Cond Type reflecting that only for familiar sentences there was a main effect of Cond Table 2 Mean percentage of accurate grammaticality judgements (standard deviation in parentheses). Responses for correct and familiar sentences are reported twice because the different numbers of subjects in the case and the word category condition. Correct

Case (n = 14) Word category (n = 19)

Incorrect

Familiar

Unfamiliar

Familiar

99.0% (1.8) 98.9% (1.7)

88.5% (11.6) 92.8% (8.6)

96.1% (5.9) 86.3% (12.5) 97.5% (4.6) 87.5% (12.1)


Unfamiliar

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(F(1,13) 20.15, p < .001, MSe 1.26). Between 600 ms and 900 ms there was a main effect of Cond and a marginal interaction of Cond Hemi which was due to a larger effect of Cond over left (F(1,13) 23.79, p < .001, MSe 2.30) than over right (F(1,13) 13.37, p < .01, MSe 1.89) electrode positions. In sum, the statistical analyses in the two case violation conditions confirmed a widely distributed N400 between 350 ms and 500 ms and slightly left lateralized P600 for sentences with familiar nouns. Sentences with unfamiliar nouns displayed only the P600. c Word category violation condition: Figures 4 and 5 illustrate the ERPs and isovoltage difference maps of the word category violation conditions involving either familiar or unfamiliar verbs for trained participants. For familiar verbs (Figure 4) the ERP pattern consists of an early, broadly distributed negativity, which is followed by a positivity. For the unfamiliar verbs (Figure 5), there was also an early negativity, which seems to be slightly more posteriorly distributed, and a late positivity, which seems to be restricted to occipito-central electrodes. Additionally, a late anterior negative shift is visible for the incorrect condition in the case of unfamiliar verbs. Table 4 shows the main ANOVAs for the word category violation conditions in both sentence types. The early negativity was confirmed by a highly significant main effect of the factor Cond. The significant threeway interaction of Cond Type Reg reflects that only in the case of unfamiliar verbs was there a significant interaction of Cond Reg (F(1,18) 11.10, p < .01, MSe 1.03) which was due to a stronger effect of Cond over posterior (F(1,18) 36.29, p < .0001, MSe 3.41) as compared to anterior (F(1,18) 20.87, p < .001, MSe 1.93) electrode sites. For the familiar verbs, the interaction of Cond Reg was non-significant (F < 1). In the time window between 500 ms and 800 ms there was a main effect of Cond, but also a strong interaction of Cond Type Reg. There was an interaction of Cond Reg for both sentence types (familiar: F(1,18) 67.48, p < .0001, MSe 3.37; unfamiliar: F(1,18) 11.52, p < .01, MSe 3.82), but only for familiar sentences was it due to a posteriorly distributed positivity. For familiar sentences the P600 was significant over posterior electrodes only (F(1,18) 52.11, p .0001, MSe 9.29). For sentences with an unfamiliar verb there was


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only the shift-like negativity significant over anterior electrode sites (F(1,18) 4.52, p < .05, MSe 8.13). As the P600 did not reach significance despite a visible positivity over occipito-central electrodes, an additional ANOVA was calculated for electrode positions on the central line for the time window from 500 ms to 800 ms. Thus, a two-factorial repeated measures ANOVA was conducted with Cond and Region (anterior–midline, comprising the electrodes FPZ, AFZ, FZ and FCZ vs. posterior–midline, comprising the electrodes CPZ, PZ, POZ and OZ) as independent variables. There was a significant interaction of Cond Region (F(1,18) 12.54, p ⬍ .01, MSe 3.80), which indicated a significant simple main effect of Cond over posterior–midline positions (F(1,18) 7.88, p .01,

Figure 1 The ERP waveform at the CZ electrode for unfamiliar and familiar correct words. The time window from –200 to 0 ms served as amplitude baseline. Topographical distributions on the scalp are illustrated in isovoltage difference maps.


Jutta L. Mueller

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Figure 2 The ERP waveforms at selected electrodes for correctly and incorrectly case marked familiar nouns in the case violation condition. The time window from 200 to 0 ms served as amplitude baseline. Topographical distributions on the scalp are illustrated in isovoltage difference maps.

MSe 3.04) due to the positivity and a marginally significant effect over anterior–midline positions due to the shift-like negativity (F(1,18) 3.12, p .09, MSe 7.62). Thus, the statistical analyses of the two types of word category violations confirmed a centrally distributed early negativity followed by a P600 in the familiar condition. In the unfamiliar word category violation the early negativity was posteriorly focused. The P600 could only be confirmed statistically over posterior–midline electrodes. Additionally, a shift-like anterior negativity was observed starting about 500 ms post word onset. V Discussion In our experiment we tested event-related potentials in response to case and word category processing and their dependency on lexical familiarity.


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Figure 3 The ERP waveforms at selected electrodes for correctly and incorrectly case-marked unfamiliar nouns in the case violation condition. The time window from 200 to 0 ms served as amplitude baseline. Topographical distributions on the scalp are illustrated in isovoltage difference maps.

In the study we replicated results of previous studies (Mueller et al., 2005; 2007) and gained additional new insights about the stability of sentence processing mechanisms in the face of lexical difficulties. With respect to the processing of sentences that contained only familiar words, the results resembled those of the previous study. Case and word category violations elicited a P600 effect. Word category violations led to an additional early, broadly distributed negativity. For case violations the learners showed an additional N400 effect. When unfamiliar lexical items were present in the sentences at the critical positions, the N400 effect proved most vulnerable, while the P600 was affected to a lesser degree and the early negativity remained unaffected. In the following the effects of lexical familiarity on the processing of correct items, on the processing of case violations and on the processing of word category violations are discussed in more detail.


Jutta L. Mueller Table 3 ANOVAs on mean amplitude levels for the case violation condition in two time windows.

df

Effect

Familiar vs. unfamiliar: 350–500ms: Cond 1,13 Cond Type 1,13 Cond Reg 1,13 Cond Hemi 1,13 Cond Type Reg 1,13 Cond Type Hemi 1,13 Cond Reg Hemi 1,13 Cond Type Reg Hemi 1,13

ω2

F value

p value

MSe

1.39 11.80