Horacio A. Barber

Nouns and verbs in the brain: A review of behavioural, electrophysiological, neuropsychological and imaging studies

In the past 30 years there has been a growing body of research using different methods (behavioural, electrophysiological, neuropsychological, TMS and imaging studies) asking whether processing words from different grammatical classes (especially nouns and verbs) engage different neural systems. To date, however, each line of investigation has provided conflicting results. Here we present a review of this literature, showing that once we take into account the confounding in most studies between semantic distinctions (objects vs. actions) and grammatical distinction (nouns vs. verbs), and the conflation between studies concerned with mechanisms of single word processing and those studies concerned with sentence integration, the emerging picture is relatively clear-cut: clear neural separability is observed between the processing of object words (nouns) and action words (typically verbs), grammatical class effects emerge or become stronger for tasks and languages imposing greater processing demands. These findings indicate that grammatical class per se is not an organisational principle of knowledge in the brain; rather, all the findings we review are compatible with two general principles described by typological linguistics as underlying grammatical class membership across languages: semantic/pragmatic, and distributional cues in language that distinguish nouns from verbs. These two general principles are incorporated within an emergentist view which takes these constraints into account.

Grammatical Gender and Number Agreement in Spanish: An ERP Comparison

The role of grammatical gender and number representations in syntactic processes during reading in Spanish was studied using the event-related potentials (ERPs) technique. The electroencephalogram was recorded with a dense array of 128 electrodes while Spanish speakers read word pairs (Experiment 1) or sentences (Experiment 2) in which gender or number agreement relationships were manipulated. Disagreement in word pairs formed by a noun and an adjective (e.g., faroalto [lighthousehigh]) produced an N400-type effect, while word pairs formed by an article and a noun (e.g., elpiano [the-piano]) showed an additional left anterior negativity effect (LAN). Agreement violations with the same words inserted in sentences (e.g., El piano estaba viejo y desafinado [the m-s piano m-s was old m-s and off-key]) resulted in a pattern of LANP600. This effect was found both when the violation occurred in the middle of the sentence (at the adjective), as well as when this happened at the beginning of the sentence (at the noun), but the last segment of the P600 effect was greater for the middle sentence position, which could indicate differences in the complexity of reanalysis processes. Differences between grammatical gender and number disagreement were found in late measures. In the word pairs experiment, P3 peak latency varied across conditions, being later for gender than for number disagreement. Similarly, in the sentence experiment, the last segment of the P600 effect was greater for gender than for number violations. These event-related potentials (ERPs) effects lend support to the idea that reanalysis or repair processes after grammatical disagreement detection could involve more steps in the case of gender disagreement, as grammatical gender is a feature of the lexical representation in contrast to number, which is considered a morphological feature that combines with the stem of the word.

Grammatical agreement processing in reading: ERP findings and future directions.

In the domain of written sentence comprehension, the computation of agreement dependencies is generally considered as a form-driven processing routine whose domain is syntactic in nature. In the present review we discuss the main findings emerging in the Event-Related Potential (ERP) literature on sentence comprehension, focusing on the different dimensions of agreement patterns (features, values, constituents involved and language): Agreement mismatches usually evoke a biphasic electrophysiological pattern (Left Anterior Negativity - LAN, 300-450 msec and P600 after 500 msec). This ERP pattern is assumed to reflect rule-based computations sensitive to formal (inflectional) covariations of related words (trigger-target). Here we claim that agreement processing is sensitive to both the type of feature involved and the constituents that express the agreement dependency. More specifically, LAN could reflect violation of expectancy (elicited by the trigger) for the target functional morphology; later, trigger and target are structurally integrated at the sentence level (early P600). However, morphosyntactic information could trigger the activation of higher-level representations that are not strictly syntactic in nature. The recruitment of this additional non-syntactic information (mirrored by N400-like effects) indicates that rule-based computations of agreement dependencies are not blind to non-syntactic information but are often recruited to establish sentence-level relations.

Syllable-frequency effects in visual word recognition: evidence from ERPs.

A lexical decision experiment was conducted while event related potentials (ERPs) were recorded. The word frequency and the first syllable frequency of each word were manipulated. Results showed that, while high frequency words produced less negative amplitudes in the N400 time window than low frequency words, the inverse pattern was found for syllable frequency. Words containing high frequency syllables produced more negative amplitudes than words containing low frequency syllables. Importantly, a significant syllable frequency effect was also obtained at the P200 time window. The results are interpreted in the framework of an interactive activation model, in which high frequency syllables produce the initial activation of a larger number of lexical candidates during the analysis of orthographic or phonological representations, which have to be inhibited later to allow the identification of a unique word. These findings support the idea that, at least in languages with clear syllabic boundaries, syllables are functional sublexical units during visual word recognition.

Morphosyntactic processing in late second-language learners

The goal of the present study was to investigate the electrophysiological correlates of second-language (L2) morphosyntactic processing in highly proficient late learners of an L2 with long exposure to the L2 environment. ERPs were collected from 22 English–Spanish late learners while they read sentences in which morphosyntactic features of the L2 present or not present in the first language (number and gender agreement, respectively) were manipulated at two different sentence positions—within and across phrases. The results for a control group of age-matched native-speaker Spanish participants included an ERP pattern of LAN-type early negativity followed by P600 effect in response to both agreement violations and for both sentence positions. The late L2 learner results included a similar pattern, consisting of early negativity followed by P600, in the first sentence position (within-phrase agreement violations) but only P600 effects in the second sentence position (across-phrase agreement violation), as well as significant amplitude and onset latency differences between the gender and the number violation effects in both sentence positions. These results reveal that highly proficient learners can show electrophysiological correlates during L2 processing that are qualitatively similar to those of native speakers, but the results also indicate the contribution of factors such as age of acquisition and transfer processes from first language to L2.

Gender and Number Processing in Chinese Learners of Spanish--Evidence from Event Related Potentials.

Traditionally, age of acquisition (AoA) has been considered the single most important factor in second language (L2) acquisition and processing, particularly in the area of syntax processing. However, there is now growing evidence of the importance of other factors, such as the level of proficiency attained and the degree of overlap or similarity between the first language (L1) and L2 structures and possibility of transfer of features and/or processing routines. However, the relative importance of these factors and the nature of L1-L2 transfer are still unclear. To shed light on these issues, we recorded the electrical brain activity of a group of Chinese proficient late learners of Spanish, using the Event Related Potentials technique, while they read Spanish sentences containing violations of number and grammatical gender agreement (adjective-noun agreement and article-noun agreement). Unlike Spanish, Mandarin Chinese is an isolating language in which morphosyntactic features such as gender and number are not computed and so the ERP results from this group can help to clarify the role of L1-L2 transfer in morpho-syntax processing routines. The results included P600 effects for both gender and number agreement violations, with no differences between these disagreement conditions. These results are taken to support second language acquisition models which stress the roles of proficiency and L1-L2 transfer in L2 syntax processing.

Concreteness in word processing: ERP and behavioral effects in a lexical decision task

Relative to abstract words, concrete words typically elicit faster response times and larger N400 and N700 event-related potential (ERP) brain responses. These effects have been interpreted as reflecting the denser links to associated semantic information of concrete words and their recruitment of visual imagery processes. Here, we examined whether there are ERP differences between concrete and abstract stimuli controlled for a large number of factors including context availability (i.e., richness of semantic associations) and imageability. We found that abstract words elicited faster behavioral responses but that concrete words still elicited larger N400 and N700 responses. We propose that once all other factors, including imageability and context availability are controlled, abstract words may trigger a larger number of superficial linguistic associations that can be quickly used for response decisions. The ERP differences, however, would index the greater semantic processing (integration of multimodal information) for concrete than abstract words during meaning activation.

Event-related Brain Potentials Elicited by Morphological, Homographic, Orthographic, and Semantic Priming

The morphological structure of words, in terms of their stem morphemes and affixes, could influence word access and representation in lexical memory. Three experiments were carried out to explore the attributes of event-related potentials evoked by different types of priming. Morphological priming, with pairs of words related by their stem (hijo/hija [son/ daughter]), produced a sustained attenuation (and even a tendency to positivity) of the N400 shown by unrelated words across the three experiments. Homographic priming (Experiment 1), using pairs of words with a superficially similar stem, but without morphological or semantic relation (foco/foca [floodlight/seal]), produced an initial attenuation similar to the morphological pairs, but which rapidly tended to form a delayed N400, due to the impossibility of integration. However, orthographic priming (rasa/rana [flat/frog]) in Experiment 2 does not produce attenuation of the N400 but an effect similar to that of unrelated pairs. Experiment 3 shows that synonyms advance more slowly than morphological pairs to meaning coherence, but finally produce a more positive peak around 600 msec.

Integrating Gender and Number Information in Spanish Word Pairs: An Erp Study

The aim of the current study was to explore the integration processes of gender and number morphological features, since it has been proposed that grammatical gender and number features might be associated with different strength with the word stem in lexical representation. Event related potentials (ERPs) were recorded using a 128-channel sensor net while twenty-four volunteers read Spanish word pairs and performed a syntactic judgment task. The word pairs which could agree or disagree in gender or number or in gender and number at the same time, were formed by a noun and an adjective (e.g. faro-alto [lighthouse-high]). A negativity around 400 msec with posterior distribution, which has been related to lexical integration processes, was found in response to both gender and number violations. No differences were found between gender disagreement, number disagreement and the double disagreement. Therefore, ERPs suggest that integration of gender and number features may not be different, and that the detection of disagreement may work under a binary state, since the double disagreement condition did not differ from the others. In addition, a subsequent component (identified as P3) showed delayed latencies in the gender disagreement condition as compared to the number disagreement condition, while the double disagreement conditions showed a shorter peak latency than the other two disagreement conditions and similar to the agreement condition. The variations in the latency of the P3 component, which has been related to categorization processes, suggest that these processes are quickly triggered by the accumulation of two incongruent as compared to one disagreement features, and that reanalysis is costlier in the case of gender disagreement as compared to the number disagreement.

Phrase Frequency Effects in Language Production

A classic debate in the psychology of language concerns the question of the grain-size of the linguistic information that is stored in memory. One view is that only morphologically simple forms are stored (e.g., ‘car’, ‘red’), and that more complex forms of language such as multi-word phrases (e.g., ‘red car’) are generated on-line from the simple forms. In two experiments we tested this view. In Experiment 1, participants produced noun+adjective and noun+noun phrases that were elicited by experimental displays consisting of colored line drawings and two superimposed line drawings. In Experiment 2, participants produced noun+adjective and determiner+noun+adjective utterances elicited by colored line drawings. In both experiments, naming latencies decreased with increasing frequency of the multi-word phrase, and were unaffected by the frequency of the object name in the utterance. These results suggest that the language system is sensitive to the distribution of linguistic information at grain-sizes beyond individual words.