Stem allomorphy in the Spanish mental lexicon: evidence from behavioral and ERP experiments

Gradations of interpretability in spoken complex word recognition

In an ERP experiment with cross-modal priming, we found evidence for graded interpretability of complex pseudowords, expressed as differences in the degree of priming between a complex pseudoword and its embedded base word. Only pseudowords that were constructed according to the morphological constraints of the language (for instance that nouns ending in {-ung} in German must be derived from a verbal base) led to significant attenuation of the N400 component relative to an unrelated control. Novel formations that consisted of the concatenation of a stem and an incompatible affix (e.g. wirr A.,'confused' and {-lein}, which can only add to nouns) did not modulate the N400 component. Moreover, gradations in degree of priming were observed with novel pseudowords that were the result of several morphological operations as a function of the composition of the full sequence of morphological operations. Any positions within the sequence that were filled by possible, but non-existing formations (thus compare hübsch (A., 'pretty') > *hübschen (V., 'beautify') > *Hübschung (N., 'beautification') versus spitz (A., 'sharp') > spitzen (V., 'sharpen') > *Spitzung (N., 'sharpening'), whereby in the former the intermediate position is expressed through a possible, but non-existing verb form) led to reduced activation of the base word. These findings corroborate previous behavioural and neuroimaging results in visual word recognition that found support for step-wise morphological decomposition in multi-affixed pseudowords and reveal that the composition of the derivational path can lead to gradations of interpretability in the recognition of spoken complex pseudowords.

Morphological processing in the brain: The good (inflection), the bad (derivation) and the ugly (compounding)

There is considerable behavioral evidence that morphologically complex words such as 'tax-able' and 'kiss-es' are processed and represented combinatorially. In other words, they are decomposed into their constituents 'tax' and '-able' during comprehension (reading or listening), and producing them might also involve on-the-spot combination of these constituents (especially for inflections). However, despite increasing amount of neurocognitive research, the neural mechanisms underlying these processes are still not fully understood. The purpose of this critical review is to offer a comprehensive overview on the state-of-the-art of the research on the neural mechanisms of morphological processing. In order to take into account all types of complex words, we include findings on inflected, derived, and compound words presented both visually and aurally. More specifically, we cover a wide range of electro- and magnetoencephalography (EEG and MEG, respectively) as well as structural/functional magnetic resonance imaging (s/fMRI) studies that focus on morphological processing. We present the findings with respect to the temporal course and localization of morphologically complex word processing. We summarize the observed findings, their interpretations with respect to current psycholinguistic models, and discuss methodological approaches as well as their possible limitations.

The Past Tense Debate Revisited: Electrophysiological Evidence for Subregularities of Irregular Verb Inflection

Neuropsychological research investigating mental grammar and lexicon has largely been based on the processing of regular and irregular inflection. Past tense inflection of regular verbs is assumed to be generated by a syntactic rule (e.g., show-ed), whereas irregular verbs consist of rather unsystematic alternations (e.g., caught) represented as lexical entries. Recent morphological accounts, however, hold that irregular inflection is not entirely rule-free but relies on morphological principles. These subregularities are computed by the syntactic system. We tested this latter hypothesis by examining alternations of irregular German verbs as well as pseudowords using ERPs. Participants read series of irregular verb inflection including present tense, past participle, and past tense forms embedded in minimal syntactic contexts. The critical past tense form was correct (e.g., er sang [he sang]) or incorrect by being either partially consistent (e.g., *er sung [*he sung]) or inconsistent (e.g., *er sing [*he sing]) with the proposed morphological principles. Correspondingly, in a second experimental block, pseudowords (e.g., tang/*tung/*ting) were presented. ERPs for real words revealed a biphasic ERP pattern consisting of a negativity and P600 for both incorrect forms in comparison to the correct equivalents. Most interestingly, the P600 amplitude for the incorrect forms was gradually modulated by the type of anomaly with medium amplitude for consistent past tense forms and largest amplitude for inconsistent past tense forms. ERPs for pseudoword past tense forms showed a similar gradual modulation of N400. The findings support the assumption that irregular verbs are processed by rule-based mechanisms because of subregularities of their past tense inflection.

Electrophysiological evidence for a neural substrate of morphological rule application in correct wordforms

A critical issue for understanding language processing in the brain is whether linguistic rule application is subserved by a distinct neural substrate. One of the evidence supporting this hypothesis stems from studies employing electroencephalographic measurements during the processing of rule misapplication. This evidence is inconclusive because it might reflect processes caused by the violation such as error handling rather than application of rules per se. Here we provide first evidence that correct regular formations, i.e., German past participles, are associated with left anterior negative-going activity (LAN) providing encephalographic evidence for rule application in the brain during the processing of correct words. Moreover, a LAN response is present regardless of the participles’ frequency, suggesting that independently from the mode of lexical access (i.e., decomposition or full-form activation), the cerebral structures associated with rule-based mechanisms are activated.

Morphological processing as we know it: an analytical review of morphological effects in visual word identification

The last 40 years have witnessed a growing interest in the mechanisms underlying the visual identification of complex words. A large amount of experimental data has been amassed, but although a growing number of studies are proposing explicit theoretical models for their data, no comprehensive theory has gained substantial agreement among scholars in the field. We believe that this is due, at least in part, to the presence of several controversial pieces of evidence in the literature and, consequently, to the lack of a well-defined set of experimental facts that any theory should be able to explain. With this review, we aim to delineate the state of the art in the research on the visual identification of complex words. By reviewing major empirical evidences in a number of different paradigms such as lexical decision, word naming, and masked and unmasked priming, we were able to identify a series of effects that we judge as reliable or that were consistently replicated in different experiments, along with some more controversial data, which we have tried to resolve and explain. We concentrated on behavioral and electrophysiological studies on inflected, derived, and compound words, so as to span over all types of complex words. The outcome of this work is an analytical summary of well-established facts on the most relevant morphological issues, such as regularity, morpheme position coding, family size, semantic transparency, morpheme frequency, suffix allomorphy, and productivity, morphological entropy, and morpho-orthographic parsing. In discussing this set of benchmark effects, we have drawn some methodological considerations on why contrasting evidence might have emerged, and have tried to delineate a target list for the construction of a new all-inclusive model of the visual identification of morphologically complex words.

Brain potentials for derivational morphology: an ERP study of deadjectival nominalizations in Spanish

This study investigates brain potentials to derived word forms in Spanish. Two experiments were performed on derived nominals that differ in terms of their productivity and semantic properties but are otherwise similar, an acceptability judgment task and a reading experiment using event-related brain potentials (ERPs) in which correctly and incorrectly formed derived words were presented in sentence contexts. The first experiment indicated productivity differences between the different nominalization processes in Spanish. The second experiment yielded a pattern of ERP responses that differed from both the familiar lexical-semantic and grammatical ERP effects. Violations of derivational morphology elicited an increased N400 component plus a late positivity (P600), unlike gender-agreement violations, which produced the biphasic LAN/P600 ERP pattern known from previous studies of morpho-syntactic violations. We conclude that the recognition of derived word forms engages both word-level (lexical-semantic) and decompositional (morpheme-based) processes.

Spatiotemporal Dynamics of the Processing of Spoken Inflected and Derived Words: A Combined EEG and MEG Study

The spatiotemporal dynamics of the neural processing of spoken morphologically complex words are still an open issue. In the current study, we investigated the time course and neural sources of spoken inflected and derived words using simultaneously recorded electroencephalography (EEG) and magnetoencephalography (MEG) responses. Ten participants (native speakers) listened to inflected, derived, and monomorphemic Finnish words and judged their acceptability. EEG and MEG responses were time-locked to both the stimulus onset and the critical point (suffix onset for complex words, uniqueness point for monomorphemic words). The ERP results showed that inflected words elicited a larger left-lateralized negativity than derived and monomorphemic words approximately 200 ms after the critical point. Source modeling of MEG responses showed one bilateral source in the superior temporal area ∼100 ms after the critical point, with derived words eliciting stronger source amplitudes than inflected and monomorphemic words in the right hemisphere. Source modeling also showed two sources in the temporal cortex approximately 200 ms after the critical point. There, inflected words showed a more systematic pattern in source locations and elicited temporally distinct source activity in comparison to the derived word condition. The current results provide electrophysiological evidence for at least partially distinct cortical processing of spoken inflected and derived words. In general, the results support models of morphological processing stating that during the recognition of inflected words, the constituent morphemes are accessed separately. With regard to derived words, stem and suffix morphemes might be at least initially activated along with the whole word representation.

Morphophonological salience as a compensatory means for deficits in the acquisition of past tense in SLI

The aim of this study is threefold: Firstly, to describe the acquisition patterns of Greek past tense by children with specific language impairment (SLI); secondly, to investigate the relationship between the phonological salience of past tense in Greek and its acquisition by children of typical and atypical language development; thirdly, to establish an account on the nature of specific language impairment by comparing the acquisition patterns exhibited by children with SLI to those presented by typically developing children. The performance of 10 children with SLI in elicited past tense production is compared to that of chronological age matched (CA) and language matched (LM) controls. Based on the claim that morphophonological salience aids acquisition (or learning), it is predicted that children with SLI will perform better in the production of past forms of higher salience than less salient forms. The results confirm this prediction, providing support for the claim that salience differences do account for better performances in tense marking in Greek SLI.

LEARNING OUTCOMES

By reading this article, the reader will be able to: (1) describe the problems children with SLI face in Greek tense marking, (2) explain the reasons why SLI performances differ from one language to the next based on the Interpretability Hypothesis, (3) discuss whether children with SLI differ qualitatively from TD controls in past tense marking and explain how.

Verbal Inflectional Morphology in L1 and L2 Spanish: A Frequency Effects Study Examining Storage versus Composition

This study examines the storage vs. composition of Spanish inflected verbal forms in L1 and L2 speakers of Spanish. L2 participants were selected to have mid-to-advanced proficiency, high classroom experience, and low immersion experience, typical of medium-to-advanced foreign language learners. Participants were shown the infinitival forms of verbs from either Class I (the default class, which takes new verbs) or Classes II and III (non-default classes), and were asked to produce either first-person singular present-tense or imperfect forms, in separate tasks. In the present tense, the L1 speakers showed inflected-form frequency effects (i.e., higher frequency forms were produced faster, which is taken as a reflection of storage) for stem-changing (irregular) verb-forms from both Class I (e.g., pensar-pienso) and Classes II and III (e.g., perder-pierdo), as well as for non-stem-changing (regular) forms in Classes II/III (e.g., vender-vendo), in which the regular transformation does not appear to constitute a default. In contrast, Class I regulars (e.g., pescar-pesco), whose non-stem-changing transformation constitutes a default (e.g., it is applied to new verbs), showed no frequency effects. L2 speakers showed frequency effects for all four conditions (Classes I and II/III, regulars and irregulars). In the imperfect tense, the L1 speakers showed frequency effects for Class II/III (-ía-suffixed) but not Class I (-aba-suffixed) forms, even though both involve non-stem-change (regular) default transformations. The L2 speakers showed frequency effects for both types of forms. The pattern of results was not explained by a wide range of potentially confounding experimental and statistical factors, and does not appear to be compatible with single-mechanism models, which argue that all linguistic forms are learned and processed in associative memory. The findings are consistent with a dual-system view in which both verb class and regularity influence the storage vs. composition of inflected forms. Specifically, the data suggest that in L1, inflected verbal forms are stored (as evidenced by frequency effects) unless they are both from Class I and undergo non-stem-changing default transformations. In contrast the findings suggest that at least these L2 participants may store all inflected verb-forms. Taken together, the results support dual-system models of L1 and L2 processing in which, at least at mid-to-advanced L2 proficiency and lower levels of immersion experience, the processing of rule-governed forms may depend not on L1 combinatorial processes, but instead on memorized representations.

Spoken verb processing in Spanish: An analysis using a new online resource

Verbs are one of the basic building blocks of grammar, yet few studies have examined the grammatical, morphological, and phonological factors contributing to lexical access and production of Spanish verb inflection. This report describes an online data set that incorporates psycholinguistic dimensions for 50 of the most common early-acquired Spanish verbs. Using this data set, predictors of response time (RT) from stimulus onset and mean differences at offset are examined. Native Spanish speakers, randomly assigned to one of two tasks, listened to prerecorded verbs and either repeated the verb (single word shadowing) or produced its corresponding pronoun. Factors such as stimulus duration, number of syllables, syllable stress position, and specific levels of initial phoneme facilitated both shadowing of a verb and production of its pronoun. Higher frequency verbs facilitated faster verb repetition, whereas verbs with alternative pronouns increased RT to pronoun production. Mean differences at offset (stimulus duration is removed) indicated that listeners begin speaking earlier when the verb is longer and multisyllabic compared to shorter, monosyllabic words. These results highlight the association between psycholinguistic factors and RT measures of verb processing, in particular, features unique to languages like Spanish, such as alternative pronoun and tense.

Syntactic complexity and ambiguity resolution in a free word order language: behavioral and electrophysiological evidences from Basque

In natural languages some syntactic structures are simpler than others. Syntactically complex structures require further computation that is not required by syntactically simple structures. In particular, canonical, basic word order represents the simplest sentence-structure. Natural languages have different canonical word orders, and they vary in the degree of word order freedom they allow. In the case of free word order, whether canonical word order plays any role in processing is still unclear. In this paper, we present behavioral and electrophysiological evidence that simpler, canonical word order preference is found even in a free word order language. Canonical and derived structures were compared in two self-paced reading and one ERPs experiment. Non-canonical sentences required further syntactic computation in Basque, they showed longer reading times and a modulation of anterior negativities and P600 components providing evidence that even in free word order, case-marking grammars, underlying canonical word order can play a relevant role in sentence processing. These findings could signal universal processing mechanisms because similar processing patterns are found in typologically very distant grammars. We also provide evidence from syntactically fully ambiguous sequences. Our results on ambiguity resolution showed that fully ambiguous sequences were processed as canonical sentences. Moreover, when fully ambiguous sequences were forced to complex interpretation by means of the world knowledge of the participants, a frontal negativity distinguished simple and complex ambiguous sequences. Thus the preference of simple structures is presumably a universal design property for language processing, despite differences on parametric variation of a given grammar.

Different neurophysiological mechanisms underlying word and rule extraction from speech

The initial process of identifying words from spoken language and the detection of more subtle regularities underlying their structure are mandatory processes for language acquisition. Little is known about the cognitive mechanisms that allow us to extract these two types of information and their specific time-course of acquisition following initial contact with a new language. We report time-related electrophysiological changes that occurred while participants learned an artificial language. These changes strongly correlated with the discovery of the structural rules embedded in the words. These changes were clearly different from those related to word learning and occurred during the first minutes of exposition. There is a functional distinction in the nature of the electrophysiological signals during acquisition: an increase in negativity (N400) in the central electrodes is related to word-learning and development of a frontal positivity (P2) is related to rule-learning. In addition, the results of an online implicit and a post-learning test indicate that, once the rules of the language have been acquired, new words following the rule are processed as words of the language. By contrast, new words violating the rule induce syntax-related electrophysiological responses when inserted online in the stream (an early frontal negativity followed by a late posterior positivity) and clear lexical effects when presented in isolation (N400 modulation). The present study provides direct evidence suggesting that the mechanisms to extract words and structural dependencies from continuous speech are functionally segregated. When these mechanisms are engaged, the electrophysiological marker associated with rule-learning appears very quickly, during the earliest phases of exposition to a new language.

How children process over-regularizations: evidence from event-related brain potentials

This study examines the mental processes involved in children's on-line recognition of inflected word forms using event-related potentials (ERPs). Sixty children in three age groups (20 six- to seven-year-olds, 20 eight- to nine-year-olds, 20 eleven- to twelve-year-olds) and 23 adults (tested in a previous study) listened to sentences containing correct or incorrect German noun plural forms. In the two older child groups, as well as in the adult group, over-regularized plural forms elicited brain responses that are characteristic of combinatorial (grammatical) violations. We also found that ERP components associated with language processing change from child to adult with respect to their onsets and their topography. The ERP violation effects obtained for over-regularizations suggest that children (aged eight years and above) and adults employ morphological computation for processing purposes, consistent with dual-mechanism models of inflection. The observed differences between children's and adults' ERP responses are argued to result from children's smaller lexicons and from slower and less efficient processing.

Recognition of morphologically complex words in Finnish: evidence from event-related potentials

The temporal dynamics of processing morphologically complex words was investigated by recording event-related brain potentials (ERPs) when native Finnish-speakers performed a visual lexical decision task. Behaviorally, there is evidence that recognition of inflected nouns elicits a processing cost (i.e., longer reaction times and higher error rates) in comparison to matched monomorphemic words. We aimed to reveal whether the processing cost stems from decomposition at the early visual word form level or from re-composition at the later semantic-syntactic level. The ERPs showed no early effects for morphology, but revealed an interaction with word frequency at a late N400-type component, as well as a late positive component that was larger for inflected words. These results suggest that the processing cost stems mainly from the semantic-syntactic level. We also studied the features of the morphological decomposition route by investigating the recognition of pseudowords carrying real morphemes. The results showed no differences between inflected vs. uninflected pseudowords with a false stem, but differences in relation to those with a real stem, suggesting that a recognizable stem is needed to initiate the decomposition route.

Brain potentials to morphologically complex words during listening

This study uses event-related brain potentials (ERPs) to investigate the processing of morphologically regular and irregular words during auditory comprehension. ERPs were recorded, while 23 German-speaking subjects listened to correctly and incorrectly inflected noun plural forms presented in sentential contexts. ERP responses to violations of morphological structure were different to those of lexical (word-level) violations: the former elicited LAN/P600 effects, and the latter an enhanced N400 component relative to the correctly inflected plural forms. This difference replicates previous results from visual ERP studies and supports the distinction between combinatorial and memory-based processing of morphologically complex words. In addition, LAN/P600 effects were found to be more prominent in the auditory domain than in a previous visual study using similar materials.