The mental lexicon: evidence from lexical diffusion.

The purpose of this paper is to bring together evidence from studies on the lexical diffusion of various sound changes to support the following characteristics of the mental lexicon: (a) it must be connectionist rather than generative; (b) it must include information about grammatical category; (c) it must provide information on lexical frequency or entrenchment; and (d) entries must contain phonetic detail. Overall, lexical diffusion studies support a fully specified, connectionist model of the lexicon.     

The mental lexicon is fully specified: evidence from eye-tracking

Four visual-world experiments, in which listeners heard spoken words and saw printed words, compared an optimal-perception account with the theory of phonological underspecification. This theory argues that default phonological features are not specified in the mental lexicon, leading to asymmetric lexical matching: Mismatching input (pin) activates lexical entries with underspecified coronal stops (tin), but lexical entries with specified labial stops (pin) are not activated by mismatching input (tin). The eye-tracking data failed to show such a pattern. Although words that were phonologically similar to the spoken target attracted more looks than did unrelated distractors, this effect was symmetric in Experiment 1 with minimal pairs (tin-pin) and in Experiments 2 and 3 with words with an onset overlap (peacock-teacake). Experiment 4 revealed that /t/-initial words were looked at more frequently if the spoken input mismatched only in terms of place than if it mismatched in place and voice, contrary to the assumption that /t/ is unspecified for place and voice. These results show that speech perception uses signal-driven information to the fullest, as was predicted by an optimal perception account.     

Morphological units in the Arabic mental lexicon: evidence from an individual with deep dyslexia

An ongoing debate in Arabic morphology concerns the nature of the smallest unit governing lexical organization and representation in this language. A standard model maintains that Arabic words are typically analyzable into a three-consonantal root morpheme carrying the core meaning of words and a prosodic template responsible mostly for grammatical information. This view has been largely supported by research in both theoretical linguistics and psycholinguistics. An alternative theory holds that the meaning of words in Arabic is, rather, encoded in the 'etymon' comprising two unordered consonants of the root only. Results from a recent priming experiment have shown that the etymon induces strong morphological priming effects, supporting its morphological/lexical status. In this paper we present data from a patient with deep dyslexia questioning the role of the etymon as a psychologically real representational unit in Arabic and arguing, instead, for the central role of the root in both morphological and lexical representation in this language.     

Cross-language lexical connections in the mental lexicon: evidence from a case of trilingual aphasia

Despite anecdotal data on lexical interference among the languages of multilingual speakers, little research evidence about the lexical connections among multilinguals' languages exists to date. In the present paper, two experiments with a multilingual speaker who had suffered aphasia are reported. The first experiment provides data about inter-language activation during natural conversations; the second experiment examines performance on a word-translation task. Asymmetric patterns of inter-language interference and translation are evident. These patterns are influenced by age of language learning, degree of language recovery and use, and prevalence of shared lexical items. We conclude that whereas age of language learning plays a role in language recovery following aphasia, the degrees of language use prior to the aphasia onset and of shared vocabulary determine the ease with which words are accessed. The findings emphasize the importance of patterns of language use and the relations between the language pair under investigation in understanding lexical connections among languages in bilinguals and multilinguals.     

Cross-linguistic evidence for morphological representation in the mental lexicon.

Three types of naturally occurring data address the question of morphological structure in the lexical entry: code-switching, novel forms, and speech errors. The data were collected from a wide variety of languages, including Austro-Polynesian, Semitic, and Altaic languages, and a heretofore untapped set of affixation types, including infixes, circumfixes, multiple affixes, reduplication, and nonconcatenative morphology. The data are used to argue for a dual-listing model of lexical representation (e.g., Pinker, 1991; Frauenfelder & Schreuder, 1992) over full-listing (e.g., Butterworth, 1983) and fully parsed (e.g., Taft & Forster, 1975) models. The paper posits three morphological parameters which are activated language-specifically.     

ERP and behavioral evidence of individual differences in metaphor comprehension

In two experiments, we examined individual differences in metaphor processing. In Experiment 1, the subjects judged the literal truth of literal, metaphorical, and scrambled sentences. Overall, metaphors were more difficult to judge as false, in comparison with scrambled controls, suggesting that the metaphorical meaning was being processed automatically. However, there were individual differences in that high-IQ subjects showed more interference. These effects were reflected in ERP amplitude differences at the onset of N400 and after the response. In Experiment 2, the subjects completed IQ tests and a series of working memory tests and then rated and interpreted the same set of metaphors. The results showed that IQ was correlated with working memory capacity and that low-IQ subjects had similar ratings but poorer quality interpretations than did high-IQ subjects. The results were most consistent with a constraint satisfaction approach to metaphor comprehension.     

Examining the evidence for an independent semantic analyzer: an ERP study in Spanish

Recent ERP findings challenge the widespread assumption that syntactic and semantic processes are tightly coupled. Syntactically well-formed sentences that are semantically anomalous due to thematic mismatches elicit a P600, the component standardly associated with syntactic anomaly. This ‘thematic P600’ effect has been attributed to detection of semantically plausible thematic relations that conflict with the surface syntactic structure of the sentence, implying a processing architecture with an independent semantic analyzer. A key finding is that the P600 is selectively sensitive to the presence of plausible verb-argument relations, and that otherwise an N400 is elicited (The hearty meal was devouring … vs. The dusty tabletop was devouring …: Kim & Osterhout, 2005). The current study investigates in Spanish whether the evidence for an independent semantic analyzer is better explained by a standard architecture that rapidly integrates multiple sources of lexical, syntactic, and semantic information. The study manipulated the presence of plausible thematic relations, and varied the choice of auxiliary between passive-biased fue and active-progressive biased estaba. Results show a late positivity that appeared as soon as comprehenders detected an improbable combination of subject animacy, auxiliary bias, or verb voice morphology. This effect appeared at the lexical verb in the fue conditions and at the auxiliary in the estaba conditions. The late positivity elicited by surface thematic anomalies was the same, regardless of the presence of a plausible non-surface interpretation, and no N400 effects were elicited. These findings do not implicate an independent semantic analyzer, and are compatible with standard language processing architectures.     

Metaphors and the mental lexicon.

In two experiments we investigate the possibility that lexicalization can account for the distinction between literal and metaphorical language. In both experiments, sentence contexts were presented with the final word missing. When subjects signaled they understood the context, two possible final words were presented and subjects were required to decide which was more appropriate. Semantic decision times over five different types of stimuli investigating literal and metaphorical word usage were consistent with a modified class inclusion model in which both the lexicalized meaning of words and the context in which they are presented make essential contributions to understanding.     

Common and modality-specific processes in the mental lexicon

Eight experiments were conducted to resolve: (1) empirical inconsistencies in repetition effects under intermodality conditions in word identification and lexical decision, and (2) an associated theoretical conflict concerning lexical organization. The results demonstrated that although more facilitation occurs under visual-prime/visual-test (VV) conditions than under auditory-prime/visual-test (AV) conditions, significant repetition facilitation also occurs under AV conditions. The results also indicated that: repetition effects observed for the VV and AV conditions apply to high- as well as to low-frequency words; they are insensitive to a variety of encoding tasks designed to emphasize different properties of words; and they are unaffected by differences in the ease of encoding of isolated auditory and visual words. The results are consistent with the existence of both modality-specific and common or modality-free processes in word recognition, in which word-frequency effects are restricted to the second and, by implication, lexical stage.     

Morphological units in the Arabic mental lexicon

Standard views of morphology in Modern Standard Arabic hold that surface word forms comprise at least two morphemes: a three-consonantal root conveying semantic meaning and a word pattern carrying syntactic information. An alternative account claims that semantic information is carried by a bi-consonantal morphological unit called the etymon. Accordingly, in the form [batara] the core meaning is carried not by the tri-consonantal root morpheme [btr] but by the etymon morpheme [b,t] which surfaces in other forms like [batta] "sever", [batala] "cut off" with the same meaning "cutting". Previous experimental research in Semitic languages has assumed the tri-consonantal root/word pattern approach. In cross-modal and masked priming experiments we ask whether the etymon, as a more fine-grained two-consonantal morphological unit, can yield the morphological priming effects typically obtained with tri-consonantal root morphemes. The results clearly show that two words sharing an etymon do facilitate each other both in cross-modal and masked priming even though they do not share a root, controlling for semantic and for form overlap effects. The bearing of these results on theories of morphological processing and representation is discussed.     

Novel word integration in the mental lexicon: Evidence from unmasked and masked semantic priming

We sought to establish whether novel words can become integrated into existing semantic networks by teaching participants new meaningful words and then using these new words as primes in two semantic priming experiments, in which participants carried out a lexical decision task to familiar words. Importantly, at no point in training did the novel words co-occur with the familiar words that served as targets in the primed lexical decision task, allowing us to evaluate semantic priming in the absence of direct association. We found that familiar words were primed by the newly related novel words, both when the novel word prime was unmasked (Experiment 1) and when it was masked (Experiment 2), suggesting that the new words had been integrated into semantic memory. Furthermore, this integration was strongest after a 1-week delay and was independent of explicit recall of the novel word meanings: Forgetting of meanings did not attenuate priming. We argue that even after brief training, newly learned words become an integrated part of the adult mental lexicon rather than being episodically represented separately from the lexicon.     

Age of avatar modulates the altercentric bias in a visual perspective-taking task: ERP and behavioral evidence

Despite being able to rapidly and accurately infer their own and other peoples’ visual perspectives, healthy adults experience difficulty ignoring the irrelevant perspective when the two perspectives are in conflict; they experience egocentric and altercentric interference. We examine for the first time how the age of an observed person (adult vs. child avatar) influences adults’ visual perspective-taking, particularly the degree to which they experience interference from their own or the other person’s perspective. Participants completed the avatar visual perspective-taking task, in which they verified the number of discs in a visual scene according to either their own or an on-screen avatar’s perspective (Experiments 1 and 2) or only from their own perspective (Experiment 3), where the two perspectives could be consistent or in conflict. Age of avatar was manipulated between (Experiment 1) or within (Experiments 2 and 3) participants, and interference was assessed using behavioral (Experiments 1–3) and ERP (Experiment 1) measures. Results revealed that altercentric interference is reduced or eliminated when a child avatar was present, suggesting that adults do not automatically compute a child avatar’s perspective. We attribute this pattern to either enhanced visual processing for own-age others or an inference on reduced mental awareness in younger children. The findings argue against a purely attentional basis for the altercentric effect, and instead support an account where both mentalising and directional processes modulate automatic visual perspective-taking, and perspective-taking effects are strongly influenced by experimental context.     

Morphological priming in the German mental lexicon.

We present results from cross-modal priming experiments on German participles and noun plurals. The experiments produced parallel results for both inflectional systems. Regular inflection exhibits full priming whereas irregularly inflected word forms show only partial priming: after hearing regularly inflected words (-t participles and -s plurals), lexical decision times on morphologically related word forms (presented visually) were similar to reaction times for a base-line condition in which prime and target were identical, but significantly shorter than in a control condition where prime and target were unrelated. In contrast, prior presentation of irregular words (-n participles and -er plurals) led to significantly longer response times on morphologically related word forms than the prior presentation of the target itself. Hence, there are clear priming differences between regularly and irregularly inflected German words. We compare the findings on German with experimental results on regular and irregular inflection in English and Italian, and discuss theoretical implications for single versus dual-mechanism models of inflection.     

The mapping from sound structure to the lexicon in aphasia: evidence from rhyme and repetition priming

Two studies were conducted to explore the hypothesis that Broca's and Wernicke's aphasics have deficits arising from the processes involved in activating the lexicon from phonological form. The first study explored whether phonologically similar lexical entries differing only in their initial consonants show "rhyme priming." Results revealed that Broca's aphasics failed to show facilitation when the target was identical to the prime (i.e. identity priming) and they showed significant inhibition when targets were preceded by rhyming words. Wernicke's aphasics showed a pattern of results similar to that of normal subjects, i.e., identity priming and rhyme priming as well as significantly slower reaction-times in the rhyming condition compared to the identity condition. The second study investigated form-based repetition priming in aphasic patients at a number of intervals including when no other stimuli intervened between repeated stimuli (0 lag) or when 4, 8, or 12 stimuli intervened. Results showed that, unlike old normal subjects who showed repetition priming for both words and nonwords, both Broca's and Wernicke's aphasics showed repetition priming for word targets only. Moreover, in contrast to old normal subjects who showed a greater magnitude of priming at 0 lag for word targets, neither Broca's aphasics or Wernicke's aphasics showed priming at 0 lag. Implications of these findings are considered with respect to the hypotheses that Broca's and Wernicke's aphasics have deficits in the nature of the activation patterns within the lexicon itself and in auditory (working) memory.     

Broca's aphasia, verbs and the mental lexicon

Verb production is notoriously difficult for individuals with Broca's aphasia, both at the word and at the sentence level. An intriguing question is at which level in the speech production these problems arise. The aim of the present study is to identify the functional locus of the impairment that results in verb production deficits in Broca's aphasia. Levelt's (1989) model is used as a theoretical framework for this study. Two experiments have been conducted, one on verb movement and one on verbs with alternating transitivity. The results suggest that the functional impairment in Broca's aphasia should be located in Levelt's "grammatical encoder."     

Phonological access of the lexicon: evidence from associative priming with pseudohomophones.

Pseudohomophones were used in a primed naming task. In Experiments 1 and 2, target pseudowords that sounded like real words (e.g., CHARE) were preceded either by context words that related associatively to the word with which the target was homophonic (TABLE-CHARE) or by context words that were not associatively related (NOVEL-CHARE). Control pairs were TABLE-THARE and NOVEL-THARE (Experiment 1) and TABLE-CHARK and NOVEL-CHARK (Experiment 2). In relation to NOVEL, TABLE benefited the naming of CHARE but not the naming of THARE or CHARK. TAYBLE-CHAIR pairs were used in Experiment 3. If the prime TAYBLE activated/table/,then/chair/would be activated associatively and the target CHAIR would be named faster than if TARBLE was the prime. Experiment 4 extended the design of Experiment 3 to include TABLE-CHAIR pairs and a comparison of a short (280 ms) and a long (500 ms) delay between context and target onsets. The priming due to associated pseudohomophones was unaffected by onset asynchrony and equal in magnitude to that due to associated words. Results suggest that lexical representations are coded and accessed phonologically.     

Mighty metaphors: behavioral and ERP evidence that power shifts attention on a vertical dimension

Thinking about the abstract concept power may automatically activate the spatial up-down image schema (powerful up; powerless down) and consequently direct spatial attention to the image schema-congruent location. Participants indicated whether a word represented a powerful or powerless person (e.g. ‘king’ or ‘servant’). Following each decision, they identified a target at the top or bottom of the visual field. In Experiment 1 participants identified the target faster when their spatial position was congruent with the perceived power of the preceding word than when it was incongruent. In Experiment 2 ERPs showed a higher N1 amplitude for congruent spatial positions. These results support the view that attention is driven to the image schema congruent location of a power word. Thus, power is partially understood in terms of vertical space, which demonstrates that abstract concepts are grounded in sensory-motor processing.     

The processing of lexical ambiguity: homonymy and polysemy in the mental lexicon

Under the theoretical assumption that lexical ambiguity is not a homogeneous phenomenon, but rather that it is subdivided into two distinct types, namely homonymy and polysemy, the present study investigated whether these different types of lexical ambiguity are psychologically real. Four types of ambiguous words, homonymous words (e.g., "pen"), polysemous words with metaphorical extensions (e.g., "eye"), polysemous words with a count/mass metonymic extension (e.g., "turkey"), and polysemous words with a producer/product metonymic extension (e.g., "Dali"), were used in a cross-modal sentence-priming lexical decision task. Overall, the theoretical distinction between homonymy and polysemy was reflected in the results of the present study, which revealed differential processing depending on the type of ambiguity.     

The role of prosody in the mental lexicon.

Current models of spoken word recognition take into account factors such as word frequency, word onset cohort size, and phonological neighborhood density. Using the word onset gating technique we tested word recognition when bandpass filtering was used to allow subjects to hear the full prosodic pattern of a word (number of syllables and syllabic stress), deprived of segmental information beyond that contained in the onset gate. Subjects also heard either word onsets plus duration information or only word onsets. Results suggest that word prosody is represented in the mental lexicon and is effectively used by listeners in spoken word recognition.     

The brain's hemispheres and controlled search of the lexicon: evidence from fixated words and pseudowords

Difference between the brain's hemispheres in efficiency of intentional search of the mental lexicon with phonological, orthographic, and semantic strategies was investigated. Letter strings for lexical decision were presented at fixation, with a lateralized distractor to the LVF or RVF. Word results revealed that both hemispheres were capable of using each of the three strategies, but the right hemisphere had better baseline processing of orthography and was better at processing semantics. Pseudoword results supported the right hemisphere advantage for orthography and showed a left hemisphere advantage for phonology and assessment of possible semantic relationships. Taken together, the data support the idea that the right hemisphere uses orthography to make efficient decisions about novelty of an item, while the left engages in grapheme-to-phoneme conversion to test hypotheses about unfamiliar items. The convergence of data with previous research reveals that the procedure, as well as analyses of pseudowords, inform laterality research.