The word frequency effect and lexical access

Frequency Effects on Spelling Error Recognition: An ERP Study

Spelling errors are ubiquitous in all writing systems. Most studies exploring spelling errors focused on the phonological plausibility of errors. However, unlike typical pseudohomophones, spelling errors occur in naturally produced written language. We investigated the time course of recognition of the most frequent orthographic errors in Russian (error in an unstressed vowel in the root) and the effect of word frequency on this process. During event-related potentials (ERP) recording, 26 native Russian speakers silently read high-frequency correctly spelled words, low-frequency correctly spelled words, high-frequency words with errors, and low-frequency words with errors. The amplitude of P200 was more positive for correctly spelled words than for misspelled words and did not depend on the frequency of the words. In addition, in the 350–500-ms time window, we found a more negative response for misspelled words than for correctly spelled words in parietal–temporal-occipital regions regardless of word frequency. Considering our results in the context of a dual-route model, we concluded that recognizing misspelled high-frequency and low-frequency words involves common orthographic and phonological processes associated with P200 and N400 components such as whole word orthography processing and activation of phonological representations correspondingly. However, at the 500–700 ms stage (associated with lexical-semantic access in our study), error recognition depends on the word frequency. One possible explanation for these differences could be that at the 500–700 ms stage recognition of high-frequency misspelled and correctly spelled words shifts from phonological to orthographic processes, while low-frequency misspelled words are accompanied by more prolonged phonological activation. We believe these processes may be associated with different ERP components P300 and N400, reflecting a temporal overlap between categorization processes based on orthographic properties for high-frequency words and phonological processes for low-frequency words. Therefore, our results complement existing reading models and demonstrate that the neuronal underpinnings of spelling error recognition during reading may depend on word frequency.

Predicting lexical complexity in English texts: the Complex 2.0 dataset

Identifying words which may cause difficulty for a reader is an essential step in most lexical text simplification systems prior to lexical substitution and can also be used for assessing the readability of a text. This task is commonly referred to as complex word identification (CWI) and is often modelled as a supervised classification problem. For training such systems, annotated datasets in which words and sometimes multi-word expressions are labelled regarding complexity are required. In this paper we analyze previous work carried out in this task and investigate the properties of CWI datasets for English. We develop a protocol for the annotation of lexical complexity and use this to annotate a new dataset, CompLex 2.0. We present experiments using both new and old datasets to investigate the nature of lexical complexity. We found that a Likert-scale annotation protocol provides an objective setting that is superior for identifying the complexity of words compared to a binary annotation protocol. We release a new dataset using our new protocol to promote the task of Lexical Complexity Prediction.

Spoken Word Segmentation in First and Second Language: When ERP and Behavioral Measures Diverge

Previous studies of word segmentation in a second language have yielded equivocal results. This is not surprising given the differences in the bilingual experience and proficiency of the participants and the varied experimental designs that have been used. The present study tried to account for a number of relevant variables to determine if bilingual listeners are able to use native-like word segmentation strategies. Here, 61 French-English bilingual adults who varied in L1 (French or English) and language dominance took part in an audiovisual integration task while event-related brain potentials (ERPs) were recorded. Participants listened to sentences built around ambiguous syllable strings (which could be disambiguated based on different word segmentation patterns), during which an illustration was presented on screen. Participants were asked to determine if the illustration was related to the heard utterance or not. Each participant listened to both English and French utterances, providing segmentation patterns that included both their native language (used as reference) and their L2. Interestingly, different patterns of results were observed in the event-related potentials (online) and behavioral (offline) results, suggesting that L2 participants showed signs of being able to adapt their segmentation strategies to the specifics of the L2 (online ERP results), but that the extent of the adaptation varied as a function of listeners' language experience (offline behavioral results).

The career of measurement

Units as they exist today are highly abstract. Meters, miles, and other modern measures have no obvious basis in tangible phenomena and can be applied broadly across domains. Historical examples suggest, however, that units have not always been so abstract. Here, we examine this issue systematically. We begin by analyzing linear measures in the Oxford English Dictionary (OED) and in an ethnographic database that spans 114 cultures (HRAF). Our survey of both datasets shows, first, that early length units have mostly come from concrete sources-body parts, artifacts, events, and other tangible phenomena-and, second, that they have often been tied to particular contexts. Measurement units have thus undergone a shift from highly concrete to highly abstract. How did this shift happen? Drawing on historical surveys and case studies-as well as data from the OED and HRAF-we next propose a reconstruction of how abstract units might have evolved gradually through a series of overlapping stages. We also consider the cognitive processes that underpin this evolution-in particular, comparison. Finally, we discuss the cognitive origins of units. Units are not only slow to emerge historically, they are also slow to be acquired developmentally, and mastering them appears to have cognitive consequences. Taken together, these observations suggest that units are not inevitable intuitions, but are best thought of as culturally evolved cognitive tools. By analyzing the career of measurement in detail, we illustrate how such tools-abstract as they are today-can arise from concrete, often bodily origins.

The Similarities Between the Target and the Intruder in Naturally Occurring Person Naming Errors: A Comparison Between Repeated and Single Naming Confusions

This study investigated the phenomenon of personal name confusion, i.e. calling a familiar person by someone else's name. Two types of name confusion were considered: single confusions (i.e. confusions that appeared only once) and repeated confusions (i.e. confusions that appeared repeatedly). The main purpose of the present study was to compare these two types of personal name confusion and to identify the similarities and differences between them. Participants were asked to fill in two questionnaires (one for each type of confusion) in order to collect information about the properties of the confusions. Results indicated that single and repeated confusions shared some similarities (the similarity of the gender and age of the bearers of the confused names, the phonological similarity between the confused names, the positive or negative valence of the relationship between the participant and the bearers of the names, the frequency of encountering the bearers of the names, and the low level of stress on the part of the participant when the confusions were made). However, some differences were also found between single and repeated confusions (the context of encountering, the length of time that the participant had known the two bearers of the names, the presence of the inverse confusion, the facial resemblance between the two bearers, the kind of relationship shared by the participant and the two bearers, and the state of tiredness on the part of the participant when the confusions were made). In addition, regression analysis indicated that the facial resemblance between the target person and the intruder, the phonological similarity of the names and the difference in age between the two bearer of the names were significant predictors of the frequency of the repeated confusions.

Planning and production of grammatical and lexical verbs in multi-word messages

Grammatical words represent the part of grammar that can be most directly contrasted with the lexicon. Aphasiological studies, linguistic theories and psycholinguistic studies suggest that their processing is operated at different stages in speech production. Models of sentence production propose that at the formulation stage, lexical words are processed at the functional level while grammatical words are processed at a later positional level. In this study we consider proposals made by linguistic theories and psycholinguistic models to derive two predictions for the processing of grammatical words compared to lexical words. First, based on the assumption that grammatical words are less crucial for communication and therefore paid less attention to, it is predicted that they show shorter articulation times and/or higher error rates than lexical words. Second, based on the assumption that grammatical words differ from lexical words in being dependent on a lexical host, it is hypothesized that the retrieval of a grammatical word has to be put on hold until its lexical host is available, and it is predicted that this is reflected in longer reaction times (RTs) for grammatical compared to lexical words. We investigated these predictions by comparing fully homonymous sentences with only a difference in verb status (grammatical vs. lexical) elicited by a specific context. We measured RTs, duration and accuracy rate. No difference in duration was observed. Longer RTs and a lower accuracy rate for grammatical words were reported, successfully reflecting grammatical word properties as defined by linguistic theories and psycholinguistic models. Importantly, this study provides insight into the span of encoding and grammatical encoding processes in speech production.

Distinguishing underlying and surface variation patterns in speech perception

This study examines the relationship between patterns of variation and speech perception using two English prefixes: 'in-'/'im-' and 'un-'. In natural speech, 'in-' varies due to an underlying process of phonological assimilation, while 'un-' shows a pattern of surface variation, assimilating before labial stems. In a go/no-go lexical decision experiment, subjects were presented a set of 'mispronounced' stimuli in which the prefix nasal was altered (replacing [n] with [m], or vice versa), in addition to real words with unaltered prefixes. No significant differences between prefixes were found in responses to unaltered words. In mispronounced items, responses to 'un-' forms were faster and more accurate than to 'in-' forms, although a significant interaction mitigated this effect in labial contexts. These results suggest the regularity of variation patterns has consequences for the lexical specification of words, and argues against radical under-specification accounts which argue for a maximally sparse lexicon.

Effect of response context and masker type on word recognition in school-age children and adults

In adults, masked speech recognition improves with the provision of a closed set of response alternatives. The present study evaluated whether school-age children (5-13 years) benefit to the same extent as adults from a forced-choice context, and whether this effect depends on masker type. Experiment 1 compared masked speech reception thresholds for disyllabic words in either an open-set or a four-alternative forced-choice (4AFC) task. Maskers were speech-shaped noise or two-talker speech. Experiment 2 compared masked speech reception thresholds for monosyllabic words in two 4AFC tasks, one in which the target and foils were phonetically similar and one in which they were dissimilar. Maskers were speech-shaped noise, amplitude-modulated noise, or two-talker speech. For both experiments, it was predicted that children would not benefit from the information provided by the 4AFC context to the same degree as adults, particularly when the masker was complex (two-talker) or when audible speech cues were temporally sparse (modulated-noise). Results indicate that young children do benefit from a 4AFC context to the same extent as adults in speech-shaped noise and amplitude-modulated noise, but the benefit of context increases with listener age for the two-talker speech masker.

Processing of Phonemic Consonant Length: Semantic and Fragment Priming Evidence from Bengali

Six cross-modal lexical decision tasks with priming probed listeners' processing of the geminate-singleton contrast in Bengali, where duration alone leads to phonemic contrast ([pata] 'leaf' vs. [pat:a] 'whereabouts'), in order to investigate the phonological representation of consonantal duration in the lexicon. Four form-priming experiments (auditory fragment primes and visual targets) were designed to investigate listeners' sensitivity to segments of conflicting duration. Each prime derived from a real word ([k(h)[symbol: see text]m]/[g(h)en:]) was matched with a mispronunciation of the opposite duration (*[k(h)[symbol: see text]m:]/*[g(h)en]) and both were used to prime the full words [k(h)[symbol: see text]ma] ('forgiveness') and [g(h)en:a] ('disgust') respectively. Although all fragments led to priming, the results showed an asymmetric pattern. The fragments of words with singletons mispronounced as geminates led to equal priming, while those with geminates mispronounced as singletons showed a difference. The priming effect of the real-word geminate fragment was significantly greater than that of its corresponding nonword singleton fragment. In two subsequent semantic priming tasks with full-word primes a stronger asymmetry was found: nonword geminates (*[k(h)[symbol: see text]m:a]) primed semantically related words ([marjona] 'forgiveness') but singleton nonword primes (*[ghena]) did not show priming. This overall asymmetry in the tolerance of geminate nonwords in place of singleton words is attributed to a representational mismatch and points towards a moraic representation of duration. While geminates require a mora which cannot be derived from singleton input, the additional information in geminate nonwords does not create a similar mismatch.

A behavioral study of the nature of verb production deficits in Alzheimer's disease

Patients with Alzheimer's disease (AD) may experience greater difficulty with verb production than with noun production. In this study, we sought to assess the nature of verb production deficits in AD by using verb fluency and verb naming tasks. We designed two hypotheses for this verb deficit: (1) executive impairment drives the deficit; (2) semantic impairment drives the deficit. Thirty-five patients with AD and 35 matched healthy controls participated in the study. Both groups performed a verb naming task composed of 45 pictures (low-, medium-, and high-frequency subsets) and a verb fluency task (scored for total correct words and for mean word frequency). Patients with AD were equally impaired in verb naming and verb fluency, with an effect of disease severity on verb naming. Word frequency influenced verb naming, but not verb fluency, performance. Our results indicate that verb production deficits in AD seem to be driven more by semantic than by executive impairment.

Asymmetric processing of durational differences - electrophysiological investigations in Bengali

Duration is used contrastively in many languages to distinguish word meaning (e.g. in Bengali, [pata] 'leaf' vs. [pat:a] 'whereabouts'). While there is a large body of research on other contrasts in speech perception (e.g. vowel contrasts and consonantal place features), little work has been done on how durational information is used in speech processing. In non-linguistic studies of low-level processing, such as visual and non-linguistic acoustic pop-out tasks, an asymmetry is found where additional information is more readily detected than missing information. In this study, event-related potentials were recorded during two cross-modal auditory-visual semantic priming studies, where nonword mispronunciations of spoken prime words were created by changing the duration of a medial consonant (real word [dana] 'seed'>nonword [dan:a]). N400 amplitudes showed an opposite asymmetric pattern of results, where increases in consonantal duration were tolerated and led to priming of the visual target, but decreases in consonantal duration were not accepted. This asymmetrical pattern of acceptability is attributed to the fact that a longer consonant includes all essential information for the recognition of the original word with a short medial consonant (a possible default category) and any additional information can be ignored. However, when a consonant is shortened, it lacks the required durational information to activate the word with the original long consonant.

Connectivity, not frequency, determines the fate of a morpheme

Morphemes are the smallest meaningful parts of words and therefore represent a natural unit to study the evolution of words. To analyze the influence of language change on morphemes, we performed a large scale analysis of German and English vocabulary covering the last 200 years. Using a network approach from bioinformatics, we examined the historical dynamics of morphemes, the fixation of new morphemes and the emergence of words containing existing morphemes. We found that these processes are driven mainly by the number of different direct neighbors of a morpheme in words (connectivity, an equivalent to family size or type frequency) and not its frequency of usage (equivalent to token frequency). This contrasts words, whose survival is determined by their frequency of usage. We therefore identified features of morphemes which are not dictated by the statistical properties of words. As morphemes are also relevant for the mental representation of words, this result might enable establishing a link between an individual's perception of language and historical language change.

Word frequency, familiarity, and laterality effects in a dichotic listening task

Although word frequency and familiarity effects are a well-established finding in visual research (Marlsen-Wilson, 1990), these variables are often overshadowed in the selection of words used in dichotic listening tasks in favour of choosing words that fuse together (Connine, Mullenix, Shernoff, & Yenn, 1990). The present study investigates the influence of word frequency and word familiarity on the right ear advantage typically found in dichotic listening. A task using words that did not fuse, and manipulating word frequency and word familiarity was developed. In the task participants were presented with dichotic pairs of words and asked to select the word that they heard the clearest. This task showed that the right ear advantage (REA) was larger when the frequency of the words presented to each ear was the same than when it was different. In addition, the magnitude of the REA was modulated independently by the familiarity of the word presented to the left and to the right ear. Overall, the results of the present study support the notion that word frequency and familiarity should be considered in dichotic tasks. The findings are interpreted in terms of their implications for models of dichotic listening.

Enhanced perception in savant syndrome: patterns, structure and creativity

According to the enhanced perceptual functioning (EPF) model, autistic perception is characterized by: enhanced low-level operations; locally oriented processing as a default setting; greater activation of perceptual areas during a range of visuospatial, language, working memory or reasoning tasks; autonomy towards higher processes; and superior involvement in intelligence. EPF has been useful in accounting for autistic relative peaks of ability in the visual and auditory modalities. However, the role played by atypical perceptual mechanisms in the emergence and character of savant abilities remains underdeveloped. We now propose that enhanced detection of patterns, including similarity within and among patterns, is one of the mechanisms responsible for operations on human codes, a type of material with which savants show particular facility. This mechanism would favour an orientation towards material possessing the highest level of internal structure, through the implicit detection of within- and between-code isomorphisms. A second mechanism, related to but exceeding the existing concept of redintegration, involves completion, or filling-in, of missing information in memorized or perceived units or structures. In the context of autistics' enhanced perception, the nature and extent of these two mechanisms, and their possible contribution to the creativity evident in savant performance, are explored.

A comparison of brain activity evoked by single content and function words: an fMRI investigation of implicit word processing

Content and function words have different roles in language and differ greatly in their semantic content. Although previous research has suggested that these different roles may be mediated by different neural substrates, the neuroimaging literature on this topic is particularly scant. Moreover, fMRI studies that have investigated differences between content and function words have utilized tasks that focus the subjects' attention on the differences between these word types. It is possible, then, that task-related differences in attention, working memory, and decision-making contribute to the differential patterns of activation observed. Here, subjects were engaged in a continuous working memory cover task while single, task-irrelevant content and function words were infrequently and irregularly presented. Nonword letter strings were displayed in black font at a fast rate (2/s). Subjects were required to either remember or retrieve occasional nonwords that were presented in colored fonts. Incidental and irrelevant to the memory task, content and function words were interspersed among nonwords at intervals of 12 to 15 s. Both word types strongly activated temporal-parietal cortex, middle and anterior temporal cortex, inferior frontal gyrus, parahippocampal gyrus, and orbital frontal cortex. Activations were more extensive in the left hemisphere. Content words elicited greater activation than function words in middle and anterior temporal cortex, a sub-region of orbital frontal cortex, and the parahippocampal region. Words also evoked extensive deactivation, most notably in brain regions previously associated with working memory and attention.

N170 ERPs could represent a logographic processing strategy in visual word recognition

BACKGROUND

Occipito-temporal N170 component represents the first step where face, object and word processing are discriminated along the ventral stream of the brain. N170 leftward asymmetry observed during reading has been often associated to prelexical orthographic visual word form activation. However, some studies reported a lexical frequency effect for this component particularly during word repetition that appears in contradiction with this prelexical orthographic step. Here, we tested the hypothesis that under word repetition condition, discrimination between words would be operated on visual rather than orthographic basis. In this case, N170 activity may correspond to a logographic processing where a word is processed as a whole.

METHODS

To test such an assumption, frequent words, infrequent words and pseudowords were presented to the subjects that had to complete a visual lexical decision task. Different repetition conditions were defined 1--weak repetition, 2--massive repetition and 3--massive repetition with font alternation. This last condition was designed to change visual word shape during repetition and therefore to interfere with a possible visual strategy during word recognition.

RESULTS

Behavioral data showed an important frequency effect for the weak repetition condition, a lower but significant frequency effect for massive repetition, and no frequency effect for the changing font repetition. Moreover alternating font repetitions slowed subject's responses in comparison to "simple" massive repetition.ERPs results evidenced larger N170 amplitude in the left hemisphere for frequent than both infrequent words and pseudowords during massive repetition. Moreover, when words were repeated with different fonts this N170 effect was not present, suggesting a visual locus for such a N170 frequency effect.

CONCLUSION

N170 represents an important step in visual word recognition, consisting probably in a prelexical orthographic processing. But during the reading of very frequent words or after a massive repetition of a word, it could represent a more holistic process where words are processed as a global visual pattern.

Enhanced perceptual functioning in autism: an update, and eight principles of autistic perception

We propose an "Enhanced Perceptual Functioning" model encompassing the main differences between autistic and non-autistic social and non-social perceptual processing: locally oriented visual and auditory perception, enhanced low-level discrimination, use of a more posterior network in "complex" visual tasks, enhanced perception of first order static stimuli, diminished perception of complex movement, autonomy of low-level information processing toward higher-order operations, and differential relation between perception and general intelligence. Increased perceptual expertise may be implicated in the choice of special ability in savant autistics, and in the variability of apparent presentations within PDD (autism with and without typical speech, Asperger syndrome) in non-savant autistics. The overfunctioning of brain regions typically involved in primary perceptual functions may explain the autistic perceptual endophenotype.

Neural Correlates of Script Event Knowledge: a Neuropsychological Study Following Prefrontal Injury

Scripts sequentially link information about daily activities and event knowledge. Patients have difficulty sequencing script events following lesions of the prefrontal cortex while showing intact access to selective aspects of script knowledge. It has been suggested that the sequencing impairment is due to a deficit in an inhibitory gating mechanisms that usually enables selection of an item from competing alternatives. If this is the case, then an inhibitory task should reveal script processing impairments on a script categorization task that is not normally associated with poor performance following prefrontal damage. To test this hypothesis, we administered a simple untimed classification task and a modified Go/NoGo task in which subjects classified events from social and non-social activities (e.g., read the menu, order the food) and related semantic items (e.g., menu, order) in terms of whether they belonged to a target activity. Participants were patients with lesions of the prefrontal cortex and matched controls. The results showed that damage to the right orbitofrontal cortex was associated with social item classification errors in the simple untimed classification task. In addition, the damage to the right prefrontal cortex was associated with increased response times to respond correctly to Go trials in the modified Go/NoGo task. The data demonstrate that damage to the right orbitofrontal cortex results in impairment in the accessibility of script and semantic representations of social activities. This impairment is exacerbated by an inefficient inhibitory gating mechanism.

Psychological structure and neural correlates of event knowledge

Humans are capable of storing and retrieving sequences of complex structured events. Here we report a study in which we establish the psychological structure of event knowledge and then use parametric event-related functional magnetic resonance imaging to identify its neural correlates. We demonstrate that event knowledge is organized along dissociable dimensions that are reflected in distinctive patterns of neural activation: social valence (amygdala and right orbitofrontal cortex), experience (medial prefrontal cortex) and engagement (left orbitofrontal cortex). Our study affirms the importance and uniqueness of the human prefrontal cortex in representing event knowledge.

Differences in brain potentials to open and closed class words: class and frequency effects

Closed class (determiners, pronouns, conjunctions, prepositions etc. ) and open class (nouns, verbs, adjectives, adverbs) words have different linguistic functions and have been proposed to be processed by different neural systems. Here, event-related potentials (ERPs) were recorded in young German-speaking subjects while they read closed class and open class words flashed upon a video-screen. In the first experiment closed class words were sorted into four different frequency categories and open class words into three categories. The words were presented in a list with the subjects' task to detect occasional non-words. A centroparietal negativity (N400) with a peak latency of about 400 ms varied in amplitude as a function of frequency in both classes. The N400 in closed class items, however, was considerably smaller than that in open class words of similar frequency. A left anterior negativity (N280/LPN) showed some degree of frequency-sensitivity regardless of word class. Only for the very high frequency closed class words a frontal negativity with an onset of about 400 ms was obtained (N400-700). This N400-700 effect was replicated in the second study, in which medium frequency closed and open class words and very high frequency closed class words were presented at the fifth position of simple German sentences. It is suggested that neither N400 nor the left anterior negativity (N280/LPN) distinguish qualitatively between the two word classes and thus claims about different brain systems involved in the processing of open and closed class words are not substantiated electrophysiologically. The N400-700 effect is possibly related to specific grammatical functions of some closed class items, such as determiners.

Lexical access of function versus content words

There has been a simmering debate as to whether evidence exists for differential processes of lexical access for function and content words. This has centered around the frequency effect (higher word frequency reducing access times for content words but not function words). Previous work has used the lexical decision paradigm, which has been shown to reflect more than lexical access times. We measured naming times for words in sentences read for meaning. Our findings confirm that lexical access for function words is indeed faster than for content words as predicted by neurolinguistic theory and electrophysiological evidence, but that this difference can be attributed to word predictability (Cloze value) and word familiarity (log frequency). We also show that differences in frequency effect for the two word types holds only for the lower frequency words and not at all for the higher frequency words. We discuss the implications of the results for neurolinguistic theory.

Lexical processing and text integration of function and content words: evidence from priming and eye fixations

The results of two experiments comparing processing of function words and content words are reported. In Experiment 1, priming was present for both related function and related content word pairs, as measured in lexical decision response times. In Experiment 2, participants' eye movements were monitored as they read sentences containing either a high- or a low-frequency function or content target word. Average word length and word frequency were matched across the function and content word conditions. Function words showed frequency effects in first-fixation and gaze duration that were similar to those seen for content words. Clear differences in on-line processing of function and content words emerged in later processing measures. These differences were reflected in reading patterns and reading time measures. There was inflated processing time in the phrase immediately following a low-frequency function word, and participants made more regressions to the target word in this condition than in the other three conditions. The priming effects in lexical decision and the word frequency effects in initial processing measures in silent reading for both word types were taken as evidence of common lexical processing for function and content words. The observed differences in later processing measures in the eye-movement data were taken as evidence of differences in the role that the two word types have in sentence processing beyond the lexical level.

Electrophysiological Signatures of Visual Lexical Processing: Open-and Closed-Class Words

n This paper presents evidence of the disputed existence of an electrophysiological marker for the lexical-categorical distinction between open-and closed-class words. Event-related brain potentials were recorded from the scalp while subjects read a story. Separate waveforms were computed for open-and closed-class words. Two aspects of the waveforms could be reliably related to vocabulary class. The first was an early negativity in the 230-to 350-msec epoch, with a bilateral anterior predominance. This negativity was elicited by open-and closed-class words alike, was not affected by word frequency or word length, and had an earlier peak latency for closed-class words.

The second was a frontal slow negative shift in the 350-to 500-msec epoch, largest over the left side of the scalp. This late negativity was only elicited by closed-class words. Although the early negativity cannot serve as a qualitative marker of the open-and closed-class distinction, it does reflect the earliest electrophysiological manifestation of the availability of categorical information from the mental lexicon. These results suggest that the brain honors the distinction between open-and closed-class words, in relation to the different roles that they play in on-line sentence processing.

Atypical memory performance in an autistic savant

This study explored the mechanisms underlying the hypermnesia of an autistic savant (NM) through three experiments. The first two served to assess whether absence of interference was responsible for NM's exceptional list memory. The third investigated the type of cues used in recall. Results indicated absence of retroactive interference but presence of slight proactive interference in list recall of proper names. Normal interference effects were found, however, in list recall of common nouns. Exceptional performance was also demonstrated in a missing-name task involving spatial and verbal recall cues. The findings suggest that the outstanding episodic memory presented by some savant persons with autism might be related to an abnormally high resistance to interference.

Dual processing of open- and closed-class words

A series of articles in the past two decades has suggested differential processing of open- and closed-class lexical items by normal adults. Difficulties in replicating a crucial study (Bradley, 1978), however, have weakened the dual route hypothesis. We matched 16 French open-class items to 16 closed-class items for phonological structure, world length, and relative word frequency. Three agrammatic aphasics revealed strikingly more phonological errors on closed-class than open-class items. Dysfluencies were greater on closed-class items and contributed to greater overall reading time for the closed-class words, consistent with a two-route model for the production of closed- and open-class lexical items in Broca's aphasics and, thus, normals.

Ability to stand alone and processing of open-class and closed-class words: isolation versus context

Four experiments investigating processing of closed-class and open-class words in isolation and in sentence contexts are reported. Taft (1990) reported that closed-class words which could not meaningfully stand alone and open-class words which could not meaningfully stand alone incurred longer lexical decision responses than did control words. Taft also reported that closed-class and open-class words which could stand alone meaningfully were not associated with longer lexical decision responses than were control words. Experiments 1 and 2 replicated Taft's effect of ability to stand alone on lexical decision responses to closed-class and open-class words presented in isolation. In Experiments 3 and 4, the same lexical decision targets were presented as part of semantically neutral context sentences in a moving window paradigm. The stand-alone effect was not present in Experiments 3 and 4. The results suggest Taft's conclusion that meaningfulness of a word influences lexical decision needs revision. An explanation is provided according to which support from message level and syntactic and lexical sources in sentence contexts influence words' perceived "meaningfulness."

Modality dependency of familiarity ratings of Japanese words

Familiarity ratings for a large number of aurally and visually presented Japanese words wer measured for 11 subjects, in order to investigate the modality dependency of familiarity. The correlation coefficient between auditory and visual ratings was .808, which is lower than that observed for English words, suggesting that a substantial portion of the mental lexicon is modality dependent. It was shown that the modality dependency is greater for low-familiarity words than it is for medium- or high-familiarity words. This difference between the low- and the medium- or high-familiarity words has a relationship to orthography. That is, the dependency is larger in words consisting only of kanji, which may have multiple pronunciations and usually represent meaning, than it is in words consisting only of hiragana or katakana, which have a single pronunciation and usually do not represent meaning. These results indicate that the idiosyncratic characteristics of Japanese orthography contribute to the modality dependency.

Electrocortical distinction of vocabulary types

Psycholinguistic theories propose that words of the 2 major vocabulary classes, content (open-class) and function (closed-class) words, are computationally distinct and have different neuronal generators. This predicts distinct EEG patterns elicited by words of these 2 classes. To test this prediction, content and function words, together with matched pseudowords, were presented in a lexical decision task (where subjects had to decide whether stimuli were meaningful words or not). Evoked potentials were recorded from 17 electrodes 12 of which were located in close vicinity of the perisylvian cortices. Already 160 msec post stimulus onset, substantial differences in activity patterns distinguish the 2 vocabulary classes. A hemisphere by word class interaction revealed interhemispheric differences for function words but not for content words. Potentials evoked by function words were more negative over the left hemisphere compared to the right. These results evidence that brain mechanisms underlying function and content word processing are different. The following explanation of the data is proposed: content words correspond to neuronal assemblies equally distributed over both hemispheres, while assemblies corresponding to function words are strongly lateralized to the left hemisphere and primarily located in the perisylvian region.

Language-Related ERPs: Scalp Distributions and Modulation by Word Type and Semantic Priming

Event-related potentials (ERPs) were recorded from the scalp to investigate the processing of word stimuli. Three tasks were used: (1) a task comparing words that provided an anomalous or normal sentence ending, (2) a word-list task in which different word types were examined, and (3) a word-list task in which semantic priming was examined. ERPs were recorded from a 50-channel montage in an attempt to dissociate overlapping ERP features by their scalp distributions. The focus of these studies was the N400, an ERP previously associated with language processing (Kutas & Hillyard, 1980). The temporal interval typically associated with N400 (250–500 msec) was found to contain overlapping ERP features. Two of these features were common to both sentence and word-list tasks—but one appeared different. Anomalous sentence endings and words with semantic content in lists both showed coincident negative left frontotemporal and midline-anterior ERP foci, peaking at 332 msec for sentences and 316 msec for word lists. The most negative voltage obtained in the sentence task peaked at 386 msec and had a midline-posterior focus. A right frontotemporal focus developed after the midline-posterior focus and outlasted its duration. The most negative voltage for content words in lists was reached at 364 msec. The distribution of this ERP was extensive over the midline and appeared to differ from that observed in the sentence task. Modulation of language-related ERPs by word type and semantic priming was investigated using the word-list tasks, which required category-detection responses. Two novel findings were obtained: (1) The ERP distributions for words serving grammatical function and content words differed substantially in word lists. Even when devoid of any sentence context, function words presented significantly attenuated measures of N400 compared to content words. These findings support hypotheses that suggest a differential processing of content and function words. (2) Semantic priming functionally dissociated two ERP features in the 250–500 msec range. The later and most negative midline ERP feature (peaking at 364 msec) was attenuated by semantic priming. However, the earlier left frontotemporal feature (peaking at 316 msec) was enhanced by semantic priming. The isolation of this novel language-related ERF' that is sensitive to semantic manipulations has important consequences for temporal and mechanistic aspects of theories of language processing.

Grammatical incongruency and vocabulary types

Four experiments conducted in French were performed to investigate the role of grammatical congruency and vocabulary class on lexical decision times. In Experiment 1, using a double lexical decision, slower reaction times were found for pairs of words that disagreed in gender or number than for congruent pairs. Experiments 2, 3, and 4 tested this effect with a standard priming procedure. The grammatical congruency effect varied according to presentation times (130, 150, or 500 msec) and to vocabulary class of context word (closed or open). Closed-class context words induced stronger grammatical effect than did open-class words. These results suggest that the grammatical link existing between the two words of a pair is more immediately computed when the first one is a closed-class item and argue for a distinct computational role of open- and closed-class words in sentence processing.

Age of acquisition, not word frequency, affects object naming, not object recognition

Word frequency is widely believed to affect object naming speed, despite several studies in which it has been reported that frequency effects may be redundant upon age of acquisition. We report, first, a reanalysis of data from the study by Oldfield and Wingfield (1965), which is standardly cited as evidence for a word frequency effect in object naming; then we report two new experiments. The reanalysis of Oldfield and Wingfield shows that age of acquisition is the major determinant of naming speed, and that frequency plays no independent role when its correlation with other variables is taken into account. In Experiment 1, age of acquisition and phoneme length proved to be the primary determinants of object naming speed. Frequency, prototypicality, and imageability had no independent effect. In Experiment 2, subjects classified objects into two semantic categories (natural or man-made). Prototypicality and semantic category were the only variables to have a significant effect on reaction time, with no effect of age of acquisition, frequency, imageability, or word length. We conclude that age of acquisition, not word frequency, affects the retrieval and/or execution of object names, not the process of object recognition. The locus of this effect is discussed, along with the possibility that words learned in early childhood may be more resistant to the effects of brain injury in at least some adult aphasics than words learned somewhat later.

An Event-Related Potential (ERP) Analysis of Semantic Congruity and Repetition Effects in Sentences

In two experiments, event-related brain potentials (ERPs) and cued-recall performance measures were used to examine the consequences of semantic congruity and repetition on the processing of words in sentences. A set of sentences, half of which ended with words that rendered them semantically incongruous, was repeated either once (eg, Experiment 1) or twice (e.g., Experiment 2). After each block of sentences, subjects were given all of the sentences and asked to recall the missing final words.

Repetition benefited the recall of both congruous and incongruous endings and reduced the amplitude and shortened the duration of the N400 component of the ERP more for (1) incongruous than congruous words, (2) open class than closed class words, and (3) low-frequency than high-frequency open class words. For incongruous sentence terminations, repetition increased the amplitude of a broad positive component subsequent to the N400.

Assuming additive factors logic and a traditional view of the lexicon, our N400 results indicate that in addition to their singular effects, semantic congruiry, repetition, and word frequency converge to influence a common stage of lexical processing. Within a parallel distributed processing framework, our results argue for substantial temporal and spatial overlap in the activation of codes subserving word recognition so as to yield the observed interactions of repetition with semantic congruity, lexical class, and word frequency effects.

The mental representation of lexical form: a phonological approach to the recognition lexicon

We propose a psycholinguistic model of lexical processing which incorporates both process and representation. The view of lexical access and selection that we advocate claims that these processes are conducted with respect to abstract underspecified phonological representations of lexical form. The abstract form of a given item in the recognition lexicon is an integrated segmental-featural representation, where all predictable and non-distinctive information is withheld. This means that listeners do not have available to them, as they process the speech input, a representation of the surface phonetic realisation of a given word-form. What determines performance is the abstract, underspecified representation with respect to which this surface string is being interpreted. These claims were tested by studying the interpretation of the same phonological feature, vowel nasality, in two languages, English and Bengali. The underlying status of this feature differs in the two languages; nasality is distinctive only in consonants in English, while both vowels and consonants contrast in nasality in Bengali. Both languages have an assimilation process which spreads nasality from a nasal consonant to the preceding vowel. A cross-linguistic gating study was conducted to investigate whether listeners would interpret nasal and oral vowels differently in two languages. The results show that surface phonetic nasality in the vowel in VN sequences is used by English listeners to anticipate the upcoming nasal consonant. In Bengali, however, nasality is initially interpreted as an underlying nasal vowel. Bengali listeners respond to CVN stimuli with words containing a nasal vowel, until they get information about the nasal consonant. In contrast, oral vowels in both languages are unspecified for nasality and are interpreted accordingly. Listeners in both languages respond with CVN words (which have phonetic nasality on the surface) as well as with CVC words while hearing an oral vowel. The results of this cross-linguistic study support, in detail, the hypothesis that the listener's interpretation of the speech input is in terms of an abstract underspecified representation of lexical form.

Influences of semantic and syntactic context on open- and closed-class words

Event-related potentials (ERPs) were recorded as subjects read semantically meaningful, syntactically legal but nonsensical and random word strings. The constraints imposed by formal sentence structure alone did not reduce the amplitude of the N400 component elicited by open-class words, whereas semantic constraints did. Semantic constraints also eliminated the word-frequency effect of a larger N400 for low-frequency words. Responses to closed-class words exhibited reduced N400 amplitudes in syntactic and congruent sentences, indicating that formal sentence structure placed greater restrictions on closed-class words than it did on open-class words. However, unlike the open-class results, the impact of sentence context on closed-class words was stable across word positions, suggesting that these syntactic constraints were applied only locally. A second ERP component, distinct from the N400, was elicited primarily by congruent closed-class words.

Closed-class immanence in sentence production

The closed-class hypothesis asserts that function words play a privileged role in syntactic processes. In language production, the claim is that such words are intrinsic to, identified with, or immanent in phrasal skeletons. Two experiments tested this hypothesis with a syntactic priming procedure. In both, subjects tended to produce utterances in the same syntactic forms as priming sentences, with the structures of the self-generated sentences varying as a function of differences in the structures of the primes. Changes in the closed-class elements of the priming sentences had no effect on this tendency over and above the impact of the structural changes. These results suggest that free-standing closed-class morphemes are not inherent components of the structural frames of English sentences.

A signal processing component to Broca's aphasia functor deficits

We conducted a modified replication of K. M. Heilman and R. J. Scholes [Cortex 12, 258-265, 1976] test of functor comprehension in aphasia, controlling the acoustic dimensions of the key function words: 9 Broca patients heard 4 sentence pairs differing only in the post-verb placement of the. They made forced choices between 4 line drawings: one which depicted the correct action, one which depicted the action of the other member in the pair, and two which contained depictions of different figures and actions altogether. Each of the 8 sentences was played in 2 conditions: one with NORMAL intonation, and another with an acoustically more SALIENT post-verbal the. Both of Heilman and Scholes' principal results were successfully replicated, and a SALIENT effect was also discovered, supporting a signal processing component to the Broca syndrome functor deficit.

Word attributes and lateralization revisited: implications for dual coding and discrete versus continuous processing

Three attributes of words are their imageability, concreteness, and familiarity. From a literature review and several experiments, I previously concluded (Boles, 1983a) that only familiarity affects the overall near-threshold recognition of words, and that none of the attributes affects right-visual-field superiority for word recognition. Here these conclusions are modified by two experiments demonstrating a critical mediating influence of intentional versus incidental memory instructions. In Experiment 1, subjects were instructed to remember the words they were shown, for subsequent recall. The results showed effects of both imageability and familiarity on overall recognition, as well as an effect of imageability on lateralization. In Experiment 2, word-memory instructions were deleted and the results essentially reinstated the findings of Boles (1983a). It is concluded that right-hemisphere imagery processes can participate in word recognition under intentional memory instructions. Within the dual coding theory (Paivio, 1971), the results argue that both discrete and continuous processing modes are available, that the modes can be used strategically, and that continuous processing can occur prior to response stages.