Bilinguals in a monolingual and a bilingual speech mode: The effect on lexical access

The time course of lexical access in fluent Portuguese-English bilinguals and in English speaking monolinguals was examined during the on-line processing of spoken sentences using the phoneme-triggered lexical decision task (Blank, 1980). The bilinguals were tested in two distinct speech modes: a monolingual, English or Portuguese, speech mode, and a bilingual, code-switching, speech mode. Although the bilingual’s lexical decision response times to word targets in the monolingual speech modes were identical to those of the monolingual subjects, their response times to code-switched word targets in the bilingual mode were significantly slower. In addition, the bilinguals took longer to detect nonwords in both the monolingual and bilingual modes. These results confirm that bilinguals cannot totally deactivate their other language when in a monolingual speech mode. It is hypothesized that bilinguals search both lexicons when confronted with nonwords, even when in a totally monolingual mode, and that they search the base-language lexicon before the other lexicon when in a bilingual, code-switching, speech mode.     

Effects of lexical competition on immediate memory span for spoken words

Current theories and models of the structural organization of verbal short-term memory are primarily based on evidence obtained from manipulations of features inherent in the short-term traces of the presented stimuli, such as phonological similarity. In the present study, we investigated whether properties of the stimuli that are not inherent in the short-term traces of spoken words would affect performance in an immediate memory span task. We studied the lexical neighbourhood properties of the stimulus items, which are based on the structure and organization of words in the mental lexicon. The experiments manipulated lexical competition by varying the phonological neighbourhood structure (i.e., neighbourhood density and neighbourhood frequency) of the words on a test list while controlling for word frequency and intra-set phonological similarity (family size). Immediate memory span for spoken words was measured under repeated and nonrepeated sampling procedures. The results demonstrated that lexical competition only emerged when a nonrepeated sampling procedure was used and the participants had to access new words from their lexicons. These findings were not dependent on individual differences in short-term memory capacity. Additional results showed that the lexical competition effects did not interact with proactive interference. Analyses of error patterns indicated that item-type errors, but not positional errors, were influenced by the lexical attributes of the stimulus items. These results complement and extend previous findings that have argued for separate contributions of long-term knowledge and short-term memory rehearsal processes in immediate verbal serial recall tasks.     

Stimulus-based lexical distinctiveness as a general word-recognition mechanism

Word recognition is generally assumed to be achieved via competition in the mental lexicon between phonetically similar word forms. However, this process has so far been examined only in the context of auditory phonetic similarity. In the present study, we investigated whether the influence of word-form similarity on word recognition holds in the visual modality and with the patterns of visual phonetic similarity. Deaf and hearing participants identified isolated spoken words presented visually on a video monitor. On the basis of computational modeling of the lexicon from visual confusion matrices of visual speech syllables, words were chosen to vary in visual phonetic distinctiveness, ranging from visually unambiguous (lexical equivalence class [LEC] size of 1) to highly confusable (LEC size greater than 10). Identification accuracy was found to be highly related to the word LEC size and frequency of occurrence in English. Deaf and hearing participants did not differ in their sensitivity to word LEC size and frequency. The results indicate that visual spoken word recognition shows strong similarities with its auditory counterpart in that the same dependencies on lexical similarity and word frequency are found to influence visual speech recognition accuracy. In particular, the results suggest that stimulus-based lexical distinctiveness is a valid construct to describe the underlying machinery of both visual and auditory spoken word recognition.     

The effect of lexical frequency on spoken word recognition in young and older listeners

When identifying spoken words, older listeners may have difficulty resolving lexical competition or may place a greater weight on factors like lexical frequency. To obtain information about age differences in the time course of spoken word recognition, young and older adults' eye movements were monitored as they followed spoken instructions to click on objects displayed on a computer screen. Older listeners were more likely than younger listeners to fixate high-frequency displayed phonological competitors. However, degradation of auditory quality in younger listeners does not reproduce this result. These data are most consistent with an increased role for lexical frequency with age.     

The oral and written side of word production in young and older adults: generation of lexical neighbors

The aim of the present study was to investigate the effects of aging on both spoken and written word production by using analogous tasks. To do so, a phonological neighbor generation task (Experiment 1) and an orthographic neighbor generation task (Experiment 2) were designed. In both tasks, young and older participants were given a word and had to generate as many words as they could think of by changing one phoneme in the target word (Experiment 1) or one letter in the target word (Experiment 2). The data of the two experiments were consistent, showing that the older adults generated fewer lexical neighbors and made more errors than the young adults. For both groups, the number of words produced, as well as their lexical frequency, decreased as a function of time. These data strongly support the assumption of a symmetrical age-related decline in the transmission of activation within the phonological and orthographic systems.     

The dynamics of lexical competition during spoken word recognition

The sounds that make up spoken words are heard in a series and must be mapped rapidly onto words in memory because their elements, unlike those of visual words, cannot simultaneously exist or persist in time. Although theories agree that the dynamics of spoken word recognition are important, they differ in how they treat the nature of the competitor set-precisely which words are activated as an auditory word form unfolds in real time. This study used eye tracking to measure the impact over time of word frequency and 2 partially overlapping competitor set definitions: onset density and neighborhood density. Time course measures revealed early and continuous effects of frequency (facilitatory) and on set based similarity (inhibitory). Neighborhood density appears to have early facilitatory effects and late inhibitory effects. The late inhibitory effects are due to differences in the temporal distribution of similarity within neighborhoods. The early facilitatory effects are due to subphonemic cues that inform the listener about word length before the entire word is heard. The results support a new conception of lexical competition neighborhoods in which recognition occurs against a background of activated competitors that changes over time based on fine-grained goodness-of-fit and competition dynamics.     

Observing neighborhood effects without neighbors

With a new metric called phonological Levenshtein distance (PLD20), the present study explores the effects of phonological similarity and word frequency on spoken word recognition, using polysyllabic words that have neither phonological nor orthographic neighbors, as defined by neighborhood density (the N-metric). Inhibitory effects of PLD20 were observed for these lexical hermits: Close-PLD20 words were recognized more slowly than distant PLD20 words, indicating lexical competition. Importantly, these inhibitory effects were found only for low- (not high-) frequency words, in line with previous findings that phonetically related primes inhibit recognition of low-frequency words. These results indicate that the properties of PLD20--a continuous measure of word-form similarity--make it a promising new metric for quantifying phonological distinctiveness in spoken word recognition research.     

Speaker variability augments phonological processing in early word learning

Infants in the early stages of word learning have difficulty learning lexical neighbors (i.e. word pairs that differ by a single phoneme), despite their ability to discriminate the same contrast in a purely auditory task. While prior work has focused on top‐down explanations for this failure (e.g. task demands, lexical competition), none has examined if bottom‐up acoustic‐phonetic factors play a role. We hypothesized that lexical neighbor learning could be improved by incorporating greater acoustic variability in the words being learned, as this may buttress still‐developing phonetic categories, and help infants identify the relevant contrastive dimension. Infants were exposed to pictures accompanied by labels spoken by either a single or multiple speakers. At test, infants in the single‐speaker condition failed to recognize the difference between the two words, while infants who heard multiple speakers discriminated between them.     

Visual word recognition in young and older adults: A study of cohort effects for lexical variables

The aim of the present research was to determine whether lexical variables corresponding to the lexicons of young and older adults are better predictors of visual word recognition latencies than lexical variables that are not specifically adapted to the populations. Three variables were considered (subjective frequency, age of acquisition, objective frequency). Subjective frequency and age of acquisition ratings were provided by the young and older adults of the experiment, while four objective frequency measures were collected in four norms for the French language based on texts dating from different periods. As a whole, 220 words were presented to 45 young adults and 40 older adults in a lexical decision task. Regression analyses showed that objective frequency, subjective frequency, and age of acquisition were better predictors of the lexical decision latencies of young and older adults when they were accorded with the lexicons of the populations.     

How does the provision of semantic information influence the lexicalization of new spoken words?

The integration of a novel spoken word with existing lexical items can proceed within 24 hours of learning its phonological form. However, previous studies have reported that lexical integration of new spoken words can be delayed if semantic information is provided during learning. One possibility is that this delay in lexical integration reflects reduced phonological processing during learning as a consequence of the need to learn the semantic associations. In the current study, adult participants learnt novel words via a phoneme monitoring task, in which half of the words were associated with a picture referent, and half were phonological forms only. Critically, participants were instructed to learn the forms of the novel words, with no explicit goal to learn the word–picture mappings. Results revealed significant lexical competition effects emerging one week after consolidation, which were equivalent for the picture-present and form-only conditions. Tests of declarative memory and shadowing showed equivalent performance for picture-present and form-only words, despite participants showing good knowledge of the picture associations immediately after learning. These data support the contention that provided phonological information is recruited sufficiently well during learning, the provision of semantic information does not slow the time-course of lexical integration.     

Tracking the Time Course of Word‐Frequency Effects in Auditory Word Recognition With Event‐Related Potentials

Although the word‐frequency effect is one of the most established findings in spoken‐word recognition, the precise processing locus of this effect is still a topic of debate. In this study, we used event‐related potentials (ERPs) to track the time course of the word‐frequency effect. In addition, the neighborhood density effect, which is known to reflect mechanisms involved in word identification, was also examined. The ERP data showed a clear frequency effect as early as 350 ms from word onset on the P350, followed by a later effect at word offset on the late N400. A neighborhood density effect was also found at an early stage of spoken‐word processing on the PMN, and at word offset on the late N400. Overall, our ERP differences for word frequency suggest that frequency affects the core processes of word identification starting from the initial phase of lexical activation and including target word selection. They thus rule out any interpretation of the word frequency effect that is limited to a purely decisional locus after word identification has been completed.     

Inhibitory neighbor priming effects in eye movements during reading

We report an eye movement experiment investigating whether prior processing of a word’s orthographic neighbor in a sentence influences subsequent word processing during reading. There was greater difficulty in early word processing when a target word’s neighbor rather than a control word appeared earlier in a sentence; this effect was uninfluenced by the relative lexical frequency of the word and its neighbor. We discuss this inhibitory neighbor priming effect in terms of competitive network models of word recognition and the process of lexical identification in the E-Z Reader model of oculomotor control (e.g., Reichle, Pollatsek, Fisher, & Rayner, 1998).     

Examining the effects of variation in emotional tone of voice on spoken word recognition

Emotional tone of voice (ETV) is essential for optimal verbal communication. Research has found that the impact of variation in nonlinguistic features of speech on spoken word recognition differs according to a time course. In the current study, we investigated whether intratalker variation in ETV follows the same time course in two long-term repetition priming experiments. We found that intratalker variability in ETVs affected reaction times to spoken words only when processing was relatively slow and difficult, not when processing was relatively fast and easy. These results provide evidence for the use of both abstract and episodic lexical representations for processing within-talker variability in ETV, depending on the time course of spoken word recognition.     

Spoken Language Activation Alters Subsequent Sign Language Activation in L2 Learners of American Sign Language

A large body of literature has characterized unimodal monolingual and bilingual lexicons and how neighborhood density affects lexical access; however there have been relatively fewer studies that generalize these findings to bimodal (M2) second language (L2) learners of sign languages. The goal of the current study was to investigate parallel language activation in M2L2 learners of sign language and to characterize the influence of spoken language and sign language neighborhood density on the activation of ASL signs. A priming paradigm was used in which the neighbors of the sign target were activated with a spoken English word and compared the activation of the targets in sparse and dense neighborhoods. Neighborhood density effects in auditory primed lexical decision task were then compared to previous reports of native deaf signers who were only processing sign language. Results indicated reversed neighborhood density effects in M2L2 learners relative to those in deaf signers such that there were inhibitory effects of handshape density and facilitatory effects of location density. Additionally, increased inhibition for signs in dense handshape neighborhoods was greater for high proficiency L2 learners. These findings support recent models of the hearing bimodal bilingual lexicon, which posit lateral links between spoken language and sign language lexical representations.     

The locus of the effects of sentential-semantic context in spoken-word processing

Models of word recognition differ with respect to where the effects of sentential-semantic context are to be located. Using a crossmodal priming technique, this research investigated the availability of lexical entries as a function of stimulus information and contextual constraint. To investigate the exact locus of the effects of sentential contexts, probes that were associatively related to contextually appropriate and inappropriate words were presented at various positions before and concurrent with the spoken word. The results show that sentential contexts do not preselect a set of contextually appropriate words before any sensory information about the spoken word is available. Moreover, during lexical access, defined here as the initial contact with lexical entries and their semantic and syntactic properties, both contextually appropriate and inappropriate words are activated. Contextual effects are located after lexical access, at a point in time during word processing where the sensory input by itself is still insufficiently informative to disambiguate between the activated entries. This suggests that sentential-semantic contexts have their effects during the process of selecting one of the activated candidates for recognition.     

The Role of Orthographic Neighborhood Size Effects in Chinese Word Recognition

Previous studies about the orthographic neighborhood size (NS) in Chinese have overlooked the morphological processing, and the co-variation between the character frequency and the the NS. The present study manipulated the word frequency and the NS simultaneously, with the leading character frequency controlled, to explore their influences on word lexical decision (Experiment 1) and naming (Experiment 2). The results showed a robust effect that words with a larger NS produced shorter reaction time than those with a smaller NS, irrespective of the word frequency and the tasks. This facilitative effect may occur due to a semantic network formed by neighbor words, resulting in the semantic activation to accelerate the word recognition. Moreover, the comparison of the effect sizes of word frequency between the two tasks showed that lexical decision responses demonstrated a larger word frequency effect, indicating that the sub-word processing was involved in the multi-character word recognition.     

Lexical and post-lexical phonological representations in spoken production

Theories of spoken word production generally assume a distinction between at least two types of phonological processes and representations: lexical phonological processes that recover relatively arbitrary aspects of word forms from long-term memory and post-lexical phonological processes that specify the predictable aspects of phonological representations. In this work we examine the spoken production of two brain-damaged individuals. We use their differential patterns of accuracy across the tasks of spoken naming and repetition to establish that they suffer from distinct deficits originating fairly selectively within lexical or post-lexical processes. Independent and detailed analyses of their spoken productions reveal contrasting patterns that provide clear support for a distinction between two types of phonological representations: those that lack syllabic and featural information and are sensitive to lexical factors such as lexical frequency and neighborhood density, and those that include syllabic and featural information and are sensitive to detailed properties of phonological structure such as phoneme frequency and syllabic constituency.     

Representation and competition in the perception of spoken words

We present data from four experiments using cross-modal priming to examine the effects of competitor environment on lexical activation during the time course of the perception of a spoken word. The research is conducted from the perspective of a distributed model of speech perception and lexical representation, which focuses on activation at the level of lexical content. In this model, the strength of competition between simultaneously active lexical items depends on the degree of coherence between their distributed semantic and phonological representations. Consistent with this model, interference effects are more complete when the purely semantic aspects of these coactive representations are probed (using semantic priming) than when phonological aspects are probed as well (using repetition priming).     

Frequency effects in spoken and visual word recognition: evidence from dual-task methodologies

The authors report 3 dual-task experiments concerning the locus of frequency effects in word recognition. In all experiments, Task 1 entailed a simple perceptual choice and Task 2 involved lexical decision. In Experiment 1, an underadditive effect of word frequency arose for spoken words. Experiment 2 also showed underadditivity for visual lexical decision. It was concluded that word frequency exerts an influence prior to any dual-task bottleneck. A related finding in similar dual-task experiments is Task 2 response postponement at short stimulus onset asynchronies. This was explored in Experiment 3, and it was shown that response postponement was equivalent for both spoken and visual word recognition. These results imply that frequency-sensitive processes operate early and automatically.     

The influence of word frequency on the transposed-phoneme priming effect

Speech input like [byt] has been shown to facilitate not only the subsequent processing of an identical target word /byt/ but also that of a target word /tyb/ that contains the same phonemes in a different order. Using the short-term phonological priming paradigm, we examined the role of lexical representations in driving the transposed-phoneme priming effect by manipulating lexical frequency. Results showed that the transposed-phoneme priming effect occurs when targets have a higher frequency than primes, but not when they have a lower frequency. Our findings thus support the view that the transposed-phoneme priming effect results from partial activation of the target word’s lexical representation during prime processing. More generally, our study provides further evidence for a role for position-independent phonemes in spoken word recognition.