Effect of Representational Distance Between Meanings on Recognition of Ambiguous Spoken Words

Previous research indicates that mental representations of word meanings are distributed along both semantic and syntactic dimensions such that nouns and verbs are relatively distinct from one another. Two experiments examined the effect of representational distance between meanings on recognition of ambiguous spoken words by comparing recognition of unambiguous words, noun–verb homonyms, and noun–noun homonyms. In Experiment 1, auditory lexical decision was fastest for unambiguous words, slower for noun–verb homonyms, and slowest for noun–noun homonyms. In Experiment 2, response times for matching spoken words to pictures followed the same pattern and eye fixation time courses revealed converging, gradual time course differences between conditions. These results indicate greater competition between meanings of ambiguous words when the meanings are from the same grammatical class (noun–noun homonyms) than when they are from different grammatical classes (noun–verb homonyms).     

Word length and lexical activation: longer is better

Many models of spoken word recognition posit the existence of lexical and sublexical representations, with excitatory and inhibitory mechanisms used to affect the activation levels of such representations. Bottom-up evidence provides excitatory input, and inhibition from phonetically similar representations leads to lexical competition. In such a system, long words should produce stronger lexical activation than short words, for 2 reasons: Long words provide more bottom-up evidence than short words, and short words are subject to greater inhibition due to the existence of more similar words. Four experiments provide evidence for this view. In addition, reaction-time-based partitioning of the data shows that long words generate greater activation that is available both earlier and for a longer time than is the case for short words. As a result, lexical influences on phoneme identification are extremely robust for long words but are quite fragile and condition-dependent for short words. Models of word recognition must consider words of all lengths to capture the true dynamics of lexical activation.     

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.     

Lexical competition and the acquisition of novel words

Three experiments examined the involvement of newly learnt words in lexical competition. Adult participants were familiarized with novel nonsense sequences that overlapped strongly with existing words (e.g. cathedruke, derived from cathedral) through repeated presentation in a phoneme-monitoring task. Experiment 1 looked at the immediate effects of exposure to these sequences, with participants showing familiarity with the form of the novel sequences in a two-alternative forced choice task. The effect of this exposure on lexical competition was examined by presenting the existing words (e.g. cathedral) in a lexical decision task. The immediate effect of the exposure was facilitatory, suggesting that the novel words had activated the representation of the closest real word rather than developing their own lexical representations. In Experiment 2, inhibitory lexical competition effects emerged over the course of 5 days for offset-diverging (e.g. cathedruke-cathedral) but not onset-diverging (e.g. yothedral-cathedral) novel words. Experiment 3 disentangled the roles of time and level-of-exposure in the lexicalization process and assessed the generality of the observed lexical inhibition using pause detection. A single, concentrated exposure session was used, which resulted in good recognition performance soon after. Lexicalization effects were absent immediately after exposure but emerged 1 week later, despite no intervening exposure to the novel items. These results suggest that integrating a novel word into the mental lexicon can be an extended process: phonological information is learnt swiftly, but full integration with existing items develops at a slower rate.     

The basis of preference for lexical words in 6-month-old infants

Six-month-old English-learning infants have been shown to prefer English lexical over English grammatical words. The preference is striking because there are few grammatical words in total number but each occurs far more frequently in input speech than any individual lexical word. This could be because lexical words are universally more salient and interesting acoustic and phonological forms than are grammatical words. Alternatively, familiarity may play a role since infants may know some specific lexical words. Here we explore the first possibility by testing Chinese-learning infants’ response to English lexical and grammatical words. These infants, who had virtually no prior exposure to English and thus were unfamiliar with any English words, nevertheless preferred to listen to English lexical words, as in the case of English-learning infants. This finding increases the plausibility that it is the acoustic and phonological salience of lexical words that determines the preference for lexical words in infants.     

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.     

Learning new vocabulary during childhood: Effects of semantic training on lexical consolidation and integration

Research suggests that word learning is an extended process, with offline consolidation crucial for the strengthening of new lexical representations and their integration with existing lexical knowledge (as measured by engagement in lexical competition). This supports a dual memory systems account, in which new information is initially sparsely encoded separately from existing knowledge and integrated with long-term memory over time. However, previous studies of this type exploited unnatural learning contexts, involving fictitious words in the absence of word meaning. In this study, 5- to 9-year-old children learned real science words (e.g., hippocampus) with or without semantic information. Children in both groups were slower to detect pauses in familiar competitor words (e.g., hippopotamus) relative to control words 24 h after training but not immediately, confirming that offline consolidation is required before new words are integrated with the lexicon and engage in lexical competition. Children recalled more new words 24 h after training than immediately (with similar improvements shown for the recall and recognition of new word meanings); however, children who were exposed to the meanings during training showed further improvements in recall after 1 week and outperformed children who were not exposed to meanings. These findings support the dual memory systems account of vocabulary acquisition and suggest that the association of a new phonological form with semantic information is critical for the development of stable lexical representations.     

Early effects of neighborhood density and phonotactic probability of spoken words on event-related potentials

All current models of spoken word recognition propose that sound-based representations of spoken words compete with, or inhibit, one another during recognition. In addition, certain models propose that higher probability sublexical units facilitate recognition under certain circumstances. Two experiments were conducted examining ERPs to spoken words and nonwords simultaneously varying in phonotactic probability and neighborhood density. Results showed that the amplitude of the P2 potential was greater for high probability-density words and nonwords, suggesting an early inhibitory effect of neighborhood density. In order to closely examine the role of phonotactic probability, effects of initial phoneme frequency were also examined. The latency of the P2 potential was shorter for words with high initial-consonant probability, suggesting a facilitative effect of phonotactic probability. The current results are consistent with findings from previous studies using reaction time and eye-tracking paradigms and provide new insights into the time-course of lexical and sublexical activation and competition.     

The role of grammatical class on word recognition

The double dissociation between noun and verb processing, well documented in the neuropsychological literature, has not been supported in imaging studies. Recent imaging studies, in fact, suggest that once confounding with semantics is eliminated, grammatical class effects only emerge as a consequence of building frames. Here we assess this hypothesis behaviorally in two visual word recognition experiments. In Experiment 1, participants made lexical decisions on verb targets. We manipulated the grammatical class of the prime words (either nouns or verbs and always introduced in a minimal phrasal context, i.e., “the + N” or “to + V”), and their semantic similarity to a target (related vs. unrelated). We found reliable effects of grammatical class, and no interaction with semantic similarity. Experiment 2 further explored this grammatical class effect, using verb targets preceded by semantically unrelated verb vs. noun primes. In one condition, prime words were presented as bare words; in the other, they were presented in the minimal phrasal context used in Experiment 1. Grammatical class effects only arose in the latter but not in the former condition thus providing evidence that word recognition does not recruit grammatical class information unless it is provided to the system.     

Integration of parafoveal orthographic information during foveal word reading: beyond the sub-lexical level?

Prior research has shown that processing of a given target word is facilitated by the simultaneous presentation of orthographically related stimuli in the parafovea. Here we investigate the nature of such spatial integration processes by presenting orthographic neighbours of target words in the parafovea, considering that neighbours have been shown to inhibit, rather than facilitate, recognition of target words in foveal masked priming research. In Experiment 1, we used the gaze-contingent boundary paradigm to manipulate the parafoveal information subjects received while they fixated a target word within a sentence. In Experiment 2, we used the Flanking Letters Lexical Decision paradigm to manipulate parafoveal information while subjects read isolated words. Parafoveal words were either a higher-frequency orthographic neighbour of targets words (e.g., blue-blur) or a high-frequency unrelated word (e.g., hand-blur). We found that parafoveal orthographic neighbours facilitated, rather than inhibited, processing of the target. Thus, the present findings provide further evidence that orthographic information is integrated across multiple words and suggest that either the integration process does not enable simultaneous access to those words’ lexical representations, or that lexical representations activated by spatially distinct stimuli do not compete for recognition.     

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 Use of Lexical Prosody for Lexical Access of the Japanese Language

It has been suggested that English listeners do not use lexical prosody for lexical access in word recognition. The present study was designed to examine whether this argument could be generalized to the Japanese language. Two experiments using a cross-modal priming task were conducted. The participants made a lexical decision regarding a visual target following an auditory prime that was either the prosodically congruent or incongruent homophone of the target. In experiment 1, the primes were presented as complete words, and in experiment 2, they were presented as word fragments. In both experiments, the priming effects were observed only in the congruent condition. These results suggest that the prime activated only the representations of prosodically congruent words. We therefore concluded that Japanese listeners use lexical prosody for lexical access of their language and that the role of lexical prosody is determined language-specifically.     

Grammatical gender in spoken word recognition in German

The role of grammatical gender for auditory word recognition in German was investigated in three experiments and two sets of corpus analyses. In the corpus analyses, gender information reduced the lexical search space as well as the amount of input needed to uniquely identify a word. To test whether this holds for on-line processing, two auditory lexical decision experiments (Experiments 1 and 3) were conducted using valid, invalid, or noise-masked articles as primes. Clear gender-priming effects were obtained in both experiments. Experiment 2 used phoneme monitoring with words and with pseudowords deviating from base words in one or more phonological features. Contrary to the lexical decision latencies, phoneme-monitoring latencies showed no influence of gender but did show similarity mismatch effects. We argue that gender information is not utilized early during word recognition. Rather, the presence of a valid article increases the initial familiarity of a word, facilitating subsequent responses.     

Studying the grammatical aspects of word recognition: lexical priming,parsing, and syntactic ambiguity resolution

Two experiments are reported examining the relationship between lexical and syntactic processing during language comprehension, combining techniques common to the on-line study of syntactic ambiguity resolution with priming techniques common to the study of lexical processing. By manipulating grammatical properties of lexical primes, we explore how lexically based knowledge is activated and guides combinatory sentence processing. Particularly, we find that nouns (like verbs, see Trueswell & Kim, 1998) can activate detailed lexically specific syntactic information and that these representations guide the resolution of relevant syntactic ambiguities pertaining to verb argument structure. These findings suggest that certain principles of knowledge representation common to theories of lexical knowledge—such as overlapping and distributed representations—also characterize grammatical knowledge. Additionally, observations from an auditory comprehension study suggest similar conclusions about the lexical nature of parsing in spoken language comprehension. They also suggest that thematic role and syntactic preferences are activated during word recognition and that both influence combinatory processing.     

Exposure to print and word recognition processes

The effect of exposure to print on the efficiency of phonological and orthographic word recognition processes was examined by comparing two groups of university students having similar reading comprehension scores but different levels of exposure to print. Participants with a high level of exposure to print were faster and more accurate in naming pseudowords, in choosing the correct member of a homophone pair, and in making lexical decisions when nonwords were pseudohomophones. In the lexical decision task, low-print-exposure participants were more sensitive to the frequency of the orthographic patterns in the stimuli. The results of a form priming task demonstrated that high-print-exposure participants more quickly and strongly activated the orthographic representations of common words and subsequently more strongly activated the corresponding phonological representations. Even among successful students, differences in exposure to print produce large differences in the efficiency of both orthographic and phonological word recognition processes.     

Spelling recognition after exposure to misspellings: Implications for abstractionist vs. episodic theories of orthographic representations

University students made spelling accuracy judgments about correctly and incorrectly spelled words that had been seen incorrectly spelled (Experiments 1 and 2). In contrast to results for spelling production, studying a misspelling produced a small benefit in classification of the correct word at test. When the studied misspelling was re-presented at test, there was a substantial cost in accuracy. Testing spelling recognition in an old context had a biassing effect, but there was little evidence of context re-instatement effects for studied words. In Experiment 3 students decided whether a correctly spelled word was spelled the same way at study and test. Participants' poor performance with words studied misspelled supports a priming explanation of the benefit for correct words. The differential effects for correct and incorrect test words cannot be explained in terms of updating abstract lexical representations, and the limitations on participants' item and context memory challenge episodic accounts of lexical representations.     

Exploring the role of lexical stress in lexical recognition

Three cross-modal priming experiments examined the role of suprasegmental information in the processing of spoken words. All primes consisted of truncated spoken Dutch words. Recognition of visually presented word targets was facilitated by prior auditory presentation of the first two syllables of the same words as primes, but only if they were appropriately stressed (e.g., OKTOBER preceded by okTO-); inappropriate stress, compatible with another word (e.g., OKTOBER preceded by OCto-, the beginning of octopus), produced inhibition. Monosyllabic fragments (e.g., OC-) also produced facilitation when appropriately stressed; if inappropriately stressed, they produced neither facilitation nor inhibition. The bisyllabic fragments that were compatible with only one word produced facilitation to semantically associated words, but inappropriate stress caused no inhibition of associates. The results are explained within a model of spoken-word recognition involving competition between simultaneously activated phonological representations followed by activation of separate conceptual representations for strongly supported lexical candidates; at the level of the phonological representations, activation is modulated by both segmental and suprasegmental information.     

Orthographic influences in spoken word recognition: The consistency effect in semantic and gender categorization tasks

According to current models, spoken word recognition is driven by the phonological properties of the speech signal. However, several studies have suggested that orthographic information also influences recognition in adult listeners. In particular, it has been repeatedly shown that, in the lexical decision task, words that include rimes with inconsistent spellings (e.g., /-ip/ spelled -eap or -eep) are disadvantaged, as compared with words with consistent rime spelling. In the present study, we explored whether the orthographic consistency effect extends to tasks requiring people to process words beyond simple lexical access. Two different tasks were used: semantic and gender categorization. Both tasks produced reliable consistency effects. The data are discussed as suggesting that orthographic codes are activated during word recognition, or that the organization of phonological representations of words is affected by orthography during literacy acquisition.     

Phi-square Lexical Competition Database (Phi-Lex): An online tool for quantifying auditory and visual lexical competition

A widely agreed-upon feature of spoken word recognition is that multiple lexical candidates in memory are simultaneously activated in parallel when a listener hears a word, and that those candidates compete for recognition (Luce, Goldinger, Auer, & Vitevitch, Perception 62:615–625, 2000; Luce & Pisoni, Ear and Hearing 19:1–36, 1998; McClelland & Elman, Cognitive Psychology 18:1–86, 1986). Because the presence of those competitors influences word recognition, much research has sought to quantify the processes of lexical competition. Metrics that quantify lexical competition continuously are more effective predictors of auditory and visual (lipread) spoken word recognition than are the categorical metrics traditionally used (Feld & Sommers, Speech Communication 53:220–228, 2011; Strand & Sommers, Journal of the Acoustical Society of America 130:1663–1672, 2011). A limitation of the continuous metrics is that they are somewhat computationally cumbersome and require access to existing speech databases. This article describes the Phi-square Lexical Competition Database (Phi-Lex): an online, searchable database that provides access to multiple metrics of auditory and visual (lipread) lexical competition for English words, available at www.juliastrand.com/phi-lex.     

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.