Brain representations of lexical ambiguity: Disentangling homonymy, polysemy, and their meanings.

In human languages, it is a common phenomenon for a single word to have multiple meanings. This study used fMRI to investigate how the brain processed different types of lexical ambiguity, and how it differentiated the meanings of ambiguous words. We focused on homonyms and polysemy that differed in the relatedness among multiple meanings. Participants (N = 35) performed a prime-target semantic relatedness task, where a specific meaning of an ambiguous word was primed. Results showed that homonyms elicited greater activation in bilateral dorsal prefrontal and posterior parietal cortices than polysemous words, suggesting that these regions may be more engaged in cognitive control when the meanings of ambiguous words are unrelated. Multivariate pattern analysis further revealed that meanings of homonyms with different syntactic categories were represented differently in the frontal and temporal cortices. The findings highlighted the importance of semantic relations and grammatical factors in the brain's representation of lexical ambiguities.

The symptoms of surface dyslexia in Arabic: the impact of orthographic ambiguity on reading abilities of a patient with Alzheimer's disease.

Like other Semitic languages, Arabic is known for its rich morphology and consonantal writing system. In this article, we report the first case of acquired surface dyslexia in an Arabic-speaking patient (HBS). Surface dyslexia is characterised by difficulty reading irregularly spelled words, while performance is better with regular words and nonwords. The purpose of this study was to describe the symptoms of surface dyslexia in Arabic and to investigate how orthographic depth may affect reading in the context of semantic impairment. In HBS, who had Alzheimer's disease, reading was impaired for both words and nonwords. Her reading performance was affected by orthographic ambiguity and by the presence of diacritics depicting short vowels. In particular, she produced mainly vowel errors, suggesting an overreliance on the sublexical route of reading. On the other hand, HBS was able to distinguish long vowels from consonants represented by the same letters, provided there was a real root. This finding can be taken as evidence that HBS could access the word's root to decide whether the vowel letter represents a long vowel or a consonant. The results of this study suggest that the characteristics of surface dyslexia appear to be universal: reading regular words is spared compared to irregular words and non-words. However, the error patterns that HBS showed in reading support a language-specific conceptualisation of the processing components of the lexical and sublexical routes of reading.

The Processing of Lexical Ambiguity: Evidence from Child and Adult Greek.

The aim of the study is to examine the effect of sentential context on lexical ambiguity resolution in Greek adults and typically developing children. Context and word frequency are factors that can affect lexical processing, however, the role of them has not been thoroughly examined in Greek. To this aim, we assessed sentence context effects in homonym meaning activation in monolingual speakers of Greek, children and adults, using a cross-modal priming paradigm. Additionally, all participants conducted a verbal working memory task and an inhibition task so as to examine whether the use of sentential context for lexical ambiguity resolution relates to age and/or cognitive processing capacity. The data analysis showed (a) major processing differences between adults and children due to ambiguity and sentential context, (b) children's processing times affected by cognitive skills while adults' processing unaffected, and (c) visual word recognition intact for all participants.

Assessing lexical ambiguity of simplified Chinese characters: Plurality and relatedness of character meanings.

Lexical ambiguity is pervasive among Chinese characters as many of them are polysemantic, with one orthographic form carrying unrelated meanings, related meanings, or sometimes both unrelated and related meanings. A large-scale database with ambiguity measures for simplified Chinese characters has yet to be developed, which could greatly benefit psycholinguistic research on the Chinese language or cross-language comparisons. This article reports two sets of ratings by native speakers, the perceived number of meanings (pNoM) for 4,363 characters and the perceived relatedness of meanings (pRoM) for a subset of 1,053 characters. These rating-based ambiguity measures capture the representational nuance about a character's meanings stored in average native speakers' mental lexicon, which tends to be obscured by dictionary- and corpus-based ambiguity measures. Consequently, they each account for a reliable portion of variance in the efficiency of character processing, above and beyond the effects of character frequency, age of acquisition, and other types of ambiguity measures. Theoretical and empirical implications with regard to the plurality and the relatedness of character meanings, the two focal aspects of debate on lexical ambiguity, are discussed.

Probing Lexical Ambiguity in Chinese Characters via Their Word Formations: Convergence of Perceived and Computed Metrics.

Lexical ambiguity is pervasive in language, and the nature of the representations of an ambiguous word's multiple meanings is yet to be fully understood. With a special focus on Chinese characters, the present study first established that native speaker's perception about a character's number of meanings was heavily influenced by the availability of its distinct word formations, while whether these meanings would be perceived to be closely related was driven by further conceptual analysis. These notions were operationalized as two computed metrics, which assessed the degree of dispersion across individual word formations and the degree of propinquity across clusters of word formations, respectively, in a distributional semantic space. The observed correlations between the computed and the perceived metrics indicated that the utility of word formations to tap into meaning representations of Chinese characters was indeed cognitively plausible. The results have demonstrated the extent to which distributional semantics could inform about meaning representations of Chinese characters, which has theoretical implications for the representation of ambiguous words more generally.

Studying Individual Differences in Language Comprehension: The Challenges of Item-Level Variability and Well-Matched Control Conditions.

Translating experimental tasks that were designed to investigate differences between conditions at the group-level into valid and reliable instruments to measure individual differences in cognitive skills is challenging (Hedge et al., 2018; Rouder et al., 2019; Rouder & Haaf, 2019). For psycholinguists, the additional complexities associated with selecting or constructing language stimuli, and the need for appropriate well-matched baseline conditions make this endeavour particularly complex. In a typical experiment, a process-of-interest (e.g. ambiguity resolution) is targeted by contrasting performance in an experimental condition with performance in a well-matched control condition. In many cases, careful between-condition matching precludes the same participant from encountering all stimulus items. Unfortunately, solutions that work for group-level research (e.g. constructing counterbalanced experiment versions) are inappropriate for individual-differences designs. As a case study, we report an ambiguity resolution experiment that illustrates the steps that researchers can take to address this issue and assess whether their measurement instrument is both valid and reliable. On the basis of our findings, we caution against the widespread approach of using datasets from group-level studies to also answer important questions about individual differences.

Pupillometric and behavioural evidence shows no differences between polyseme and homonym processing.

Ambiguous words can have related meanings (polysemes, e.g., newspaper) or unrelated meanings (homonyms, e.g., bat). Here we examined the processing of both types of ambiguous words (as well as unambiguous words) in tasks of increasing level of semantic engagement. Four experiments were conducted in which the degree of semantic engagement of the task was manipulated: lexical decision task (Experiments 1 and 2), semantic categorization task (Experiment 3) and number-of-meanings task (Experiment 4). RTs and pupillary response were recorded. To our knowledge, pupillary response had never been used before to study ambiguous words processing in isolation. Results showed faster RTs for ambiguous words with respect to unambiguous words in LDT, and larger pupil dilation was observed for ambiguous words in comparison to unambiguous ones in number-of-meanings task. However, differences between polysemes and homonyms were not observed in any task. These results provide no evidence that polysemes and homonyms are processed differently.

Interactions of lexical and conceptual representations: Evidence from EEG.

We examined whether meanings automatically activate linguistic forms, and whether these forms affect semantic decisions. Participants were presented sequentially with pairs of pictures and decided whether the objects in the pictures were related. At no point did they name the pictures. The object names of the experimental stimuli were ambiguous either in orthography (homographs), phonology (homophones), or both (homonyms), or unambiguous. We show that the lexical characteristics of the name of the objects affect a semantic decision about real world relations, in an online measure (N400), in addition to offline behavioral measures. We show a dissociation between conceptual and lexical recognition, where an earlier component (N230), was affected by relatedness, but was not sensitive to the lexical characteristics. We interpret this as supporting the hypothesis that semantic recognition occurs before the automatic lexical activation of the object name, but that once linguistic representations are activated, they affect semantic integration.

The Role of Sleep in Learning New Meanings for Familiar Words through Stories.

Adults often learn new meanings for familiar words, and in doing so they must integrate information about the newly-acquired meanings with existing knowledge about the prior meanings of the words in their mental lexicon. Numerous studies have confirmed the importance of sleep for learning novel word forms (e.g., "cathedruke") either with or without associated meanings. By teaching participants new meanings for familiar word forms, this is the first study to focus exclusively on the specific role of sleep on learning word meanings. In two experiments participants were trained on new meanings for familiar words through a naturalistic story reading paradigm to minimize explicit learning strategies. Experiment 1 confirmed the benefit of sleep for recall and recognition of word meanings, with better retention after 12 hours including overnight sleep than 12 hours awake. Experiment 2, which was preregistered, further explored this sleep benefit. Recall performance was best in the condition in which participants slept immediately after exposure and were tested soon after they woke up, compared with three conditions which all included an extended period of wake during which they would encounter their normal language environment. The results are consistent with the view that, at least under these learning conditions, a benefit of sleep arises due to passive protection from linguistic interference while asleep, rather than being due to active consolidation.

Learning about the meanings of ambiguous words: evidence from a word-meaning priming paradigm with short narratives.

Fluent language comprehension requires people to rapidly activate and integrate context-appropriate word meanings. This process is challenging for meanings of ambiguous words that are comparatively lower in frequency (e.g., the "bird" meaning of "crane"). Priming experiments have shown that recent experience makes such subordinate (less frequent) word meanings more readily available at the next encounter. These experiments used lists of unconnected sentences in which each ambiguity was disambiguated locally by neighbouring words. In natural language, however, disambiguation may occur via more distant contextual cues, embedded in longer, connected communicative contexts. In the present experiment, participants (N = 51) listened to 3-sentence narratives that ended in an ambiguous prime. Cues to disambiguation were relatively distant from the prime; the first sentence of each narrative established a situational context congruent with the subordinate meaning of the prime, but the remainder of the narrative did not provide disambiguating information. Following a short delay, primed subordinate meanings were more readily available (compared with an unprimed control), as assessed by responses in a word association task related to the primed meaning. This work confirms that listeners reliably disambiguate spoken ambiguous words on the basis of cues from wider narrative contexts, and that they retain information about the outcome of these disambiguation processes to inform subsequent encounters of the same word form.

Stimulus data and experimental design for a self-paced reading study on emoji-word substitutions.

This data paper presents the experimental design and stimuli from an online self-paced reading study on the processing of emojis substituting lexically ambiguous nouns. We recorded reading times for the target ambiguous nouns and for emojis depicting either the intended target referent or a contextually inappropriate homophonous noun. Furthermore, we recorded comprehension accuracy, demographics and a self-assessment of the participants' emoji usage frequency. The data includes all stimuli used, the raw data, the full JavaScript code for the online experiment, as well as Python and R code for the data analysis. We believe that our dataset may give important insights related to the comprehension mechanisms involved in the cognitive processing of emojis. For interpretation and discussion of the experiment, please see the original article entitled "The processing of emoji-word substitutions: A self-paced-reading study".

Word-meaning priming extends beyond homonyms.

When a homonym (e.g., bark) is encountered in a sentential context that biases its interpretation towards a less frequent meaning, subsequent interpretations of the word are more likely to favour that subordinate meaning. Such word-meaning priming effects have been shown to be maintained via sleep-related consolidation, leading some to suggest that declarative memory systems play a crucial role in language comprehension, providing a relatively enduring contextually bound memory trace for the ambiguous word. By this account, word-meaning priming effects should be observable for all words, not just homonyms. In three experiments, participants were exposed to non-homonym targets (e.g., "balloon") in sentences that biased interpretation towards a specific aspect of the word's meaning (e.g., balloon­helium vs. balloon-float). After a ~ 10-30 min delay, the targets were presented in relatedness judgement and associate production tasks to assess whether the sentential contexts enhanced access to the primed aspect of the word's meaning. The results reveal that word-meaning priming effects do extend to non-homonyms. Indeed, there was also some evidence of a more generalised priming that did not rely on prior presentation of the non-homonym itself. We argue that context-specific interpretations of words are maintained during recognition in order to facilitate comprehension over longer periods.

Semantic diversity is best measured with unscaled vectors: Reply to Cevoli, Watkins and Rastle (2020).

Semantic diversity refers to the degree of semantic variability in the contexts in which a particular word is used. We have previously proposed a method for measuring semantic diversity based on latent semantic analysis (LSA). In a recent paper, Cevoli et al. (2020) attempted to replicate our method and obtained different semantic diversity values. They suggested that this discrepancy occurred because they scaled their LSA vectors by their singular values, while we did not. Using their new results, they argued that semantic diversity is not related to ambiguity in word meaning, as we originally proposed. In this reply, we demonstrate that the use of unscaled vectors provides better fits to human semantic judgements than scaled ones. Thus we argue that our original semantic diversity measure should be preferred over the Cevoli et al. version. We replicate Cevoli et al.'s analysis using the original semantic diversity measure and find (a) our original measure is a better predictor of word recognition latencies than the Cevoli et al. equivalent and (b) that, unlike Cevoli et al.'s measure, our semantic diversity is reliably associated with a measure of polysemy based on dictionary definitions. We conclude that the Hoffman et al. semantic diversity measure is better-suited to capturing the contextual variability among words and that words appearing in a more diverse set of contexts have more variable semantic representations. However, we found that homonyms did not have higher semantic diversity values than non-homonyms, suggesting that the measure does not capture this special case of ambiguity.

Probing Lexical Ambiguity: Word Vectors Encode Number and Relatedness of Senses.

Lexical ambiguity-the phenomenon of a single word having multiple, distinguishable senses-is pervasive in language. Both the degree of ambiguity of a word (roughly, its number of senses) and the relatedness of those senses have been found to have widespread effects on language acquisition and processing. Recently, distributional approaches to semantics, in which a word's meaning is determined by its contexts, have led to successful research quantifying the degree of ambiguity, but these measures have not distinguished between the ambiguity of words with multiple related senses versus multiple unrelated meanings. In this work, we present the first assessment of whether distributional meaning representations can capture the ambiguity structure of a word, including both the number and relatedness of senses. On a very large sample of English words, we find that some, but not all, distributional semantic representations that we test exhibit detectable differences between sets of monosemes (unambiguous words; N = 964), polysemes (with multiple related senses; N = 4,096), and homonyms (with multiple unrelated senses; N = 355). Our findings begin to answer open questions from earlier work regarding whether distributional semantic representations of words, which successfully capture various semantic relationships, also reflect fine-grained aspects of meaning structure that influence human behavior. Our findings emphasize the importance of measuring whether proposed lexical representations capture such distinctions: In addition to standard benchmarks that test the similarity structure of distributional semantic models, we need to also consider whether they have cognitively plausible ambiguity structure.

Word Senses as Clusters of Meaning Modulations: A Computational Model of Polysemy.

Most words in natural languages are polysemous; that is, they have related but different meanings in different contexts. This one-to-many mapping of form to meaning presents a challenge to understanding how word meanings are learned, represented, and processed. Previous work has focused on solutions in which multiple static semantic representations are linked to a single word form, which fails to capture important generalizations about how polysemous words are used; in particular, the graded nature of polysemous senses, and the flexibility and regularity of polysemy use. We provide a novel view of how polysemous words are represented and processed, focusing on how meaning is modulated by context. Our theory is implemented within a recurrent neural network that learns distributional information through exposure to a large and representative corpus of English. Clusters of meaning emerge from how the model processes individual word forms. In keeping with distributional theories of semantics, we suggest word meanings are generalized from contexts of different word tokens, with polysemy emerging as multiple clusters of contextually modulated meanings. We validate our results against a human-annotated corpus of polysemy focusing on the gradedness, flexibility, and regularity of polysemous sense individuation, as well as behavioral findings of offline sense relatedness ratings and online sentence processing. The results provide novel insights into how polysemy emerges from contextual processing of word meaning from both a theoretical and computational point of view.

What is semantic diversity and why does it facilitate visual word recognition?

Previous research has speculated that semantic diversity and lexical ambiguity may be closely related constructs. Our research sought to test this claim in respect of the semantic diversity measure proposed by Hoffman et al. (2013). To this end, we replicated the procedure described by Hoffman et al., Behavior Research Methods, 45(3), 718-730 (2013) for computing multidimensional representations of contextual information using Latent Semantic Analysis, and from these we derived semantic diversity values for 28,555 words. We then replicated the facilitatory effect of semantic diversity on word recognition using existing data resources and observed this effect to be greater for low-frequency words. Yet, we found no relationship between this measure and lexical ambiguity effects in word recognition. Further analysis of the LSA-based contextual representations used to compute Hoffman et al. (2013) measure of semantic diversity revealed that they do not capture the distinct meanings of ambiguous words. Instead, these contextual representations appear to capture general information about the topics and types of written material in which words occur. These analyses suggest that the semantic diversity metric previously proposed by Hoffman et al. (2013) facilitates word recognition because high-diversity words are likely to have been encountered no matter what one has read, whereas many participants may not have encountered lower-diversity words simply because the topics and types of written material in which they occur are more restricted.

Reflection on modern methods: Statistics education beyond 'significance': novel plain English interpretations to deepen understanding of statistics and to steer away from misinterpretations.

Concerns have been expressed over standards of statistical interpretation. Results with P <0.05 are often referred to as 'significant' which, in plain English, implies important. This leads some people directly into the misconception that this provides proof that associations are clinically relevant. There are calls for statistics educators to respond to these concerns. This article provides novel plain English interpretations that are designed to deepen understanding. Experience teaching postgraduates at Imperial College is discussed. A key issue with focusing on 'significance' is the common inappropriate practice of implying no association exists, simply because P >0.05. Referring to strengths of association in 'study participants' gives them gravitas, which may help to avoid this. This contrasts with the common practice of focusing on imprecision, by referring to the 'sample' and to 'point estimates'. Unlike formal statistical definitions, interpretations developed and presented here are rooted in the application of statistics. They are based on one set of study participants (not many random samples). Precision of strengths of association are based on using strengths in study participants to estimate strengths of association in the population (from which participants were selected by probability random sampling). Reference to 'compatibility with study data, dependent on statistical modelling assumptions' reminds us of the importance of data quality and modelling assumptions. A straightforward graph shows the relationship between P-values and test statistics. This figure and associated interpretations were developed to illuminate the continuous nature of P-values. This is designed to discourage focus on whether P <0.05, and encourage interpretation of exact P-values.

Settling Into Semantic Space: An Ambiguity-Focused Account of Word-Meaning Access.

Most words are ambiguous: Individual word forms (e.g., run) can map onto multiple different interpretations depending on their sentence context (e.g., the athlete/politician/river runs). Models of word-meaning access must therefore explain how listeners and readers can rapidly settle on a single, contextually appropriate meaning for each word that they encounter. I present a new account of word-meaning access that places semantic disambiguation at its core and integrates evidence from a wide variety of experimental approaches to explain this key aspect of language comprehension. The model has three key characteristics. (a) Lexical-semantic knowledge is viewed as a high-dimensional space; familiar word meanings correspond to stable states within this lexical-semantic space. (b) Multiple linguistic and paralinguistic cues can influence the settling process by which the system resolves on one of these familiar meanings. (c) Learning mechanisms play a vital role in facilitating rapid word-meaning access by shaping and maintaining high-quality lexical-semantic knowledge throughout the life span. In contrast to earlier models of word-meaning access, I highlight individual differences in lexical-semantic knowledge: Each person's lexicon is uniquely structured by specific, idiosyncratic linguistic experiences.

I Scream for Ice Cream: Resolving Lexical Ambiguity with Sub-phonemic Information.

This study uses a response mouse-tracking paradigm to examine the role of sub-phonemic information in online lexical ambiguity resolution of continuous speech. We examine listeners' sensitivity to the sub-phonemic information that is specific to the ambiguous internal open juncture /s/-stop sequences in American English (e.g., "place kin" vs. "play skin"), that is, voice onset time (VOT) indicating different degrees of aspiration (e.g., long VOT for "kin" vs. short VOT for "skin") in connected speech contexts. A cross-splicing method was used to create two-word sequences (e.g., "place kin" or "play skin") with matching VOTs (long for "kin"; short for "skin") or mismatching VOTs (short for "kin"; long for "skin"). Participants (n = 20) heard the two-word sequences, while looking at computer displays with the second word in the left/right corner ("KIN" and "SKIN"). Then, listeners' click responses and mouse movement trajectories were recorded. Click responses show significant effects of VOT manipulation, while mouse trajectories do not. Our results show that stop-release information, whether temporal or spectral, can (mis)guide listeners' interpretation of the possible location of a word boundary between /s/ and a following stop, even when other aspects in the acoustic signal (e.g., duration of /s/) point to the alternative segmentation. Taken together, our results suggest that segmentation and lexical access are highly attuned to bottom-up phonetic information; our results have implications for a model of spoken language recognition with position-specific representations available at the prelexical level and also allude to the possibility that detailed phonetic information may be stored in the listeners' lexicons.

The Effects of Meaning Dominance in the Time-Course of Activation of L2 Lexical Ambiguity Processing.

This paper investigates the effects of meaning dominance in the time-course of activation for ambiguous words out of context in a second language (L2) based on two models: the ordered access model, where the most frequent dominant meaning is always accessed first, and the multiple access model, where dominant and subordinate meanings are activated. Non-native speakers of English (divided into high and low proficiency groups) and native English speakers completed a lexical decision task. While both L2 high and low proficiency groups retrieved multiple meanings of the ambiguous words at different stimulus-onset asynchronies supporting the multiple access model, the move from the ordered access model to the multiple access model was confirmed for the native English speaker group. The findings indicated developmental change of sensitivity to meaning dominance. The results also demonstrated that the rate of facilitation differed among the groups due to slow and more transient L2 activation.