Comparing phoneme frequency, age of acquisition, and loss in aphasia: Implications for phonological universals

Word Forms Reflect Trade-Offs Between Speaker Effort and Robust Listener Recognition

How do cognitive pressures shape the lexicons of natural languages? Here, we reframe George Kingsley Zipf's proposed "law of abbreviation" within a more general framework that relates it to cognitive pressures that affect speakers and listeners. In this new framework, speakers' drive to reduce effort (Zipf's proposal) is counteracted by the need for low-frequency words to have word forms that are sufficiently distinctive to allow for accurate recognition by listeners. To support this framework, we replicate and extend recent work using the prevalence of subword phonemic sequences (phonotactic probability) to measure speakers' production effort in place of Zipf's measure of length. Across languages and corpora, phonotactic probability is more strongly correlated with word frequency than word length. We also show this measure of ease of speech production (phonotactic probability) is strongly correlated with a measure of perceptual difficulty that indexes the degree of competition from alternative interpretations in word recognition. This is consistent with the claim that there must be trade-offs between these two factors, and is inconsistent with a recent proposal that phonotactic probability facilitates both perception and production. To our knowledge, this is the first work to offer an explanation why long, phonotactically improbable word forms remain in the lexicons of natural languages.

Contributions of semantic and phonological working memory to narrative language independent of single word production: Evidence from acute stroke

ABSTRACTNeuropsychological case studies have provided evidence that individuals with semantic, but not phonological, working memory (WM) deficits have difficulty producing phrases containing several content words. These findings supported the claim of a phrasal scope of planning at the grammatical formulation stage of production, where semantic WM supports the maintenance of lexical-semantic representations as they are inserted into slots in phrasal constituents. Recent narrative production results for individuals at the acute stage of stroke supported the role for semantic WM in phrasal elaboration while suggesting a role for phonological WM at a subsequent phonological encoding stage in supporting fluent, rapid speech. In the present study, we employed a larger participant sample while controlling for single word production abilities at semantic and phonological levels. Results confirmed the relations between semantic WM and phrasal elaboration whereas the relation between phonological WM and speech rate was eliminated. There was, however, evidence that both impaired phonological retrieval and restricted phonological WM were related to the tendency to produce short, highly frequent words such as pronouns rather than longer, less frequent words. Future research is needed to address whether the results relating to phonological WM depend on damage specific to an output rather than an input phonological capacity.

Precision of phonological errors in aphasia supports resource models of phonological working memory in language production

Working memory (WM) is critical for many cognitive functions including language production. A key feature of WM is its capacity limitation. Two models have been proposed to account for such capacity limitation: slot models and resource models. In recent years, resource models have found support in both visual and auditory perception, but do they also extend to production? We investigate this by analyzing sublexical errors from four individuals with aphasia. Using tools from computational linguistics, we first define the concept of "precision" of sublexical errors. We then demonstrate that such precision decreases with increased working memory load, i.e., word length, as predicted by resource models. Finally, we rule out alternative accounts of this effect, such as articulatory simplification. These data provide the first evidence for the applicability of the resource model to production and further point to the generalizability of this account as a model of resource division in WM.

An access deficit or a deficit in the phonological representations themselves: What can we learn from naming errors?

Anomic aphasia is characterized by good comprehension and non-word repetition but poor naming. Two sub-types of deficits might be hypothesized: faulty access to preserved phonological representations or preserved access to impaired representations. Phonological errors may occur only when representations are impaired or in post-lexical deficits (conduction aphasia). We analysed the incidence of phonological naming errors of 30 individuals, 25 with anomic aphasia based on poor naming but good repetition and comprehension, and five with conduction aphasia based on poor naming and poor repetition. Individuals with anomic aphasia produced very few phonological errors compared to individuals with conduction aphasia (0-19.1% versus 42-66%). However, six individuals with anomia produced more than 11% phonological errors, suggesting two patterns of deficit: either impaired lexical representations or impaired access to them. The lack of phonological errors in most individuals with anomic aphasia suggests that access to the phonological output lexicon is semantically, not phonologically driven.

Stimulus- and Person-Level Variables Influence Word Production and Response to Anomia Treatment for Individuals With Chronic Poststroke Aphasia

PURPOSE

The impact of stimulus-level psycholinguistic variables and person-level semantic and phonological processing skills on treatment outcomes in individuals with aphasia requires further examination to inform clinical decision making in treatment prescription and stimuli selection. This study investigated the influence of stimulus-level psycholinguistic properties and person-level semantic and phonological processing skills on word production accuracy and treatment response.

METHOD

This retrospective analysis included 35 individuals with chronic, poststroke aphasia, 30 of whom completed typicality-based semantic feature treatment. Mixed-effects logistic regression models were used to predict binary naming accuracy (a) at baseline and (b) over the course of treatment using stimulus-level psycholinguistic word properties and person-level semantic and phonological processing skills as predictors.

RESULTS

In baseline naming, words with less complex lexical-semantic and phonological properties showed greater predicted accuracy. There was also an interaction at baseline between stimulus-level lexical-semantic properties and person-level semantic processing skills in predicting baseline naming accuracy. With treatment, words that were more complex from a lexical-semantic standpoint (vs. less complex) and less complex from a phonological standpoint (vs. more complex) improved more. Individuals with greater baseline semantic and phonological processing skills showed a greater treatment response.

CONCLUSIONS

This study suggests that future clinical research and clinical work should consider semantic and phonological properties of words in selecting stimuli for semantically based treatment. Furthermore, future clinical research should continue to evaluate baseline individual semantic and phonological profiles as predictors of response to semantically based treatment.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21256341.

Effects of delay, length, and frequency on onset RTs and word durations: Articulatory planning uses flexible units but cannot be prepared

There is debate regarding whether most articulatory planning occurs offline (rather than online) and whether the products of off-line processing are stored in a separate articulatory buffer until a large enough chunk is ready for production. This hypothesis predicts that delayed naming conditions should reduce not only onset RTs but also word durations because articulatory plans will be buffered and kept ready. We have tested this hypothesis with young control speakers, an aphasic speaker , and an age and education-matched speaker, using repetition, reading and picture-naming tasks. Contrary to the off-line hypothesis, delayed conditions strongly reduced onset RTs, but had no benefit for word durations. In fact, we found small effects in the opposite direction. Moreover, frequency and imageability affected word durations even in delayed conditions, consistent with articulatory processing continuing on-line. The same pattern of results was found in CS and in control participants, strengthening confidence in our results. There is debate regarding whether most articulatory planning occurs offline (rather than online) and whether the results of off-line processing are stored in a separate articulatory buffer until a large enough chunk is ready for production. This hypothesis predicts that delayed naming conditions should reduce not only onset RTs but also word durations because articulatory plans will be buffered and kept ready. We have tested young control speakers, an aphasic speaker, and an age and education matched speaker, using repetition, reading and picture naming tasks. Contrary to the off-line hypothesis, delayed conditions strongly reduced onset RTs, but had no benefit for word durations. In fact, we found small effects in the opposite direction. Moreover, frequency and imageability affected word durations even in delayed conditions, consistent with articulatory processing continuing on-line. The same pattern of results was found in CS and in control participants, strengthening confidence in our results.

Psycholinguistic effects, types of impairments and processing levels in word production: Can we reduce confusions?

This commentary highlights three common difficulties faced by the literature that aims to specify models of speech production based on the performance of aphasic speakers, taking as a springboard a recent study by Mailend et al. These include: (1) difficulties with theoretical assumptions which linki psycholinguistic effects unequivocally to one processing level; (2) difficulties using clinical classifications to localize experimental effects; (3) difficulties making theoretical inferences given the controversial nature of the representations that characterize different processing levels. We argue that these three types of difficulties could be ameliorated by studies in which: (1) the level of psycholinguistic effects is demonstrated with converging analyses; (2) clinical classification is not taken as a starting point in studies investigating the nature of an impairment, but, instead, associations between clusters of symptoms are carefully analysed; (3) The nature of processing levels associated with deficits is made clear and results are not over-interpreted as supporting models whose characteristics go beyond an explanation of the results.

Preferred sound groups of vocal iconicity reflect evolutionary mechanisms of sound stability and first language acquisition: evidence from Eurasia

In speech, the connection between sounds and word meanings is mostly arbitrary. However, among basic concepts of the vocabulary, several words can be shown to exhibit some degree of form-meaning resemblance, a feature labelled vocal iconicity. Vocal iconicity plays a role in first language acquisition and was likely prominent also in pre-historic language. However, an unsolved question is how vocal iconicity survives sound evolution, which is assumed to be inevitable and 'blind' to the meaning of words. We analyse the evolution of sound groups on 1016 basic vocabulary concepts in 107 Eurasian languages, building on automated homologue clustering and sound sequence alignment to infer relative stability of sound groups over time. We correlate this result with the occurrence of sound groups in iconic vocabulary, measured on a cross-linguistic dataset of 344 concepts across single-language samples from 245 families. We find that the sound stability of the Eurasian set correlates with iconic occurrence in the global set. Further, we find that sound stability and iconic occurrence of consonants are connected to acquisition order in the first language, indicating that children acquiring language play a role in maintaining vocal iconicity over time. This article is part of the theme issue 'Reconstructing prehistoric languages'.

Examining speech motor planning difficulties in apraxia of speech and aphasia via the sequential production of phonetically similar words

This study investigated the underlying nature of apraxia of speech (AOS) by testing two competing hypotheses. The Reduced Buffer Capacity Hypothesis argues that people with AOS can plan speech only one syllable at a time Rogers and Storkel [1999. Planning speech one syllable at a time: The reduced buffer capacity hypothesis in apraxia of speech. Aphasiology, 13(9-11), 793-805. https://doi.org/10.1080/026870399401885]. The Program Retrieval Deficit Hypothesis states that selecting a motor programme is difficult in face of competition from other simultaneously activated programmes Mailend and Maas [2013. Speech motor programming in apraxia of speech: Evidence from a delayed picture-word interference task. American Journal of Speech-Language Pathology, 22(2), S380-S396. https://doi.org/10.1044/1058-0360(2013/12-0101)]. Speakers with AOS and aphasia, aphasia without AOS, and unimpaired controls were asked to prepare and hold a two-word utterance until a go-signal prompted a spoken response. Phonetic similarity between target words was manipulated. Speakers with AOS had longer reaction times in conditions with two similar words compared to two identical words. The Control and the Aphasia group did not show this effect. These results suggest that speakers with AOS need additional processing time to retrieve target words when multiple motor programmes are simultaneously activated.

Attentional engagement during syllable discrimination: The role of salient prosodic cues in 6- to 8-month-old infants

Prosodic cues drive speech segmentation and guide syllable discrimination. However, less is known about the attentional mechanisms underlying an infant's ability to benefit from prosodic cues. This study investigated how 6- to 8-month-old Italian infants allocate their attention to strong vs. weak syllables after familiarization with four repeats of a single CV sequence with alternating strong and weak syllables (different syllables on each trial). In the discrimination test-phase, either the strong or the weak syllable was replaced by a pure tone matching the suprasegmental characteristics of the segmental syllable, i.e., duration, loudness and pitch, whereas the familiarized stimulus was presented as a control. By using an eye-tracker, attention deployment (fixation times) and cognitive resource allocation (pupil dilation) were measured under conditions of high and low saliency that corresponded to the strong and weak syllabic changes, respectively. Italian learning infants were found to look longer and also to show, through pupil dilation, more attention to changes in strong syllable replacement rather than weak syllable replacement, compared to the control condition. These data offer insights into the strategies used by infants to deploy their attention towards segmental units guided by salient prosodic cues, like the stress pattern of syllables, during speech segmentation.

Complexity of articulation planning in apraxia of speech: The limits of phoneme-based approaches

This report presents evidence suggesting that the phoneme-based approach taken by Romani, Galuzzi, Guariglia, and Goslin (Comparing phoneme frequency, age of acquisition, and loss in aphasia: Implications for phonological universals. Cognitive Neuropsychology, this issue) falls short of capturing the complexity of articulation planning in patients with apraxia of speech. Empirical and modelling data are reported to demonstrate that the apraxic pathomechanism resides in the hierarchical architecture of phonological words rather than in the context-independent properties of phonemes. Because the factors determining complexity of articulation planning are interlaced between gestural, syllabic, and metrical levels, they cannot be captured by markedness rankings limited to any of these levels.

Phonological regularity, perceptual biases, and the role of phonotactics in speech error analysis

Speech errors involving manipulations of sounds tend to be phonologically regular in the sense that they obey the phonotactic rules of well-formed words. We review the empirical evidence for phonological regularity in prior research, including both categorical assessments of words and regularity at the granular level involving specific segments and contexts. Since the reporting of regularity is affected by human perceptual biases, we also document this regularity in a new data set of 2,228 sublexical errors that was collected using methods that are demonstrably less prone to bias. These facts validate the claim that sound errors are overwhelmingly regular, but the new evidence suggests speech errors admit more phonologically ill-formed words than previously thought. Detailed facts of the phonological structure of errors, including this revised standard, are then related to model assumptions in contemporary theories of phonological encoding. This article is categorized under: Linguistics > Linguistic Theory Linguistics > Computational Models of Language Psychology > Language.

The difficulty of articulatory complexity

In our commentary, we offer some support for the view that frequency rather than a language-independent definition of complexity is a main factor determining speech production in healthy adults. We further discuss the limits of defining articulatory complexity based on transcription data. If we want to gauge the impact of substantive constraints on speech production, context-specific production dynamics should be considered, as has been underscored by articulatory-acoustic work on speech errors.

Is markedness a confused concept?

It is well known that, across languages, certain phonological features are more frequent than others. But whether these facts reflect abstract universal markedness constraints or functional pressures (auditory and articulatory difficulties and lexical frequency) is unknown. Romani, Galuzzi, Guariglia, and Goslin (2017) report that the putative markedness of phonological features captures their order of acquisition and their propensity to elicit errors in patients with an apraxia of speech (but not in phonological aphasia). The authors believe these results challenge the existence of abstract markedness constraints. They also raise some concerns about the explanatory utility of the markedness hypothesis. This commentary demonstrates that markedness is not inherently vague or vacuous nor is it falsified by Romani et al.'s empirical findings. As such, these results leave wide open the possibility that some phonological markedness constraints are abstract.