Different Electrophysiological Signatures of Similarity-induced and Stroop-like Interference in Language Production.

Contextual similarity between targets and competitors, whether semantic or phonological, often leads to behavioral interference in language production. It has been assumed that resolving such interference relies on control processes similar to those involved in tasks such as Stroop. This article tests this assumption by comparing the electrophysiological signatures of interference resulting from a contextual similarity versus a Stroop-like manipulation. In blocks containing two items, participants repeatedly named pictures that were semantically related, phonologically related, or unrelated (contextual similarity manipulation). In straight blocks, the pictures were named by their canonical names. In reverse blocks, participants had to reverse the names (Stroop-like manipulation). Both manipulations led to behavioral interference, but with different electrophysiological profiles. Whole-scalp stimulus-locked and response-locked analyses of semantic and phonological similarity pointed to a system with global modularity with some degree of cascading and interactivity, whereas the effect of phase reversal was sustained and of the opposite polarity. More strikingly, a representational similarity analysis showed a biphasic pattern for Stroop-like reversal, with earlier higher similarity scores for the reverse phase flipping into lower scores ~500 msec poststimulus onset. In contrast, contextual similarity induced higher similarity scores up to articulation. Finally, response-locked mediofrontal components indexing performance monitoring differed between manipulations. Correct response negativity's amplitude was lower in the phonological blocks, whereas a pre-correct response negativity component had higher amplitude in reverse versus straight blocks. These results argue against the involvement of Stroop-like control mechanisms in resolving interference from contextual similarity in language production.

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.

Electrophysiological Correlates of Monitoring in Typing with and without Visual Feedback.

New theories of monitoring in language production, regardless of their mechanistic differences, all posit monitoring mechanisms that share general computational principles with action monitoring. This perspective, if accurate, would predict that many electrophysiological signatures of performance monitoring should be recoverable from language production tasks. In this study, we examined both error-related and feedback-related EEG indices of performance monitoring in the context of a typing-to-dictation task. To disentangle the contribution of the external from internal monitoring processes, we created a condition where participants immediately saw the word they typed (the immediate-feedback condition) versus one in which displaying the word was delayed until the end of the trial (the delayed-feedback condition). The removal of immediate visual feedback prompted a stronger reliance on internal monitoring processes, which resulted in lower correction rates and a clear error-related negativity. Compatible with domain-general monitoring views, an error positivity was only recovered under conditions where errors were detected or had a high likelihood of being detected. Examination of the feedback-related indices (feedback-related negativity and frontocentral positivity) revealed a two-stage process of integration of internal and external information. The recovery of a full range of well-established EEG indices of action monitoring in a language production task strongly endorses domain-general views of monitoring. Such indices, in turn, are helpful in understanding how information from different monitoring channels are combined.

The dual origin of semantic errors in access deficit: activation vs. inhibition deficit.

According to most models of language production, to name a picture one must first map semantic features onto lexical items. Even if both sets of representations are intact, problems in mapping semantic to lexical representations can impair production. Individuals with this problem, sometimes referred to as "access deficit", often demonstrate evidence of preserved semantic knowledge (e.g., good comprehension), increased rate of lexical (usually semantic) errors in production, and inconsistent accuracy on naming the same picture on different occasions. In this paper, I argue that access deficit can have two distinct etiologies. I will present a case of double dissociation between two individuals with chronic post-stroke aphasia, one of whom shows a profile compatible with impaired activation of the target lexical item from semantic features (activation deficit), while the other shows a profile compatible with impaired inhibition of competing lexical items (inhibition deficit). These results have three key implications: (a) they provide support for the theoretical separation between activation and selection processes in computational models of word production, (b) they point to the critical role of inhibitory control in lexical selection, and (c) they invite a closer inspection of the origin of semantic errors in individuals with access deficit in order to choose the best treatment option.

To select or to wait? The importance of criterion setting in debates of competitive lexical selection.

Competitive accounts of lexical selection propose that the activation of competitors slows down the selection of the target. Non-competitive accounts, on the other hand, posit that target response latencies are independent of the activation of competing items. In this paper, we propose a signal detection framework for lexical selection and show how a flexible selection criterion affects claims of competitive selection. Specifically, we review evidence from neurotypical and brain-damaged speakers and demonstrate that task goals and the state of the production system determine whether a competitive or a non-competitive selection profile arises. We end by arguing that there is conclusive evidence for a flexible criterion in lexical selection, and that integrating criterion shifts into models of language production is critical for evaluating theoretical claims regarding (non-)competitive selection.

To select or to wait? Response to the commentaries.

In [Nozari, N., & Hepner, C. R. (2018). To select or to wait? The importance of criterion setting in debates of competitive lexical selection. Cognitive Neuropsychology. Advance online publication. doi:10.1080/02643294.2018.1476335], we proposed a theoretical framework for reconciling two seemingly irreconcilable theories of lexical selection: competitive vs. non-competitive selection. The key point in this framework is the division of language production into two separate-albeit interacting-systems: a decision-making framework and a multi-layered system which maps meaning to sound. Technically, this can be accomplished by superimposing a signal detection model onto the distributions of conflict derived from the core dynamics of mapping semantic features to lexical representations. Based on this framework, we argued that a flexible selection criterion could accommodate patterns predicted by both competitive and non-competitive models of lexical selection. Five excellent commentaries posed various questions regarding the necessity, applicability, and scope of the proposed framework. This paper addresses those questions.

Did I say dog or cat? A study of semantic error detection and correction in children.

Although naturalistic studies of spontaneous speech suggest that young children can monitor their speech, the mechanisms for detection and correction of speech errors in children are not well understood. In particular, there is little research on monitoring semantic errors in this population. This study provides a systematic investigation of detection and correction of semantic errors in children between the ages of 5 and 8years as they produced sentences to describe simple visual events involving nine highly familiar animals (the moving animals task). Results showed that older children made fewer errors and corrected a larger proportion of the errors that they made than younger children. We then tested the prediction of a production-based account of error monitoring that the strength of the language production system, and specifically its semantic-lexical component, should be correlated with the ability to detect and repair semantic errors. Strength of semantic-lexical mapping, as well as lexical-phonological mapping, was estimated individually for children by fitting their error patterns, obtained from an independent picture-naming task, to a computational model of language production. Children's picture-naming performance was predictive of their ability to monitor their semantic errors above and beyond age. This relationship was specific to the strength of the semantic-lexical part of the system, as predicted by the production-based monitor.

Is working memory domain-general or domain-specific?

Given the fundamental role of working memory (WM) in all domains of cognition, a central question has been whether WM is domain-general. However, the term 'domain-general' has been used in different, and sometimes misleading, ways. By reviewing recent evidence and biologically plausible models of WM, we show that the level of domain-generality varies substantially between three facets of WM: in terms of computations, WM is largely domain-general. In terms of neural correlates, it contains both domain-general and domain-specific elements. Finally, in terms of application, it is mostly domain-specific. This variance encourages a shift of focus towards uncovering domain-general computational principles and away from domain-general approaches to the analysis of individual differences and WM training, favoring newer perspectives, such as training-as-skill-learning.

Similarity-induced interference or facilitation in language production reflects representation, not selection.

Researchers have long interpreted the presence or absence of semantic interference in picture naming latencies as confirming or refuting theoretical claims regarding competitive lexical selection. But inconsistent empirical results challenge any mechanistic interpretation. A behavioral experiment first verified an apparent boundary condition in a blocked picture naming task: when orthogonally manipulating association type, taxonomic associations consistently elicit interference, while thematic associations do not. A plausible representational difference is that thematic feature activations depend more on supporting contexts. Simulations show that context-sensitivity emerges from the distributional statistics that are often used to measure thematic associations: residual semantic activation facilitates the retrieval of words that share semantic features, counteracting learning-based interference, and training a production model with greater sequential cooccurrence for thematically related words causes it to acquire stronger residual activation for thematic features. Modulating residual activation, either directly or through training, allows the model to capture gradient values of interference and facilitation, and in every simulation competitive and noncompetitive selection algorithms produce qualitatively equivalent results.

Trust my gesture or my word: How do listeners choose the information channel during communication?

Information can be conveyed via multiple channels such as verbal and gestural (visual) channels during communication. Sometimes the information from different channels does not match (e.g., saying right while pointing to the left). How do addressees choose which information to act upon in such cases? In two experiments, we investigated this issue by having participants follow instructions on how to move objects on the screen. Experiment 1 examined whether people's choice of channel can be altered by feedback favoring either the verbal or the gestural channel. In Experiment 2, there was no feedback and participants were free to choose either channel. We also assessed participants' verbal and visuospatial working memory capacities. Results showed that, when faced with contradicting information, there is a natural bias at the group level toward relying on the verbal channel, although this bias can be temporarily altered by probabilistic feedback. Moreover, when labels were shorter and of higher frequency, participants relied more on the verbal channel. In the absence of feedback, the capacity of individuals' visual, but not verbal, working memory determined reliance on one channel versus the other. Collectively, these results show that information selection in communication is influenced by group-level biases, as well as the properties of items and characteristics of individuals. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

A narrative review of the anatomy and function of the white matter tracts in language production and comprehension.

Much is known about the role of cortical areas in language processing. The shift towards network approaches in recent years has highlighted the importance of uncovering the role of white matter in connecting these areas. However, despite a large body of research, many of these tracts' functions are not well-understood. We present a comprehensive review of the empirical evidence on the role of eight major tracts that are hypothesized to be involved in language processing (inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, extreme capsule, middle longitudinal fasciculus, superior longitudinal fasciculus, arcuate fasciculus, and frontal aslant tract). For each tract, we hypothesize its role based on the function of the cortical regions it connects. We then evaluate these hypotheses with data from three sources: studies in neurotypical individuals, neuropsychological data, and intraoperative stimulation studies. Finally, we summarize the conclusions supported by the data and highlight the areas needing further investigation.

Transfer of statistical learning from passive speech perception to speech production.

Communicating with a speaker with a different accent can affect one's own speech. Despite the strength of evidence for perception-production transfer in speech, the nature of transfer has remained elusive, with variable results regarding the acoustic properties that transfer between speakers and the characteristics of the speakers who exhibit transfer. The current study investigates perception-production transfer through the lens of statistical learning across passive exposure to speech. Participants experienced a short sequence of acoustically variable minimal pair (beer/pier) utterances conveying either an accent or typical American English acoustics, categorized a perceptually ambiguous test stimulus, and then repeated the test stimulus aloud. In the canonical condition, /b/-/p/ fundamental frequency (F0) and voice onset time (VOT) covaried according to typical English patterns. In the reverse condition, the F0xVOT relationship reversed to create an "accent" with speech input regularities atypical of American English. Replicating prior studies, F0 played less of a role in perceptual speech categorization in reverse compared with canonical statistical contexts. Critically, this down-weighting transferred to production, with systematic down-weighting of F0 in listeners' own speech productions in reverse compared with canonical contexts that was robust across male and female participants. Thus, the mapping of acoustics to speech categories is rapidly adjusted by short-term statistical learning across passive listening and these adjustments transfer to influence listeners' own speech productions.

Evidence for a non-lexical influence on children's auditory repetition of familiar words.

This paper examines evidence for a nonlexical influence on children's repetition of real words. We investigate the extent to which two computational models of auditory repetition can simulate the performance of 68 children aged between 5 and 11 years-old when they are attempting to repeat familiar words. Both computational accounts were derived from Foygel and Dell's (J Mem Lang 43:182-216, 2000) semantic-phonological model of picture-naming. Results showed that a dual-route model in which a lexical and a nonlexical route work together to repeat familiar words (Hanley et al. in Cogn Neuropsychol 21:147-158, 2004) provided an accurate simulation of children's repetition, whereas Foygel and Dell (J Mem Lang 43:182-216, 2000) single lexical-route model under-predicted performance. The only exception was the repetition performance of 5 year-old children, which was over-predicted by the dual-route model. It is argued that at 5 years of age, some children have available both a lexical and a nonlexical repetition route but the output of the two routes does not summate when real words are being repeated. Some young children may lack the attentional skills that would enable them to co-ordinate the activity of the lexical and nonlexical repetition routes.

Is comprehension necessary for error detection? A conflict-based account of monitoring in speech production.

Despite the existence of speech errors, verbal communication is successful because speakers can detect (and correct) their errors. The standard theory of speech-error detection, the perceptual-loop account, posits that the comprehension system monitors production output for errors. Such a comprehension-based monitor, however, cannot explain the double dissociation between comprehension and error-detection ability observed in the aphasic patients. We propose a new theory of speech-error detection which is instead based on the production process itself. The theory borrows from studies of forced-choice-response tasks the notion that error detection is accomplished by monitoring response conflict via a frontal brain structure, such as the anterior cingulate cortex. We adapt this idea to the two-step model of word production, and test the model-derived predictions on a sample of aphasic patients. Our results show a strong correlation between patients' error-detection ability and the model's characterization of their production skills, and no significant correlation between error detection and comprehension measures, thus supporting a production-based monitor, generally, and the implemented conflict-based monitor in particular. The successful application of the conflict-based theory to error-detection in linguistic, as well as non-linguistic domains points to a domain-general monitoring system.

Correction Without Consciousness in Complex Tasks: Evidence from Typing.

It has been demonstrated that with practice, complex tasks can become independent of conscious control, but even in those cases, repairing errors is thought to remain dependent on conscious control. This paper reports two studies probing conscious awareness over repairs in nearly 15,000 typing errors collected from 145 participants in a single-word typing-to-dictation task. We provide evidence for subconscious repairs by ruling out alternative accounts, and report two sets of analyses showing that a) such repairs are not confined to a specific stage of processing and b) that they are sensitive to the final outcome of repair. A third set of analyses provides a detailed comparison of the timeline of trials with conscious and subconscious repairs, revealing that the difference is confined to the repair process itself. We propose an account of repair processing that accommodates these empirical findings.

The limited role of hippocampal declarative memory in transient semantic activation during online language processing.

Recent findings point to a role for hippocampus in the moment-by-moment processing of language, including the use and generation of semantic features in certain contexts. What role the hippocampus might play in the processing of semantic relations in spoken language comprehension, however, is unknown. Here we test patients with bilateral hippocampal damage and dense amnesia in order to examine the necessity of hippocampus for lexico-semantic mapping processes in spoken language understanding. In two visual-world eye-tracking experiments, we monitor eye movements to images that are semantically related to spoken words and sentences. We find no impairment in amnesia, relative to matched healthy comparison participants. These findings suggest, at least for close semantic links and simple language comprehension tasks, a lack of necessity for hippocampus in lexico-semantic mapping between spoken words and simple pictures.

A Comprehension- or a Production-Based Monitor? Response to Roelofs (2020).

Roelofs (2020) has put forth a rebuttal of the criticisms raised against comprehension-based monitoring and has also raised a number of objections against production-based monitors. In this response, I clarify that the model defended by Roelofs is not a comprehension-based monitor, but belongs to a class of monitoring models which I refer to as production-perception models. I review comprehension-based and production-perception models, highlight the strength of each, and point out the differences between them. I then discuss the limitations of both for monitoring production at higher levels, which has been the motivation for production-based monitors. Next, I address the specific criticisms raised by Roelofs (2020) in light of the current evidence. I end by presenting several lines of arguments that preclude a single monitoring mechanism as meeting all the demands of monitoring in a task as complex as communication. A more fruitful avenue is perhaps to focus on what theories are compatible with the nature of representations at specific levels of the production system and with specific aims of monitoring in language production.

The dual origin of lexical perseverations in aphasia: Residual activation and incremental learning.

Lexical perseveration, the inappropriate repetition of a previous response, is common in aphasia. Two underlying mechanisms have been proposed: residual activation and incremental learning. Previous attempts to differentiate the two have relied on experimental paradigms that encourage semantically related errors and analysis techniques designed to detect perseverations over short distances, resulting in a bias towards detecting short-lag, semantically related perseverations that both mechanisms can account for. Two key predictions that differentiate these accounts remain untested: only residual activation can explain short-lag, semantically unrelated perseverations, whereas only incremental learning can explain long-lag, semantically related perseverations. In this paper, we used a large set of picture naming trials and a novel analysis technique to test these key predictions in a multi-session study involving six individuals with aphasia. We found clear evidence for both mechanisms in different individuals, demonstrating that either one is sufficient to cause perseveration. Importantly, perseverations due to residual activation were associated with more severely impaired systems than those due to incremental learning, suggesting that a certain degree of structural and functional integrity was necessary for incremental learning. Finally, the results supported a key prediction of the incremental learning account by showing perseverations over longer lags than have previously been reported.

Learning in complex, multi-component cognitive systems: Different learning challenges within the same system.

Using word learning as an example of a complex system, we investigated how differences in the structure of the subcomponents in which learning occurs can have significant consequences for the challenge of integrating new information within such systems. Learning a new word involves integrating information into the two key stages/subcomponents of processing within the word production system. In the first stage, multiple semantic features are mapped onto a single word. Conversely, in the second stage, a single word is mapped onto multiple segmental features. We tested whether the unitary goal of word learning leads to different local outcomes in these two stages because of their reversed mapping patterns. Neurotypical individuals (N = 17) learned names and semantic features for pictures of unfamiliar objects presented in semantically related, segmentally related and unrelated blocks. Both similarity types interfered with word learning. However, feature learning was differentially affected within the two subcomponents of word production. Semantic similarity facilitated learning distinctive semantic features (i.e., features unique to each item), whereas segmental similarity facilitated learning shared segmental features (i.e., features common to several items in a block). These results are compatible with an incremental learning model in which learning not only strengthens certain associations but also weakens others according to the local goals of each subcomponent. More generally, they demonstrate that the same overall learning goal can lead to opposite learning outcomes in the subcomponents of a complex system. The general principles uncovered may extend beyond word learning to other complex systems with multiple subcomponents. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Is adaptive control in language production mediated by learning?

Recent work using the Picture Word Interference (PWI) paradigm has revealed that language production, similar to non-verbal tasks, shows a robust Congruency Sequence Effect (CSE), defined as a decreased congruency effect following incongruent trials. Although CSE is considered an index of adaptive control, its mechanism is debated. In two experiments, we tested the predictions of a learning model of adaptive control in production, using a task-switching paradigm fully balanced to evaluate CSE on a PWI trial as a function of the congruency of a 2-back PWI trial (within-task CSE), as well as a 1-back trial belonging to a different task (cross-task CSE). The second task was a visuospatial task with congruent and incongruent trials in Experiment 1, and a self-paced reading task with ambiguous and unambiguous sentences in Experiment 2 that imposed a gap between the two PWI trials twice as long of that in Experiment 1. A learning model posits that CSE is the result of changes to the connection weights between task-specific representations and a control center, which leads to two predictions in our paradigm: (a) a robust within-task CSE unaffected by the intervening trial and the gap duration, and (b) an absent or reversed cross-task CSE. These predictions were contrasted with two versions of an activation model of CSE. In accord with the predictions of the learning model, we found robust within-task CSE in PWI in both Experiments with a comparable effect size. Similarly, evidence of within-task CSE was also found in the visuospatial and sentence reading tasks. On the other hand, examination of cross-task CSE from PWI to the other tasks and vice versa revealed either absent or reversed CSE. Collectively, these results support a learning model of adaptive control in language production.