Error Biases in Spoken Word Planning and Monitoring by Aphasic and Nonaphasic Speakers: Comment on Rapp and Goldrick (2000)

M-MAT Meta: Treatment of Self-Awareness and Language for Individuals With Severe Wernicke's Aphasia

PURPOSE

In this study, we evaluated the feasibility and efficacy of language plus goal management training program for individuals with aphasia. The intervention targeted expressive language, while concurrently integrating tasks designed to improve executive function and error awareness.

METHOD

A single-subject repeated-measures design was utilized to determine whether a combined treatment (Multi-Modal Aphasia Therapy PLUS Goal Management Training [M-MAT Meta]) would be efficacious for individuals with aphasia. This article reports on two participants with severe Wernicke's aphasia, who comprised one of the four dyads of the study. Treatment was administered in a small group setting (N = 2) for 2 hr per day, 3 days per week for 4 weeks. Individual video feedback sessions were conducted once a week. Analysis of outcomes included visual inspection and calculation of Tau-U effect sizes of probed treatment data as well as statistical analysis of standardized language and executive function assessments.

RESULTS

Visual inspection indicated improvements in naming and discourse skills, which were maintained at the 1-month follow-up. Both participants' standardized scores indicated a significant decrease in aphasia severity, which was maintained 1 month posttreatment. Error awareness improved for one of the two participants, but this improvement was not maintained. Participants demonstrated increased inhibition of unwanted responses and took longer on the planning and problem-solving time required to complete the assessment, indicating a decrease in impulsivity.

CONCLUSION

The results of this preliminary study suggest that M-MAT Meta may be an effective way to increase self-awareness and communication in individuals with severe Wernicke's aphasia.

The relationship between semantics, phonology, and naming performance in aphasia: a structural equation modeling approach

The exploration of naming error patterns in aphasia provides insights into the cognitive processes underlying naming performance. We investigated how semantic and phonological abilities correlate and how they influence naming performance in aphasia. Data from 296 individuals with aphasia, drawn from the Moss Aphasia Psycholinguistics Project Database, were analyzed using a structural equation model. The model incorporated latent variables for semantics and phonology and manifest variables for naming accuracy and error patterns. There was a moderate positive correlation between semantics and phonology after controlling for overall aphasia severity. Both semantic and phonological abilities influenced naming accuracy. Semantic abilities negatively related to semantic, mixed, unrelated errors, and no responses. Interestingly, phonology positively affected semantic errors. Additionally, phonological abilities negatively related to each of phonological and neologism errors. These results highlight the role of semantic and phonological skills on naming performance in aphasia and reveal a relationship between these cognitive processes.

Listening to Yourself and Watching Your Tongue: Distinct Abilities and Brain Regions for Monitoring Semantic and Phonological Speech Errors

Despite the many mistakes we make while speaking, people can effectively communicate because we monitor our speech errors. However, the cognitive abilities and brain structures that support speech error monitoring are unclear. There may be different abilities and brain regions that support monitoring phonological speech errors versus monitoring semantic speech errors. We investigated speech, language, and cognitive control abilities that relate to detecting phonological and semantic speech errors in 41 individuals with aphasia who underwent detailed cognitive testing. Then, we used support vector regression lesion symptom mapping to identify brain regions supporting detection of phonological versus semantic errors in a group of 76 individuals with aphasia. The results revealed that motor speech deficits as well as lesions to the ventral motor cortex were related to reduced detection of phonological errors relative to semantic errors. Detection of semantic errors selectively related to auditory word comprehension deficits. Across all error types, poor cognitive control related to reduced detection. We conclude that monitoring of phonological and semantic errors relies on distinct cognitive abilities and brain regions. Furthermore, we identified cognitive control as a shared cognitive basis for monitoring all types of speech errors. These findings refine and expand our understanding of the neurocognitive basis of speech error monitoring.

Lexicality-Modulated Influence of Auditory Cortex on Subthalamic Nucleus During Motor Planning for Speech

Speech requires successful information transfer within cortical-basal ganglia loop circuits to produce the desired acoustic output. For this reason, up to 90% of Parkinson's disease patients experience impairments of speech articulation. Deep brain stimulation (DBS) is highly effective in controlling the symptoms of Parkinson's disease, sometimes alongside speech improvement, but subthalamic nucleus (STN) DBS can also lead to decreases in semantic and phonological fluency. This paradox demands better understanding of the interactions between the cortical speech network and the STN, which can be investigated with intracranial EEG recordings collected during DBS implantation surgery. We analyzed the propagation of high-gamma activity between STN, superior temporal gyrus (STG), and ventral sensorimotor cortices during reading aloud via event-related causality, a method that estimates strengths and directionalities of neural activity propagation. We employed a newly developed bivariate smoothing model based on a two-dimensional moving average, which is optimal for reducing random noise while retaining a sharp step response, to ensure precise embedding of statistical significance in the time-frequency space. Sustained and reciprocal neural interactions between STN and ventral sensorimotor cortex were observed. Moreover, high-gamma activity propagated from the STG to the STN prior to speech onset. The strength of this influence was affected by the lexical status of the utterance, with increased activity propagation during word versus pseudoword reading. These unique data suggest a potential role for the STN in the feedforward control of speech.

Disentangling the Psycholinguistic Loci of Anomia with Cognitive Psychometric Models

This article reviews advanced statistical techniques for measuring impairments in object naming, particularly in the context of stroke-induced aphasia. Traditional testing strategies can be challenged by the multifaceted nature of impairments that arise due to the complex relationships between localized brain damage and disruption to the cognitive processes required for successful object naming. Cognitive psychometric models can combine response-type analysis with item-response theory to yield accurate estimates of multiple abilities using data collected from a single task. The models also provide insights about how the test items can be challenging in different ways. Although more work is needed to fully optimize their clinical utility in practice, these formal concepts can guide thoughtful selection of stimuli used in treatment or assessment, as well as providing a framework to interpret response-type data.

Disrupting self-evaluative processing with electrostimulation mapping during awake brain surgery

Brain awake surgery with cognitive monitoring for tumor removal has become a standard of treatment for functional purpose. Yet, little attention has been given to patients' interpretation and awareness of their own responses to selected cognitive tasks during direct electrostimulation (DES). We aim to report disruptions of self-evaluative processing evoked by DES during awake surgery. We further investigate cortico-subcortical structures involved in self-assessment process and report the use of an intraoperative self-assessment tool, the self-confidence index (SCI). Seventy-two patients who had undergone awake brain tumor resections were selected. Inclusion criteria were the occurrence of a DES-induced disruption of an ongoing task followed by patient's failure to remember or criticize these impairments, or a dissociation between patient's responses to an ongoing task and patient's SCI. Disruptions of self-evaluation were frequently associated with semantic disorders and critical sites were mostly found along the left/right ventral semantic streams. Disconnectome analyses generated from a tractography-based atlas confirmed the high probability of the inferior fronto-occipital fasciculus to be transitory 'disconnected'. These findings suggest that white matters pathways belonging to the ventral semantic stream may be critically involved in human self-evaluative processing. Finally, the authors discuss the implementation of the SCI task during multimodal intraoperative monitoring.

Connections and selections: Comparing multivariate predictions and parameter associations from latent variable models of picture naming

Connectionist simulation models and processing tree mathematical models of picture naming have complementary advantages and disadvantages. These model types were compared in terms of their predictions of independent language measures and their associations between model components and measures that should be related according to their theoretical interpretations. The models were tasked with predicting independent picture naming data, neuropsychological test scores of semantic association and speech production, grammatical categories of formal errors, and lexical properties of target items. In all cases, the processing tree model parameters provided better predictions and stronger associations between parameters and independent language measures than the connectionist simulation model. Given the enhanced generalizability of latent variable measurements afforded by the processing tree model, evidence regarding mechanistic and representational features of the speech production system are re-evaluated. Several areas are indicated as being potentially viable targets for elaboration of the mechanistic descriptions of picture naming errors.

Self-Monitoring in Speaking: In Defense of a Comprehension-Based Account

Speakers occasionally make speech errors, which may be detected and corrected. According to the comprehension-based account proposed by Levelt, Roelofs, and Meyer (1999) and Roelofs (2004), speakers detect errors by using their speech comprehension system for the monitoring of overt as well as inner speech. According to the production-based account of Nozari, Dell, and Schwartz (2011), speakers may use their comprehension system for external monitoring but error detection in internal monitoring is based on the amount of conflict within the speech production system, assessed by the anterior cingulate cortex (ACC). Here, I address three main arguments of Nozari et al. and Nozari and Novick (2017) against a comprehension-based account of internal monitoring, which concern cross-talk interference between inner and overt speech, a double dissociation between comprehension and self-monitoring ability in patients with aphasia, and a domain-general error-related negativity in the ACC that is allegedly independent of conscious awareness. I argue that none of the arguments are conclusive, and conclude that comprehension-based monitoring remains a viable account of self-monitoring in speaking.

On (Correctly Representing) Comprehension-Based Monitoring in Speaking: Rejoinder to Nozari (2020)

Misunderstanding exists about what constitutes comprehension-based monitoring in speaking and what it empirically implies. Here, I make clear that the use of the speech comprehension system is the defining property of comprehension-based monitoring rather than conscious and deliberate processing, as maintained by Nozari (2020). Therefore, contrary to what Nozari claims, my arguments in Roelofs (2020) are suitable for addressing her criticisms raised against comprehension-based monitoring. Also, I indicate that Nozari does not correctly describe my view in a review of her paper. Finally, I further clarify what comprehension-based monitoring entails empirically, thereby dealing with Nozari's new criticisms and inaccurate descriptions of empirical findings. I conclude that comprehension-based monitoring remains a viable account of self-monitoring in speaking.

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.

Tone slips in Cantonese: Evidence for early phonological encoding

This article examines speech errors in Cantonese with the aim of fleshing out a larger speech production architecture for encoding phonological tone. A corpus was created by extracting 2462 speech errors, including 668 tone errors, from audio recordings of natural conversations. The structure of these errors was then investigated in order to distinguish two contemporary approaches to tone in speech production. In the tonal frames account, tone is encoded like metrical stress, represented in abstract structural frames for a word. Because tone cannot be mis-selected in tonal frames, tone errors are expected to be rare and non-contextual, as observed with stress. An alternative is that tone is actively selected in phonological encoding like phonological segments. This approach predicts that tone errors will be relatively common and exhibit the contextual patterns observed with segments, like perseveration and anticipation. In our corpus, tone errors are the second most common type of error, and the majority of errors exhibit contextual patterns that parallel segmental errors. Building on prior research, a two-stage model of phonological tone encoding is proposed, following the patterns seen in tone errors: Tone is phonologically selected concurrently with segments, but then sequentially assigned after segments to a syllable.

Priming production: Neural evidence for enhanced automatic semantic activity preceding language production in schizophrenia

Introduction

Lexico-semantic disturbances are considered central to schizophrenia. Clinically, their clearest manifestation is in language production. However, most studies probing their underlying mechanisms have used comprehension or categorization tasks. Here, we probed automatic semantic activity prior to language production in schizophrenia using event-related potentials (ERPs).

Methods

19 people with schizophrenia and 16 demographically-matched healthy controls named target pictures that were very quickly preceded by masked prime words. To probe automatic semantic activity prior to production, we measured the N400 ERP component evoked by these targets. To determine the origin of any automatic semantic abnormalities, we manipulated the type of relationship between prime and target such that they overlapped in (a) their semantic features (semantically related, e.g. "cake" preceding a < picture of a pie >, (b) their initial phonemes (phonemically related, e.g. "stomach" preceding a < picture of a starfish >), or (c) both their semantic features and their orthographic/phonological word form (identity related, e.g. "socks" preceding a < picture of socks >). For each of these three types of relationship, the same targets were paired with unrelated prime words (counterbalanced across lists). We contrasted ERPs and naming times to each type of related target with its corresponding unrelated target.

Results

People with schizophrenia showed abnormal N400 modulation prior to naming identity related (versus unrelated) targets: whereas healthy control participants produced a smaller amplitude N400 to identity related than unrelated targets, patients showed the opposite pattern, producing a larger N400 to identity related than unrelated targets. This abnormality was specific to the identity related targets. Just like healthy control participants, people with schizophrenia produced a smaller N400 to semantically related than to unrelated targets, and showed no difference in the N400 evoked by phonemically related and unrelated targets. There were no differences between the two groups in the pattern of naming times across conditions.

Conclusion

People with schizophrenia can show abnormal neural activity associated with automatic semantic processing prior to language production. The specificity of this abnormality to the identity related targets suggests that that, rather than arising from abnormalities of either semantic features or lexical form alone, it may stem from disruptions of mappings (connections) between the meaning of words and their form.

Executive control in spoken noun-phrase production: Contributions of updating, inhibiting, and shifting

The present study examined how the updating, inhibiting, and shifting abilities underlying executive control influence spoken noun-phrase production. Previous studies provided evidence that updating and inhibiting, but not shifting, influence picture-naming response time (RT). However, little is known about the role of executive control in more complex forms of language production like generating phrases. We assessed noun-phrase production using picture description and a picture–word interference procedure. We measured picture description RT to assess length, distractor, and switch effects, which were assumed to reflect, respectively, the updating, inhibiting, and shifting abilities of adult participants. Moreover, for each participant we obtained scores on executive control tasks that measured verbal and nonverbal updating, nonverbal inhibiting, and nonverbal shifting. We found that both verbal and nonverbal updating scores correlated with the overall mean picture description RTs. Furthermore, the length effect in the RTs correlated with verbal but not nonverbal updating scores, while the distractor effect correlated with inhibiting scores. We did not find a correlation between the switch effect in the mean RTs and the shifting scores. However, the shifting scores correlated with the switch effect in the normal part of the underlying RT distribution. These results suggest that updating, inhibiting, and shifting each influence the speed of phrase production, thereby demonstrating a contribution of all three executive control abilities to language production.

Simulation of impairment: Commentary on Nickels, Rapp, and Kohnen (2015)

Nickels, L., Rapp, B., and Kohnen, S. (2015. Challenges in the use of treatment to investigate cognition. Cognitive Neuropsychology, 32, 91-103) argue that impairment and treatment may be used to test computational models of cognition. They state that, contrary to their view, the authors of the WEAVER++ model of spoken word production have explicitly rejected simulation of impairment [i.e., Levelt, W. J. M., Roelofs, A., & Meyer, A. S. (1999b). Multiple perspectives on word production. Behavioral and Brain Sciences, 22, 61-69]. Here, I argue that this incorrectly characterizes the position of Levelt et al. Moreover, I further clarify this position, which holds that simulation of impairment requires both a theory of the intact system and assumptions about the underlying deficit, which is a widely accepted view. To demonstrate this position, I outline the approach taken in WEAVER++ simulations of aphasic performance reported in Roelofs, A. (2014. A dorsal-pathway account of aphasic language production: The WEAVER++/ARC model. Cortex, 59, 33-48). These simulations not only prove that the developers of WEAVER++ endorse simulation of impairment, but also highlight the importance of integrating psycholinguistic, functional neuroimaging, and tractographic evidence in testing models of impaired performance.

Challenges in the use of treatment to investigate cognition

The use of data from people with cognitive impairments to inform theories of cognition is an established methodology, particularly in the field of cognitive neuropsychology. However, it is less well known that studies that aim to improve cognitive functioning using treatment can also inform our understanding of cognition. This paper discusses a range of challenges that researchers face when testing theories of cognition and particularly when using treatment as a tool for doing so. It highlights the strengths of treatment methodology for testing causal relations and additionally discusses how generalization of treatment effects can shed light on the nature of cognitive representations and processes. These points are illustrated using examples from the Special Issue of Cognitive Neuropsychology entitled Treatment as a tool for investigating cognition.

Dimensions of similarity in the mental lexicon

During language production planning, multiple candidate representations are implicitly activated prior to articulation. Lexical representations that are phonologically related to the target (phonological neighbors) are known to influence phonetic properties of the target word. However, the question of which dimensions of phonological similarity contribute to such lexical-phonetic effects remains unanswered. In the present study, we reanalyze phonetic data from a previous study, examining the contrasting predictions of different definitions of phonological similarity. Our results suggest that similarity at the level of position-specific phonological segments best predicts the influence of neighbor activation on phonetic properties of initial consonants.

A dorsal-pathway account of aphasic language production: the WEAVER++/ARC model

It has long been assumed that a dorsal pathway running from temporal to inferior frontal cortex underpinned by the left arcuate fasciculus (AF) underlies both repetition and spoken language production. However, according to a recent proposal, a ventral pathway underpinned by extreme capsule (EmC) and uncinate fasciculus (UF) fiber tracts is primarily responsible for language production, whereas the AF primarily underlies repetition. Here, a computational implementation of the dorsal-pathway account of language production is presented, called WEAVER++/ARC (for WEAVER++ Arcuate Repetition and Conversation), which synthesizes behavioral psycholinguistic, functional neuroimaging, and tractographic evidence. The results of computer simulations revealed that the model accounts for the typical patterns of impaired and spared language performance associated with classic acute-onset and progressive aphasias. Moreover, the model accounts for recent evidence that damage to the AF but not the EmC/UF pathway predicts impaired production performance. It is concluded that the results demonstrate the viability of a dorsal-pathway account of language production.

Attention for speaking: domain-general control from the anterior cingulate cortex in spoken word production

Accumulating evidence suggests that some degree of attentional control is required to regulate and monitor processes underlying speaking. Although progress has been made in delineating the neural substrates of the core language processes involved in speaking, substrates associated with regulatory and monitoring processes have remained relatively underspecified. We report the results of an fMRI study examining the neural substrates related to performance in three attention-demanding tasks varying in the amount of linguistic processing: vocal picture naming while ignoring distractors (picture-word interference, PWI); vocal color naming while ignoring distractors (Stroop); and manual object discrimination while ignoring spatial position (Simon task). All three tasks had congruent and incongruent stimuli, while PWI and Stroop also had neutral stimuli. Analyses focusing on common activation across tasks identified a portion of the dorsal anterior cingulate cortex (ACC) that was active in incongruent trials for all three tasks, suggesting that this region subserves a domain-general attentional control function. In the language tasks, this area showed increased activity for incongruent relative to congruent stimuli, consistent with the involvement of domain-general mechanisms of attentional control in word production. The two language tasks also showed activity in anterior-superior temporal gyrus (STG). Activity increased for neutral PWI stimuli (picture and word did not share the same semantic category) relative to incongruent (categorically related) and congruent stimuli. This finding is consistent with the involvement of language-specific areas in word production, possibly related to retrieval of lexical-semantic information from memory. The current results thus suggest that in addition to engaging language-specific areas for core linguistic processes, speaking also engages the ACC, a region that is likely implementing domain-general attentional control.

An integrated theory of language production and comprehension

Currently, production and comprehension are regarded as quite distinct in accounts of language processing. In rejecting this dichotomy, we instead assert that producing and understanding are interwoven, and that this interweaving is what enables people to predict themselves and each other. We start by noting that production and comprehension are forms of action and action perception. We then consider the evidence for interweaving in action, action perception, and joint action, and explain such evidence in terms of prediction. Specifically, we assume that actors construct forward models of their actions before they execute those actions, and that perceivers of others' actions covertly imitate those actions, then construct forward models of those actions. We use these accounts of action, action perception, and joint action to develop accounts of production, comprehension, and interactive language. Importantly, they incorporate well-defined levels of linguistic representation (such as semantics, syntax, and phonology). We show (a) how speakers and comprehenders use covert imitation and forward modeling to make predictions at these levels of representation, (b) how they interweave production and comprehension processes, and (c) how they use these predictions to monitor the upcoming utterances. We show how these accounts explain a range of behavioral and neuroscientific data on language processing and discuss some of the implications of our proposal.

A funny thing happened on the way to articulation: N400 attenuation despite behavioral interference in picture naming

We measured Event-Related Potentials (ERPs) and naming times to picture targets preceded by masked words (stimulus onset asynchrony: 80 ms) that shared one of three different types of relationship with the names of the pictures: (1) Identity related, in which the prime was the name of the picture ("socks" - <picture of socks>), (2) Phonemic Onset related, in which the initial segment of the prime was the same as the name of the picture ("log" - <picture of a leaf>), and (3) Semantically related in which the prime was a co-category exemplar and associated with the name of the picture ("cake" - <picture of a pie>). Each type of related picture target was contrasted with an Unrelated picture target, resulting in a 3×2 design that crossed Relationship Type between the word and the target picture (Identity, Phonemic Onset and Semantic) with Relatedness (Related and Unrelated). Modulation of the N400 component to related (versus unrelated) pictures was taken to reflect semantic processing at the interface between the picture's conceptual features and its lemma, while naming times reflected the end product of all stages of processing. Both attenuation of the N400 and shorter naming times were observed to pictures preceded by Identity related (versus Unrelated) words. No ERP effects within 600 ms, but shorter naming times, were observed to pictures preceded by Phonemic Onset related (versus Unrelated) words. An attenuated N400 (electrophysiological semantic priming) but longer naming times (behavioral semantic interference) were observed to pictures preceded by Semantically related (versus Unrelated) words. These dissociations between ERP modulation and naming times suggest that (a) phonemic onset priming occurred late, during encoding of the articulatory response, and (b) semantic behavioral interference was not driven by competition at the lemma level of representation, but rather occurred at a later stage of production.

Attention demands of spoken word planning: a review

Attention and language are among the most intensively researched abilities in the cognitive neurosciences, but the relation between these abilities has largely been neglected. There is increasing evidence, however, that linguistic processes, such as those underlying the planning of words, cannot proceed without paying some form of attention. Here, we review evidence that word planning requires some but not full attention. The evidence comes from chronometric studies of word planning in picture naming and word reading under divided attention conditions. It is generally assumed that the central attention demands of a process are indexed by the extent that the process delays the performance of a concurrent unrelated task. The studies measured the speed and accuracy of linguistic and non-linguistic responding as well as eye gaze durations reflecting the allocation of attention. First, empirical evidence indicates that in several task situations, processes up to and including phonological encoding in word planning delay, or are delayed by, the performance of concurrent unrelated non-linguistic tasks. These findings suggest that word planning requires central attention. Second, empirical evidence indicates that conflicts in word planning may be resolved while concurrently performing an unrelated non-linguistic task, making a task decision, or making a go/no-go decision. These findings suggest that word planning does not require full central attention. We outline a computationally implemented theory of attention and word planning, and describe at various points the outcomes of computer simulations that demonstrate the utility of the theory in accounting for the key findings. Finally, we indicate how attention deficits may contribute to impaired language performance, such as in individuals with specific language impairment.

Motor movement matters: the flexible abstractness of inner speech

Inner speech is typically characterized as either the activation of abstract linguistic representations or a detailed articulatory simulation that lacks only the production of sound. We present a study of the speech errors that occur during the inner recitation of tongue-twister-like phrases. Two forms of inner speech were tested: inner speech without articulatory movements and articulated (mouthed) inner speech. Although mouthing one's inner speech could reasonably be assumed to require more articulatory planning, prominent theories assume that such planning should not affect the experience of inner speech and, consequently, the errors that are "heard" during its production. The errors occurring in articulated inner speech exhibited the phonemic similarity effect and the lexical bias effect--two speech-error phenomena that, in overt speech, have been localized to an articulatory-feature-processing level and a lexical-phonological level, respectively. In contrast, errors in unarticulated inner speech did not exhibit the phonemic similarity effect--just the lexical bias effect. The results are interpreted as support for a flexible abstraction account of inner speech. This conclusion has ramifications for the embodiment of language and speech and for the theories of speech production.

Attentional control adjustments in Eriksen and Stroop task performance can be independent of response conflict

In the Eriksen flanker and colour-word Stroop tasks, the response time (RT) difference between incongruent and congruent trials is smaller following incongruent trials than following congruent trials: the "Gratton effect" (Gratton, Coles, & Donchin, 1992). According to the prevailing conflict-monitoring theory (Botvinick, Braver, Barch, Carter, & Cohen, 2001), the Gratton effect reflects attentional control adjustment following response conflict on incongruent trials. However, because previous studies compared incongruent and congruent trials, it remains unclear to what extent the Gratton effect is driven by incongruent rather than congruent trials. To resolve this issue, we included neutral trials in addition to incongruent and congruent trials in the Eriksen (Experiment 1) and Stroop (Experiment 2) tasks. Participants responded manually and vocally in both tasks. Moreover, we assessed responding to Stroop stimuli that were preceded by neutral cues or by incongruent- or congruent-predicting cues (Experiment 3). In all three experiments, the RT difference between incongruent and congruent trials was larger for postcongruent trials than for postincongruent and postneutral trials. These findings suggest that control adjustments can be independent of response conflict, challenging conflict-monitoring theory.

Density pervades: an analysis of phonological neighbourhood density effects in aphasic speakers with different types of naming impairment

We investigated the influence of phonological neighbourhood density (PND) on the performance of aphasic speakers whose naming impairments differentially implicate phonological or semantic stages of lexical access. A word comes from a dense phonological neighbourhood if many words sound like it. Limited evidence suggests that higher density facilitates naming in aphasic speakers, as it does in healthy speakers. Using well-controlled stimuli, Experiment 1 confirmed the influence of PND on accuracy and phonological error rates in two aphasic speakers with phonological processing deficits. In Experiments 2 and 3, we extended the investigation to an aphasic speaker who is prone to semantic errors, indicating a semantic deficit and/or a deficit in the mapping from semantics to words. This individual had higher accuracy, and fewer semantic errors, in naming targets from high- than from low-density neighbourhoods. It is argued that the Results provide strong support for interactive approaches to lexical access, where reverberatory feedback between word- and phoneme-level lexical representations not only facilitates phonological level processes but also privileges the selection of a target word over its semantic competitors.

Mrs. Malaprop's Neighborhood: Using Word Errors to Reveal Neighborhood Structure

Many theories of language production and perception assume that in the normal course of processing a word, additional non-target words (lexical neighbors) become active. The properties of these neighbors can provide insight into the structure of representations and processing mechanisms in the language processing system. To infer the properties of neighbors, we examined the non-semantic errors produced in both spoken and written word production by four individuals who suffered neurological injury. Using converging evidence from multiple language tasks, we first demonstrate that the errors originate in disruption to the processes involved in the retrieval of word form representations from long-term memory. The targets and errors produced were then examined for their similarity along a number of dimensions. A novel statistical simulation procedure was developed to determine the significance of the observed similarities between targets and errors relative to multiple chance baselines. The results reveal that in addition to position-specific form overlap (the only consistent claim of traditional definitions of neighborhood structure) the dimensions of lexical frequency, grammatical category, target length and initial segment independently contribute to the activation of non-target words in both spoken and written production. Additional analyses confirm the relevance of these dimensions for word production showing that, in both written and spoken modalities, the retrieval of a target word is facilitated by increasing neighborhood density, as defined by the results of the target-error analyses.

The relation between content and structure in language production: an analysis of speech errors in semantic dementia

In order to explore the impact of a degraded semantic system on the structure of language production, we analysed transcripts from autobiographical memory interviews to identify naturally-occurring speech errors by eight patients with semantic dementia (SD) and eight age-matched normal speakers. Relative to controls, patients were significantly more likely to (a) substitute and omit open class words, (b) substitute (but not omit) closed class words, (c) substitute incorrect complex morphological forms and (d) produce semantically and/or syntactically anomalous sentences. Phonological errors were scarce in both groups. The study confirms previous evidence of SD patients' problems with open class content words which are replaced by higher frequency, less specific terms. It presents the first evidence that SD patients have problems with closed class items and make syntactic as well as semantic speech errors, although these grammatical abnormalities are mostly subtle rather than gross. The results can be explained by the semantic deficit which disrupts the representation of a pre-verbal message, lexical retrieval and the early stages of grammatical encoding.

Mechanisms of interaction in speech production

Many theories predict the presence of interactive effects involving information represented by distinct cognitive processes in speech production. There is considerably less agreement regarding the precise cognitive mechanisms that underlie these interactive effects. For example, are they driven by purely production-internal mechanisms (e.g., Dell, 1986) or do they reflect the influence of perceptual monitoring mechanisms on production processes (e.g., Roelofs, 2004)? Acoustic analyses reveal the phonetic realization of words is influenced by their word-specific properties-supporting the presence of interaction between lexical-level and phonetic information in speech production. A second experiment examines what mechanisms are responsible for this interactive effect. The results suggest the effect occurs on-line and is not purely driven by listener modeling. These findings are consistent with the presence of an interactive mechanism that is online and internal to the production system.

More on Lexical Bias: How Efficient Can a "Lexical Editor" Be?

The lexical bias effect (the tendency for phonological speech errors to create words more often than nonwords) has been debated for over 30 years. One account attributes the effect to a lexical editor, a strategic component of the production system that examines each planned phonological string, and suppresses it if it is a nonword. The alternative explanation is that the effect occurs automatically as a result of phonological-lexical feedback. Using a new paradigm, we explicitly asked participants to do lexical editing on their planned speech and compared performance on this inner lexical decision task to results obtained from the standard lexical decision task in three subsequent experiments. Our experimentally created "lexical editor" needed 300 ms to recognize and suppress nonwords, as determined by comparing reaction times when editing was and was not required. Therefore, we concluded that even though strategic lexical editing can be done, any such editing that occurs in daily speech occurs sporadically, if at all.

Are phonological influences on lexical (mis)selection the result of a monitoring bias?

A monitoring bias account is often used to explain speech error patterns that seem to be the result of an interactive language production system, like phonological influences on lexical selection errors. A biased monitor is suggested to detect and covertly correct certain errors more often than others. For instance, this account predicts that errors that are phonologically similar to intended words are harder to detect than those that are phonologically dissimilar. To test this, we tried to elicit phonological errors under the same conditions as those that show other kinds of lexical selection errors. In five experiments, we presented participants with high cloze probability sentence fragments followed by a picture that was semantically related, a homophone of a semantically related word, or phonologically related to the (implicit) last word of the sentence. All experiments elicited semantic completions or homophones of semantic completions, but none elicited phonological completions. This finding is hard to reconcile with a monitoring bias account and is better explained with an interactive production system. Additionally, this finding constrains the amount of bottom-up information flow in interactive models.

Inner speech slips exhibit lexical bias, but not the phonemic similarity effect

Inner speech, that little voice that people often hear inside their heads while thinking, is a form of mental imagery. The properties of inner speech errors can be used to investigate the nature of inner speech, just as overt slips are informative about overt speech production. Overt slips tend to create words (lexical bias) and involve similar exchanging phonemes (phonemic similarity effect). We examined these effects in inner and overt speech via a tongue-twister recitation task. While lexical bias was present in both inner and overt speech errors, the phonemic similarity effect was evident only for overt errors, producing a significant overtness by similarity interaction. We propose that inner speech is impoverished at lower (featural) levels, but robust at higher (phonemic) levels.

The lexical bias effect in bilingual speech production: evidence for feedback between lexical and sublexical levels across languages

The lexical bias effect (LBE) is the tendency for phonological substitution errors to result in existing words (rather than nonwords) at a rate higher than would be predicted by chance. This effect is often interpreted as revealing feedback between the phonological and lexical levels of representation during speech production. We report two experiments in which we tested for the LBE (1) in second-language production (Experiment 1) and (2) across the two languages of a bilingual (Experiment 2). There was an LBE in both situations. Thus, to the extent that the LBE reveals the presence of interactivity between the phonological and the lexical levels of representation, these effects suggest that there is feedback in second-language production and that it extends across the two languages of a bilingual.

Spoonish spanerisms: A lexical bias effect in Spanish

Lexical bias is the tendency for phonological errors to form existing words at a rate above chance. This effect has been observed in experiments and corpus analyses in Germanic languages, but S. del Viso, J. M. Igoa, and J. E. García-Albea (1991) found no effect in a Spanish corpus study. Because lexical bias plays an important role in the debate on interactivity in language production, the authors reconsidered its absence in Spanish. A corpus analysis, which considered relatively many errors and which used a method of estimating chance rate that is relatively independent of total error number, and a speech-error elicitation experiment provided converging evidence for lexical bias in Spanish. The authors conclude that the processing mechanisms underlying this effect hold cross-linguistically.

Top-down influences on lexical selection during spoken word production: A 4T fMRI investigation of refractory effects in picture naming

Spoken word production is assumed to involve stages of processing in which activation spreads through layers of units comprising lexical-conceptual knowledge and their corresponding phonological word forms. Using high-field (4T) functional magnetic resonance imaging (fMRI), we assessed whether the relationship between these stages is strictly serial or involves cascaded-interactive processing, and whether central (decision/control) processing mechanisms are involved in lexical selection. Participants performed the competitor priming paradigm in which distractor words, named from a definition and semantically related to a subsequently presented target picture, slow picture-naming latency compared to that with unrelated words. The paradigm intersperses two trials between the definition and the picture to be named, temporally separating activation in the word perception and production networks. Priming semantic competitors of target picture names significantly increased activation in the left posterior temporal cortex, and to a lesser extent the left middle temporal cortex, consistent with the predictions of cascaded-interactive models of lexical access. In addition, extensive activation was detected in the anterior cingulate and pars orbitalis of the inferior frontal gyrus. The findings indicate that lexical selection during competitor priming is biased by top-down mechanisms to reverse associations between primed distractor words and target pictures to select words that meet the current goal of speech.

Perceptual uniqueness point effects in monitoring internal speech

Disagreement exists about how speakers monitor their internal speech. Production-based accounts assume that self-monitoring mechanisms exist within the production system, whereas comprehension-based accounts assume that monitoring is achieved through the speech comprehension system. Comprehension-based accounts predict perception-specific effects, like the perceptual uniqueness-point effect, in the monitoring of internal speech. We ran an extensive experiment testing this prediction using internal phoneme monitoring and picture naming tasks. Our results show an effect of the perceptual uniqueness point of a word in internal phoneme monitoring in the absence of such an effect in picture naming. These results support comprehension-based accounts of the monitoring of internal speech.

The spatial and temporal signatures of word production components

This paper presents the results of a comprehensive meta-analysis of the relevant imaging literature on word production (82 experiments). In addition to the spatial overlap of activated regions, we also analyzed the available data on the time course of activations. The analysis specified regions and time windows of activation for the core processes of word production: lexical selection, phonological code retrieval, syllabification, and phonetic/articulatory preparation. A comparison of the word production results with studies on auditory word/non-word perception and reading showed that the time course of activations in word production is, on the whole, compatible with the temporal constraints that perception processes impose on the production processes they affect in picture/word interference paradigms.