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.

Typing expertise in a large student population.

Typing has become a pervasive mode of language production worldwide, with keyboards fully integrated in a large part of many daily activities. The bulk of the literature on typing expertise concerns highly trained professional touch-typists, but contemporary typing skills mostly result from unconstrained sustained practice. We measured the typing performance of a large cohort of 1301 university students through an online platform and followed a preregistered plan to analyse performance distributions, practice factors, and cognitive variables. The results suggest that the standard model with a sharp distinction between novice and expert typists may be inaccurate to account for the performance of the current generation of young typists. More generally, this study shows how the mere frequent use of a new tool can lead to the incidental development of high expertise.

Characterizing multi-word speech production using event-related potentials.

Event-related potentials (ERPs) derived from electroencephalography (EEG) have proven useful for understanding linguistic processes during language perception and production. Words are commonly produced in sequences, yet most ERP studies have used single-word experimental designs. Single-word designs reduce potential ERP overlap in word sequence production. However, word sequence production engages brain mechanisms in different ways than single word production. In particular, speech monitoring and planning mechanisms are more engaged than for single words since several words must be produced in a short period of time. This study evaluates the feasibility of recording ERP components in the context of word sequence production, and whether separate components could be isolated for each word. Scalp EEG data were acquired, while participants recited word sequences from memory at a regular pace, using a tongue-twister paradigm. The results revealed fronto-central error-related negativity, previously associated with speech monitoring, which could be distinguished for each word. Its peak amplitude was sensitive to Cycle and Phonological Similarity. However, an effect of sequential production was also observable on baseline measures, indicating baseline shifts throughout the word sequence due to concurrent sustained medial-frontal EEG activity. We also report a late left anterior negativity (LLAN), associated with verbal response planning and execution, onsetting around 100 ms before the first word in each cycle and sustained throughout the rest of the cycle. This work underlines the importance of considering the contribution of transient and sustained EEG activity on ERPs, and provides evidence that ERPs can be used to study sequential word production.

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.

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.

Tracking Keystroke Sequences at the Cortical Level Reveals the Dynamics of Serial Order Production.

Response selection is often studied by examining single responses, although most actions are performed within an overarching sequence. Understanding processes that order and execute items in a sequence is thus essential to give a complete picture of response selection. In this study, we investigate response selection by comparing single responses and response sequences as well as unimanual and bimanual sequences. We recorded EEG while participants were typing one- or two-keystroke sequences. Irrespective of stimulus modality (visual or auditory), response-locked analysis revealed distinct contralateral and ipsilateral components previously associated with activation and inhibition of alternative responses. Unimanual sequences exhibited a similar activation/inhibition pattern as single responses, but with the activation component of the pattern expressed more strongly, reflecting the fact that the hand will be used for two strokes. In contrast, bimanual sequences were associated with successive activation of each of the corresponding motor cortices controlling each keystroke and no traceable inhibitory component. In short, the activation component of the two-keystroke sequence EEG pattern can be understood from the addition of activation components of single-stroke sequences; the inhibition of the hand not being used is only evidenced when that hand is not planned for the next stroke.

"Twisting fingers": The case for interactivity in typed language production.

Despite the obvious linguistic nature of typing, current psychological models of typing are, to a large extent, divorced from models of spoken language production. This gap has left unanswered many questions regarding the cognitive architecture of typing. In this article we advocate the use of a psycholinguistic framework for studying typing, by showing that such a framework could reveal important similarities and differences between spoken and typed production. Specifically, we investigated the interaction between the lexical and postlexical layers by using a phenomenon known in spoken production as the "repeated-phoneme effect." Participants typed four-word sequences of "finger-twisters" (equivalent to tongue-twisters in spoken production), in which the vowel in the last two words was either repeated (e.g., "fog top") or not (e.g., "fog tip"). We found reliably more migration errors between the consonants of the two typed words when the vowel was repeated, even after the effect of phonology was accounted for. This finding is compatible with an interactive typing system in which postlexical representations send feedback to lexical representations and reveals similar dynamics between spoken and typed production. Additional analyses showed further similarities to spoken production, such as distinct lexical and postlexical error categories, but also revealed that typing errors were much more likely than spoken errors to violate phonotactic constraints. These results provide the first demonstration of feedback between the postlexical and lexical layers in typing, and more generally demonstrate the utility of adopting a psycholinguistic framework tailored specifically to the study of typing.

Word onset phonetic properties and motor artifacts in speech production EEG recordings.

Electrophysiological research using verbal response paradigms faces the problem of muscle artifacts that occur during speech production or in the period preceding articulation. In this context, this paper has two related aims. The first is to show how the nature of the first phoneme influences the alignment of the ERPs. The second is to further characterize the EEG signal around the onset of articulation, both in temporal and frequency domains. Participants were asked to name aloud pictures of common objects. We applied microstate analyses and time-frequency transformations of ERPs locked to vocal onset to compare the EEG signal between voiced and unvoiced labial plosive word onset consonants. We found a delay of about 40 ms in the set of stable topographic patterns for /b/ relative to /p/ onset words. A similar shift was observed in the power increase of gamma oscillations (30-50 Hz), which had an earlier onset for /p/ trials (∼150 ms before vocal onset). This 40-ms shift is consistent with the length of the voiced proportion of the acoustic signal prior to the release of the closure in the vocal responses. These results demonstrate that phonetic features are an important parameter affecting response-locked ERPs, and hence that the onset of the acoustic energy may not be an optimal trigger for synchronizing the EEG activity to the response in vocal paradigms. The indexes explored in this study provide a step forward in the characterization of muscle-related artifacts in electrophysiological studies of speech and language production.

Response retrieval and motor planning during typing.

Recent work in language production research suggests complex relationships between linguistic and motor processes. Typing is an interesting candidate for investigating further this issue. First, typing presumably relies on the same distributed left-lateralized brain network as handwriting and speech production. Second, typing has its own set of highly specific motor constraints, such as internal keystroke representations that hold information about both letter identity and spatial characteristics of the key to strike. The present study aims to further develop research on typed production, by targeting the dynamics between linguistic and motor neural networks. Specifically, we used a typed picture-naming task to examine the interplay between response retrieval and motor planning. To track processes associated with both linguistic processing and keystroke representation, we manipulated, respectively, the semantic context in which the target appeared and the side of the first keystrokes of the word. We recorded high-density electroencephalography (EEG) continuously from the presentation of a picture, to the typing of its name, and computed both event-related potentials (ERP) and beta-band power analyses. Non-parametric data-driven analysis revealed a clear pattern of response preparation over both hemispheres close to response time, in both the ERP and beta-band power modulations. This was preceded by a left-lateralized power decrease in the beta-band, presumably representing memory retrieval, and an early contrast in ERP, between left and right keystrokes' preparation. We discuss these results in terms of a dynamic access approach for internal keystroke representations, and argue for an integrative rather than separatist view of linguistic and motor processes.

Typing is writing: Linguistic properties modulate typing execution.

Typing is becoming our preferred way of writing. Perhaps because of the relative recency of this change, very few studies have investigated typing from a psycholinguistic perspective. In addition, and despite obvious similarities between typing and handwriting, typing research has remained rather disconnected from handwriting research. The current study aimed at bridging this gap by evaluating how typing is affected by a number of psycholinguistic variables defined at the word, syllable, and letter levels. In a writing-to-dictation task, we assessed typing performance by measuring response accuracy, onset latencies - an index of response preparation and initiation - and interkeystroke intervals (IKIs) - an index of response execution processes. The lexical and sublexical factors revealed a composite pattern of effects. Lexical frequency improved response latencies and accuracy, while bigram frequency speeded up IKIs. Sound-spelling consistency improved latencies, but had an inhibitory effect on IKI. IKIs were also longer at syllable boundaries. Together, our findings can be fit within a framework for typed production that combines the previously developed theories of spelling and typing execution. At their interface, we highlight the need for an intermediate hierarchical stage, perhaps in the form of a graphemic buffer for typing.

"When" Does Picture Naming Take Longer Than Word Reading?

Differences between the cognitive processes involved in word reading and picture naming are well established (e.g., visual or lexico-semantic stages). Still, it is commonly thought that retrieval of phonological forms is shared across tasks. We report a test of this second hypothesis based on the time course of electroencephalographic (EEG) neural activity, reasoning that similar EEG patterns might index similar processing stages. Seventeen participants named objects and read aloud the corresponding words while their behavior and EEG activity were recorded. The latter was analyzed from stimulus onset onward (stimulus-locked analysis) and from response onset backward (response-locked analysis), using non-parametric statistics and the spatio-temporal segmentation of ERPs. Behavioral results confirmed that reading entails shorter latencies than naming. The analysis of EEG activity within the stimulus-to-response period allowed to distinguish three phases, broadly successive. Early on, we observed identical distribution of electric field potentials (i.e., topographies) albeit with large amplitude divergences between tasks. Then, we observed sustained cross-task differences in topographies accompanied by extended amplitude differences. Finally, the two tasks again revealed the same topographies, with significant cross-task delays in their onsets and offsets, and still significant amplitude differences. In the response-locked ERPs, the common topography displayed an offset closer to response articulation in word reading compared with picture naming, that is the transition between the offset of this shared map and the onset of articulation was significantly faster in word reading. The results suggest that the degree of cross-task similarity varies across time. The first phase suggests similar visual processes of variable intensity and time course across tasks, while the second phase suggests marked differences. Finally, similarities and differences within the third phase are compatible with a shared processing stage (likely phonological processes) with different temporal properties (onset/offset) across tasks. Overall, our results provide an overview of when, between stimulus and response, word reading and picture naming are subtended by shared- versus task-specific neural signatures. This in turn is suggestive of when the two tasks involve similar vs. different cognitive processes.

Response planning in word typing: evidence for inhibition.

Typing is a pervasive phenomenon, yet the underlying neural processes have hardly been studied. Here, the mechanisms of keystroke preparation were studied with a typed picture-naming task performed by expert typists. Electroencephalographic activities recorded over sensorimotor areas prior to first-keystroke onset were examined with time-frequency and event-related potential (ERP) analyses. In the time-frequency domain, a beta event-related desynchronization was present bilaterally. In the ERP analyses, the activity was asymmetric, with negativity and positivity patterns developing over, respectively, contra- and ipsilateral recording sites. This pattern is similar to that observed in choice reaction time tasks, and thus can be interpreted as evidence of contralateral motor cortex activation accompanied by inhibition of the ipsilateral motor cortex. These data constitute the first electrophysiological demonstration of inhibitory activity in typing and pave the way to a thorough study of typing.