The time course of contextual effects on visual word recognition

Understanding words in context: A naturalistic EEG study of children's lexical processing

When listening to speech, adults rely on context to anticipate upcoming words. Evidence for this comes from studies demonstrating that the N400, an event-related potential (ERP) that indexes ease of lexical-semantic processing, is influenced by the predictability of a word in context. We know far less about the role of context in children's speech comprehension. The present study explored lexical processing in adults and 5-10-year-old children as they listened to a story. ERPs time-locked to the onset of every word were recorded. Each content word was coded for frequency, semantic association, and predictability. In both children and adults, N400s reflect word predictability, even when controlling for frequency and semantic association. These findings suggest that both adults and children use top-down constraints from context to anticipate upcoming words when listening to stories.

Current exposure to a second language modulates bilingual visual word recognition: An EEG study

Bilingual word recognition has been the focus of much empirical work, but research on potential modulating factors, such as individual differences in L2 exposure, are limited. This study represents a first attempt to determine the impact of L2-exposure on bilingual word recognition in both languages. To this end, highly fluent bilinguals were split into two groups according to their L2-exposure, and performed a semantic categorisation task while recording their behavioural responses and electro-cortical (EEG) signal. We predicted that lower L2-exposure should produce less efficient L2 word recognition processing at the behavioural level, alongside neurophysiological changes at the early pre-lexical and lexical levels, but not at a post-lexical level. Results confirmed this hypothesis in accuracy and in the N1 component of the EEG signal. Precisely, bilinguals with lower L2-exposure appeared less accurate in determining semantic relatedness when target words were presented in L2, but this condition posed no such problem for bilinguals with higher L2-exposure. Moreover, L2-exposure modulates early processes of word recognition not only in L2 but also in L1 brain activity, thus challenging a fully non-selective access account (cf. BIA + model, Dijkstra and van Heuven, 2002). We interpret our findings with reference to the frequency-lag hypothesis (Gollan et al., 2011).

Predictive pre-activation of orthographic and lexical-semantic representations facilitates visual word recognition

To a crucial extent, the efficiency of reading results from the fact that visual word recognition is faster in predictive contexts. Predictive coding models suggest that this facilitation results from pre-activation of predictable stimulus features across multiple representational levels before stimulus onset. Still, it is not sufficiently understood which aspects of the rich set of linguistic representations that are activated during reading-visual, orthographic, phonological, and/or lexical-semantic-contribute to context-dependent facilitation. To investigate in detail which linguistic representations are pre-activated in a predictive context and how they affect subsequent stimulus processing, we combined a well-controlled repetition priming paradigm, including words and pseudowords (i.e., pronounceable nonwords), with behavioral and magnetoencephalography measurements. For statistical analysis, we used linear mixed modeling, which we found had a higher statistical power compared to conventional multivariate pattern decoding analysis. Behavioral data from 49 participants indicate that word predictability (i.e., context present vs. absent) facilitated orthographic and lexical-semantic, but not visual or phonological processes. Magnetoencephalography data from 38 participants show sustained activation of orthographic and lexical-semantic representations in the interval before processing the predicted stimulus, suggesting selective pre-activation at multiple levels of linguistic representation as proposed by predictive coding. However, we found more robust lexical-semantic representations when processing predictable in contrast to unpredictable letter strings, and pre-activation effects mainly resembled brain responses elicited when processing the expected letter string. This finding suggests that pre-activation did not result in "explaining away" predictable stimulus features, but rather in a "sharpening" of brain responses involved in word processing.

Clinical applications of neurolinguistics in neurosurgery

The protection of language function is one of the major challenges of brain surgery. Over the past century, neurosurgeons have attempted to seek the optimal strategy for the preoperative and intraoperative identification of language-related brain regions. Neurosurgeons have investigated the neural mechanism of language, developed neurolinguistics theory, and provided unique evidence to further understand the neural basis of language functions by using intraoperative cortical and subcortical electrical stimulation. With the emergence of modern neuroscience techniques and dramatic advances in language models over the last 25 years, novel language mapping methods have been applied in the neurosurgical practice to help neurosurgeons protect the brain and reduce morbidity. The rapid advancements in brain-computer interface have provided the perfect platform for the combination of neurosurgery and neurolinguistics. In this review, the history of neurolinguistics models, advancements in modern technology, role of neurosurgery in language mapping, and modern language mapping methods (including noninvasive neuroimaging techniques and invasive cortical electroencephalogram) are presented.

EEG-based Identification of Evidence Accumulation Stages in Decision-Making

Dating back to the 19th century, the discovery of processing stages has been of great interest to researchers in cognitive science. The goal of this paper is to demonstrate the validity of a recently developed method, hidden semi-Markov model multivariate pattern analysis (HsMM-MVPA), for discovering stages directly from EEG data, in contrast to classical reaction-time-based methods. To test the validity of stages discovered with the HsMM-MVPA method, we applied it to two relatively simple tasks where the interpretation of processing stages is straightforward. In these visual discrimination EEG data experiments, perceptual processing and decision difficulty were manipulated. The HsMM-MVPA revealed that participants progressed through five cognitive processing stages while performing these tasks. The brain activation of one of those stages was dependent on perceptual processing, whereas the brain activation and the duration of two other stages were dependent on decision difficulty. In addition, evidence accumulation models (EAMs) were used to assess to what extent the results of HsMM-MVPA are comparable to standard reaction-time-based methods. Consistent with the HsMM-MVPA results, EAMs showed that nondecision time varied with perceptual difficulty and drift rate varied with decision difficulty. Moreover, nondecision and decision time of the EAMs correlated highly with the first two and last three stages of the HsMM-MVPA, respectively, indicating that the HsMM-MVPA gives a more detailed description of stages discovered with this more classical method. The results demonstrate that cognitive stages can be robustly inferred with the HsMM-MVPA.

Word's Contextual Predictability and Its Character Frequency Effects in Chinese Reading: Evidence From Eye Movements

The present study sought to establish how a word's contextual predictability impacts the early stages of word processing when reading Chinese. Two eye-movement experiments were conducted in which the predictability of the target two-character word was manipulated; the frequency of the target's initial character was manipulated in Experiment 1, as was the target's end character frequency in Experiment 2. No reliable interaction effect of predictability with initial character frequency was observed in Experiment 1. Reliable interactions of word predictability with end character frequency were observed in Experiment 2. The end character frequency effects, in which the words with high-frequency end characters were fixated for a shorter time and re-fixated less often, were only observed when reading unpredictable words. Reliable interactions were also observed with incoming saccade length, as high-frequency end character words elicited longer saccades to themselves than low-frequency end character words when reading predictable words. The effects of pervasive predictability on measures of fixation time, probability, and saccade length were noted in both experiments. Our findings suggest that a word's contextual predictability facilitates the processing of its constituent characters.

Studying brain activity during word-by-word interactions using wireless EEG

We introduce here the word-by-word paradigm, a dynamic setting, in which two people take turns in producing a single sentence. This task requires a high degree of coordination between the partners and the simplicity of the task allows us to study with sufficient experimental control behavioral and neural processes that underlie this controlled interaction. For this study, 13 pairs of individuals engaged in a scripted word-by-word interaction, while we recorded the neural activity of both participants simultaneously using wireless EEG. To study expectation building, different semantic contexts were primed for each participant. Semantically unexpected continuations were introduced in 25% of all sentences. In line with the hypothesis, we observed amplitude differences for the P200-N400-P600 ERPs for unexpected compared to expected words. Moreover, we could successfully assess speech and reaction times. Our results show that it is possible to measure ERPs and RTs to semantically unexpected words in a dyadic interactive scenario.

(Early) context effects on event-related potentials over natural inputs

Language understanding requires the integration of the input with preceding context. Event-related potentials (ERPs) have contributed significantly to our understanding of what contextual information is accessed and when. Much of this research has, however, been limited to experimenter-designed stimuli with highly atypical lexical and context statistics. This raises questions about the extent to which previous findings generalize to everyday language processing of natural stimuli with typical linguistic statistics. We ask whether context can affect ERPs over natural stimuli early, before the N400 time window. We re-analyzed a data set of ERPs over ~700 visually presented content words in sentences from English novels. To increase power, we employed linear mixed effects regression simultaneously modeling random variance by subject and by item. To reduce concerns about Type I error inflation common to any type of time series analysis, we introduced a simple approach to model and discount auto-correlations at multiple, empirically determined, time lags. We compared this approach to Bonferroni correction. Planned follow-up analyses used Generalized Additive Mixture Models to assess the linearity of contextual effects, including lexical surprisal, found within the N400 time window. We found that contextual information affects ERPs in both early (~200ms after word onset) and late (N400) time windows, supporting a cascading, interactive account of lexical access.

Modulation of parafoveal word processing by cognitive load during modified visual search tasks

During visual search for simple items, the amount of information that can be processed in parafoveal vision depends on the cognitive resources that are available. However, whether this applies to the semantic processing of words remains controversial. This work was designed to manipulate simultaneously two sources of cognitive load to study their impact on the depth of parafoveal word processing during a modified visual search task. The participants had to search for target words among parafoveally presented semantic, orthographic or target-unrelated distractor words while their electroencephalogram was recorded. The task-related load was manipulated by either giving target words in advance (literal task) or giving only a semantic clue to define them (categorical task). The foveal load was manipulated by displaying either a word or hash symbols at the centre of the screen. Parafoveal orthographic and semantic distractors had an impact on the early event-related potential component P2a only in the literal task and when hash symbols were displayed at the fovea, i.e., when both the task-related and foveal loads were low. The data show that all sources of cognitive load must be considered to understand how parafoveal words are processed in visual search contexts.

Co-registration of eye movements and neuroimaging for studying contextual predictions in natural reading

Sixteen years ago, Sereno and Rayner (2003. Measuring word recognition in reading: eye movements and event-related potentials. Trends in Cognitive Sciences, 7(11), 489-493) illustrated how "by means of review and comparison" eye movement (EM) and event-related potential (ERP) studies may advance our understanding of visual word recognition. Attempts to simultaneously record EMs and ERPs soon followed. Recently, this co-registration approach has also been transferred to fMRI and oscillatory EEG. With experimental settings close to natural reading, co-registration enables us to directly integrate insights from EM and neuroimaging studies. This should extend current experimental paradigms by moving the field towards studying sentence-level processing including effects of context and parafoveal preview. This article will introduce the basic principles and applications of co-registration and selectively review how this approach may shed light on one of the most controversially discussed issues in reading research, contextual predictions in online language processing.

Context-Based Facilitation in Visual Word Recognition: Evidence for Visual and Lexical But Not Pre-Lexical Contributions

Word familiarity and predictive context facilitate visual word processing, leading to faster recognition times and reduced neuronal responses. Previously, models with and without top-down connections, including lexical-semantic, pre-lexical (e.g., orthographic/phonological), and visual processing levels were successful in accounting for these facilitation effects. Here we systematically assessed context-based facilitation with a repetition priming task and explicitly dissociated pre-lexical and lexical processing levels using a pseudoword (PW) familiarization procedure. Experiment 1 investigated the temporal dynamics of neuronal facilitation effects with magnetoencephalography (MEG; N = 38 human participants), while experiment 2 assessed behavioral facilitation effects (N = 24 human participants). Across all stimulus conditions, MEG demonstrated context-based facilitation across multiple time windows starting at 100 ms, in occipital brain areas. This finding indicates context-based facilitation at an early visual processing level. In both experiments, we furthermore found an interaction of context and lexical familiarity, such that stimuli with associated meaning showed the strongest context-dependent facilitation in brain activation and behavior. Using MEG, this facilitation effect could be localized to the left anterior temporal lobe at around 400 ms, indicating within-level (i.e., exclusively lexical-semantic) facilitation but no top-down effects on earlier processing stages. Increased pre-lexical familiarity (in PWs familiarized utilizing training) did not enhance or reduce context effects significantly. We conclude that context-based facilitation is achieved within visual and lexical processing levels. Finally, by testing alternative hypotheses derived from mechanistic accounts of repetition suppression, we suggest that the facilitatory context effects found here are implemented using a predictive coding mechanism.

Is There a Processing Preference for Object Relative Clauses in Chinese? Evidence From ERPs

A consistent finding across head-initial languages, such as English, is that subject relative clauses (SRCs) are easier to comprehend than object relative clauses (ORCs). However, several studies in Mandarin Chinese, a head-final language, revealed the opposite pattern, which might be modulated by working memory (WM) as suggested by recent results from self-paced reading performance. In the present study, event-related potentials (ERPs) were recorded when participants with high and low WM spans (measured by forward digit span and operation span tests) read Chinese ORCs and SRCs. The results revealed an N400-P600 complex elicited by ORCs on the relativizer, whose magnitude was modulated by the WM span. On the other hand, a P600 effect was elicited by SRCs on the head noun, whose magnitude was not affected by the WM span. These findings paint a complex picture of relative clause processing in Chinese such that opposing factors involving structural ambiguities and integration of filler-gap dependencies influence processing dynamics in Chinese relative clauses.

Event Related Potential Study of Language Interaction in Bilingual Aphasia Patients

Half of the global population can be considered bilingual. Nevertheless when faced with patients with aphasia, clinicians and therapists usually ignore the patient's second language (L2) albeit its interference in first language (L1) processing has been shown. The excellent temporal resolution by which each individual linguistic component can be gaged during word-processing, promoted the event-related potential (ERP) technique for studying language processing in healthy bilinguals and monolingual aphasia patients. However, this technique has not yet been applied in the context of bilingual aphasia. In the current study, we report on L2 interference in L1 processing using the ERP technique in bilingual aphasia. We tested four bilingual- and one trilingual patients with aphasia, as well as several young and older (age-matched with patients) healthy subjects as controls. We recorded ERPs when subjects were engaged in a semantic association judgment task on 122 related and 122 unrelated Dutch word-pairs (prime and target words). In 61 related and 61 unrelated word-pairs, an inter-lingual homograph was used as prime. In these word-pairs, when the target was unrelated to the prime in Dutch (L1), it was associated to the English (L2) meaning of the homograph. Results showed a significant effect of homograph use as a prime on early and/or late ERPs in response to word-pairs related in Dutch or English. Each patient presented a unique pattern of L2 interference in L1 processing as reflected by his/her ERP image. These interferences depended on the patient's pre- and post-morbid L2 proficiency. When the proficiency was high, the L2 interference in L1 processing was higher. Furthermore, the mechanism of interference in patients that were pre-morbidly highly proficient in L2 additionally depended on the frequency of pre-morbid L2 exposure. In summary, we showed that the mechanism behind L2 interference in L1 processing in bilingual patients with aphasia depends on a complex interaction between pre- and post-morbid L2 proficiency, pre- and post-morbid L2 exposure, impairment and the presented stimulus (inter-lingual homographs). Our ERP study complements the usually adopted behavioral approach by providing new insights into language interactions on the level of individual linguistic components in bilingual patients with aphasia.

Sweet-cheeks vs. pea-brain: embodiment, valence, and task all influence the emotional salience of language

Previous research has found that more embodied insults (e.g. numbskull) are identified faster and more accurately than less embodied insults (e.g. idiot). The linguistic processing of embodied compliments has not been well explored. In the present study, participants completed two tasks where they identified insults and compliments, respectively. Half of the stimuli were more embodied than the other half. We examined the late positive potential (LPP) component of event-related potentials in early (400-500 ms), middle (500-600 ms), and late (600-700 ms) time windows. Increased embodiment resulted in improved response accuracy to compliments in both tasks, whereas it only improved accuracy for insults in the compliment detection task. More embodied stimuli elicited a larger LPP than less embodied stimuli in the early time window. Insults generated a larger LPP in the late time window in the insult task; compliments generated a larger LPP in the early window in the compliment task. These results indicate that electrophysiological correlates of emotional language perception are sensitive to both top-down and bottom-up processes.

The N400 Effect during Speaker-Switch-Towards a Conversational Approach of Measuring Neural Correlates of Language

Language occurs naturally in conversations. However, the study of the neural underpinnings of language has mainly taken place in single individuals using controlled language material. The interactive elements of a conversation (e.g., turn-taking) are often not part of neurolinguistic setups. The prime reason is the difficulty to combine open unrestricted conversations with the requirements of neuroimaging. It is necessary to find a trade-off between the naturalness of a conversation and the restrictions imposed by neuroscientific methods to allow for ecologically more valid studies. Here, we make an attempt to study the effects of a conversational element, namely turn-taking, on linguistic neural correlates, specifically the N400 effect. We focus on the physiological aspect of turn-taking, the speaker-switch, and its effect on the detectability of the N400 effect. The N400 event-related potential reflects expectation violations in a semantic context; the N400 effect describes the difference of the N400 amplitude between semantically expected and unexpected items. Sentences with semantically congruent and incongruent final words were presented in two turn-taking modes: (1) reading aloud first part of the sentence and listening to speaker-switch for the final word, and (2) listening to first part of the sentence and speaker-switch for the final word. A significant N400 effect was found for both turn-taking modes, which was not influenced by the mode itself. However, the mode significantly affected the P200, which was increased for the reading aloud mode compared to the listening mode. Our results show that an N400 effect can be detected during a speaker-switch. Speech articulation (reading aloud) before the analyzed sentence fragment did also not impede the N400 effect detection for the final word. The speaker-switch, however, seems to influence earlier components of the electroencephalogram, related to processing of salient stimuli. We conclude that the N400 can effectively be used to study neural correlates of language in conversational approaches including speaker-switches.

When "He" Can Also Be "She": An ERP Study of Reflexive Pronoun Resolution in Written Mandarin Chinese

The gender information in written Chinese third person pronouns is not symmetrically encoded: the character for "he" (, with semantic radical , meaning human) is used as a default referring to every individual, while the character for "she" (, with semantic radical , meaning woman) indicates females only. This critical feature could result in different patterns of processing of gender information in text, but this is an issue that has seldom been addressed in psycholinguistics. In Chinese, the written forms of the reflexive pronouns are composed of a pronoun plus the reflexive "/self" (/himself and /herself). The present study focuses on how such gender specificity interacts with the gender type of an antecedent, whether definitional (proper name) or stereotypical (stereotypical role noun) during reflexive pronoun resolution. In this event-related potential (ERP) study, gender congruity between a reflexive pronoun and its antecedent was studied by manipulating the gender type of antecedents and the gender specificity of reflexive pronouns (default: /himself vs. specific: /herself). Results included a P200 "attention related" congruity effect for /himself and a P600 "integration difficulty" congruity effect for /herself. Reflexive pronoun specificity independently affected the P200 and N400 components. These results highlight the role of /himself as a default applicable to both genders and indicate that only the processing of /herself supports a two-stage model for anaphor resolution. While both reflexive pronouns are evaluated at the bonding stage, the processing of the gender-specific reflexive pronoun is completed in the resolution stage.

Form-to-expectation matching effects on first-pass eye movement measures during reading

Recent Electroencephalography/Magnetoencephalography (EEG/MEG) studies suggest that when contextual information is highly predictive of some property of a linguistic signal, expectations generated from context can be translated into surprisingly low-level estimates of the physical form-based properties likely to occur in subsequent portions of the unfolding signal. Whether form-based expectations are generated and assessed during natural reading, however, remains unclear. We monitored eye movements while participants read phonologically typical and atypical nouns in noun-predictive contexts (Experiment 1), demonstrating that when a noun is strongly expected, fixation durations on first-pass eye movement measures, including first fixation duration, gaze duration, and go-past times, are shorter for nouns with category typical form-based features. In Experiments 2 and 3, typical and atypical nouns were placed in sentential contexts normed to create expectations of variable strength for a noun. Context and typicality interacted significantly at gaze duration. These results suggest that during reading, form-based expectations that are translated from higher-level category-based expectancies can facilitate the processing of a word in context, and that their effect on lexical processing is graded based on the strength of category expectancy.

Task-dependent modulation of word processing mechanisms during modified visual search tasks

During visual search for words, the impact of the visual and semantic features of words varies as a function of the search task. This event-related potential (ERP) study focused on the way these features of words are used to detect similarities between the distractor words that are glanced at and the target word, as well as to then reject the distractor words. The participants had to search for a target word that was either given literally or defined by a semantic clue among words presented sequentially. The distractor words included words that resembled the target and words that were semantically related to the target. The P2a component was the first component to be modulated by the visual and/or semantic similarity of distractors to the target word, and these modulations varied according to the task. The same held true for the later N300 and N400 components, which confirms that, depending on the task, distinct processing pathways were sensitized through attentional modulation. Hence, the process that matches what is perceived with the target acts during the first 200 ms after word presentation, and both early detection and late rejection processes of words depend on the search task and on the representation of the target stored in memory.

Beyond the N400: complementary access to early neural correlates of novel metaphor comprehension using combined electrophysiological and haemodynamic measurements

The simultaneous application of different neuroimaging methods combining high temporal and spatial resolution can uniquely contribute to current issues and open questions in the field of pragmatic language perception. In the present study, comprehension of novel metaphors was investigated using near-infrared spectroscopy (NIRS) combined with the simultaneous acquisition of electroencephalography (EEG)/event-related potentials (ERPs). For the first time, we investigated the effects of figurative language on early electrophysiological markers (P200, N400) and their functional relationship to cortical haemodynamic responses within the language network (Broca's area, Wernicke's area). To this end, 20 healthy subjects judged 120 sentences with respect to their meaningfulness, whereby phrases were either literal, metaphoric, or meaningless. Our results indicated a metaphor-specific P200 reduction and a linear increase of N400 amplitudes from literal over metaphoric to meaningless sentences. Moreover, there were metaphor related effects on haemodynamic responses accessed with NIRS, especially within the left lateral frontal cortex (Broca's area). Significant correlations between electrophysiological and haemodynamic responses indicated that P200 reductions during metaphor comprehension were associated with an increased recruitment of neural activity within left Wernicke's area, indicating a link between variations in neural activity and haemodynamic changes within Wernicke's area. This link may reflect processes related to interindividual differences regarding the ability to classify novel metaphors. The present study underlines the usefulness of simultaneous NIRS measurements in language paradigms - especially for investigating the functional significance of neurophysiological markers that have so far been rarely examined - as these measurements are easily and efficiently realizable and allow for a complementary examination of neural activity and associated metabolic changes in cortical areas.

Decision-making in information seeking on texts: an eye-fixation-related potentials investigation

Reading on a web page is known to be not linear and people need to make fast decisions about whether they have to stop or not reading. In such context, reading, and decision-making processes are intertwined and this experiment attempts to separate them through electrophysiological patterns provided by the Eye-Fixation-Related Potentials technique (EFRPs). We conducted an experiment in which EFRPs were recorded while participants read blocks of text that were semantically highly related, moderately related, and unrelated to a given goal. Participants had to decide as fast as possible whether the text was related or not to the semantic goal given at a prior stage. Decision making (stopping information search) may occur when the paragraph is highly related to the goal (positive decision) or when it is unrelated to the goal (negative decision). EFRPs were analyzed on and around typical eye fixations: either on words belonging to the goal (target), subjected to a high rate of positive decisions, or on low frequency unrelated words (incongruent), subjected to a high rate of negative decisions. In both cases, we found EFRPs specific patterns (amplitude peaking between 51 to 120 ms after fixation onset) spreading out on the next words following the goal word and the second fixation after an incongruent word, in parietal and occipital areas. We interpreted these results as delayed late components (P3b and N400), reflecting the decision to stop information searching. Indeed, we show a clear spill-over effect showing that the effect on word N spread out on word N + 1 and N + 2.

Automatic processing of unattended lexical information in visual oddball presentation: neurophysiological evidence

Previous electrophysiological studies of automatic language processing revealed early (100–200 ms) reflections of access to lexical characteristics of speech signal using the so-called mismatch negativity (MMN), a negative ERP deflection elicited by infrequent irregularities in unattended repetitive auditory stimulation. In those studies, lexical processing of spoken stimuli became manifest as an enhanced ERP in response to unattended real words, as opposed to phonologically matched but meaningless pseudoword stimuli. This lexical ERP enhancement was explained by automatic activation of word memory traces realized as distributed strongly intra-connected neuronal circuits, whose robustness guarantees memory trace activation even in the absence of attention on spoken input. Such an account would predict the automatic activation of these memory traces upon any presentation of linguistic information, irrespective of the presentation modality. As previous lexical MMN studies exclusively used auditory stimulation, we here adapted the lexical MMN paradigm to investigate early automatic lexical effects in the visual modality. In a visual oddball sequence, matched short word and pseudoword stimuli were presented tachistoscopically in perifoveal area outside the visual focus of attention, as the subjects' attention was concentrated on a concurrent non-linguistic visual dual task in the center of the screen. Using EEG, we found a visual analogue of the lexical ERP enhancement effect, with unattended written words producing larger brain response amplitudes than matched pseudowords, starting at ~100 ms. Furthermore, we also found significant visual MMN, reported here for the first time for unattended perifoveal lexical stimuli. The data suggest early automatic lexical processing of visually presented language which commences rapidly and can take place outside the focus of attention.