Bridging Stories and Science: An fNIRS-based hyperscanning investigation into child learning in STEM

Early STEM education is crucial for later learning. This novel study utilised fNIRS to examine how STEM teaching methods (i.e., traditional, storytelling, storyboarding) affect neural activity synchronisation between teachers and students. Our results showed that left and right inferior frontal gyrus (IFG) for storytelling teaching versus traditional teaching, superior temporal gyrus for storyboard teaching versus traditional teaching, and left angular gyrus for storyboard and storytelling teaching were significant different in brain synchronisation. In the storytelling teaching condition, left supramarginal gyrus brain synchrony was found to improve STEM learning outcomes. In the storyboard teaching condition, IFG brain synchrony correlated positively with STEM learning improvement. The findings confirmed that story-based teaching and storyboarding can improve STEM learning efficacy at the neural level and unscored the significant role of neural synchronization as a predictor of learning outcomes.

The myth of categorical perception

Categorical perception (CP) is likely the single finding from speech perception with the biggest impact on cognitive science. However, within speech perception, it is widely known to be an artifact of task demands. CP is empirically defined as a relationship between phoneme identification and discrimination. As discrimination tasks do not appear to require categorization, this was thought to support the claim that listeners perceive speech solely in terms of linguistic categories. However, 50 years of work using discrimination tasks, priming, the visual world paradigm, and event related potentials has rejected the strongest forms of CP and provided little strong evidence for any form of it. This paper reviews the origins and impact of this scientific meme and the work challenging it. It discusses work showing that the encoding of auditory input is largely continuous, not categorical, and describes the modern theoretical synthesis in which listeners preserve fine-grained detail to enable more flexible processing. This synthesis is fundamentally inconsistent with CP. This leads to a different understanding of how to use and interpret the most basic paradigms in speech perception-phoneme identification along a continuum-and has implications for understanding language and hearing disorders, development, and multilingualism.

A Theoretical Framework for Human and Nonhuman Vocal Interaction

Vocal communication is a critical feature of social interaction across species; however, the relation between such behavior in humans and nonhumans remains unclear. To enable comparative investigation of this topic, we review the literature pertinent to interactive language use and identify the superset of cognitive operations involved in generating communicative action. We posit these functions comprise three intersecting multistep pathways: (a) the Content Pathway, which selects the movements constituting a response; (b) the Timing Pathway, which temporally structures responses; and (c) the Affect Pathway, which modulates response parameters according to internal state. These processing streams form the basis of the Convergent Pathways for Interaction framework, which provides a conceptual model for investigating the cognitive and neural computations underlying vocal communication across species.

The time course of normalizing speech variability in vowels

To achieve perceptual constancy, listeners utilize contextual cues to normalize speech variabilities in speakers. The present study tested the time course of this cognitive process with an event-related potential (ERP) experiment. The first neurophysiological evidence of speech normalization is observed in P2 (130-250 ms), which is functionally related to phonetic and phonological processes. Furthermore, the normalization process was found to ease lexical retrieval, as indexed by smaller N400 (350-470 ms) after larger P2. A cross-language vowel perception task was carried out to further specify whether normalization was processed in the phonetic and/or phonological stage(s). It was found that both phonetic and phonological cues in the speech context contributed to vowel normalization. The results suggest that vowel normalization in the speech context can be observed in the P2 time window and largely overlaps with phonetic and phonological processes.

Lexical Influences on Categorical Speech Perception Are Driven by a Temporoparietal Circuit

Categorical judgments of otherwise identical phonemes are biased toward hearing words (i.e., "Ganong effect") suggesting lexical context influences perception of even basic speech primitives. Lexical biasing could manifest via late stage postperceptual mechanisms related to decision or, alternatively, top-down linguistic inference that acts on early perceptual coding. Here, we exploited the temporal sensitivity of EEG to resolve the spatiotemporal dynamics of these context-related influences on speech categorization. Listeners rapidly classified sounds from a /gɪ/-/kɪ/ gradient presented in opposing word-nonword contexts (GIFT-kift vs. giss-KISS), designed to bias perception toward lexical items. Phonetic perception shifted toward the direction of words, establishing a robust Ganong effect behaviorally. ERPs revealed a neural analog of lexical biasing emerging within ~200 msec. Source analyses uncovered a distributed neural network supporting the Ganong including middle temporal gyrus, inferior parietal lobe, and middle frontal cortex. Yet, among Ganong-sensitive regions, only left middle temporal gyrus and inferior parietal lobe predicted behavioral susceptibility to lexical influence. Our findings confirm lexical status rapidly constrains sublexical categorical representations for speech within several hundred milliseconds but likely does so outside the purview of canonical auditory-sensory brain areas.

Decoding of single-trial EEG reveals unique states of functional brain connectivity that drive rapid speech categorization decisions

OBJECTIVE

Categorical perception (CP) is an inherent property of speech perception. The response time (RT) of listeners' perceptual speech identification is highly sensitive to individual differences. While the neural correlates of CP have been well studied in terms of the regional contributions of the brain to behavior, functional connectivity patterns that signify individual differences in listeners' speed (RT) for speech categorization is less clear. In this study, we introduce a novel approach to address these questions.

APPROACH

We applied several computational approaches to the EEG, including graph mining, machine learning (i.e., support vector machine), and stability selection to investigate the unique brain states (functional neural connectivity) that predict the speed of listeners' behavioral decisions.

MAIN RESULTS

We infer that (i) the listeners' perceptual speed is directly related to dynamic variations in their brain connectomics, (ii) global network assortativity and efficiency distinguished fast, medium, and slow RTs, (iii) the functional network underlying speeded decisions increases in negative assortativity (i.e., became disassortative) for slower RTs, (iv) slower categorical speech decisions cause excessive use of neural resources and more aberrant information flow within the CP circuitry, (v) slower responders tended to utilize functional brain networks excessively (or inappropriately) whereas fast responders (with lower global efficiency) utilized the same neural pathways but with more restricted organization.

SIGNIFICANCE

Findings show that neural classifiers (SVM) coupled with stability selection correctly classify behavioral RTs from functional connectivity alone with over 92% accuracy (AUC  =  0.9). Our results corroborate previous studies by supporting the engagement of similar temporal (STG), parietal, motor, and prefrontal regions in CP using an entirely data-driven approach.

Plasticity in auditory categorization is supported by differential engagement of the auditory-linguistic network

To construct our perceptual world, the brain categorizes variable sensory cues into behaviorally-relevant groupings. Categorical representations are apparent within a distributed fronto-temporo-parietal brain network but how this neural circuitry is shaped by experience remains undefined. Here, we asked whether speech and music categories might be formed within different auditory-linguistic brain regions depending on listeners' auditory expertise. We recorded EEG in highly skilled (musicians) vs. less experienced (nonmusicians) perceivers as they rapidly categorized speech and musical sounds. Musicians showed perceptual enhancements across domains, yet source EEG data revealed a double dissociation in the neurobiological mechanisms supporting categorization between groups. Whereas musicians coded categories in primary auditory cortex (PAC), nonmusicians recruited non-auditory regions (e.g., inferior frontal gyrus, IFG) to generate category-level information. Functional connectivity confirmed nonmusicians' increased left IFG involvement reflects stronger routing of signal from PAC directed to IFG, presumably because sensory coding is insufficient to construct categories in less experienced listeners. Our findings establish auditory experience modulates specific engagement and inter-regional communication in the auditory-linguistic network supporting categorical perception. Whereas early canonical PAC representations are sufficient to generate categories in highly trained ears, less experienced perceivers broadcast information downstream to higher-order linguistic brain areas (IFG) to construct abstract sound labels.

Neurophysiological and Behavioral Responses of Mandarin Lexical Tone Processing

Language experience enhances discrimination of speech contrasts at a behavioral- perceptual level, as well as at a pre-attentive level, as indexed by event-related potential (ERP) mismatch negativity (MMN) responses. The enhanced sensitivity could be the result of changes in acoustic resolution and/or long-term memory representations of the relevant information in the auditory cortex. To examine these possibilities, we used a short (ca. 600 ms) vs. long (ca. 2,600 ms) interstimulus interval (ISI) in a passive, oddball discrimination task while obtaining ERPs. These ISI differences were used to test whether cross-linguistic differences in processing Mandarin lexical tone are a function of differences in acoustic resolution and/or differences in long-term memory representations. Bisyllabic nonword tokens that differed in lexical tone categories were presented using a passive listening multiple oddball paradigm. Behavioral discrimination and identification data were also collected. The ERP results revealed robust MMNs to both easy and difficult lexical tone differences for both groups at short ISIs. At long ISIs, there was either no change or an enhanced MMN amplitude for the Mandarin group, but reduced MMN amplitude for the English group. In addition, the Mandarin listeners showed a larger late negativity (LN) discriminative response than the English listeners for lexical tone contrasts in the long ISI condition. Mandarin speakers outperformed English speakers in the behavioral tasks, especially under the long ISI conditions with the more similar lexical tone pair. These results suggest that the acoustic correlates of lexical tone are fairly robust and easily discriminated at short ISIs, when the auditory sensory memory trace is strong. At longer ISIs beyond 2.5 s language-specific experience is necessary for robust discrimination.

Brain Network Connectivity During Language Comprehension: Interacting Linguistic and Perceptual Subsystems

The dynamic neural processes underlying spoken language comprehension require the real-time integration of general perceptual and specialized linguistic information. We recorded combined electro- and magnetoencephalographic measurements of participants listening to spoken words varying in perceptual and linguistic complexity. Combinatorial linguistic complexity processing was consistently localized to left perisylvian cortices, whereas competition-based perceptual complexity triggered distributed activity over both hemispheres. Functional connectivity showed that linguistically complex words engaged a distributed network of oscillations in the gamma band (20-60 Hz), which only partially overlapped with the network supporting perceptual analysis. Both processes enhanced cross-talk between left temporal regions and bilateral pars orbitalis (BA47). The left-lateralized synchrony between temporal regions and pars opercularis (BA44) was specific to the linguistically complex words, suggesting a specific role of left frontotemporal cross-cortical interactions in morphosyntactic computations. Synchronizations in oscillatory dynamics reveal the transient coupling of functional networks that support specific computational processes in language comprehension.

Induced neural beta oscillations predict categorical speech perception abilities

Neural oscillations have been linked to various perceptual and cognitive brain operations. Here, we examined the role of these induced brain responses in categorical speech perception (CP), a phenomenon in which similar features are mapped to discrete, common identities despite their equidistant/continuous physical spacing. We recorded neuroelectric activity while participants rapidly classified sounds along a vowel continuum (/u/ to /a/). Time-frequency analyses applied to the EEG revealed distinct temporal dynamics in induced (non-phase locked) oscillations; increased β (15-30Hz) coded prototypical vowel sounds carrying well-defined phonetic categories whereas increased γ (50-70Hz) accompanied ambiguous tokens near the categorical boundary. Notably, changes in β activity were strongly correlated with the slope of listeners' psychometric identification functions, a measure of the "steepness" of their categorical percept. Our findings demonstrate that in addition to previously observed evoked (phase-locked) correlates of CP, induced brain activity in the β-band codes the ambiguity and strength of categorical speech percepts.

Emergence of category-level sensitivities in non-native speech sound learning

Over the course of development, speech sounds that are contrastive in one's native language tend to become perceived categorically: that is, listeners are unaware of variation within phonetic categories while showing excellent sensitivity to speech sounds that span linguistically meaningful phonetic category boundaries. The end stage of this developmental process is that the perceptual systems that handle acoustic-phonetic information show special tuning to native language contrasts, and as such, category-level information appears to be present at even fairly low levels of the neural processing stream. Research on adults acquiring non-native speech categories offers an avenue for investigating the interplay of category-level information and perceptual sensitivities to these sounds as speech categories emerge. In particular, one can observe the neural changes that unfold as listeners learn not only to perceive acoustic distinctions that mark non-native speech sound contrasts, but also to map these distinctions onto category-level representations. An emergent literature on the neural basis of novel and non-native speech sound learning offers new insight into this question. In this review, I will examine this literature in order to answer two key questions. First, where in the neural pathway does sensitivity to category-level phonetic information first emerge over the trajectory of speech sound learning? Second, how do frontal and temporal brain areas work in concert over the course of non-native speech sound learning? Finally, in the context of this literature I will describe a model of speech sound learning in which rapidly-adapting access to categorical information in the frontal lobes modulates the sensitivity of stable, slowly-adapting responses in the temporal lobes.

The cortical evoked response elicited by nine plosives in normal hearing listeners

Background and Objectives

P1-N1-P2 complex reflecting pre-attentive processing of sound presents several temporally overlapping and spatially distributed neural sources in or near primary auditory cortex. This study investigated cortical evoked responses to the P1-N1-P2 complex to determine the perceptual contributions of the acoustic features.

Subjects and Methods

Eleven young native-speaking Korean adults with normal hearing participated. The stimuli were three bilabial, three alveolar, and three velar syllables, and each place of articulation had one lax, one tense, and one aspirate syllable as the manner of articulation.

Results

The results indicate the cortical responses to the velar syllables significantly differed from the bilabial and alveolar groups at the P1-N1 and N1-P2 interamplitude. However, there is no significant difference in the cortical responses between Korean lax and tense syllables, which is significant for English phonology in terms of voice onset time. Further, the cortical responses to aspirate syllables significantly differed from two other groups in the interamplitude, demonstrating that the /t^ha/ syllable had the largest response at N1-P2 interamplitude.

Conclusions

Different speech sounds evoked different P1-N1-P2 patterns in the place and the manner of articulation in terms of interamplitude, but not of the latency and interlatency although further studies should be followed.

To what extent do we hear phonemic contrasts in a non-native regional variety? Tracking the dynamics of perceptual processing with EEG

This combined ERP and behavioral experiment explores the dynamics of processing during the discrimination of vowels in a non-native regional variety. Southern listeners were presented with three word forms, two of which are encountered in both Standard and Southern French ([kot] and [kut]), whereas the third one exists in Standard but not Southern French ([kot]). EEG recordings suggest that all of the word pairs were discriminated by the listeners, although discrimination arose about 100ms later for the pairs which included the non-native word form than for those which contained word forms common to both French varieties. Behavioral data provide evidence that vowel discrimination is sensitive to the influence of the listeners' native phonemic inventory at a late decisional stage of processing.

The role of stimulus cross-splicing in an event-related potentials study. Misleading formant transitions hinder automatic phonological processing

The mental organization of linguistic knowledge and its involvement in speech processing can be investigated using the mismatch negativity (MMN) component of the auditory event-related potential. A contradiction arises, however, between the technical need for strict control of acoustic stimulus properties and the quest for naturalness and acoustic variability of the stimuli. Here, two methods of preparing speech stimulus material were compared. Focussing on the automatic processing of a phonotactic restriction in German, two corresponding sets of various vowel-fricative syllables were used as stimuli. The former syllables were naturally spoken while the latter ones were created by means of cross-splicing. Phonetically, natural and spliced syllables differed with respect to the appropriateness of coarticulatory information about the forthcoming fricative within the vowels. Spliced syllables containing clearly misleading phonetic information were found to elicit larger N2 responses compared to their natural counterparts. Furthermore, MMN results found for the natural syllables could not be replicated with these spliced stimuli. These findings indicate that the automatic processing of the stimuli was considerably affected by the stimulus preparation method. Thus, in spite of its unquestioned benefits for MMN experiments, the splicing technique may lead to interference effects on the linguistic factors under investigation.

The brain basis of language processing: from structure to function

Language processing is a trait of human species. The knowledge about its neurobiological basis has been increased considerably over the past decades. Different brain regions in the left and right hemisphere have been identified to support particular language functions. Networks involving the temporal cortex and the inferior frontal cortex with a clear left lateralization were shown to support syntactic processes, whereas less lateralized temporo-frontal networks subserve semantic processes. These networks have been substantiated both by functional as well as by structural connectivity data. Electrophysiological measures indicate that within these networks syntactic processes of local structure building precede the assignment of grammatical and semantic relations in a sentence. Suprasegmental prosodic information overtly available in the acoustic language input is processed predominantly in a temporo-frontal network in the right hemisphere associated with a clear electrophysiological marker. Studies with patients suffering from lesions in the corpus callosum reveal that the posterior portion of this structure plays a crucial role in the interaction of syntactic and prosodic information during language processing.

Auditory Sensitivity to Formant Ratios:Toward an Account of Vowel Normalization

A long-standing question in speech perception research is how do listeners extract linguistic content from a highly variable acoustic input. In the domain of vowel perception, formant ratios, or the calculation of relative bark differences between vowel formants, have been a sporadically proposed solution. We propose a novel formant ratio algorithm in which the first (F1) and second (F2) formants are compared against the third formant (F3). Results from two magnetoencephelographic (MEG) experiments are presented that suggest auditory cortex is sensitive to formant ratios. Our findings also demonstrate that the perceptual system shows heightened sensitivity to formant ratios for tokens located in more crowded regions of the vowel space. Additionally, we present statistical evidence that this algorithm eliminates speaker-dependent variation based on age and gender from vowel productions. We conclude that these results present an impetus to reconsider formant ratios as a legitimate mechanistic component in the solution to the problem of speaker normalization.

Localization of sublexical speech perception components

Models of speech perception are in general agreement with respect to the major cortical regions involved, but lack precision with regard to localization and lateralization of processing units. To refine these models we conducted two Activation Likelihood Estimation (ALE) meta-analyses of the neuroimaging literature on sublexical speech perception. Based on foci reported in 23 fMRI experiments, we identified significant activation likelihoods in left and right superior temporal cortex and the left posterior middle frontal gyrus. Sub-analyses examining phonetic and phonological processes revealed only left mid-posterior superior temporal sulcus activation likelihood. A lateralization analysis demonstrated temporal lobe left lateralization in terms of magnitude, extent, and consistency of activity. Experiments requiring explicit attention to phonology drove this lateralization. An ALE analysis of eight fMRI studies on categorical phoneme perception revealed significant activation likelihood in the left supramarginal gyrus and angular gyrus. These results are consistent with a speech processing network in which the bilateral superior temporal cortices perform acoustic analysis of speech and non-speech auditory stimuli, the left mid-posterior superior temporal sulcus performs phonetic and phonological analysis, and the left inferior parietal lobule is involved in detection of differences between phoneme categories. These results modify current speech perception models in three ways: (1) specifying the most likely locations of dorsal stream processing units, (2) clarifying that phonetic and phonological superior temporal sulcus processing is left lateralized and localized to the mid-posterior portion, and (3) suggesting that both the supramarginal gyrus and angular gyrus may be involved in phoneme discrimination.

The mismatch negativity (MMN) in basic research of central auditory processing: a review

In the present article, the basic research using the mismatch negativity (MMN) and analogous results obtained by using the magnetoencephalography (MEG) and other brain-imaging technologies is reviewed. This response is elicited by any discriminable change in auditory stimulation but recent studies extended the notion of the MMN even to higher-order cognitive processes such as those involving grammar and semantic meaning. Moreover, MMN data also show the presence of automatic intelligent processes such as stimulus anticipation at the level of auditory cortex. In addition, the MMN enables one to establish the brain processes underlying the initiation of attention switch to, conscious perception of, sound change in an unattended stimulus stream.

MMN to natural Arabic CV syllables: 2 – cross language study

Mismatch negativity response parameters; latency, amplitude, and duration - to natural Arabic and natural English CV syllables - were obtained from normal-hearing adult Egyptians, in two experiments. In the first experiment, MMN was obtained in response to English CV syllable paradigms (Ba-Wa) and (Ga-Da) differing in formant duration and start of third formant, respectively. In the second experiment, MMN response for Arabic paradigm (Baa-Waa), English paradigm (Ba-Wa), and for Arabic-English paradigm (Waa-Wa) was obtained. Results revealed that the three levels of speech representation; acoustic, phonetic and phonologic could be probed preattentatively by MMN. The acoustic properties of speech signal are processed earlier than the phonetic and phonologic properties.

MMN to natural Arabic CV syllables: 1-normative data

Mismatch negativity response parameters; latency, amplitude, and duration to natural Arabic CV syllables differing in durational change (Baa-Waa) and in spectrotemporal change (Gaa-Daa) were obtained from normal hearing young adult Egyptians. The aim was to get normative data for MMN response parameters and to find any differences between both primary and non-primary auditory pathways in encoding and processing speech signals. Statistically significant differences between durational and spectrotemporal contrasts for latency and duration were found. This was attributed to acoustic differences and to physiological differences between primary and non-primary auditory pathways.

Cortical differentiation of speech and nonspeech sounds at 100 ms: implications for dyslexia

Neurophysiological measures indicate cortical sensitivity to speech sounds by 150 ms after stimulus onset. In this time window dyslexic subjects start to show abnormal cortical processing. We investigated whether phonetic analysis is reflected in the robust auditory cortical activation at approximately 100 ms (N100m), and whether dyslexic subjects show abnormal N100m responses to speech or nonspeech sounds. We used magnetoencephalography to record auditory responses of 10 normally reading and 10 dyslexic adults. The speech stimuli were synthetic Finnish speech sounds (/a/, /u/, /pa/, /ka/). The nonspeech stimuli were complex nonspeech sounds and simple sine wave tones, composed of the F1+F2+F3 and F2 formant frequencies of the speech sounds, respectively. All sounds evoked a prominent N100m response in the bilateral auditory cortices. The N100m activation was stronger to speech than nonspeech sounds in the left but not in the right auditory cortex, in both subject groups. The leftward shift of hemispheric balance for speech sounds is likely to reflect analysis at the phonetic level. In dyslexic subjects the overall interhemispheric amplitude balance and timing were altered for all sound types alike. Dyslexic individuals thus seem to have an unusual cortical organization of general auditory processing in the time window of speech-sensitive analysis.

Sensitivity to prosodic structure in left- and right-hemisphere-damaged individuals

An experiment was conducted in order to determine whether left- (LHD) and right-hemisphere-damaged (RHD) patients exhibit sensitivity to prosodic information that is used in syntactic disambiguation. Following the work of, a cross-modal lexical decision task was performed by LHD and RHD subjects, as well as by adults without brain pathology (NC). Subjects listened to sentences with attachment ambiguities with either congruent or incongruent prosody, while performing a visual lexical decision task. Results showed that each of the unilaterally damaged populations differed from each other, as well as from the NCs in terms of sensitivity regarding prosodic cues. Specifically, the RHD group was insensitive to sentence prosody as a whole. This was in contrast to the LHD patients, who responded to the prosodic manipulation, but in the unexpected direction. Results are discussed in terms of current hypotheses regarding the hemispheric lateralization of prosodic cues.

Plastic cortical changes induced by learning to communicate with non-speech sounds

With Morse code, an acoustic message is transmitted using combinations of tone patterns rather than the spectrally and temporally complex speech sounds that constitute the spoken language. Using MEG recordings of the mismatch negativity (MMN, an index of permanent auditory cortical representations of native language speech sounds), we probed the dominant hemisphere for the developing Morse code representations in adult Morse code learners. Initially, the MMN to the Morse coded syllables was, on average, stronger in the hemisphere opposite to the one dominant for the MMN to native language speech sounds. After a training period of 3 months, the pattern reversed, however: the mean Morse code MMN became lateralized to the hemisphere that was predominant for the speech-sound MMN. This suggests that memory traces for the Morse coded acoustic language units develop within the hemisphere that already accommodates the permanent traces for natural speech sounds. These plastic changes manifest, presumably, the close associations formed between the neural representations of the tone patterns and phonemes.

The mismatch negativity and reaction time as indices of the perceptual distance between the corresponding vowels of two related languages

Two experiments were conducted to determine whether vowel familiarity affects automatic and conscious vowel discrimination. Familiar (Finnish) and unfamiliar (Komi) vowels were presented to Finnish subjects. The good representatives of Finnish and Komi mid vowels were grouped into three pairs: front /e- epsilon /, central /ø-oe/, and back /o-o/. The acoustic difference for /e- epsilon / and /o-o/ was smaller than that for /ø-oe/. For /e- epsilon /, the Komi vowel / epsilon / was at the boundary between the Finnish /e/ and /ae/. The stimuli were presented in an oddball paradigm. In three different blocks, each Komi vowel in turn served as the standard (probability 0.86) and the corresponding Finnish vowel as the deviant stimulus (probability 0.14), and vice versa. In Experiment 1, subjects were instructed to press a button as soon as they detected a deviant stimulus. In Experiment 2, event-related potentials (ERPs) were recorded to these stimuli in order to use the mismatch negativity (MMN) as an index of the perceptual distance between the members of each vowel pair, while subjects did not attend to the stimuli. There were similar effects of the acoustic distance within a vowel pair for both the reaction time (RT) and the MMN amplitude; the RT decreased and the MMN amplitude increased when the acoustic difference between the stimuli increased. However, the RT was longer when the Komi / epsilon / was the standard and the Finnish /e/ was the deviant than vice versa. No such pattern was found for the MMN. Thus, the phonemic status of the standard stimulus seems to play a role at the attentive but not at the pre-attentive level.