Individual Differences In Cognition Research Articles

Personalized functional brain network topography is associated with individual differences in youth cognition

Individual differences in cognition during childhood are associated with important social, physical, and mental health outcomes in adolescence and adulthood. Given that cortical surface arealization during development reflects the brain’s functional prioritization, quantifying variation in the topography of functional brain networks across the developing cortex may provide insight regarding individual differences in cognition. We test this idea by defining personalized functional networks (PFNs) that account for interindividual heterogeneity in functional brain network topography in 9–10 year olds from the Adolescent Brain Cognitive Development℠ Study. Across matched discovery (n = 3525) and replication (n = 3447) samples, the total cortical representation of fronto-parietal PFNs positively correlates with general cognition. Cross-validated ridge regressions trained on PFN topography predict cognition in unseen data across domains, with prediction accuracy increasing along the cortex’s sensorimotor-association organizational axis. These results establish that functional network topography heterogeneity is associated with individual differences in cognition before the critical transition into adolescence.

Explaining the Validity of the ASVAB for Job-Relevant Multitasking Performance: The Role of Placekeeping Ability.

Scores on the Armed Services Vocational Aptitude Battery (ASVAB) predict military job (and training) performance better than any single variable so far identified. However, it remains unclear what factors explain this predictive relationship. Here, we investigated the contributions of fluid intelligence (Gf) and two executive functions-placekeeping ability and attention control-to the relationship between the Armed Forces Qualification Test (AFQT) score from the ASVAB and job-relevant multitasking performance. Psychometric network analyses revealed that Gf and placekeeping ability independently contributed to and largely explained the AFQT-multitasking performance relationship. The contribution of attention control to this relationship was negligible. However, attention control did relate positively and significantly to Gf and placekeeping ability, consistent with the hypothesis that it is a cognitive "primitive" underlying the individual differences in higher-level cognition. Finally, hierarchical regression analyses revealed stronger evidence for the incremental validity of Gf and placekeeping ability in the prediction of multitasking performance than for the incremental validity of attention control. The results shed light on factors that may underlie the predictive validity of global measures of cognitive ability and suggest how the ASVAB might be augmented to improve its predictive validity.

Tau PET burden in Brodmann areas 35 and 36 is associated with individual differences in cognition in non-demented older adults.

The accumulation of neurofibrillary tau tangles, a neuropathological hallmark of Alzheimer's disease (AD), occurs in medial temporal lobe (MTL) regions early in the disease process, with some of the earliest deposits localized to subregions of the entorhinal cortex. Although functional specialization of entorhinal cortex subregions has been reported, few studies have considered functional associations with localized tau accumulation. In this study, stepwise linear regressions were used to examine the contributions of regional tau burden in specific MTL subregions, as measured by 18F-MK6240 PET, to individual variability in cognition. Dependent measures of interest included the Clinical Dementia Rating Sum of Boxes (CDR-SB), Mini Mental State Examination (MMSE), and composite scores of delayed episodic memory and language. Other model variables included age, sex, education, APOE4 status, and global amyloid burden, indexed by 11C-PiB. Tau burden in right Brodmann area 35 (BA35), left and right Brodmann area 36 (BA36), and age each uniquely contributed to the proportion of explained variance in CDR-SB scores, while right BA36 and age were also significant predictors of MMSE scores, and right BA36 was significantly associated with delayed episodic memory performance. Tau burden in both left and right BA36, along with education, uniquely contributed to the proportion of explained variance in language composite scores. Importantly, the addition of more inclusive ROIs, encompassing less granular segmentation of the entorhinal cortex, did not significantly contribute to explained variance in cognition across any of the models. These findings suggest that the ability to quantify tau burden in more refined MTL subregions may better account for individual differences in cognition, which may improve the identification of non-demented older adults who are on a trajectory of decline due to AD.

Tau PET accumulation in Brodmann areas 35 and 36 is associated with individual differences in cognition in non‐demented older adults

AbstractBackgroundMounting evidence indicates that tau accumulation in the entorhinal cortex (EC) occurs early in the course of Alzheimer’s disease (AD). Recent advances in automated segmentation methods allow for the investigation of smaller regions of the medial temporal lobes (MTL), including subregions of the EC. This study examined tau deposition in relation to individual differences in cognition among older adults, assessing whether MTL subregions explained a greater proportion of variance in cognition, when compared to standard labeling methods.MethodAnalyses included 91 BIOCARD study participants who were cognitively unimpaired (CU; n = 82) or had mild cognitive impairment (MCI; n = 9). Stepwise linear regressions were used to examine the contributions of regional tau burden to individual differences in the CDR sum of boxes (CDR‐SB), MMSE, and composite scores of global cognition and memory. Other model variables included amyloid burden, APOE4 status, sex, and education. Amyloid burden was assessed by 11C‐PiB and regional tau was assessed by 18F‐MK‐6240 PET. SUVR values representing tau accumulation were extracted using two MRI segmentation methods: (1) the FreeSurfer‐derived EC label, and (2) Automatic Segmentation of Hippocampal Subfields (ASHS)‐derived MTL subregions, including the EC and Brodmann areas 35 and 36 (Br35, Br36) defined in 1mm‐MNI space. Partial volume correction was applied to the motion‐corrected PET data.ResultTau burden in the right Br35, right Br36, and age were significant predictors of CDR‐SB scores, with the greatest proportion of variance explained when all three were included. The FreeSurfer‐labeled EC and other variables did not significantly contribute to the model. Right Br36 and age were significant predictors of MMSE while right Br36 and APOE4 status were significant predictors of the global cognition composite score, and right Br36 was a significant predictor of the memory composite score. Follow‐up analyses showed that addition of the FreeSurfer EC region did not significantly contribute to any of the models.ConclusionQuantifying tau burden in Br35 and Br36 better accounted for individual variability in cognition, when compared to standard EC labeling approaches. This suggests tau burden in these subregions may help identify CU and MCI individuals who are on a trajectory of decline due to AD.

Dynamic fluctuations in foreign language enjoyment during cognitively simple and complex interactive speaking tasks

Despite evidence on the interaction between cognitive individual differences (IDs) and task complexity, our knowledge of how affective IDs, such as foreign language enjoyment (FLE), interact with task complexity and other factors is limited. Since tasks and activities were found by Dewaele and MacIntyre (2014) to be most relevant to FLE, and since task complexity might interact with learners’ perceptions of task difficulty, it is important to investigate how task complexity impacts FLE changes. Informed by the complex dynamic systems theory, this study employed a mixed-methods multiple case study design to study patterns and causes of high and low FLE arousals. The participants were four pairs of Taiwanese high-intermediate EFL university students who were engaged in simple or complex storytelling tasks with speech acts of refusals. The speakers’ interactions were triangulated with an individual learner’s rating of FLE on a per-second scale and stimulated recalls. Results revealed idiosyncratic patterns of FLE fluctuations of peer interlocutors and a high degree of overlap in sources of low and high FLE in both groups. Speakers reported high FLE as a result of interesting storylines inherent in task design and created by peers, the use of picture prompts, peer collaboration, and task performance. Performance problems, failure to retrieve appropriate vocabulary, task design, and lack of ideas led to low FLE arousals. The findings suggest that task complexity combined with other task-induced, social, and individual factors to affect the fluctuations of FLE. Implications for task design and oral communication instruction to promote FLE are discussed.

As easy as cake or a piece of pie? Processing idiom variation and the contribution of individual cognitive differences.

Language users routinely use canonical, familiar idioms in everyday communication without difficulty. However, creativity in idiom use is more widespread than sometimes assumed, and little is known about how we process creative uses of idioms, and how individual differences in cognitive skills contribute to this. We used eye-tracking while reading and cross-modal priming to investigate the processing of idioms (e.g., play with fire) compared with creative variants (play with acid) and literal controls (play with toys), amongst a group of 47 university-level native speakers of English. We also conducted a series of tests to measure cognitive abilities (working memory capacity, inhibitory control, and processing speed). Eye-tracking results showed that in early reading behaviour, variants were read no differently to literal phrases or idioms but showed significantly longer overall reading times, with more rereading required compared with other conditions. Idiom variables (familiarity, decomposability, literal plausibility) and individual cognitive variables had limited effects throughout, although more decomposable phrases of all kinds required less overall reading time. Cross-modal priming-which has often shown a robust idiom advantage in past studies-demonstrated no difference between conditions, but decomposability again led to faster processing. Overall, results suggest that variants were treated more like literal phrases than novel metaphors, with subsequent effort required to make sense of these in the way that was consistent with the context provided.

Trajectories across the healthy adult lifespan on sense of direction, spatial anxiety, and attitude in exploring places.

Self-evaluations about orientation and navigation in the environment contribute to individual differences in spatial cognition. Evidence suggests that they may change, even slightly, with the progression of adulthood. It is necessary to improve the framing of environment-related subjective self-evaluations in adulthood and aging by examining how they change and the factors related to them. Therefore, this study aimed to examine the developmental trajectories of sense of direction, spatial anxiety, and attitude in exploring place across the adult lifespan while also considering gender and education. A sample of 1,946 participants (1,068 women), aged 18-87 years, completed the sense of direction and spatial representation, spatial anxiety, and attitude in exploring scales. The regression models showed a linear increase in sense of direction with age, stable spatial anxiety until age 66 years when anxiety began increasing, and a stable attitude in exploring with a deflection by age 71 years. Gender played a role in all three types of self-evaluations, with men reporting higher ratings in sense of direction and attitude toward exploring (especially in older men), and lower levels of spatial anxiety than women did. Education also played a role, with higher education years associated with lower ratings in spatial anxiety and a higher sense of direction, nullifying gender differences in the latter. These results offer, in the spatial cognition framework, a better understanding of how specific environment-related self-evaluations develop with age and related factors, such as education. This underscores the importance of enhancing them, particularly in women and older adults.

Relationships between the race implicit association test and other measures of implicit and explicit social cognition.

The race-based Implicit Association Test (IAT) was proposed to measure individual differences in implicit racial bias subsumed within social cognition. In recent years, researchers have debated the theoretical tenets underpinning the IAT, questioning whether performance on this task: (1) measures implicit attitudes that operate automatically outside of conscious awareness; (2) reflects individual differences in social cognition; and (3) can predict social behavior. One way to better address these research questions is to assess whether the race-IAT correlates with other implicit processes that are subsumed within social cognition. The current study assessed whether the race-IAT was related to other commonly used individual difference measures of implicit (and explicit) social cognition. Experiment 1 assessed whether dissociable patterns of performance on the race-IAT were related to measures of implicit imitative tendencies, emotion recognition and perspective taking toward White task actors, as well as explicit measures of trait and state affective empathy and racial bias. Overcoming limitations of task conceptual correspondence, Experiment 2 assessed whether these latter tasks were sensitive in detecting racial biases by using both White and Black task actors and again examined their relationships with the race-IAT. In two lab-based experiments, 226 and 237 participants completed the race-IAT followed by an extensive battery of social cognition measures. Across both experiments, pro-White/anti-Black bias on the race-IAT was positively related to a pro-White bias on explicit measures of positive affective empathy. However, relationships between the race-IAT and implicit imitative tendencies, perspective taking, emotion recognition, and explicit trait and negative state affective empathy were statistically equivalent. The race-IAT was consistently related to explicit measures of positive state affective empathy but not to other individual difference measures of implicit social cognition. These findings are discussed with regards to the theoretical underpinnings of the race-IAT as an individual difference measure of implicit social cognition, as well as alternative explanations relating to the reliability of social cognition measures and the various combinations of general-purpose (social and non-social) executive processes that underpin performance on these tasks.

Listening efficiency in adult cochlear-implant users compared with normally-hearing controls at ecologically relevant signal-to-noise ratios.

Due to having to work with an impoverished auditory signal, cochlear-implant (CI) users may experience reduced speech intelligibility and/or increased listening effort in real-world listening situations, compared to their normally-hearing (NH) peers. These two challenges to perception may be usefully integrated in a measure of listening efficiency: conceptually, the amount of accuracy achieved for a certain amount of effort expended. We describe a novel approach to quantifying listening efficiency based on the rate of evidence accumulation toward a correct response in a linear ballistic accumulator (LBA) model of choice decision-making. Estimation of this objective measure within a hierarchical Bayesian framework confers further benefits, including full quantification of uncertainty in parameter estimates. We applied this approach to examine the speech-in-noise performance of a group of 24 CI users (M age: 60.3, range: 20-84 years) and a group of 25 approximately age-matched NH controls (M age: 55.8, range: 20-79 years). In a laboratory experiment, participants listened to reverberant target sentences in cafeteria noise at ecologically relevant signal-to-noise ratios (SNRs) of +20, +10, and +4 dB SNR. Individual differences in cognition and self-reported listening experiences were also characterised by means of cognitive tests and hearing questionnaires. At the group level, the CI group showed much lower listening efficiency than the NH group, even in favourable acoustic conditions. At the individual level, within the CI group (but not the NH group), higher listening efficiency was associated with better cognition (i.e., working-memory and linguistic-closure) and with more positive self-reported listening experiences, both in the laboratory and in daily life. We argue that listening efficiency, measured using the approach described here, is: (i) conceptually well-motivated, in that it is theoretically impervious to differences in how individuals approach the speed-accuracy trade-off that is inherent to all perceptual decision making; and (ii) of practical utility, in that it is sensitive to differences in task demand, and to differences between groups, even when speech intelligibility remains at or near ceiling level. Further research is needed to explore the sensitivity and practical utility of this metric across diverse listening situations.

TANGO: A reliable, open-source, browser-based task to assess individual differences in gaze understanding in 3 to 5-year-old children and adults.

Traditional measures of social cognition used in developmental research often lack satisfactory psychometric properties and are not designed to capture variation between individuals. Here, we present theTANGO (Task for Assessing iNdividual differences in Gaze understanding-Open); a brief (approx. 5-10min), reliable, open-source task to quantify individual differences in the understanding of gaze cues. Localizing the attentional focus of an agent is crucial in inferring their mental states, building common ground, and thus, supporting cooperation. Our interactive browser-based task works across devices and enables in-person and remote testing. The implemented spatial layout allows for discrete and continuous measures of participants' click imprecision and is easily adaptable to different study requirements. Our task measures inter-individual differences in a child (N = 387) and an adult (N = 236) sample. Our two study versions and data collection modes yield comparable results that show substantial developmental gains: the older children are, the more accurately they locate the target. High internal consistency and test-retest reliability estimates underline that the captured variation is systematic. Associations with social-environmental factors and language skills speak to the validity of the task. This work shows a promising way forward in studying individual differences in social cognition and will help us explore the structure and development of our core social-cognitive processes in greater detail.

Cognitive individual differences in the process and product of L2 writing

AbstractThis paper examines how research in second language acquisition has approached the study of cognitive individual differences in the process and product of L2 writing from a theoretical and empirical perspective, paying special attention to the three empirical studies included in this special issue. The paper is divided into three sections. The first section examines the cognitive abilities that have been investigated in L2 writing research, among which working memory stands out as the most widely studied. The second section synthesizes the findings reported by the empirical studies in this issue in relation to the role of working memory in L2 writing behaviors and outcomes. The last section suggests future lines of research that can broaden the current scope of research on writing and cognitive individual differences, mostly centered on the components of the working memory system. This research has important theoretical implications, as little is known about how different cognitive individual differences are implicated in writing, as well as pedagogical implications, as the findings can inform about optimal performance and learning conditions for learners with diverse cognitive ability profiles.

Introduction to the special issue on working memory and L2 writing: Implications for SLA individual differences research

AbstractThis Introduction to the special issue first elaborates on the rationale for advocating the inclusion of L2 writing in SLA individual differences (IDs) research and subsequently provides an overview of empirical work on IDs in the domain of writing, with a focus on cognitive IDs and specifically working memory. Against this background, we synthesize the focus, structure, and contents of the special issue. We finish with substantive and methodological suggestions for moving forward in research agendas on IDs and L2 writing.

The role of cognitive factors in second language writing and writing to learn a second language

AbstractThis article revisits the role of cognitive individual differences in creating synergies between second language (L2) writing and second language acquisition research that were proposed by Kormos (2012). It takes stock of the advances in research findings, in the past decade, on the role of working memory and language learning aptitude in L2 writing processes and performance. The article offers an overview of how cognitive factors can mediate learning gains when L2 users engage in writing. Using theoretical accounts of cognitive individual differences, the article discusses how the characteristics of writing tasks can interact with individual variation in cognitive functioning. The article concludes by proposing a Task-Mediated Cognitive Model of L2 Writing and Writing to Learn that describes the role of cognitive factors in L2 writing processes and in learning through writing, and an outline of a research agenda for future studies.

Adaptive phenotypic plasticity induces individual variability along a cognitive trade-off

Animal species, including humans, display patterns of individual variability in cognition that are difficult to explain. For instance, some individuals perform well in certain cognitive tasks but show difficulties in others. We experimentally analysed the contribution of cognitive plasticity to such variability. Theory suggests that diametrically opposed cognitive phenotypes increase individuals' fitness in environments with different conditions such as resource predictability. Therefore, if selection has generated plasticity that matches individuals’ cognitive phenotypes to the environment, this might produce remarkable cognitive variability. We found that guppies, Poecilia reticulata , exposed to an environment with high resource predictability (i.e. food available at the same time and in the same location) developed enhanced learning abilities. Conversely, guppies exposed to an environment with low resource predictability (i.e. food available at a random time and location) developed enhanced cognitive flexibility and inhibitory control. These cognitive differences align along a trade-off between functions that favour the acquisition of regularities such as learning and functions that adjust behaviour to changing conditions (cognitive flexibility and inhibitory control). Therefore, adaptive cognitive plasticity in response to resource predictability (and potentially similar factors) is a key determinant of cognitive individual differences.

Individual differences in attention control and the processing of phonological contrasts in a second language.

This study investigated attention control in L2 phonological processing from a cognitive individual differences perspective, to determine its role in predicting phonological acquisition in adult L2 learning. Participants were 21 L1-Spanish learners of English, and 19 L1-English learners of Spanish. Attention control was measured through a novel speech-based attention-switching task. Phonological processing was assessed through a speeded ABX categorization task (perception) and a delayed sentence repetition task (production). Correlational analyses indicated that learners with more efficient attention switching skill and faster speed in correctly identifying the target phonetic features in the speech dimension under focus could perceptually discriminate L2 vowels at higher processing speed, but not at higher accuracy rates. Thus, attentional flexibility provided a processing advantage for difficult L2 contrasts but did not predict the extent to which precise representations for the target L2 vowels had been established. However, attention control was related to L2 learners' ability to distinguish the contrasting L2 vowels in production. In addition, L2 learners' accuracy in perceptually distinguishing between two contrasting vowels was significantly related to how much of a quality distinction between them they could make in production.

Cognitive style and creativity: The role of education in shaping cognitive style profiles and creativity of adolescents.

Previous research on cognitive styles (CSs) has often overlooked their complexity and the effect of the environment on their development. While research supports visual abilities as predictors of domain-specific creativity, there is a lack of studies on the predictive power of CS in relation to creativity beyond abilities. The current study aimed to explore the validity of the CS construct as environmentally sensitive individual differences in cognition. We examined the internal structure of the CS construct, its predictive power in creativity beyond visual abilities, and how CSs of Singaporean secondary school students are shaped with age under specific sociocultural influences (Singapore's emphasis on STEM disciplines). Data were collected from 347 students aged 13-16 from a secondary school in Singapore. Students were administered nine tasks assessing their visual abilities and learning preferences, artistic and scientific creativity, and questionnaires assessing their CS profiles. The confirmatory factor analyses provided evidence for a matrix-type CS structure consisting of four orthogonal CS dimensions and third levels of information processing. Structural equation models demonstrated significant contributions of context independence and intuitive processing to artistic and scientific creativity, respectively, beyond visual abilities. The results also suggested that Singapore's education system could be contributing to significantly shaping adolescents' CS profiles. Our findings support the validity of CS as individual differences in cognition that develop to cope with environmental demands. They highlight the importance of providing an appropriate environment in shaping adolescents' CS profiles to support the development of domain-specific creativity according to their strengths and talent.

Linearly integrating speed and accuracy to measure individual differences in theory of mind: Evidence from autistic and neurotypical adults.

It has long been theorised that there is a direct link between individual differences in social cognition and behaviour. One of the most popular tests of this theory has involved examination of Theory of Mind (ToM) difficulties in Autism Spectrum Disorder (ASD). However, evidence for associations between ToM and social behaviour is mixed, both when testing the ToM explanation of ASD and when investigating individual differences in ToM in the general population. We argue that this is due to methodological limitations of many ToM measures, such as a lack of variability in task performance, inappropriate non-ToM control tasks, and a failure to account for general mental ability. To overcome these issues, we designed a novel task, which probed individual differences in ToM fluency through mental state attribution in response to cartoons (Cartoons Theory of Mind [CarToM] task). This task, enabling the linear combination of speed and accuracy, was used to quantify ToM ability and its association with self-reported (a)typical social behaviour in adults with and without ASD. In a large sample (N = 237), we found that having an ASD diagnosis and higher autistic traits predicted lower ToM ability, even after accounting for performance on a well-matched non-ToM condition and general mental ability. Overall, our findings provide fresh support for the existence of a link between individual differences in social cognition (specifically, ToM) and behaviour (specifically, autism). This has implications for social-cognitive theory and research, allowing large-scale, online assessment of individual differences in ToM in clinical groups and the general population.

Effect of acute exercise on cognitive flexibility: Role of baseline cognitive performance

A wealth of evidence has shown that acute aerobic exercise can enhance executive function. However, empirical evidence lacks consensus regarding whether acute aerobic exercise has a beneficial effect on cognitive flexibility when individual baseline cognitive differences are considered. Therefore, the aim of our study was to examine the effects of high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MICE) on cognitive flexibility in young adults with differences in baseline cognitive performance. One hundred and ten college students (mean age = 20.17 ± 1.15 years) were divided into lower-performers (n = 55) and higher-performers (n = 55) groups based on their cognitive performance on the pre-test of the first cognitive flexibility test. Both groups were asked to complete a more-odd shifting task, which assesses cognitive flexibility, before and approximately 5 min after a 20 min HIIE session, a 20 min MICE session, and a reading control session. The results showed that individuals with lower baseline cognitive performance gained greater cognitive flexibility benefits from the 20 min HIIE and the 20 min MICE, whereas those with higher baseline cognitive performance had improved cognitive flexibility only from the 20 min HIIE. These findings indicate that baseline cognitive performance is a variable that influences the beneficial effects of acute exercise on cognitive flexibility. We recommend that young adults should consider their individual cognitive capacity when adopting effective and appropriate exercise modalities to improve cognitive performance.

Implicit Statistical Learning in L2 Sentence Processing: Individual Cognitive Differences.

This study investigates whether statistical learning ability, conceptualized as a cognitive ability to learn regularities implicitly, is a good predictor for L2 learners' online language processing performance. Native-English-speaking adults, as a control group, and native-Korean-speaking adult L2 learners of English participated. They completed: (a) an artificial grammar learning task containing nonadjacent dependencies in sequences of non-words, to test statistical learning ability; and (b) a self-paced English reading task containing relative clauses (RC) in which the "filler" and the "gap" formed a long-distance dependency, to test language processing. Both tasks' stimuli were presented element-by-element to mimic the incremental nature of online language processing. The results for the L1 group show that higher accuracy scores on the artificial grammar learning task did not predict higher sentence comprehension scores. The results for the L2 group, however, show a marginally significant correlation between accuracy scores on the artificial grammar learning task and sentence comprehension scores. For both groups, the reading time difference between grammatical and ungrammatical items in the artificial grammar learning task did predict the speed of reading times for items with RCs with a long-distance dependency in the sentence processing task: Larger differences in RTs in the artificial grammar task correlated with slower reading at the critical region of English RCs. These findings suggest a similar mechanism for online first and second language processing of core syntactic phenomena and for statistical learning ability that involves implicitly tracking distributional relations across elements.

Can object identification difficulty be predicted based on disfluencies and eye-movements in connected speech?

In the current study, we asked whether delays in the earliest stages of picture naming elicit disfluency. To address this question, we used a network task, where participants describe the route taken by a marker through visually presented networks of objects. Additionally, given that disfluencies are arguably multifactorial, we combined this task with eye tracking, to be able to disentangle disfluency related to word preparation from other factors (e.g., stalling strategy). We used visual blurring, which hinders visual identification of the items and thereby slows down selection of a lexical concept. We tested the effect of this manipulation on disfluency production and visual attention. Blurriness did not lead to more disfluency on average and viewing times decreased with blurred pictures. However, multivariate pattern analyses revealed that a classifier could predict above chance, from the pattern of disfluency, whether each participant was about to name blurred or control pictures. Impeding the conceptual generation of a message therefore affected the pattern of disfluencies of each participant individually, but this pattern was not consistent from one participant to another. Additionally, some of the disfluency and eye-movement variables correlated with individual cognitive differences, in particular with inhibition.