Verbal fluency tasks are widely used to assess language abilities and executive functions in both clinical and research settings. In post-stroke patients, prior research has indicated a significant hodological contribution to the neural basis of verbal fluency; however, this has largely been examined using lesion-based measures, predefined tractography approaches, and traditional diffusion metrics.

Quantitative anisotropy-based structural connectometry derived from correlational tractography was employed to determine the white matter circuits underlying semantic and phonemic fluency in 44 patients with post-stroke aphasia.

Both task types were found to be linked to anterior frontal connections of left-hemisphere dorsal and ventral associative pathways, as well as domain-general projection pathways. However, visual inspection of the connectomes, supported by supplementary cross-control analyses, suggested differences in the relative emphasis and distribution of pathways, with phonemic fluency aligning more with the dorsal stream, while semantic fluency showed greater reliance on the ventral stream and a wider range of cortico-subcortical connections.

The findings contribute to current understanding of the neural networks of verbal fluency in aphasia, with potential relevance for clinical practice and research.

Difficulty with word finding is a pervasive symptom in aphasia and a common target of treatment. This review explored whether therapy-induced naming gains induce improvements to everyday (naturalistic) communication.

Online databases were searched for naming interventions that also assessed discourse or functional communication, and for studies of therapies that directly treated them.

Among the studies that found word production gains following therapy, only about half found that the gains generalized to improved discourse or functional communication. However, discourse and functional communication can be improved by therapies that target them, and often improve word finding as well.

Generalization of rehabilitation is complex and difficult to achieve. If the therapeutic goal in aphasia is to improve everyday communication, then intervention research needs to shift focus from “building blocks” like word production to the building of discourse and functional communication.

The Word List subtest of the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) neuropsychological battery has been widely used in clinical research to identify and track cognitive disorders. However, normative data and change scores are lacking. The current study aimed to create normative data for the Word List subtest.

CERAD Word List data from 1,530 older adults diagnosed as cognitively intact, Mild Cognitive Impairment (MCI), or dementia were seen for two annual visits in a longitudinal observational study from the Uniform Data Set of the National Alzheimer’s Coordinating Center. Multiple linear regression predicted Time 2 scores from Time 1 scores, demographic variables (age, education, sex, and race), and retest interval. Validation included comparing predicted scores to observed scores in the original sample, and additional validation across five comparison groups (cognitively intact, MCI, dementia, worsening cognition, or improving cognition) and one-sample chi-square test of probabilities to compare group classification to predicted categorization based on chance alone.

The four demographic variables significantly predicted test scores for the six primary scores from the Word List subtest. For change data, when predicted Time 2 scores were compared to observed Time 2 scores, there were significant differences for 4 of the 6 scores, but the effect sizes were small. Significant differences were found across the five comparison groups for Total Recall and Delayed Recall (p-values < .001).

The current study provides normative data and regression-based change scores for the CERAD Word List subtest for older adults.

Recent advancements in the development of novel therapies to treat phenylketonuria (PKU) have fueled a call for new assessment tools that are sensitive to PKU-related neurocognitive disruptions. The present study evaluated the NIH Toolbox, a computer-administered battery of neurobehavioral measures, for assessing cognitive function in children and adults with early-treated PKU.

Data were examined from 91 individuals with PKU (aged 8–55 years) enrolled in an ongoing NIH-funded longitudinal study of hyperphenylalaninemia. Participants completed the NIH Toolbox as well as several validation instruments including the Wechsler Abbreviated Scale of Intelligence-Second Edition, Cambridge Neuropsychological Test Automated Battery (CANTAB), and Conners’ Continuous Performance Test.

Consistent with prior research, crystallized cognition was intact in both children and adults. In contrast, fluid cognition deficits were observed primarily in younger children while older children and adults generally performed within expectations. NIH Toolbox composite scores demonstrated strong concurrent validity with Wechsler indices and moderate correlations with other established measures.

The NIH Toolbox shows promise as a valid and practical measure of neurocognitive function in PKU, supporting its potential integration into clinical trials and research protocols. Future research should prioritize longitudinal designs to assess test–retest reliability, sensitivity to change, and subgroup differences related to treatment modalities. Ongoing efforts, such as the PHEFREE consortium, will be critical for establishing the NIH Toolbox as a robust outcome measure for PKU intervention studies.

Individuals with ADHD have difficulty providing precise estimates of time. Nevertheless, they may still be able to harness temporally predictable information to guide behavior and regulate action control. We therefore examined whether temporal cueing improves impulse control or, conversely, exacerbates impulsive tendencies, in adults with ADHD.

Adults with ADHD and matched controls performed a temporally cued Simon task. Target onset time was either predictable or unpredictable, and lateralized responses were either compatible or incompatible with target location. Analysis of reaction time (RT) distributions allowed us to decompose impulsive behavior into two key elements: the initial urge to react impulsively and the top-down suppression of these impulses. Individual differences in attention and impulsivity were assessed using a Continuous Performance Test (CPT).

Temporal cueing increased fast impulsive errors in both groups. However, temporal cues sped responses to compatible targets in controls but to incompatible targets in adults with ADHD. Distributional analyses revealed that although temporal predictability reduced inhibitory efficiency over time in controls, it actually improved the late-stage engagement of inhibitory processes in adults with ADHD. Furthermore, in the clinical group, greater RT variability in the CPT – reflecting attentional instability – was associated with larger cueing benefits, whereas higher CPT commission errors predicted weaker benefits.

By compensating for endogenous deficits in action control, temporal cues facilitated top-down suppression of impulsive responses, particularly in individuals with high attentional instability. Our findings demonstrate that temporal predictability can act as a functional scaffold for inhibitory control in ADHD.

The present study investigated Stroop interference effects in young adult and older deaf American Sign Language (ASL) and English bilinguals with ASL and English stimuli.

Deaf ASL-English bilinguals (n = 108; aged 21–88) signed their responses in two computerized Stroop tasks, one with ASL videos of color signs and one with printed English color words. Participants saw 120 trials in each language with 84 congruent and 36 incongruent trials.

Even though participants responded in ASL in both tasks, Stroop effects were larger with English than with ASL stimuli in both response times (RTs) and errors, a pattern of results not typically seen in spoken-language bilinguals (in which Stroop effects are often smaller between-languages than within-languages). Older participants showed larger Stroop effects than younger participants, especially in English RTs. Aging effects in error rates were not significant in either language.

The finding of larger Stroop effects in deaf signers with English rather than ASL stimuli suggests a possibly critical role for modality of presentation in eliciting Stroop effects. Additional work is needed to determine why English is more sensitive to aging effects in deaf signers, and which language will be most sensitive for detecting cognitive impairment in this population.

Neurosurgical resection of frontal lobe tumors poses specific challenges to the patients. Even when lesions involve the so-called “non-eloquent” areas, such as the prefrontal cortex, neurosurgery can still affect critical functions, because the prefrontal regions are essential for executive functions and other complex cognitive processes. The aim of this study is to systematically review the literature and quantitatively assess the impact of frontal lobe tumor resection on patients’ cognitive functioning.

In the present systematic review and meta-analysis, we synthesized data from 50 studies that included pre- and post-neurosurgery neuropsychological assessments. In addition, we conducted a meta-analysis of a subset of studies (n = 15) including sufficient data to quantitatively evaluate the cognitive effects of frontal lobe tumor resections.

We found that cognitive performance, after neurosurgery, was not significantly changed compared to pre-neurosurgery performance. We also identified several limitations in the literature, including variability in neuropsychological assessment protocols, differences in follow-up time points, inconsistent reporting of baseline cognitive functioning, and underpowered sample sizes.

In future studies, researchers should adopt standardized, comprehensive assessments, with well-powered cohorts and long-term follow-ups, to better characterize post-neurosurgical cognitive outcomes, including those regarding “non-eloquent” frontal regions. A multidisciplinary and harmonized approach remains crucial for understanding the cognitive impact of frontal lobe tumor neurosurgery and for improving patient care.

Recent studies indicate that anxiety is one of the most prevalent mental health challenges faced by children and adolescents diagnosed with autism spectrum disorder (ASD).

For young individuals with concurrent Intellectual disability disorder, these rates are projected to be significantly elevated.

Despite the estimated high prevalence of anxiety among young individuals with co-occurring ASD and intellectual developmental disorder (IDD), significant uncertainty remains in the field about the most effective methods for identifying, diagnosing, and treating anxiety in this distinct group.

The main objective of this narrative review is to examine the current literature on effective strategies and adjustments for evaluating and treating anxiety in children and adolescents who have co-occurring ASD and IDD, aiming to support professionals engaged with this significantly neglected group.

Digital testing is being regularly used in neuropsychological research. However, critical questions remain regarding its psychometric robustness, availability, and usability, potentially limiting its clinical impact.

This systematic review focused on the characteristics of digital tools for assessing attention and executive functions (EFs), two cognitive domains particularly suitable for being digitally tested. A systematic search was performed across three electronic databases (PubMed, Scopus, Embase). We only included studies performed on adults with validated tools.

Of 2,583 identified records, 236 studies met the inclusion criteria. From those, we extracted information about 107 distinct digital tools, ranging from computerized versions of traditional paper-and-pencil tests to emerging technologies such as virtual reality and eye-tracking hybrid systems. Most tools were administered in person (85%), while only 12% involved remote unsupervised assessment. Information on licensing, normative data, or source code availability was reported for approximately one-third of tools (34.9%). Most operated under paid licensing models, and only 6.5% were freely accessible. Only one had also source code available.

Several tools are available for assessing attention and EFs; however, most are not widely used. We discuss an imbalance between accessibility and validity whereby standardized batteries are often commercial and not necessarily more validated than less commonly adopted free-access tools. The limited validation of emerging technologies currently prevents their broader implementation. Overall, distinct digital tools offer complementary strengths rather than a single optimal solution. More standardized validation approaches and broader adoption of Open Science practices might support their integration into routine clinical practice.

Engagement in sports is associated with cognitive and academic functioning in youth. However, heterogenous methodology has resulted in mixed findings across the literature. We propose a new method for investigating how sports activity may affect cognition through metabolic equivalents (MET)-minutes per week during sports engagement and compare it against total number of sports engaged.

Using the Adolescent Brain Cognitive Development Study, 9,973 children between the ages of 9 and 10 years old were included. Parent report of children’s engagement in sports over the past year were utilized to calculate total MET-minutes per week. Youth participants completed the National Institutes of Health Toolbox. Generalized Additive Mixed Models were run to examine the relationship between MET-minutes on cognition, while controlling for Body Mass Index. The contribution of MET-minutes compared to total count of sports on cognitive performance were compared using Akaike Information Criterion values.

Both total MET-minutes per week and past-year total sports were non-linearly associated with increased performance on multiple tasks of executive functioning and decreased expressive vocabulary. MET-minutes were shown to contribute more robustly to models of cognition than total number of sports.

Past year MET-minutes per week was associated with increased cognitive performance, particularly in the domain of executive functioning, and was more sensitive to differences in cognition in contrast to total sports engagement. Indicating that greater measurement sensitivity for physical activity may increase predictive power on cognitive performance outcomes. Our findings provide more support for increasing physical activity in youth to promote cognitive trajectories.

Cognitive impairment is associated with language changes that emerge during verbal responses to neuropsychological assessments that traditional scoring does not capture. The current study investigated the utility of a linguistic analysis of paragraph recall responses for detecting cognitive impairment.

Digital voice recordings of logical memory (LM) were available from 598 Long Life Family Study participants with normal cognition and 112 with cognitive impairment. Linguistic polyfeature scores for immediate (PFS-IR) and delayed recall (PFS-DR) were created from weighted sums of features associated with cognitive impairment. Logistic regression models assessed the predictive value of each PFS for classifying cognitive impairment. Repeated measures models with generalized estimating equations assessed whether PFSs predict cognitive screener performance over time.

Twelve linguistic features and higher PFSs were associated with cognitive impairment (PFS-IR OR = 1.05; PFS-DR OR = 1.07). PFS-DR scores approximated the accuracy of traditional LM scoring (AUC-PR = 0.77 vs. 0.81, respectively). A higher PFS-DR was also associated with lower cognitive screener scores over an average of 7 years of follow-up (β = –0.08, 95% CI [–0.11, –0.06]).

Quantification of linguistic features from paragraph recall identified distinct linguistic markers that reflect differences in learning, retention, and self-monitoring. Summary feature scores detected cognitive impairment and predicted lower cognitive performance over time. This approach has potential implications for automated testing, recording, and scoring pipelines allowing for implementation of gold-standard neuropsychological assessments in broader clinical and research settings. Further studies are needed to validate these findings across clinical and community-based populations.

This prospective, longitudinal cohort study investigated cognitive functioning acutely and up to 6 months after pediatric mild traumatic brain injury (mTBI) relative to orthopedic injury (OI).

Children age 8–17 years with acute (≤48 hours) mTBI or OI were consecutively recruited from five pediatric Emergency Departments. Acute Predicting and Preventing Postconcussive Problems in Pediatrics (5P) clinical risk scores were calculated. Children completed three CNS Vital Signs computerized cognitive battery subtests acutely (≤48 hours) and at 7 days, 3 months, and 6 months post-injury, and performance validity testing at all post-acute assessments. Generalized least squares models were fitted for Reaction Time, Visual Memory, and Executive Function standard scores.

For children (N = 841; 556 mTBI/285 OI; 12.45 ± 2.41 years; 57.91% male; 68.13% White) with valid performance validity and cognitive test scores, Reaction Time was lower after mTBI relative to OI for older (but not younger) children; differences declined in magnitude from acutely (d = −1.11) to 6 months (d = −0.21). Visual Memory was mildly lower across time after mTBI (d = −0.20). Odds of clinically impaired (standard score < 80) Reaction Time were higher acutely and post-acutely after mTBI for older children (OR = 51.33 to 8.01), but did not differ by group for Visual Memory or Executive Function. 5P clinical risk scores did not predict cognitive scores after mTBI.

Pediatric mTBI negatively impacts cognition, especially for reaction time, ≤48 hours post-injury and among adolescents. Early cognitive dysfunction persists up to 6 months after mTBI in some children.

Traditional risk factors for cognitive impairment in non-Latino White adults do not manifest the same level of risk in Latinos. Despite research investigating culturally relevant factors, including acculturation, as it relates to Latino cognition, few studies have incorporated contextual factors for a more wholistic approach. We investigated acculturation-related factors within the context of socioenvironmental factors to study cognition in 8,476 self-identified Hispanic/Latino adults 45 years and older participating in the Hispanic Community Health Study/Study of Latinos baseline visit (2008–2011).

Acculturation-related (e.g., nativity, social/language-based) and socioenvironmental contextualizing factors at the individual-level (e.g., social network size, social isolation) as well as the neighborhood-level (e.g., income inequality, deprivation) were determined via questionnaire or geospatial coding. Cognitive tests included verbal learning and memory, letter fluency and digit symbol substitution. We included all acculturation in context variables in the same regression models as predictors of the separate cognitive outcomes (i.e., global and the four test-specific cognitive scores) adjusting for age at baseline, sex, and education.

Higher language- and social-based acculturation scores, later ages of migration, US-based parental nativity, greater familial structural support, fewer experiences of unfair treatment, as well as lower levels of neighborhood gentrification, income inequality, and deprivation were associated with higher global cognition. Many of these same variables were associated with test-specific cognitive performance.

This study, one of the first of its kind in Hispanic Community Health Study/Study of Latinos, suggests that contextualizing acculturation as it relates to cognition may point toward specific factors that may influence successful aging in middle-aged and older Hispanics/Latinos.

More than two decades ago, normative data for two interference indices (Error Interference Effect, EIE; Time Interference Effect, TIE) from a short form of the Stroop Color–Word Test (SCWT-SF) were established in Italy. The present study aimed to update the normative data for the Italian SCWT-SF by extending the assessment beyond interference indices to include completion times and error counts across the three task conditions, namely Word Reading (W), Color Naming (C), and Color–Word Interference (CW), and to provide evidence supporting its construct validity.

N = 317 healthy adults (195 females; age: 62.79 ± 11.97 years, range = 40–89; education 13.17 ± 4.03 years, range = 5–23) completed the SCWT-SF (3 color; 30 items per condition) and a test battery assessing processing speed (Psychomotor Speed Test; Trail-Making Test – Part A) and executive functioning (EF) (Saccade and Antisaccade Test; Digit Ordering Test; Trail-Making Test – Part B). Norms were derived for each SCWT-SF measure using the Equivalent Score method. Correlational analyses explored construct validity.

Older age and lower education negatively affected SCWT-SF scores. Female sex was associated with lower completion times on C condition. No predictors emerged for errors in W condition. Word-reading and color-naming outcomes were associated with measures of processing speed, while the CW condition and interference indices with tests of inhibitory control, working memory, and set-shifting.

We provided updated, regression-based normative data for the Italian SCWT-SF, encompassing individual scores across its three conditions and the original interference indices, and evidence supporting its convergent validity with measures of processing speed and EF.

Estimating functional independence is a critical component of neuropsychological evaluations in older adults. Commonly, three methods are used to estimate a patient’s ability to engage in instrumental activities of daily living (IADLs): (1) rating scales of functional independence and (2) performance-based measures comprising IADL tasks (reflecting two face-valid approaches), and (3) performance-based measures of executive functions (EF; reflecting a more theory-based approach). The purpose of the present study was to compare these three methods’ abilities to predict independent IADL capacity at home.

Community-dwelling older adults (n = 114) completed self-report and performance-based measures of IADLs, as well as traditional tests of EF at baseline. Following, participants completed the DAILIES protocol comprising 3 weeks of IADL tasks (e.g., paying bills, rescheduling appointments, etc.) performed independently at home.

Analyses showed that (a) EF performance speed and self-reported IADLs emerged as unique predictors (i.e., beyond each other) of the accuracy of the DAILIES task completion, and (b) EF performance speed also accounted for variance in the timeliness of DAILIES task completion. These relationships held beyond general cognitive status. However, receiver operating characteristic (ROC) analyses revealed that only EF performance speed had utility in identifying participants with below average accuracy and timeliness on the DAILIES protocol.

These findings suggest that traditionally measured EF may have more incremental utility than at least some more face-valid predictors (i.e., certain performance-based or self-reported IADLs) in predicting independent IADL capacity at home, at least among older adults without a diagnosis of a cognitive disorder.

Research has indicated that many medical and psychosocial factors contribute to cognitive deficits in sickle cell disease (SCD). Some studies of SCD in early childhood found cognitive functioning to be associated with socioeconomic status but not disease severity. The current study examined how the home environment is associated with cognitive functioning and school readiness in children with SCD.

Young children (n = 29; Mage = 4.4 years SD = 0.3) with SCD underwent an evaluation of cognitive and academic skills. Subsequently, researchers and caregivers completed the Home Observation for Measurement of the Environment (HOME), an in-home measure of cognitive stimulation. Linear regression was used to examine the relationship between each of the HOME subscales and cognitive and academic measures while controlling for genotype.

The total score from the HOME inventory was associated with overall IQ, working memory, and school readiness. Among the subscales of the HOME inventory, Learning Materials, Modeling, and Variety were associated with cognitive and academic outcomes.

Stimulation in a child’s home may affect cognitive and academic development in young children with SCD. Future research should examine the benefits of increasing learning materials and the variety of activities in the homes of young SCD patients.

To compare associations between neurocognitive testing and two different self-report paradigms: (1) recall-based (PROMIS Cognitive Function) and (2) real-time, task-specific (NASA-Task Load Index [NASA-TLX]) among 56 patients with breast cancer.

This is a secondary analysis from a phase II, single-arm trial of memantine to prevent cognitive decline among patients receiving chemotherapy for breast cancer (NCT04033419). Before chemotherapy and 4 weeks after their final cycle, participants completed neuropsychological assessment and self-report measures. Memantine was administered between assessments. At pre-chemotherapy, multivariable linear regression evaluated associations between a unit-weighted, composite neurocognitive test score with PROMIS Cognitive Function and NASA-TLX, controlling for age, cancer stage, and cognitive reserve. Explanatory analyses examined associations within individual neurocognitive subtests. Multivariable regression explored the extent to which pre-treatment self-reported cognition predicted post-treatment performance.

Pre-chemotherapy, higher NASA-TLX scores (greater perceived workload) were robustly associated with worse performance (β = −0.31 [−0.50, −0.12], p = .002). Relationships were strongest for executive function: Animal Fluency (IQR = 35): −3.3 (−5.8, −0.8), p = .011; COWA (IQR = 36) = −6.7 (−12.8, −0.7), p = .031; One Touch Stockings (IQR = 31): −0.70 (−1.0, −0.3), p < .001. Pre-treatment NASA-TLX was also associated with post-treatment performance in univariable but not multivariable models. PROMIS Cognitive Function and neurocognitive performance were not associated.

The NASA-TLX and neurocognitive performance were strongly associated, particularly in the executive function domain. Future work involving the NASA-TLX in cancer populations, including its use in everyday contexts, will help clarify whether it may enhance CRCI characterization.

Reading ability is commonly used as a proxy for educational quality but may be unsuitable for cross-cultural comparisons. This study aimed to evaluate a novel Brief Mathematics Achievement Test (BMAT) as a proxy measure of quality of education (QoE) in culturally and linguistically diverse populations.

Data on demographic variables, socioeconomic status (SES), country-level QoE, and performance on the BMAT and brief cognitive tests, were collected from 157 cognitively healthy participants (18–89 years) including native-born and immigrant populations in five European countries.

No significant differences were found between females and males or between participants with native-born and immigrant backgrounds in BMAT scores. In correlation analyses, BMAT scores were strongly correlated with SES, level of education, and performance on a brief cognitive composite, moderately with student–teacher ratio, country income classification, and a quality of education index, and weakly with age. In regression models controlling for key demographic variables and socioeconomic status, BMAT scores were significantly associated with level of education and the QoE index, while showing no significant relationship with immigrant status. Also, after controlling for demographic variables, SES, and the quality of education index, BMAT scores were the only significant predictor of performance on the brief cognitive composite.

These findings provide preliminary evidence supporting the potential utility of the BMAT as an objective proxy measure of QoE in culturally and linguistically diverse populations.

Few studies have examined how differing diagnostic criteria for mild cognitive impairment (MCI) relate to neuroimaging markers of cerebrovascular disease and neurodegeneration in Veterans. We compared three MCI diagnostic schemes on their associations with white matter hyperintensity (WMH) burden, hippocampal volume, and cortical thickness in nondemented Vietnam-era Veterans.

228 Veterans (mean age = 69.65) were classified using: (1) Alzheimer’s Disease Neuroimaging Initiative (ADNI) criteria (subjective memory concerns, impaired Logical Memory, global Clinical Dementia Rating = 0.5); (2) neuropsychological criteria (>1 standard deviation [SD] below norms on two tests within a domain or one test across three domains); and (3) typical criteria (subjective memory concerns and >1.5 SD below norms on one test). Regression models predicting WMH burden adjusted for age and intracranial volume and included MCI status and hippocampal volume; ADNI-based models also included posttraumatic stress disorder symptom severity.

Neuropsychological criteria were associated with greater WMH burden (β = 0.45, p = .024), whereas typical and ADNI criteria were not. Sensitivity analyses found that meeting neuropsychological criteria for amnestic MCI interacted with lower hippocampal volume to predict greater WMH burden (β = −0.001, p = .028). No criteria were associated with cortical thickness.

Neuropsychological criteria more sensitively identified Veterans with greater WMH burden and demonstrated a small, hippocampal volume-dependent effect in amnestic MCI. These findings support the clinical utility of multi-test neuropsychological approaches for detecting complex brain changes in high-comorbidity populations, with implications for risk stratification and targeted intervention in aging Veterans.

Poor social function in people with psychosis has been linked to impairments in social cognition and neurocognition, which in turn have been identified as promising treatment targets. We developed a novel social cognitive intervention, Understanding Social Situations (USS), that minimizes cognitive load by leveraging delivery methods common to cognitive rehabilitation. USS focuses on making good judgments about what others may be feeling and thinking, and how they might respond in various social scenarios. In the current trial, we evaluated the efficacy of USS versus an active control.

103 Veterans with psychotic spectrum disorders were randomized to two months of USS training or a problem-solving training matched for nonspecific treatment factors. Comprehensive assessments included clinician-aided self-report social functioning, social skills performance, and pre/post/follow-up ecological momentary assessments about the extent and quality of social interactions.

Participants in USS had significant within but not between group improvements on a clinician-aided self-report measure of social function. Social skills performance did not change for either condition. Momentary assessments revealed no change in frequency of social contacts, but those in the USS condition showed within-group improvements on comfort level during current social interactions and anticipated positive appraisals of future interactions. Those randomized to problem-solving training had significantly greater improvements in depression at post-training.

More rigorous trials are needed evaluating the impact of social cognitive interventions on real-world social functioning. It may be particularly important to link interventions to lived social experience and to assess the quality of social interactions.