Inhibitory Control Performance Research Articles

Neuromodulation of inhibitory control using phase-lagged transcranial alternating current stimulation

BackgroundTranscranial alternating current stimulation (tACS) is a prominent non-invasive brain stimulation method for modulating neural oscillations and enhancing human cognitive function. This study aimed to investigate the effects of individualized theta tACS delivered in-phase and out-of-phase between the dorsal anterior cingulate cortex (dACC) and left dorsolateral prefrontal cortex (lDLPFC) during inhibitory control performance.MethodsThe participants engaged in a Stroop task with phase-lagged theta tACS over individually optimized high-density electrode montages targeting the dACC and lDLPFC. We analyzed task performance, event-related potentials, and prestimulus electroencephalographic theta and alpha power.ResultsWe observed significantly reduced reaction times following out-of-phase tACS, accompanied by reduced frontocentral N1 and N2 amplitudes, enhanced parieto-occipital P1 amplitudes, and pronounced frontocentral late sustained potentials. Out-of-phase stimulation also resulted in significantly higher prestimulus frontocentral theta and alpha activity.ConclusionsThese findings suggest that out-of-phase theta tACS potently modulates top-down inhibitory control, supporting the feasibility of phase-lagged tACS to enhance inhibitory control performance.

Development of working memory and inhibitory control in early childhood: Cross-sectional analysis by age intervals and gender in Ecuadorian preschoolers.

Working memory (WM) and inhibitory control (IC) play a crucial role in learning during early childhood. The literature suggests a non-linear developmental trajectory of executive functions (EFs) with varied results according to gender, usually attributed to environmental factors. However, there is insufficient and inconclusive data on whether this pattern is reproduced in the Latin American preschool population since most studies have been conducted in English-speaking, European, and Asian environments. Thus, objectively comparing children's executive performance across diverse international geographical contexts becomes challenging. This study aimed to conduct a cross-sectional analysis of the performance in WM and IC of 982 Ecuadorian preschoolers aged between 42 and 65 months (M = 53.71; SD = 5.714) and belonging to medium-high, medium, and low-medium socioeconomic strata. The participants consisted of 496 boys (M = 53.77; SD = 5.598) and 486 girls (M = 53.65; SD = 5.834), representing nine cities in Ecuador. To assess the effect of age and gender on performance in these two domains, the sample was divided into four 6-month age intervals. Two tests were administered to the participants, and a survey was conducted with 799 of their usual caregivers. Viewing the cross-sectional mean scores of the WM and IC tests as a temporal continuum reveals an upward trend in each age interval studied. Girls outperformed boys on the IC test, showing statistically significant differences in the earliest age interval. The gender differences in executive performance reported in the literature emphasize the need to explore the modulating effect of environmental variables on early childhood development. This information could offer valuable insights for adapting and optimizing cognitive and didactic strategies in early childhood tailored to the characteristics and needs of the preschool population.

An investigation of the acute effects of aerobic exercise on executive function and cortical excitability in adolescents with attention deficit hyperactivity disorder (ADHD).

Previous studies have shown that aerobic exercise has beneficial effects on executive function in adolescents with attention-deficit hyperactivity disorder (ADHD). The underlying mechanisms could be partially due to aerobic exercise-induced cortical excitability modulation. The aim of this study was to explore the effects of acute aerobic exercise on executive functions and cortical excitability and the association between these phenomena in adolescents with ADHD. The study was conducted using a complete crossover design. Executive functions (inhibitory control, working memory, and planning) and cortical excitability were assessed in twenty-four drug-naïve adolescents with ADHD before and after acute aerobic exercise or a control intervention. Inhibitory control, working memory, and planning improved after acute aerobic exercise in adolescents with ADHD. Moreover, cortical excitability monitored by transcranial magnetic stimulation (TMS) decreased after intervention in this population. Additionally, improvements in inhibitory control and working memory performance were associated with enhanced cortical inhibition. The findings provide indirect preliminary evidence for the assumption that changes in cortical excitability induced by aerobic exercise partially contribute to improvements in executive function in adolescents with ADHD.

The effect of financial stress on inhibitory control and economic decisions

Financial scarcity, both real and imagined, is associated with impaired executive functions and present-focused economic decisions. What is the mechanism that connects the lack of financial resources to these cognitive and behavioral effects? The present work will test the hypothesis that the experience of financial stress contributes to these deficits by reducing executive functions related to self-control and causing present-focused, real-world economic decisions. In a preliminary experiment (N = 215), we found support for the hypothesis that financial stress (as compared to social stress) causes a reduction in inhibitory control performance. In the registered study, we recruited participants (N = 1014) from diverse socioeconomic backgrounds and assessed inhibitory control before and after a financial stress manipulation, and economic preferences. The results did not support the hypothesis that momentary financial stress reduces inhibitory control or alters time preference. However, chronic financial stress was associated with reduced inhibitory control and VWM, and real-world economic decisions. Several interactions between SES and the effect of conditions highlight the relevance of a person's SES in the association between affective experiences and cognitive and behavioral responses. We discuss the implications of this work for future study of the association between SES, executive function, and economic decisions.

The relationship between cardiorespiratory fitness and inhibitory control following acute stress: An ERP study.

Although the relationships among acute stress, cardiorespiratory fitness (CRF), and cognitive function have been examined, whether CRF is related to behavioral and neuroelectric indices of inhibitory control following acute stress remains unknown. The purpose of the current study was to investigate the combined influence of acute stress and CRF on inhibitory control. Participants, aged 20-30 years, were stratified into the Higher-Fit (n = 31) and the Lower-Fit (n = 32) groups, and completed a Stroop task following the modified Maastricht Acute Stress Test (MAST) in the stress condition and the sham-MAST in the non-stress condition, during which electroencephalography was recorded. Behavioral (i.e., response time and accuracy) and neuroelectric (N2 and P3b components of the event-related potential) outcomes of inhibitory control were obtained. While the Higher-Fit group demonstrated shorter response times and higher accuracy than the Lower-Fit group following both the MAST and the sham-MAST, they also exhibited selective benefits of acute stress on inhibitory control performance (i.e., decreased response times and diminished interference scores). CRF-dependent alterations in neuroelectric indices were also observed, with the Higher-Fit group displaying smaller N2 and greater P3b amplitudes than the Lower-Fit group following the sham-MAST, and increased N2 and attenuated P3b amplitudes following the MAST. Collectively, these findings not only confirm the positive relationship between CRF and inhibitory control but also provide novel insights into the potential influence of CRF on inhibitory control and associated neuroelectric activity following acute stress.

Left OFC Activation in Functional Near-Infrared Spectroscopy during an Inhibitory Control Task in an Early Years Sample: Integrating Stress Responses with Cognitive Function and Brain Activation.

Previous functional near-infrared spectroscopy (fNIRS) studies using Go/No-Go (GNG) tasks have focused on brain activation in relation to cognitive processes, particularly inhibitory control (IC). The results of these studies commonly describe right hemispheric engagement of the dorsolateral, ventromedial, or inferior frontal regions of the prefrontal cortex. Considering that typical healthy cognitive development is negatively correlated with higher cortisol levels (which may alter brain development), the overarching aim of the current study was to investigate how elevated stress (due to unforeseeable events such as the pandemic) impacts early cognitive development. In this study, we examined fNIRS data collected from a sample of children (aged 2-4 years) during a GNG task relative to the response to stressors measured via hair cortisol concentrations. We acquired data in an ecological setting (Early Childhood Education and Care) during the coronavirus pandemic. We found that children with higher stress levels and a less efficient IC recruited more neural terrain and our group-level analysis indicated activation in the left orbitofrontal area during IC performance. A contextual stressor may disrupt accuracy in the executive function of IC early in development. More research efforts are needed to understand better how an orbitofrontal network subserves goal-directed behavior.

Shifts in intrinsic neural timescale of hippocampus support the maturation of inhibitory control and working memory in youth

The intrinsic neural timescale (INT) provides temporal windows in brain activity that process information of different durations, crucial for the integration and segregation of external inputs and ultimately shaping cognition and behavior. Recent research has uncovered a pronounced INT hierarchy along the adult hippocampus's long-axis. Yet, the development of INT organization within the hippocampus—particularly the pattern of its hierarchical structure and its impact on cognitive development—has not been thoroughly investigated in youth. Here, we discovered that the INT distribution in youth presents a distinct hierarchical structure along both posterior-anterior and proximal-distal axes of the hippocampus. Strikingly, this hierarchical structure correlates significantly with the first principal gradient of the hippocampal-cortical functional connectome and the thickness of hippocampal grey matter. Furthermore, we observed notable changes in the hippocampal INT landscape during youth, characterized by a general narrowing of timescales, alongside dedifferentiation along the hippocampal organizational axes. These maturational changes significantly link to improvements in inhibitory control and working memory performance. Collectively, our findings reveal the developmental patterns of temporal integration and segregation hierarchies within hippocampus, and highlights the profound significance of INT as a neural underpinning that orchestrates cognitive growth.

Enhancing Executive Functions in Pediatric Epilepsy: Feasibility and Efficacy of a Computerized Cognitive Training Program.

Epilepsy, a prevalent neurological disorder characterized by recurrent seizures, significantly impacts individuals' neurobiological, cognitive, and social lives. This report presents a feasibility study investigating the effects of a computerized cognitive training program on enhancing executive functions, particularly inhibitory control, in children and adolescents with epilepsy. Employing a pre-test-intervention-post-test design, the study involved 26 participants with diverse epileptic syndromes, focusing on those without severe intellectual disabilities. The intervention, based on the CogniFit Inc. platform, consisted of personalized tasks aiming to improve participants' inhibitory skills over 16 weeks, with an average of 40 sessions completed per participant. Results indicated significant improvements in reaction times and error rates in an anti-saccade task, demonstrating enhanced inhibitory control and general performance post-intervention. These findings suggest that targeted cognitive training is a feasible approach to bolster executive functions in young individuals with epilepsy, potentially improving their academic performance, employability, and social interactions. The study underscores the importance of early cognitive interventions in epilepsy management, highlighting the potential for computerized programs to aid in mitigating cognitive deficits associated with the condition.

Interplay among Anxiety, Digital Environmental Exposure, and Cognitive Control: Implications of Natural Settings.

Inhibitory control performance may differ greatly as a function of individual differences such as anxiety. Nonetheless, how cognitive control proficiency might be influenced by exposure to various environments and how anxiety traits might impact these effects remain unexplored. A cohort of thirty healthy volunteers participated in the study. Participants performed a Go/No-Go task before exposure to a 'forest' and 'urban' virtual environment, in a counterbalanced design, before repeating the GNG task. The State-Trait Anxiety Inventory (STAI) was finally filled-in. Our findings unveiled an initial negative correlation between anxiety trait levels and GNG task performance, consistent with the established literature attributing difficulties in inhibitory functionality to anxiety. Additionally, different environmental exposures reported opposite trends. Exposure to the 'forest' environment distinctly improved the GNG performance in relation to anxiety traits, while the 'urban' setting demonstrated adverse effects on task performance. These results underscore the intricate relationship among cognitive control, environmental exposure, and trait anxiety. In particular, our findings highlight the potential of natural settings, such as forests, to mitigate the impact of anxiety on inhibition. This might have implications for interventions aimed at improving cognitive control.

Out-of-phase transcranial alternating current stimulation modulates the neurodynamics of inhibitory control

Transcranial alternating current stimulation (tACS) is an efficient neuromodulation technique that enhances cognitive function in a non-invasive manner. Using functional magnetic resonance imaging, we investigated whether tACS with different phase lags (0° and 180°) between the dorsal anterior cingulate and left dorsolateral prefrontal cortices modulated inhibitory control performance during the Stroop task. We found out-of-phase tACS mediated improvements in task performance, which was neurodynamically reflected as putamen, dorsolateral prefrontal, and primary motor cortical activation as well as prefrontal-based top-down functional connectivity. Our observations uncover the neurophysiological bases of tACS-phase-dependent neuromodulation and provide a feasible non-invasive approach to effectively modulate inhibitory control.

Effects of aerobic exercise on children's executive function and academic performance: A systematic review and meta-analysis

ObjectiveTo investigate the effects of exercise on executive function in children, providing an evidence-based foundation to inform future research in school physical education and health education. MethodsWe searched ten databases: Cochrane Library, Scopus, OVID, Web of Science, PubMed, EBSCOhost, SPORTDiscus, PsycINFO, CNKI, WANFANG DATA, VIP, and SinoMed, and eight articles were included. Applying the revised Cochrane Risk of Bias Tool for Randomized Trials (RoB2), funnel plots and Egger regression analysis were integrated with R meta-analysis to screen for publication bias. The quality of the evidence was appraised using the Grading system. ResultsThe included literature contained 2655 participants, with 1308 in the experimental group and 1347 in the control group. The results indicated that the aerobic exercise group considerably improved inhibitory control in children compared to the control group [SMD = 0.29, 95% CI (0.05, 0.54), P = 0.018]; working memory [SMD = 0.25, 95% CI (0.07, 0.42), P = 0.005]; and cognitive flexibility [SMD = 0.36, 95% CI (0.17, 0.54), P < 0.001]. However, the findings indicated that only aerobic exercise interventions extending beyond 50 weeks positively influenced academic performance in children [SMD = 1.19, 95% CI (0.34, 2.04), P = 0.006]. The results of an Egger regression analysis revealed that the p-values for inhibitory control, working memory, cognitive flexibility, and academic performance were more significant than 0.1. The Grade system said that the quality of evidence was all low regarding the level of evidence. ConclusionAerobic exercise enhanced executive function but only aerobic exercise interventions extending beyond 50 weeks demonstrated a significant effect on the academic performance of children. Due to the low quality of evidence presented in this study, additional high-quality randomized controlled trials are needed to confirm these findings.

The phase of tACS-entrained pre-SMA beta oscillations modulates motor inhibition

Inhibitory control has been linked to beta oscillations in the fronto-basal ganglia network. Here we aim to investigate the functional role of the phase of this oscillatory beta rhythm for successful motor inhibition. We applied 20 Hz transcranial alternating current stimulation (tACS) to the pre-supplementary motor area (pre-SMA) while presenting stop signals at 4 (Experiment 1) and 8 (Experiment 2) equidistant phases of the tACS entrained beta oscillations. Participants showed better inhibitory performance when stop signals were presented at the trough of the beta oscillation whereas their inhibitory control performance decreased with stop signals being presented at the oscillatory beta peak. These results are consistent with the communication through coherence theory, in which postsynaptic effects are thought to be greater when an input arrives at an optimal phase within the oscillatory cycle of the target neuronal population. The current study provides mechanistic insights into the neural communication principles underlying successful motor inhibition and may have implications for phase-specific interventions aimed at treating inhibitory control disorders such as PD or OCD.

Connectivity-based neuromarker for children’s inhibitory control ability and its relevance to body mass index

ABSTRACT Preserving a normal body mass index (BMI) is crucial for the healthy growth and development of children. As a core aspect of executive functions, inhibitory control plays a pivotal role in maintaining a normal BMI, which is key to preventing issues of childhood obesity. By studying individual variations in inhibitory control performance and its associated connectivity-based neuromarker in a sample of primary school students (N = 64; 9–12 yr), we aimed to unravel the pathway through which inhibitory control impacts children’s BMI. Utilizing resting-state functional MRI scans and a connectivity-based psychometric prediction framework, we found that enhanced inhibitory control abilities were primarily associated with increased functional connectivity in brain structures vital to executive functions, such as the superior frontal lobule, superior parietal lobule, and posterior cingulate cortex. Conversely, inhibitory control abilities displayed a negative relationship with functional connectivity originating from reward-related brain structures, such as the orbital frontal and ventral medial prefrontal lobes. Furthermore, we revealed that both inhibitory control and its corresponding neuromarker can moderate the association between food-related delayed gratification and BMI in children. However, only the neuromarker of inhibitory control maintained its moderating effect on children’s future BMI, as determined in the follow-up after one year. Overall, our findings shed light on the potential mechanisms of how inhibitory control in children impacts BMI, highlighting the utility of the connectivity-based neuromarker of inhibitory control in the context of childhood obesity.

Inhibitory control expertise through sports practice: A scoping review

Introduction&#x0D; The stopping of a planned motor response is called motor inhibitory control (IC) and allows humans to produce appropriate goal-directed behaviour. The ever-changing environment of many sports requires athletes to rapidly adapt to unpredictable situations in which split-second suppressions of planned or current actions are needed.&#x0D; Methods&#x0D; In this scoping review, the approach of the PRISMA-ScR was used to determine whether sports practice develops IC and, if so, which sports factors are key to building IC expertise. The PubMed, Web of Science Core Collection, ScienceDirect and APA PsycNet Advanced Search databases were searched with predefined combinations of keywords.&#x0D; Results&#x0D; Twenty-six articles were selected and analysed. Most of the publications (n = 21) compared athletes with non-athletes, or athletes from other sports. Only a few articles (n = 5) reported results from intra-sport comparison. Overall, the studies reported better IC performance in athletes compared to non-athletes.&#x0D; Discussion/Conclusion&#x0D; The correlational link from sports practice to IC improvement is observed but additional longitudinal protocols are needed to prove its direct link. Findings have implication for determining whether IC could represent a marker of performance and thus for supporting the implementation of cognitive training in sport.

Impact of Training Discipline and Experience on Inhibitory Control and Cognitive Performance in Pet Dogs

Training experience has been shown to enhance a dog’s cognitive performance when comparing highly trained working or sporting dogs with untrained dogs. However, whether the type or level of training a pet dog receives can alter their performance in cognitive tasks requiring inhibitory control has not been assessed. Here, we tested whether pet dogs trained in scent work, agility, and obedience differ in cognitive performance. The impact of primary training discipline and combined training experience was assessed using two well-defined tasks that require inhibitory control: (1) the A-not-B task, in which dogs must inhibit a previously learned response in favour of an alternative response; and (2) the detour task, in which dogs must inhibit a direct approach to food to gain a reward. Dogs trained in scent work demonstrated higher levels of inhibitory control and persistence across the two tasks, but this did not affect individual task performance. Increased combined training experience improved learning in the A-not-B task training phase, but did not alter performance during the test phase, whereas it had no effect on success in the detour task. Overall, dogs that performed better in the A-not-B task were also more likely to succeed in the detour task, showing a relationship in the cognitive ability underpinning performance in the two tasks. The effect of the primary discipline on the behavioural phenotype shows that this should be accounted for in future studies, rather than applying the practice of partitioning dogs into highly trained vs. untrained groups.

Cognitive dysfunction in systemic lupus erythematosus is associated with disease activity and oxidative stress: a comparative study with rheumatoid arthritis for identifying biomarkers

BackgroundThe prevalence and pathophysiological mechanisms of cognitive deficits (CD) Systemic Lupus Erythematosus (SLE) and Rheumatoid arthritis (RA) are very heterogeneous and poorly understood. We characterized CD in patients with SLE compared with RA patients and healthy controls. We compared the neuropsychological profile of SLE and RA with patients’ oxidative/inflammatory biomarkers for CD.MethodsWe performed a cross-sectional study, including 50 SLE patients, 29 RA patients, and 32 healthy controls. SLEDAI and DAS28 assessed disease activity. SF-36 questionnaire and a battery of cognitive tests were applied to all participants. Blood samples were collected to determine IL-6, S100ß, myeloperoxidase (MPO), malondialdehyde and reduced glutathione (GSH) alterations.ResultsIn the SLE group, higher GSH was associated with the absence of CD (With CD = 69 ± 49, Without CD = 112 ± 81, p = 0.030), while higher IL-6 was associated with the presence of CD in the RA group (With CD = 603 ± 173, Without CD = 431 ± 162, p = 0.032). Regarding specific cognitive domains, in SLE higher MPO was associated with poor performance in reasoning and abstraction (p = 0.039), higher IL-6 was associated with poor performance in inhibitory control and attention (p = 0.031), and higher GSH was associated with better performance in memory(p = 0.021). Higher SLEDAI was associated with poor performance in semantic fluency(p = 0.031), inhibitory control, and attention in the SLE group(p = 0.037). In the RA group, higher DAS-28 was associated with poor performance in executive functions(p = 0.016) and phonemic fluency (p = 0.003).ConclusionSLE patients’ disease activity, inflammatory state, and oxidative stress were associated with CD. In RA patients, CD was associated with disease activity and inflammatory state. These results encourage further studies with larger samples aiming to confirm oxidative stress parameters as biomarkers of CD in SLE patients.

Effectiveness of social management training on executive functions in males with Klinefelter syndrome (47, XXY)

Men with an extra X chromosome are at risk for social difficulties in which executive functions are known to play an important role. The aim of this study was to examine the potential efficacy of a novel neurocognitive-behavioral treatment program tailored to the specific vulnerabilities of Klinefelter syndrome (47, XXY). Social Management Training (SMT) aimed to increase the ability of individuals to regulate their thoughts, emotions and behaviors in ways that are socially adaptive. 16 Adolescents and men with Klinefelter Syndrome participated in SMT. This novel group treatment program consists of 10 sessions and includes psychoeducation, cognitive-behavioral skills training, home-assignments, and relaxation exercises. There were pre- and posttest cognitive assessments (five months apart) of executive functioning including sustained attention, inhibition, cognitive flexibility and working memory, as well as self-evaluation of executive functioning in daily life. Significant pre- to posttest improvements in inhibitory control (performance test) and metacognition skills (self-report) were found, with effects sizes of 1.3 and 0.5, respectively. No effects of intervention were found on sustained attention, cognitive flexibility and working memory. These findings suggest that SMT, with a key focus on executive dysfunction and tailored to the behavioral and cognitive profile of males with Klinefelter syndrome, may be a promising and potentially efficacious treatment approach for improving self-control and social adaptation, although larger and randomized controlled studies are warranted.

Genetic and context-specific effects on individual inhibitory control performance in the guppy (Poecilia reticulata).

Among-individual variation in cognitive traits, widely assumed to have evolved under adaptive processes, is increasingly being demonstrated across animal taxa. As variation among individuals is required for natural selection, characterizing individual differences and their heritability is important to understand how cognitive traits evolve. Here, we use a quantitative genetic study of wild-type guppies repeatedly exposed to a 'detour task' to test for genetic variance in the cognitive trait of inhibitory control. We also test for genotype-by-environment interactions (GxE) by testing related fish under alternative experimental treatments (transparent vs. semi-transparent barrier in the detour-task). We find among-individual variation in detour task performance, consistent with differences in inhibitory control. However, analysis of GxE reveals that heritable factors only contribute to performance variation in one treatment. This suggests that the adaptive evolutionary potential of inhibitory control (and/or other latent variables contributing to task performance) may be highly sensitive to environmental conditions. The presence of GxE also implies that the plastic response of detour task performance to treatment environment is genetically variable. Our results are consistent with a scenario where variation in individual inhibitory control stems from complex interactions between heritable and plastic components.

High temperatures are associated with reduced cognitive performance in wild southern pied babblers.

Global temperatures are increasing rapidly. While considerable research is accumulating regarding the lethal and sublethal effects of heat on wildlife, its potential impact on animal cognition has received limited attention. Here, we tested wild southern pied babblers (Turdoides bicolor) on three cognitive tasks (associative learning, reversal learning and inhibitory control) under naturally occurring heat stress and non-heat stress conditions. We determined whether cognitive performance was explained by temperature, heat dissipation behaviours, individual and social attributes, or proxies of motivation. We found that temperature, but not heat dissipation behaviours, predicted variation in associative learning performance. Individuals required on average twice as many trials to learn an association when the maximum temperature during testing exceeded 38°C compared with moderate temperatures. Higher temperatures during testing were also associated with reduced inhibitory control performance, but only in females. By contrast, we found no temperature-related decline in performance in the reversal learning task, albeit individuals reached learning criterion in only 14 reversal learning tests. Our findings provide novel evidence of temperature-mediated cognitive impairment in a wild animal and indicate that its occurrence depends on the cognitive trait examined and individual sex.

Repeatability and heritability of inhibitory control performance in wild toutouwai (Petroica longipes).

Despite increasing interest in the evolution of inhibitory control, few studies have examined the validity of widespread testing paradigms, the long-term repeatability and the heritability of this cognitive ability in the wild. We investigated these aspects in the inhibitory control performance of wild toutouwai (North Island robin; Petroica longipes), using detour and reversal learning tasks. We assessed convergent validity by testing whether individual performance correlated across detour and reversal learning tasks. We then further evaluated task validity by examining whether individual performance was confounded by non-cognitive factors. We tested a subset of subjects twice in each task to estimate the repeatability of performance across a 1-year period. Finally, we used a population pedigree to estimate the heritability of task performance. Individual performance was unrelated across detour and reversal learning tasks, indicating that these measured different cognitive abilities. Task performance was not influenced by body condition, boldness or prior experience, and showed moderate between-year repeatability. Yet despite this individual consistency, we found no evidence that task performance was heritable. Our findings suggest that detour and reversal learning tasks measure consistent individual differences in distinct forms of inhibitory control in toutouwai, but this variation may be environmentally determined rather than genetic.