Information processing and intelligence: Some implications of task complexity

Can you tell people's cognitive ability level from their response patterns in questionnaires?

Questionnaires are ever present in survey research. In this study, we examined whether an indirect indicator of general cognitive ability could be developed based on response patterns in questionnaires. We drew on two established phenomena characterizing connections between cognitive ability and people's performance on basic cognitive tasks, and examined whether they apply to questionnaires responses. (1) The worst performance rule (WPR) states that people's worst performance on multiple sequential tasks is more indicative of their cognitive ability than their average or best performance. (2) The task complexity hypothesis (TCH) suggests that relationships between cognitive ability and performance increase with task complexity. We conceptualized items of a questionnaire as a series of cognitively demanding tasks. A graded response model was used to estimate respondents' performance for each item based on the difference between the observed and model-predicted response ("response error" scores). Analyzing data from 102 items (21 questionnaires) collected from a large-scale nationally representative sample of people aged 50+ years, we found robust associations of cognitive ability with a person's largest but not with their smallest response error scores (supporting the WPR), and stronger associations of cognitive ability with response errors for more complex than for less complex questions (supporting the TCH). Results replicated across two independent samples and six assessment waves. A latent variable of response errors estimated for the most complex items correlated .50 with a latent cognitive ability factor, suggesting that response patterns can be utilized to extract a rough indicator of general cognitive ability in survey research.

The assessment of executive function abilities in healthy and neurodegenerative aging-A selective literature review

Numerous studies have examined executive function (EF) abilities in cognitively healthy older adults and those living with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Currently, there are no standard accepted protocols for testing specific EFs; thus, researchers have used their preferred tool, which leads to variability in assessments of decline in a particular ability across studies. Therefore, there is a need for guidance as to the most sensitive tests for assessing EF decline. A search of the most current literature published between 2000 and 2022 on EF studies assessing cognitively healthy older adults and individuals living with MCI and AD was conducted using PubMed/Medline, PsycINFO, Embase, Web of Science, and Google Scholar. Emphasis was placed on the EF's dual-tasking, inhibition, shifting or switching, and working memory updating. Many tasks and their outcomes were reviewed. Of particular importance was the difference in outcomes for tasks applied to the same group of participants. These various EF assessment tools demonstrate differences in effectively identifying decline in EF ability due to the aging process and neurodegenerative conditions, such as MCI and AD. This review identifies various factors to consider in using particular EF tasks in particular populations, including task demand and stimuli factors, and also when comparing differing results across studies.

Mental counters as an online tool for assessing working memory capacity

Working memory capacity (WMC) describes an individual's ability to focus their attention in the face of interference which allows them to actively maintain and manipulate information in immediate memory. Individual differences in WMC predict a wide range of psychological constructs. The development of online measures can enable data collection from broader, more diverse samples than those typically collected in person in laboratory settings. In addition, logistical challenges brought on by the COVID-19 pandemic have mandated the need for reliable and valid remote assessments of individual differences that are both culture-fair and less susceptible to cheating. This study reports details of a new online version of a Mental Counters task that takes only 10 min to collect and provides evidence for its reliability and convergent validity with other measures including Picture Span and Paper Folding.

Graph Mapping: A novel and simple test to validly assess fluid reasoning

We present Graph Mapping - a simple and effective computerized test of fluid intelligence (reasoning ability). The test requires structure mapping - a key component of the reasoning process. Participants are asked to map a pair of corresponding nodes across two mathematically isomorphic but visually different graphs. The test difficulty can be easily manipulated - the more complex structurally and dissimilar visually the graphs, the higher response error rate. Graph Mapping offers high flexibility in item generation, ranging from trivial to extremally difficult items, supporting progressive item sequences suitable for correlational studies. It also allows multiple item instances (clones) at a fixed difficulty level as well as full item randomization, both particularly suitable for within-subject experimental designs, longitudinal studies, and adaptive testing. The test has short administration times and is unfamiliar to participants, yielding practical advantages. Graph Mapping has excellent psychometric properties: Its convergent validity and reliability is comparable to the three leading traditional fluid reasoning tests. The convenient software allows a researcher to design the optimal test variant for a given study and sample. Graph Mapping can be downloaded from: https://osf.io/wh7zv/.

Executive Function Poststroke: Concepts, Recovery, and Interventions

Executive function is frequently impaired among people who have sustained stroke. This review provides an overview of definitions, concepts, and measures. The review also summarizes current best evidence examining executive function impairment and recovery trajectories after stroke, correlates of change over time, and emerging intervention research. Finally, this review provides recommendations for research and clinical practices, as well as priorities for future executive function research.

Executive functions in primary progressive aphasia: A meta-analysis

Executive functions (EFs) refer to a set of cognitive processes, specifically shifting, inhibition, updating of working memory, and are involved in the cognitive control of behavior. Conflicting results have been reported regarding impairments of EFs in Primary Progressive Aphasia (PPA). We performed a multi-level meta-analysis to confirm whether deficits of EFs exist in this population, focusing on a common EFs composite, and the components shifting, inhibition and updating separately. We included 141 studies that report on 294 EFs tasks. The overall mean weighted effect size was large (d = -1,28), indicating poorer EFs in PPA as compared to age-matched cognitively healthy controls. Differences between effect sizes of the EFs components were not significant, indicating all components are affected similarly. Overall, moderator analysis revealed that PPA variant and disease duration were significant moderators of performance, while task modality and years of education were not. The non-fluent/agrammatic PPA and the logopenic PPA variants were similarly affected, but the semantic variant was affected to a lesser extent. We discuss implications for clinical and research settings, and future research.

Uncovering the course of analogical mapping using eye tracking

Analogical mapping - the core component of analogical reasoning - consists of establishing the relational structure shared by two analogous situations and inferring the missing elements in a less familiar situation from a more familiar one. Several existing models of analogy predicted that the complete relational structure can be considered in parallel. Other models postulated that mapping can be less or more incremental - it can access only a relatively small part of the structure, and needs to move to its other parts in steps in order to construct the final relational correspondence. However, the precise time course of analogical mapping, especially in sufficiently complex analogies, to date was rarely studied empirically. In two studies, eye tracking was used to assess in a rigorous way the extent to which mapping can be incremental. In a newly designed geometric A:B::C:D task, pattern D was generated from C according to the same shape transformations that generated pattern B from A. The six possible response options differed systematically in the number of correct transformations, from no transformation matching, via partial relational match, up to the full match. In Study 1, the relational match of options fixated on by participants was initially low but increased monotonically over the course of analogy. The number of corresponding eye fixations predicted 68% variance in relational match of the final response. The correct option was chosen only if fixated on for a sufficiently long time. Study 2 replicated the findings using a more ecologically valid and less demanding task variant that required to map the changes in people's appearance. The results support these theoretical models of analogy which postulate strictly incremental mapping.

Binding Costs in Processing Efficiency as Determinants of Cognitive Ability

Performance in elementary cognitive tasks is moderately correlated with fluid intelligence and working memory capacity. These correlations are higher for more complex tasks, presumably due to increased demands on working memory capacity. In accordance with the binding hypothesis, which states that working memory capacity reflects the limit of a person's ability to establish and maintain temporary bindings (e.g., relations between items or relations between items and their context), we manipulated binding requirements (i.e., 2, 4, and 6 relations) in three choice reaction time paradigms (i.e., two comparison tasks, two change detection tasks, and two substitution tasks) measuring mental speed. Response time distributions of 115 participants were analyzed with the diffusion model. Higher binding requirements resulted in generally reduced efficiency of information processing, as indicated by lower drift rates. Additionally, we fitted bi-factor confirmatory factor analysis to the elementary cognitive tasks to separate basal speed and binding requirements of the employed tasks to quantify their specific contributions to working memory capacity, as measured by Recall-1-Back tasks. A latent factor capturing individual differences in binding was incrementally predictive of working memory capacity, over and above a general factor capturing speed. These results indicate that the relation between reaction time tasks and working memory capacity hinges on the complexity of the reaction time tasks. We conclude that binding requirements and, therefore, demands on working memory capacity offer a satisfactory account of task complexity that accounts for a large portion of individual differences in ability.

How physical interaction with insight problems affects solution rates, hint use, and cognitive load

So-called insight problems are widely studied because they tap into the creative thinking that is crucial for solving real problems. However, insight problems are typically presented in static formats (on paper, computer) that allow no physical interaction with the problem elements, whereas such an interaction might in fact reduce the load on limited cognitive resources, such as working memory (WM) capacity, thereby facilitating solutions. To test this proposition, 124 young adults were allowed to interact physically with nine established insight problems, while another 124 people attempted to solve these problems using paper and pencil. Additionally, hints were provided for three problems that typically no-one solves. No general facilitating effect of physical interaction was found, with only one problem clearly benefitting from it. Furthermore, making use of hints was actually hindered by physical interaction. No difference in perceived task load and correlation with WM capacity was observed between the formats, and subjective ratings of insight were virtually unaffected by presentation format. Overall, physical interaction minimally affected insight problem-solving, which appears to rely strongly on internalized cognitive processing involving WM.

A moderate financial incentive can increase effort, but not intelligence test performance in adult volunteers

A positive correlation between self-reported test-taking motivation and intelligence test performance has been reported. Additionally, some financial incentive experimental evidence suggests that intelligence test performance can be improved, based on the provision of financial incentives. However, only a small percentage of the experimental research has been conducted with adults. Furthermore, virtually none of the intelligence experimental research has measured the impact of financial incentives on test-taking motivation. Consequently, we conducted an experiment with 99 adult volunteers who completed a battery of intelligence tests under two conditions: no financial incentive and financial incentive (counterbalanced). We also measured self-reported test-taking importance and effort at time 1 and time 2. The financial incentive was observed to impact test-taking effort statistically significantly. By contrast, no statistically significant effects were observed for the intelligence test performance scores. Finally, the intelligence test scores were found to correlate positively with both test-taking importance (r_c  = .28) and effort (r_c  = .37), although only effort correlated uniquely with intelligence (partial r_c  = .26). In conjunction with other empirical research, it is concluded that a financial incentive can increase test-taking effort. However, the potential effects on intelligence test performance in adult volunteers seem limited.

Global associations between regional gray matter volume and diverse complex cognitive functions: evidence from a large sample study

Correlations between regional gray matter volume (rGMV) and psychometric test scores have been measured to investigate the neural bases for individual differences in complex cognitive abilities (CCAs). However, such studies have yielded different rGMV correlates of the same CCA. Based on the available evidence, we hypothesized that diverse CCAs are all positively but only weakly associated with rGMV in widespread brain areas. To test this hypothesis, we used the data from a large sample of healthy young adults [776 males and 560 females; mean age: 20.8 years, standard deviation (SD) = 0.8] and investigated associations between rGMV and scores on multiple CCA tasks (including non-verbal reasoning, verbal working memory, Stroop interference, and complex processing speed tasks involving spatial cognition and reasoning). Better performance scores on all tasks except non-verbal reasoning were associated with greater rGMV across widespread brain areas. The effect sizes of individual associations were generally low, consistent with our previous studies. The lack of strong correlations between rGMV and specific CCAs, combined with stringent corrections for multiple comparisons, may lead to different and diverse findings in the field.

The Nature and Structure of Children's Abilities: Evidence from the Differential Ability Scales

The nature and the structure of children's abilities are considered in the light of evidence from the Differential Ability Scales (DAS), a newly published, individually administered cognitive test battery for children age 2 years 6 months through 17 years 11 months. The DAS was developed primarily to assess children's cognitive profiles. Evidence is presented on its relatively high levels of reliable specific variance (a requirement for identifying reliable intertest differences in a profile). The DAS cognitive battery also yields a number of focused composite scores: a measure of psychometric g, called General Conceptual Ability (GCA) and measures of Verbal and Nonverbal Ability at the preschool level, and of Verbal, Nonverbal Reasoning and Spatial Ability at the school-age level. The case is argued against the use of terms “intelligence” and “IQ” in describing children's abilities, and evidence on the factorial structure of the DAS is presented through both confirmatory and exploratory factor analyses.

Relative Cognitive Complexity of the Kaufman Assessment Battery for Children (K-ABC) and the WISC-R

We evaluated whether abilities measured by the Kaufman Assessment Battery for Children (K-ABC)are as complex as those measured by the Wechsler Intelligence Scale for Children-Revised (WISC-R)within a sample of referred children. Results of factor and multidimensional scaling analyses indicated that abilities tapped by the K-ABC Mental Processing scale are not as complex as those assessed by the WISC-R. K-ABC Achievement scale subtests, however, seemed to assess skills as complex as those measured by many WISC-R subtests. The relative cognitive complexity of the K-ABC and the WISC-R seem comparable, but only when all the K-ABC subtests are administered.

Executive function and intelligence in the resolution of temporary syntactic ambiguity: an individual differences investigation

In the current study, we examined the role of intelligence and executive functions in the resolution of temporary syntactic ambiguity using an individual differences approach. Data were collected from 174 adolescents and adults who completed a battery of cognitive tests as well as a sentence comprehension task. The critical items for the comprehension task consisted of object/subject garden paths (e.g., While Anna dressed the baby that was small and cute played in the crib), and participants answered a comprehension question (e.g., Did Anna dress the baby?) following each one. Previous studies have shown that garden-path misinterpretations tend to persist into final interpretations. Results showed that both intelligence and processing speed interacted with ambiguity. Individuals with higher intelligence and faster processing were more likely to answer the comprehension questions correctly and, specifically, following ambiguous as opposed to unambiguous sentences. Inhibition produced a marginal effect, but the variance in inhibition was largely shared with intelligence. Conclusions focus on the role of individual differences in cognitive ability and their impact on syntactic ambiguity resolution.

Longitudinal development of frontoparietal activity during feedback learning: Contributions of age, performance, working memory and cortical thickness

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We performed a longitudinal study on feedback learning (N = 208, age 8–27 years).

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We tested linear and nonlinear patterns in frontoparietal activity during learning.

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DLPFC and parietal cortex showed a late-adolescent peak in activity.

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SMA showed a linear increase, and ACC a linear decrease in brain activity with age.

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Performance predicted DLPFC and parietal activity, thickness predicted SMA activity.

Feedback learning is a crucial skill for cognitive flexibility that continues to develop into adolescence, and is linked to neural activity within a frontoparietal network. Although it is well conceptualized that activity in the frontoparietal network changes during development, there is surprisingly little consensus about the direction of change. Using a longitudinal design (N = 208, 8–27 years, two measurements in two years), we investigated developmental trajectories in frontoparietal activity during feedback learning. Our first aim was to test for linear and nonlinear developmental trajectories in dorsolateral prefrontal cortex (DLPFC), superior parietal cortex (SPC), supplementary motor area (SMA) and anterior cingulate cortex (ACC). Second, we tested which factors (task performance, working memory, cortical thickness) explained additional variance in time-related changes in activity besides age. Developmental patterns for activity in DLPFC and SPC were best characterized by a quadratic age function leveling off/peaking in late adolescence. There was a linear increase in SMA and a linear decrease with age in ACC activity. In addition to age, task performance explained variance in DLPFC and SPC activity, whereas cortical thickness explained variance in SMA activity. Together, these findings provide a novel perspective of linear and nonlinear developmental changes in the frontoparietal network during feedback learning.

Age-related differences in working memory updating components

The aim of this study was to investigate possible age-related changes throughout childhood and adolescence in different component processes of working memory updating (WMU): retrieval, transformation, and substitution. A set of numerical WMU tasks was administered to four age groups (8-, 11-, 14-, and 21-year-olds). To isolate the effect of each of the WMU components, participants performed different versions of a task that included different combinations of the WMU components. The results showed an expected overall decrease in response times and an increase in accuracy performance with age. Most important, specific age-related changes in the retrieval component were found, demonstrating that the effect of retrieval on accuracy was larger in children than in adolescents or young adults. These findings indicate that the availability of representations from outside the focus of attention may change with age. Thus, the retrieval component of updating could contribute to the age-related changes observed in the performance of many updating tasks.

The differential contribution of executive functions to temporal generalisation, reproduction and verbal estimation

Evidence from dual-task studies suggests that executive resources are recruited during timing. However, there has been little exploration of whether executive recruitment is universal across temporal tasks, or whether different temporal tasks recruit different executive resources. The current study explored this further by examining how individual differences in updating, switching, inhibition and access affected performance on temporal generalisation, reproduction and verbal estimation tasks. It was found that temporal tasks differentially loaded onto different executive resources. Temporal generalisation performance was related to updating and access ability. Reproduction performance was related to updating, access and switching. Verbal estimation performance was only related to access. The results suggest that executive resources may be recruited when monitoring and maintaining multiple durations in memory at the same time, and when retrieving duration representations from long-term memory. The findings emphasise the need to consider timing behaviour as the product of a wide range of complex, integrated, cognitive systems, rather than as the output of a clock in isolation.

Revisiting the continuum hypothesis: toward an in-depth exploration of executive functions in korsakoff syndrome

Korsakoff syndrome (KS) is a neurological state mostly caused by alcohol-dependence and leading to disproportionate episodic memory deficits. KS patients present more severe anterograde amnesia than Alcohol-Dependent Subjects (ADS), which led to the continuum hypothesis postulating a progressive increase in brain and cognitive damages during the evolution from ADS to KS. This hypothesis has been extensively examined for memory but is still debated for other abilities, notably executive functions (EF). EF have up to now been explored by unspecific tasks in KS, and few studies explored their interactions with memory. Exploring EF in KS by specific tasks based on current EF models could thus renew the exploration of the continuum hypothesis. This paper will propose a research program aiming at: (1) clarifying the extent of executive dysfunctions in KS by tasks focusing on specific EF subcomponents; (2) determining the differential EF deficits in ADS and KS; (3) exploring EF-memory interactions in KS with innovative tasks. At the fundamental level, this exploration will test the continuum hypothesis beyond memory. At the clinical level, it will propose new rehabilitation tools focusing on the EF specifically impaired in KS.

Is the fluency of language outputs related to individual differences in intelligence and executive function?

There has been little research on the fluency of language production and individual difference variables, such as intelligence and executive function. In this study, we report data from 106 participants who completed a battery of standardized cognitive tasks and a sentence production task. For the sentence production task, participants were presented with two objects and a verb and their task was to formulate a sentence. Four types of disfluency were examined: filled pauses (e.g. uh, um), unfilled pauses, repetitions, and repairs. Repetitions occur when the speaker suspends articulation and then repeats the previous word/phrase, and repairs occur when the speaker suspends articulation and then starts over with a different word/phrase. Hierarchical structural equation modeling revealed a significant relationship between repair disfluencies and inhibition. Conclusions focus on the role of individual differences in cognitive ability and their role in models and theories of language production.

What do we know about the relationship between source monitoring deficits and executive dysfunction?

In clinical neuropsychology, source monitoring deficits have been classically attributed to executive dysfunction. Nevertheless, in this review we identified only 16 papers that provided statistical data about the relationships between source monitoring and executive processes. Surprisingly, they reported either a total, partial or non-existent relationship between source monitoring and executive tasks. In order to understand and explain these contradictions, we classified the source and executive tasks of the 16 papers according to two well-accepted definitions. Source tasks were classified using the Source Monitoring Framework (Johnson, Hashtroudi, & Lindsay, 1993 ) which specifies reality and external and internal source monitoring. Executive tasks were classified according to the model of Miyake Friedman, Emerson, Witzki, and Howerter (2000) which specifies complex, shifting, updating and inhibition tasks. We found that evaluation of reality and internal source monitoring was limited. Regarding executive functions, there was no assessment of updating and only a limited assessment of shifting and inhibition. Therefore, the relationship between source monitoring and executive functions remains an open question. Our findings point to the need for the simultaneous assessment of source monitoring and executive functions as defined by multidimensional theoretical frameworks. Such investigations would help in understanding the relationship between specific source monitoring deficits and specific executive decline in clinical populations.

Neural correlates of the difference between working memory speed and simple sensorimotor speed: an fMRI study

The difference between the speed of simple cognitive processes and the speed of complex cognitive processes has various psychological correlates. However, the neural correlates of this difference have not yet been investigated. In this study, we focused on working memory (WM) for typical complex cognitive processes. Functional magnetic resonance imaging data were acquired during the performance of an N-back task, which is a measure of WM for typical complex cognitive processes. In our N-back task, task speed and memory load were varied to identify the neural correlates responsible for the difference between the speed of simple cognitive processes (estimated from the 0-back task) and the speed of WM. Our findings showed that this difference was characterized by the increased activation in the right dorsolateral prefrontal cortex (DLPFC) and the increased functional interaction between the right DLPFC and right superior parietal lobe. Furthermore, the local gray matter volume of the right DLPFC was correlated with participants' accuracy during fast WM tasks, which in turn correlated with a psychometric measure of participants' intelligence. Our findings indicate that the right DLPFC and its related network are responsible for the execution of the fast cognitive processes involved in WM. Identified neural bases may underlie the psychometric differences between the speed with which subjects perform simple cognitive tasks and the speed with which subjects perform more complex cognitive tasks, and explain the previous traditional psychological findings.

Whole genome association scan for genetic polymorphisms influencing information processing speed

Processing speed is an important cognitive function that is compromised in psychiatric illness (e.g., schizophrenia, depression) and old age; it shares genetic background with complex cognition (e.g., working memory, reasoning). To find genes influencing speed we performed a genome-wide association scan in up to three cohorts: Brisbane (mean age 16 years; N = 1659); LBC1936 (mean age 70 years, N = 992); LBC1921 (mean age 82 years, N = 307), and; HBCS (mean age 64 years, N =1080). Meta-analysis of the common measures highlighted various suggestively significant (p < 1.21 × 10⁻⁵) SNPs and plausible candidate genes (e.g., TRIB3). A biological pathways analysis of the speed factor identified two common pathways from the KEGG database (cell junction, focal adhesion) in two cohorts, while a pathway analysis linked to the GO database revealed common pathways across pairs of speed measures (e.g., receptor binding, cellular metabolic process). These highlighted genes and pathways will be able to inform future research, including results for psychiatric disease.

Age-related change in executive function: developmental trends and a latent variable analysis

This study examined the developmental trajectories of three frequently postulated executive function (EF) components, Working Memory, Shifting, and Inhibition of responses, and their relation to performance on standard, but complex, neuropsychological EF tasks, the Wisconsin Card Sorting Task (WCST), and the Tower of London (ToL). Participants in four age groups (7-, 11-, 15-, and 21-year olds) carried out nine basic experimental tasks (three tasks for each EF), the WCST, and the ToL. Analyses were done in two steps: (1) analyses of (co)variance to examine developmental trends in individual EF tasks while correcting for basic processing speed, (2) confirmatory factor analysis to extract latent variables from the nine basic EF tasks, and to explain variance in the performance on WCST and ToL, using these latent variables. Analyses of (co)variance revealed a continuation of EF development into adolescence. Confirmatory factor analysis yielded two common factors: Working Memory and Shifting. However, the variables assumed to tap Inhibition proved unrelated. At a latent level, again correcting for basic processing speed, the development of Shifting was seen to continue into adolescence, while Working Memory continued to develop into young-adulthood. Regression analyses revealed that Working Memory contributed most strongly to WCST performance in all age groups. These results suggest that EF component processes develop at different rates, and that it is important to recognize both the unity and diversity of EF component processes in studying the development of EF.

Working memory and intelligence: the same or different constructs?

Several investigators have claimed over the past decade that working memory (WM) and general intelligence (g) are identical, or nearly identical, constructs, from an individual-differences perspective. Although memory measures are commonly included in intelligence tests, and memory abilities are included in theories of intelligence, the identity between WM and intelligence has not been evaluated comprehensively. The authors conducted a meta-analysis of 86 samples that relate WM to intelligence. The average correlation between true-score estimates of WM and g is substantially less than unity (p=.479). The authors also focus on the distinction between short-term memory and WM with respect to intelligence with a supplemental meta-analysis. The authors discuss how consideration of psychometric and theoretical perspectives better informs the discussion of WM-intelligence relations.

Impaired executive function in male MDMA ("ecstasy") users

RATIONALE

Long-term users of ecstasy have shown impaired performance on a multitude of cognitive abilities (most notably memory, attention, executive function). Research into the pattern of MDMA effects on executive functions remains fragmented, however.

OBJECTIVES

To determine more systematically what aspects of executive function are affected by a history of MDMA use, by using a model that divides executive functions into cognitive flexibility, information updating and monitoring, and inhibition of pre-potent responses.

METHODS

MDMA users and controls who abstained from ecstasy and other substances for at least 2 weeks were tested with a computerized cognitive test battery to assess their abilities on tasks that measure the three submodalities of executive function, and their combined contribution on two more complex executive tasks. Because of sex-differential effects of MDMA reported in the literature, data from males and females were analyzed separately.

RESULTS

Male MDMA users performed significantly worse on the tasks that tap on cognitive flexibility and on the combined executive function tasks; no differences were found on the other cognitive tasks. Female users showed no impairments on any of the tasks.

CONCLUSIONS

The present data suggest that a history of MDMA use selectively impairs executive function. In male users, cognitive flexibility was impaired and increased perseverative behavior was observed. The inability to adjust behavior rapidly and flexibly may have repercussions for daily life activities.