Young children's performance on a design fluency task: longitudinal data on total number of designs, clustering and switching, and regression-based norms.

INTRODUCTION: Design fluency (DF) tasks are commonly used to assess executive functions such as attentional control, cognitive flexibility, self-monitoring and strategy use. Next to the total number of correct designs, the standard outcome of a DF task, clustering and switching can help disentangle the processes underlying DF performance. We present the first longitudinal study of 4-8-year-old children's developmental DF trajectories. METHOD: At initial enrollment, children (n = 228) were aged between 4.05 and 6.88 years (M = 5.18, SD = 0.59) and attended Dutch primary schools. The DF task was administered at three time points, each time point separated by approximately 1 year. Data were analyzed using mixed regression for total number of correct designs and switching, and mixed logistic regression analysis for clustering. RESULTS: The total number of correct designs increased linearly across the three time points. Across all time points, children made very few clusters, and most clusters consisted of only 3 designs. Clustering only increased at the third assessment compared to the two previous assessments. Switching increased up to the second assessment, but not after that. The number of switches was highly correlated with the total number of correct designs at all time points (r = 0.78 to r = 0.85). These developmental trajectories were similar for all children regardless of their baseline age. Normative data are given for the total number of correct designs and switching. CONCLUSIONS: Children as of age 4 onwards can perform a DF task. For children as young as 4-8 years old, computing clustering, and switching measures is of limited value to study cognitive processes underlying DF performance, next to the total number of correct designs. There were no sex differences on any of the DF outcomes. Level of parental education (LPE) was positively associated with the total number of correct designs and switching.

DEcreased Cognitive functiON, NEurovascular CorrelaTes and myocardial changes in women with a history of pre-eclampsia (DECONNECT): research protocol for a cross-sectional pilot study.

INTRODUCTION: Pre-eclampsia is a hypertensive disorder affecting up to 8% of pregnancies. After pre-eclampsia, women are at increased risk of cognitive problems, and cerebrovascular and cardiovascular disorders. These sequelae could result from microvascular dysfunction persisting after pre-eclampsia. This study will explore differences in cerebral and myocardial microvascular function between women after pre-eclampsia and women after normotensive gestation. We hypothesise that pre-eclampsia alters cerebral and myocardial microvascular functions, which in turn are related to diminished cognitive and cardiac performance. METHODS AND ANALYSIS: The cross-sectional 'DEcreased Cognitive functiON, NEurovascular CorrelaTes and myocardial changes in women with a history of pre-eclampsia' (DECONNECT) pilot study includes women after pre-eclampsia and controls after normotensive pregnancy between 6 months and 20 years after gestation. We recruit women from the Queen of Hearts study, a study investigating subclinical heart failure after pre-eclampsia. Neuropsychological tests are employed to assess different cognitive domains, including attention, processing speed, and cognitive control. Cerebral images are recorded using a 7 Tesla MRI to assess blood-brain barrier integrity, perfusion, blood flow, functional and structural networks, and anatomical dimensions. Cardiac images are recorded using a 3 Tesla MRI to assess cardiac perfusion, strain, dimensions, mass, and degree of fibrosis. We assess the effect of a history of pre-eclampsia using multivariable regression analyses. ETHICS AND DISSEMINATION: This study is approved by the Ethics Committee of Maastricht University Medical Centre (METC azM/UM, NL47252.068.14). Knowledge dissemination will include scientific publications, presentations at conferences and public forums, and social media. TRIAL REGISTRATION NUMBER: NCT02347540.

Effects of psychedelic microdosing versus conventional ADHD medication use on emotion regulation, empathy, and ADHD symptoms in adults with severe ADHD symptoms: A naturalistic prospective comparison study.

Adults with attention-deficit hyperactivity disorder (ADHD) often struggle with emotion regulation (ER), impacting their empathic skills and relationships. ADHD medication might not be as effective for ER issues as for ADHD symptoms. Microdosing (MD) psychedelics has shown promise for ADHD treatment and previous studies reported social-emotional benefits. Two online prospective studies investigated MD effects on ER and empathy in adults with severe ADHD symptoms across three assessments: baseline, two-, and four-week post-initiation. Study 1 examined adults initiating MD on their own (n = 233, n = 64, and n = 44) and found positive effects on ER (cognitive reappraisal and expressive suppression) and aspects of empathy (perspective-taking and personal distress). Study 2, including a control group and an ADHD symptom scale, compared individuals only MD (n = 180, n = 50, and n = 38) to individuals using conventional ADHD medication (n = 37, n = 27, and n = 28). After 4 weeks, ADHD symptoms were lower in the MD group. Only improvements in expressive suppression persisted after adding the control group. This study indicates the positive effects of MD psychedelics on ADHD symptoms and ER in adults with severe ADHD symptoms while lacking evidence for effects on empathy.

Trait mindfulness and personality characteristics in a microdosing ADHD sample: a naturalistic prospective survey study.

Background: Microdosing (MD), repeatedly taking psychedelics in small, non-hallucinogenic amounts, has been practiced by individuals to relieve attention deficit hyperactivity disorder (ADHD) symptoms. Generally, adults diagnosed with ADHD have lower levels of mindfulness and differ in personality structure from non-ADHD adults. How MD affects mindfulness and personality in adults with ADHD remains unexplored. Aim: This study aimed to investigate the effects of 4 weeks of MD on mindfulness and personality traits in adults diagnosed with ADHD and those experiencing severe ADHD symptoms. It was expected that mindfulness and the personality traits conscientiousness, extraversion, agreeableness, and openness would increase and neuroticism would decrease after 4 weeks of MD compared to baseline. It was explored if using conventional ADHD medication alongside MD and/or having comorbidities influenced MD-induced effects. Methods: An online prospective naturalistic design was used to measure participants before MD initiation and 2 and 4 weeks later. Validated self-report measures were used assessing mindfulness (15-item Five Facet Mindfulness Questionnaire) and personality traits (10-item version of the Big Five Inventory) at three time points. Results: The sample included n = 233, n = 66, and n = 44 participants at the three time points, respectively. Trait mindfulness, specifically description and non-judging of inner experience, was increased, and neuroticism was decreased after 4 weeks of MD compared to baseline. The remaining personality traits remained unchanged. Using conventional medication and/or having comorbid diagnoses did not change the MD-induced effects on mindfulness and personality traits after 4 weeks. Conclusion: MD induced changes in otherwise stable traits. Future placebo-controlled studies are warranted to confirm whether these changes occur in a controlled setting.

Further validation of a new ADHD screening questionnaire measuring parents' explanations (time processing, cognition, and motivation) of inattention symptoms in their school-aged children.

The triple pathway model suggests that different neuropsychological factors underlie symptoms of inattention (i.e., time, cognition and/or motivation problems). However, screening instruments asking individuals to judge the link between these neuropsychological factors and inattention are lacking. The recently developed screening questionnaire, PASSC, aims to examine these factors possibly causing inattention by asking parents to indicate to what extent their child experiences inattention symptoms and to what extent different neuropsychological factors explain this inattention. The present study extends prior validation research of the PASSC by examining associations between PASSC inattention explained by time, cognition, and/or motivation and children's performance on tests measuring these same three constructs. Results indicated positive correlations between PASSC inattention explained by time and less accurate performance on a time discrimination test, and between PASSC inattention explained by cognition and more working memory errors as well as higher attention switching costs. Furthermore, children whose parents indicated that their inattention was best explained by cognition showed higher switching costs than children whose inattention was best explained by motivation. This support for construct validity of the PASSC is limited to two PASSC explanations (i.e., time, cognition) and a subset of tests (i.e., time discrimination, attention switching, memory span). Future research should focus on integrating PASSC and performance test results to differentiate between children with attention problems but different underlying neuropsychological problems. Concluding, the PASSC can be a promising screening tool to identify inattention in children and the underlying explanation indicated by parents.

Attenuated cognitive functioning decades after preeclampsia.

BACKGROUND: Preeclampsia, a hypertensive pregnancy disorder, is a leading cause of maternal and fetal morbidity and mortality, with remote cardio- and cerebrovascular implications. After preeclampsia, women may report serious disabling cognitive complaints, especially involving executive function, but the extent and time course of these complaints are unknown. OBJECTIVE: This study aimed to determine the impact of preeclampsia on perceived maternal cognitive functioning decades after pregnancy. STUDY DESIGN: This study is part of a cross-sectional case-control study named Queen of Hearts (ClinicalTrials.gov Identifier: NCT02347540), a collaboration study of 5 tertiary referral centers within the Netherlands investigating long-term effects of preeclampsia. Eligible participants were female patients aged ≥18 years after preeclampsia and after normotensive pregnancy between 6 months and 30 years after their first (complicated) pregnancy. Preeclampsia was defined as new-onset hypertension after 20 weeks of gestation along with proteinuria, fetal growth restriction, or other maternal organ dysfunction. Women with a history of hypertension, autoimmune disease, or kidney disease before their first pregnancy were excluded. Attenuation of higher-order cognitive functions, that is, executive function, was measured with the Behavior Rating Inventory of Executive Function for Adults. Crude and covariate-adjusted absolute and relative risks of clinical attenuation over time after (complicated) pregnancy were determined with moderated logistic and log-binomial regression. RESULTS: This study included 1036 women with a history of preeclampsia and 527 women with normotensive pregnancies. Regarding overall executive function, 23.2% (95% confidence interval, 19.0-28.1) of women experienced clinically relevant attenuation after preeclampsia, as opposed to 2.2% (95% confidence interval, 0.8-6.0) of controls immediately after childbirth (adjusted relative risk, 9.20 [95% confidence interval, 3.33-25.38]). Group differences diminished yet remained statistically significant (P < .05) at least 19 years postpartum. Regardless of history of preeclampsia, women with lower educational attainment, mood or anxiety disorders, or obesity were especially at risk. Neither severity of preeclampsia, multiple gestation, method of delivery, preterm birth, nor perinatal death was related to overall executive function. CONCLUSION: After preeclampsia, women were 9 times more likely to experience clinical attenuation of higher-order cognitive functions as opposed to after normotensive pregnancy. Despite overall steady improvement, elevated risks persisted over decades after childbirth.

Wechsler Scale Intelligence Testing in Males with Dystrophinopathies: A Review and Meta-Analysis.

BACKGROUND: Intelligence scores in males with Duchenne Muscular Dystrophy (DMD) and Becker Muscular Dystrophy (BMD) remain a major issue in clinical practice. We performed a literature review and meta-analysis to further delineate the intellectual functioning of dystrophinopathies. METHOD: Published, peer-reviewed articles assessing intelligence, using Wechsler Scales, of males with DMD or BMD were searched from 1960 to 2022. Meta-analysis with random-effects models was conducted, assessing weighted, mean effect sizes of full-scale IQ (FSIQ) scores relative to normative data (Mean = 100, Standard Deviation = 15). Post hoc we analysed differences between performance and verbal intelligence scores. RESULTS: 43 studies were included, reporting data on 1472 males with dystrophinopathies; with FSIQ scores available for 1234 DMD (k = 32) and 101 BMD (k = 7). DMD males score, on average, one standard deviation below average (FSIQ = 84.76) and significantly lower than BMD (FSIQ = 92.11). Compared to a previous meta-analysis published in 2001, we find, on average, significantly higher FSIQ scores in DMD. CONCLUSION: Males with Duchenne have, on average, significantly lower FSIQ scores than BMD males and the general population. Clinicians must consider lower intelligence in dystrophinopathies to ensure good clinical practice.

Clinical Utility of Eye Tracking in Assessing Distractibility in Children with Neurological Disorders or ADHD: A Cross-Sectional Study.

This study aims to investigate distractibility quantified by recording and analyzing eye movements during task-irrelevant distraction in children with and without ADHD and in children with and without neurological disorders. Gaze behavior data and press latencies of 141 participants aged 6−17 that were collected during a computerized distraction paradigm with task-irrelevant stimuli (IDistrack) were analyzed. Children using attention-regulating medication were excluded from participation. Data were analyzed for subgroups that were formed based on the presence of neurological disorders and the presence of ADHD separately. Participants with ADHD and participants with neurological disorders spent less time fixating on the target stimuli compared to their peers without ADHD (p = 0.025) or their peers without neurological disorders (p < 0.001). Participants with and without ADHD had equal press latencies (p = 0.79). Participants with neurological disorders had a greater press latency compared to their typically developing peers (p < 0.001). Target fixation duration shows a significant association with parent-reported attention problems (r = −0.39, p < 0.001). We conclude that eye tracking during a distraction task reveals potentially valid clinical information that may contribute to the assessment of dysfunctional attentional processes. Further research on the validity and reliability of this paradigm is recommended.

Psychometric properties of a new ADHD screening questionnaire: Parent report on the (potential) underlying explanation of inattention in their school-aged children.

The present study examined psychometric properties of a recently developed parent report screening questionnaire, i.e., Parent ADHD Screening questionnaire: Signaling the Core explanation underlying behavioral symptoms (PASSC). The PASSC aims to measure (1) ADHD symptoms and (2) what parents view to be the main underlying explanation(s) of these symptoms. The PASSC questions 3 (potential) underlying explanations based on the triple pathway model (TPM): i.e., time, cognition and/or motivation problems. Parents of 1166 Dutch children aged 4-12 filled in the PASSC, as well as 2 questionnaires measuring time, cognition and motivation (i.e., the FTF and the SPSRQ-C). Reliability of the PASSC is good, indicated by high internal consistency of the sumscores. Principal component analyses supported the distinction between inattention and hyperactivity-impulsivity symptoms as defined in the DSM-5, and the distinction between the 3 TPM explanations given by parents for inattention, but not for hyperactivity-impulsivity symptoms. The majority of parents selected one and the same explanation for inattention problems of their child, most often being cognition (31.2%) and motivation (28.2%). PASSC validity was further supported by positive associations between the explanation sumscores for inattention symptoms and other parent questionnaires measuring the same constructs (i.e., time, cognition and motivation; convergent validity), although we found no evidence for discriminant validity. Groups (based on age group, sex and ADHD diagnosis) differed on the PASSC sumscores in the expected directions. Concluding, the PASSC is a promising tool to assess a child's ADHD symptoms as well as the parent view on (potential) explanation(s) of inattention.

[Formula: see text] Measuring visual matching and short-term recognition memory with the CANTAB® Delayed Matching to Sample task in schoolchildren: Effects of demographic influences, multiple outcome measures and regression-based normative data.

The study aims to establish demographically corrected, pediatric norms for the computerized Delayed Matching to Sample (DMS) test, a measure of "visual matching ability and short-term visual recognition memory, for non-verbalisable problems". The DMS was administered to n = 184 children aged 5.10 to 14.5 years old. The DMS is a 4-choice recognition task of non-verbal, abstract patterns. The child has "to select, among four different choice patterns, the one that matches a complex visual pattern presented," i.e., (the target stimulus). The DMS consists of two conditions: a) the overt condition in which the target stimulus and four choice patterns are shown simultaneously and b) the covert condition, in which the choice patterns are shown after the target pattern is covered. The DMS test provides three outcome measures: the accuracy score (i.e., the number of correct patterns selected), latency (i.e., the response speed) and the probability of making an error after an incorrect response. These outcome measures were calculated for both conditions and for both conditions combined. Results showed that demographic variables, such as age, sex, and/or level of parental education (LPE) affected scores on these outcome measures. Based on these data, demographically corrected norms were established for all outcome measures, per condition and for both conditions combined.

Age-dependent differences in the impact of paediatric traumatic brain injury on executive functions: A prospective study using susceptibility-weighted imaging.

Childhood and adolescence represent sensitive developmental periods for brain networks implicated in a range of complex skills, including executive functions (EF; inhibitory control, working memory, and cognitive flexibility). As a consequence, these skills may be particularly vulnerable to injuries sustained during these sensitive developmental periods. The present study investigated 1) whether age at injury differentially affects EF 6 months and 2 years after TBI in children aged 5-15 years, and 2) whether the association between brain lesions and EF depend on age at injury. Children with TBI (n = 105) were categorized into four age-at-injury groups based on previous studies and proposed timing of cerebral maturational spurts: early childhood (5-6 years, n = 14), middle childhood (7-9 years, n = 24), late childhood (10-12 years, n = 52), and adolescence (13-15 years, n = 15). EF were assessed with performance-based tasks and a parent-report of everyday EF. TBI patients' EF scores 6 months and 2 years post-injury were compared to those of typically developing (TD) controls (n = 42). Brain lesions were identified using susceptibility weighted imaging (SWI). Results indicated that inhibitory control performance 2 years post-injury was differentially affected by the impact of TBI depending on age at injury. Follow-up analyses did not reveal significant differences within the age groups, preventing drawing strong conclusions regarding the contribution of age at injury to EF outcome after TBI. Tentatively, large effect sizes suggest that vulnerability is most apparent in early childhood and adolescence. Everyday inhibitory control behaviour was worse for children with TBI than TD children across childhood and adolescence at the 2-year assessment. There was no evidence for impairment in working memory or cognitive flexibility after TBI at the group level. Given small group sizes, findings from analyses into correlations between EF and SWI lesions should be interpreted with caution. Extent, number and volume of brain lesions correlated with adolescent everyday EF behaviour 6 months post-injury. Taken together, the results emphasize the need for long-term follow-up after paediatric TBI during sensitive developmental periods given negative outcomes 2-year post injury. Inhibitory control seems to be particular vulnerable to the impact of TBI. Findings of associations between EF and SWI lesions need to be replicated with larger samples.

Accuracy of WISC-III and WAIS-IV short forms in patients with neurological disorders.

The assessment of intellectual abilities is intensive, time-consuming, and might be considered burdensome for patients. We examined psychometric qualities of short forms (SFs) of the Wechsler Intelligence Scales for Children (WISC-third edition) and for adults (WAIS-fourth edition), in children (n = 986; Mage = 10.9) and adults (n = 324; Mage = 40.9) with neurological disorders. SF estimates were compared with Full Scale IQ (FSIQ), obtained by a complete administration, for the entire sample and for the subgroups FSIQ < 80 and FSIQ ≥ 80. The FSIQ was correctly identified within ± 7 points in 86% of children and 87% of adults. There were, however, some differences regarding the optimal SF subtest combination between subgroups. Although clinical inferences should not be made, SFs may be useful in research settings to obtain a global estimate of intelligence, and in clinical settings to screen periodically for possible intellectual deterioration.

Both facilitatory and inhibitory impairments underlie age-related differences of proactive cognitive control across the adult lifespan.

We investigated two components of proactive cognitive control, response facilitation and response inhibition, in an adult lifespan sample (N=544, age range=18-91years) by administering two response-preparation tasks: a procue task, primarily involving facilitation, and an anticue task, involving both facilitation and inhibition. Cues in both tasks corresponded with the index and middle fingers of either the left or right hand. After a random preparation interval (PI) of 100-850ms following the onset of the cue signal, a single-target stimulus indicated the required response. Where procues were spatially aligned with the two fingers of the responding hand, anticues consistently indicated the two fingers of the opposite hand, requiring a remapping of cue location and response hand. This remapping requires inhibition to suppress the automatic activation of the ipsilateral responses. Previous research revealed typical reaction time (RT) profiles for procues and anticues as a function of PI. Whereas procues generate RT benefits (relative to a neutral-cue condition) already at short PIs, which increase with longer PIs, anticues generate RT costs at short PIs and RT benefits at longer PIs. Our results showed that, in the anticue task, older participants needed more preparation time to turn RT costs into RT benefits than younger participants, revealing an age-related deficit of response inhibition. Moreover, in both tasks, older participants were less able to increase RT benefits with longer PIs, revealing a deficit of response facilitation. We conclude that both facilitatory and inhibitory impairments contribute to age-related deficiencies in proactive cognitive control.

Can IQ predict parent-reported behavioral and emotional problems in children with neurological deficiencies?

OBJECTIVE: The aim of the current study was to investigate whether total intelligence scores (FSIQ) and/or a discrepancy in intelligence can predict behavioral or emotional problems in children with neurological deficiencies. METHOD: The population consists of children with neurological deficiencies (N = 610, ranging from 6 to 17 years), referred due to concerns on the (educational) development of the child to a tertiary outpatient clinic. All children were tested with the Dutch Wechsler Intelligence Scale for Children - third edition (WISC-III-NL). A VIQ-PIQ discrepancy score was calculated by subtracting the performance capacities of the verbal capacities. The effects of demographic variables, FSIQ, and the VIQ-PIQ discrepancy on two parent-rated questionnaires measuring behavior and emotions in children were analyzed with linear and logistic regression models. RESULTS AND CONCLUSION: The VIQ-PIQ discrepancy was not predictive of behavioral or emotional problems recorded on the above-mentioned parent-rated questionnaires. The FSIQ score, age, and sex were predictive to some extent: increases in age and FSIQ led to a decrease of reported problems, and boys showed more problems than girls. Children with neurological deficiencies had on average significantly higher verbal capacities than performance capacities, in line with the neuropsychological principle that language survives brain damage whereas performance capacities are more affected.

Switch hands! Mapping proactive and reactive cognitive control across the life span.

We investigated the effects of age on proactive and reactive cognitive control in a large population sample of 809 individuals, ranging in age between 5 and 97 years. For that purpose, we used an anticue paradigm, which required a consistent remapping of cue location and response hand: Left-sided cues required right-hand responses and vice versa. After a random preparation interval of 100-850 ms, these anticues were followed by a target stimulus, which prompted a response with the index or middle finger of 1 of 2 hands. A neutral control condition involved uninformative cues, indicating all 4 possible response locations. The primary outcome measure was the difference between neutral and anticue reaction time (RT). Negative values indicated RT costs of the anticue, relative to the neutral condition, reflecting reactive cognitive control. Positive values indicated RT benefits, reflecting proactive cognitive control. Results were twofold. First, the switch from RT costs to benefits took place at longer preparation intervals in the youngest and oldest age groups than in the intermediate age groups. Second, irrespective of preparation interval, anticue performance followed an inverted U-shaped trajectory as a function of age, with a relatively steep improvement during childhood and adolescence, relative stability between 26 and 60 years, and a slightly accelerating decline into old age. Both patterns of results suggest an age-related transition from a primarily reactive, to a primarily proactive mode of cognitive control in early life and back again from a primarily proactive, to a primarily reactive mode of control in later life. (PsycINFO Database Record

Inter-individual differences in how presentation modality affects verbal learning performance in children aged 5 to 16.

This study examines inter-individual differences in how presentation modality affects verbal learning performance. Children aged 5 to 16 performed a verbal learning test within one of three presentation modalities: pictorial, auditory, or textual. The results indicated that a beneficial effect of pictures exists over auditory and textual presentation modalities and that this effect increases with age. However, this effect is only found if the information to be learned is presented once (or at most twice) and only in children above the age of 7. The results may be explained in terms of single or dual coding of information in which the phonological loop is involved. Development of the (sub)vocal rehearsal system in the phonological loop is believed to be a gradual process that begins developing around the age of 7. The developmental trajectories are similar for boys and girls. Additionally, auditory information and textual information both seemed to be processed in a similar manner, namely without labeling or recoding, leading to single coding. In contrast, pictures are assumed to be processed by the dual coding of both the visual information and a (verbal) labeling of the pictures.

Switch hands! Mapping temporal dynamics of proactive manual control with anticues.

This study uses a novel behavioral paradigm-the anticue task-to investigate the temporal dynamics of proactive control aimed at the resolution of response conflict in the manual motor system. The anticue task is a 4-choice reaction time (RT) task, with left and right anticues indicating mirror-symmetrical response hands. In particular, anticues require participants to prepare fingers on the hand opposite to the side of the cue (counter-corresponding mapping), which contrasts with the more standard procues that prompt participants to prepare fingers on the hand spatially in line with the cue (corresponding mapping). In Experiment 1, we examined the effects of anticues and procues as a function of cue-target interval (range: 100-850ms). Results showed that procues produced RT benefits (relative to neutral cues), which increased with longer cue-target intervals. Anticues, however, produced RT costs with short cue-target intervals and RT benefits with longer cue-target intervals. These findings support the view that anticues are mediated by a time-consuming, proactive control process that, using inhibition and activation, redirects the initial but wrong activation of the ipsilateral hand to the correct contralateral hand. In Experiment 2, we used a simple detection response to test, and reject, an alternative (attentional) account of these findings. Theoretical and practical implications are discussed in the context of dual-route models of response selection, the activation-suppression model, and related experimental protocols such as antisaccade, Simon, Stroop, Eriksen flanker, and task switching paradigms.

Time estimation deficits in childhood mathematics difficulties.

Time perception has not been comprehensively examined in mathematics difficulties (MD). Therefore, verbal time estimation, production, and reproduction were tested in 13 individuals with MD and 16 healthy controls, matched for age, sex, and intellectual skills. Individuals with MD performed comparably to controls in time reproduction, but showed a tendency to be less accurate on tasks of verbal time estimation and time production. More specifically, these individuals overestimated the duration of a time interval in the verbal time estimation task and showed underproduction when required to produce a time sample. All previous significant comparisons remained significant after controlling for the effects of interval duration, working memory, attention allocation, and quantity estimation. These findings lead us to suggest that time estimation, and more specifically the "internal clock," is abnormally fast in individuals with MD. Results are discussed in terms of Meck and Church's model of temporal processing and Dehaene's triple code model for number processing.

Administering design fluency tests in school-aged children: analyses of design productivity over time, clustering, and switching.

This study investigated the effects of child-related factors (age, sex, and intellectual abilities) upon design fluency (DF) test scores. A DF test, a semantic verbal fluency (VF) test, and a Block Design test, as a proxy of intelligence, were administered to N = 80 healthy native Dutch-speaking children aged 8.45-12.82 years. Three components of DF performance were examined, i.e., design productivity over time, clustering (i.e., generating designs that share visual-spatial similarities, such as addition, deletion, or rotation), and switching (i.e., shifting between strategies that children use to draw the designs). The relation between DF design productivity over time and age was curvilinear, that is, improvements in test scores were much more pronounced for younger children than for older children. No (curvi)linear age effects were found in DF productivity scores, clustering, and switching. Also, our results did not reveal a relation between intellectual abilities and DF test scores. Furthermore, DF test scores and VF test scores were only partially significant, i.e., only significant positive correlations were found between the productivity scores of the VF test and the DF test. Finally, higher order sex by age interactions were found in all DF test scores, i.e., girls <10.5 years produced more designs, made longer clusters, and switched less than boys. Opposite sex differences were found for children >10.5 years. This illustrates the utility of combining quantitative scoring procedures with in-depth clustering and switching to understand interactions between age and sex during DF tests.

Does instruction in semantic clustering and switching enhance verbal fluency in children?

This study investigated (1) test-retest reliabilities of Verbal Fluency (VF) outcome measures (i.e., word productivity, clustering, and switching) and (2) the effects of a brief training on semantic clustering to improve performance on a VF task. A total of 81 children enrolled in grades 3-6 completed a traditional VF task twice. In between task administrations half of the children were given instruction on using semantic clustering and switching to improve their VF, while the other half served as a control group. Test-retest reliability coefficients of the control group (N = 40) were substantial for "word productivity over 60 seconds" (riccs varied between 0.45 and 0.64) but only moderate for "clustering" (0.31) and "switching" (0.31). Next only the older children improved on VF after instruction on semantic clustering; the younger children appeared to understand the instruction but had to use up a great deal of cognitive load trying to implement this new strategy. This paper describes (1) the impact of strategy instruction on performance and (2) the need to analyze, at a process level, multi-factorial tasks, so as to gain a better understanding of their functional components.