Complex Cognitive Performance Research Articles

Exploring the relationship between office lighting, cognitive performance, and psychophysiological responses: A multidimensional approach

Recognizing the growing importance of optimizing work environments for better cognitive performance, this study examined the relationships between general office lighting, psychophysiological responses and cognitive performance. Sixteen healthy adults in their 20s participated in experiments under nine different lighting conditions combining three levels of correlated color temperature (i.e., 4,000K, 5,000K, and 6,500K) and three levels of illuminance (i.e., 200 lx, 500 lx, and 800 lx). In the experiments, subjects’ primary and complex cognitive performances were measured and their psychophysiological responses such as mental workload, drowsiness, mental fatigue and stress, and visual fatigue were evaluated. Statistical analyses revealed that higher correlated color temperature and illuminance significantly enhanced primary cognitive performance but did not significantly impact complex cognitive performance or most psychophysiological responses. Notably, psychophysiological responses and cognitive performances were found to have mutual relationships rather than one being an absolute independent variable for another. The study suggests that tailored smart lighting systems could enhance cognitive performance in office environments by dynamically adjusting lighting conditions based on real-time psychophysiological feedback.

Personal comfort systems and cognitive performance: Effects on subjective measures, cognitive performance, and heart rate measures

Personal comfort systems (PCS) that warm or cool local body parts promise individual thermal comfort, energy saving and (metabolic) health in non-neutral thermal environments. However, research on work performance while using a PCS is scarce. We previously tested a PCS that warms the extremities and cools the head and reported that the PCS improved thermal comfort during a ramp of 17-23˚C but did not at a stable temperature of 25˚C. In the current study, its effects on cognitive performance, subjective measures and task-induced heart rate measures are investigated. Eighteen participants completed two randomized, eight-hour-long dynamic office scenarios: one is PCS scenario and another one is without PCS scenario. The results show warming the extremities slightly slowed reaction time for a simple task at 19˚C (p < 0.05) whereas it exerted no effect on complex task performance in 17-21˚C. At 25˚C however, cooling the head improved complex task performance (p = 0.053), which derived from participants’ effort increase, whereas it did not affect simple task performance. These findings suggest that the PCS’ effects on cognitive performance depended on the task type. Cooling the head, independent from its influence on thermal comfort, plays a significant role in complex cognitive performance in slightly warm conditions.

Skeletonized mean diffusivity and neuropsychological performance in relapsing-remitting multiple sclerosis.

BackgroundPeak width of Skeletonized Mean Diffusivity (PSMD), as a novel marker of white matter (WM) microstructure damage, is associated with cognitive decline in several WM pathologies (i.e., small vessel disorders). We hypothesized that markers combining alterations in whole WM could be associated with cognitive dysfunction in relapsing‐remitting multiple sclerosis (RRMS) patients.MethodsWe used PSMD based on tract‐based spatial statistics (TBSS) of diffusion tensor imaging (DTI) magnetic resonance (MR) scans. We investigated RRMS patients (n = 73) undergoing interferon beta (IFN‐β) therapy. In this cross‐sectional study, we investigated the association between neuropsychological data and clinical and MRI variables: PSMD, WM hypointensities, and normalized brain volume (NBV).ResultsIn our cohort, 37 (50.7%) patients were recognized as cognitively impaired (CI) and 36 (49.3%) patients were cognitively normal (CN). In regression analysis, PSMD was a statistically significant contributor in the California Verbal Learning Test (CVLT) list A (p = 0.04) and semantic fluency (p = 0.036). PSMD (p < 0.001, r 2 = 0.35), NBV (p = 0.002, r 2 = 2.6) and WM hypointensities (p < 0.001, r 2 = 0.40) were major contributors to upper extremity disability (9HPT) in the CN subgroup. A significant contributor in the majority of neuropsychological measures was education attainment.ConclusionWe investigated PSMD as a new parameter of WM microstructure damage that is a contributor in complex cognitive tasks, CVLT performance, and semantic fluency. PSMD was a statistically significant contributor to upper extremity disability (9HPT) together with WM hypointensities and NBV. Education attainment proved to be relevant in the majority of cognitive domains. Further studies are needed to estimate PSMD relevance as a marker of CI in MS.

Surprise, Curiosity, and Confusion Promote Knowledge Exploration: Evidence for Robust Effects of Epistemic Emotions.

Research has started to acknowledge the importance of emotions for complex learning and cognitive performance. However, research on epistemic emotions has only recently become more prominent. Research in educational psychology in particular has mostly focused on examining achievement emotions instead of epistemic emotions. Furthermore, only few studies have addressed functional mechanisms underlying multiple different epistemic emotions simultaneously, and only one study has systematically compared the origins and effects of epistemic emotions with other emotions relevant to knowledge generation (i.e., achievement emotions; Vogl et al., 2019). The present article aimed to replicate the findings from Vogl et al. (2019) exploring within-person interrelations, origins, and outcomes of the epistemic emotions surprise, curiosity, and confusion, and the achievement emotions pride and shame, as well as to analyze their robustness and generalizability across two different study settings (online; Study 1, n = 169 vs. lab; Study 2, n = 79). In addition, the previous findings by Vogl et al. (2019, Study 3) and the present two new studies were meta-analytically integrated to consolidate evidence on origins and outcomes of epistemic emotions. The results of the two new studies largely replicated the findings by Vogl et al. (2019). Combined with the meta-analytic results, the findings confirm distinct patterns of antecedents for epistemic vs. achievement emotions: Pride and shame were more strongly associated with the correctness of a person’s answer (i.e., accuracy), whereas surprise, curiosity, and confusion were more strongly related to incorrect responses a person was confident in (i.e., high-confidence errors) producing cognitive incongruity. Furthermore, in contrast to achievement emotions, epistemic emotions had positive effects on the exploration of knowledge. Implications for research and practice are discussed.

Severity-dependent influence of isocapnic hypoxia on reaction time is independent of neurovascular coupling

With exposure to acute normobaric hypoxia, global cerebral oxygen delivery is maintained via increases in cerebral blood flow (CBF); therefore, regional and localized changes in oxygen tension may explain neurocognitive impairment. Neurovascular coupling (NVC) is the close temporal and regional relationship of CBF to changes in neural activity and may aid in explaining the localized CBF response with cognitive activation. High-altitude related cognitive impairment is likely affected by hypocapnic cerebral vasoconstriction that may influence regional CBF regulation independent of hypoxia. We assessed neurocognition and NVC following 30 min of acute exposure to isocapnic hypoxia (decreased partial pressure of end-tidal oxygen; PETO2) during moderate hypoxia (MOD HX; 55 mm Hg PETO2), and severe hypoxia (SEV HX; 45 mm Hg PETO2) in 10 healthy individuals (25.5 ± 3.3 yrs). Transcranial Doppler ultrasound was used to assess mean posterior and middle cerebral blood velocity (PCAv and MCAv, respectively) and neurocognitive performance was assessed via validated computerized tests. The main finding was that reaction time (i.e., kinesthetic and visual-motor ability via Stroop test) was selectively impaired in SEV HX (−4.6 ± 5.2%, P = 0.04), but not MOD HX, while complex cognitive performance (e.g., psychomotor speed, cognitive flexibility, processing speed, executive function, and motor speed) was unaffected with hypoxia (P > 0.05). Additionally, severity of hypoxia had no effect on NVC (PCAv CON vs. SEV HX relative peak response 13.7 ± 6.4% vs. 16.2 ± 11.5%, P = 0.71, respectively). In summary, severe isocapnic hypoxia impaired reaction time, but not complex cognitive performance or NVC. These findings have implications for recreational and military personnel who may experience acute hypoxia.

General, crystallized and fluid intelligence are not associated with functional global network efficiency: A replication study with the human connectome project 1200 data set

One hallmark example of a link between global topological network properties of complex functional brain connectivity and cognitive performance is the finding that general intelligence may depend on the efficiency of the brain's intrinsic functional network architecture. However, although this association has been featured prominently over the course of the last decade, the empirical basis for this broad association of general intelligence and global functional network efficiency is quite limited. In the current study, we set out to replicate the previously reported association between general intelligence and global functional network efficiency using the large sample size and high quality data of the Human Connectome Project, and extended the original study by testing for separate association of crystallized and fluid intelligence with global efficiency, characteristic path length, and global clustering coefficient. We were unable to provide evidence for the proposed association between general intelligence and functional brain network efficiency, as was demonstrated by van den Heuvel et al. (2009), or for any other association with the global network measures employed. More specifically, across multiple network definition schemes, ranging from voxel-level networks to networks of only 100 nodes, no robust associations and only very weak non-significant effects with a maximal R2 of 0.01 could be observed. Notably, the strongest (non-significant) effects were observed in voxel-level networks. We discuss the possibility that the low power of previous studies and publication bias may have led to false positive results fostering the widely accepted notion of general intelligence being associated to functional global network efficiency.

Abstract TMP97: Demyelination, Cognition and Imaging in a Translational Model of Rat Vascular Cognitive Impairment

Small vessel disease and/or atherosclerosis produce microvascular and parenchymal inflammation in white matter and results in vascular cognitive impairment (VCI). We have performed bilateral carotid artery stenosis in hypertensive rats (SHR) to better understand disease pathology, targets for intervention and markers. Hypothesis: Complex cognitive deficits and diffuse fiber tract changes relevant to human VCI can be quantified and validated for future use. Methodology: We performed a series of behavioral assays to test declarative memory and executive functioning in stenosis compared to sham surgery SHR. Behavioral assays included T-maze decision making and alternation, novel object recognition (NOR) and active place avoidance (APA). MRI (DTI, DWI, Arterial Spin Labeling; ASL) and FDG-PET imaging was done in Corpus Callosum (CC). Histology-immunohistochemistry included measurements of microglia (Iba-1), astrocytes (GFAP) and Luxol fast blue (for myelin) in CC. Results: Stenosis resulted in consistent executive function decision making (T-maze) deficits (p&lt;0.05) and impaired complex cognitive performance (APA). No significant differences occurred between sham and stenosis animals in NOR and T-maze alternation. DTI analysis indicated significant (p&lt;0.05) changes in the CC of stenosis compared to sham SHR including: (1) decreased fractional anisotropy, (2) increased radial diffusivity, and (3) unchanged axial diffusivity. MRI ASL revealed significant (p&lt;0.05) decreases in white matter perfusion. No significant changes were seen in FDG-PET. In summary, stenosis animals exhibited increased white matter glial cell inflammation related to demyelination and lost cognition. The inflammatory microglia phenotype was verified using TNFα plus Iba-1 double staining. CC changes were significantly (p&lt;0.05) greater in the anterior, periventricular forebrain. Conclusion: We have successfully modeled the behavioral, imaging and histologic profile of human VCI in the rat. Currently pre/mature oligodendrocyte changes are being evaluated. This approach provides future opportunities to localize forebrain white matter changes using MR imaging parameters as markers for monitoring VCI demyelination/pathology and intervention.

Chapter 31 - Language impairments in traumatic brain injury: a window into complex cognitive performance

Often, standard aphasia batteries do not fully characterize higher-order cognitive-linguistic sequelae associated with a traumatic brain injury (TBI). Limited understanding and detection of complex linguistic deficits have thwarted efforts to comprehensively remediate higher-order language deficits that persist even in chronic stages of recovery post-TBI. This chapter reviews key precursor metrics that have motivated efforts to elucidate higher-order language proficiencies after a TBI. The chapter further expounds on a paradigmatic shift away from sole focus on lower level basic skills, towards a more top-down cognitive control approach to measure, retrain, and strengthen complex language abilities in TBI. The intricate relations between complex language abilities and cognitive control functions are also discussed. The concluding section offers promising directions for future research and clinical management based on new discoveries of higher-order language impairments and their modifiability in TBI populations.

Effects of sleep restriction, sleep inertia, and overload on complex cognitive performance before and after workload transition

We describe performance models and meta-analytic data in a period before and after an unexpected workload transition typical, for example, of a catastrophic automation failure, experienced by a fatigued operator. We first present meta-analytic findings on the effects of sleep restriction and sleep inertia on the complex cognitive performance that might typify such a “failure response”. We then present a workload overload task management model whose parameters are based on meta-analyses, relevant to predicting multi-task performance in the post-transition phase performance (independent of sleep disruption effects). We cite the lack of research intersecting these two areas.

Correlational structure of ‘frontal’ tests and intelligence tests indicates two components with asymmetrical neurostructural correlates in old age

Both general fluid intelligence (gf) and performance on some ‘frontal tests’ of cognition decline with age. Both types of ability are at least partially dependent on the integrity of the frontal lobes, which also deteriorate with age. Overlap between these two methods of assessing complex cognition in older age remains unclear. Such overlap could be investigated using inter-test correlations alone, as in previous studies, but this would be enhanced by ascertaining whether frontal test performance and gf share neurobiological variance. To this end, we examined relationships between gf and 6 frontal tests (Tower, Self-Ordered Pointing, Simon, Moral Dilemmas, Reversal Learning and Faux Pas tests) in 90 healthy males, aged ~73years. We interpreted their correlational structure using principal component analysis, and in relation to MRI-derived regional frontal lobe volumes (relative to maximal healthy brain size). gf correlated significantly and positively (.24≤r≤.53) with the majority of frontal test scores. Some frontal test scores also exhibited shared variance after controlling for gf. Principal component analysis of test scores identified units of gf-common and gf-independent variance. The former was associated with variance in the left dorsolateral (DL) and anterior cingulate (AC) regions, and the latter with variance in the right DL and AC regions. Thus, we identify two biologically-meaningful components of variance in complex cognitive performance in older age and suggest that age-related changes to DL and AC have the greatest cognitive impact.

Effects of Central Vision, Peripheral Vision, and Haptic Inputs on Complex Verbal and Spatial Tasks

The aim of the present study is to investigate how quite specific sensory inputs (visual inputs from central or peripheral regions of the retina and haptic inputs) relate to complex cognitive performance. We compare individuals with severe peripheral visual field loss, Braille reader with central scotomata (SDB group), print readers with central scotomata, and normally sighted people on visual reading and spatial imagery tasks. Experiment 1 showed that the SDB subjects were significantly less accurate than the other groups on reading visual print letters, words, digits, and 4-digit numbers aloud. In experiment 2, SDB subjects also performed worse than the other subjects on imagery tasks that required indicating spatial characteristics of orally presented print letters, rotated capital letters, print words, and number shapes. Experiment 3 revealed that the SDB group improved their performance when instructed to draw the outlines of imagined stimuli shapes haptically. The findings suggest that visual memory needs perceptual practice to be maintained and that haptic inputs can be used to improve verbal and spatial imagery skills in visually impaired individuals.

The Disruptive Effects of Pain on Complex Cognitive Performance and Executive Control

Pain interferes and disrupts attention. What is less clear is how pain affects performance on complex tasks, and the strategies used to ensure optimal outcomes. The aim of the current study was to examine the effect of pain on higher-order executive control processes involved in managing complex tasks. Sixty-two adult volunteers (40 female) completed two computer-based tasks: a breakfast making task and a word generation puzzle. Both were complex, involving executive control functions, including goal-directed planning and switching. Half of those recruited performed the tasks under conditions of thermal heat pain, and half with no accompanying pain. Whilst pain did not affect central performance on either task, it did have indirect effects. For the breakfast task, pain resulted in a decreased ability to multitask, with performance decrements found on the secondary task. However, no effects of pain were found on the processes thought to underpin this task. For the word generation puzzle, pain did not affect task performance, but did alter subjective accounts of the processes used to complete the task; pain affected the perceived allocation of time to the task, as well as switching perceptions. Sex differences were also found. When studying higher-order cognitive processes, pain-related interference effects are varied, and may result in subtle or indirect changes in cognition.

Changes in the suprachiasmatic nucleus during aging: Implications for biological rhythms.

have neural structures that allow them to anticipate environmental changes and then regulate physiological and behavioral functions in response to these alterations. The suprachiasmatic nucleus of the hypothalamus (SCN) is the main circadian pacemaker in many mammalian species. This structure synchronizes the biological rhythm based on photic information that is transmitted to the SCN through the retinohypothalamic tract. The aging process changes the structural complexity of the nervous system, from individual nerve cells to global changes, including the atrophy of total gray matter. Aged animals show internal time disruptions caused by morphological and neurochemical changes in SCN components. The effects of aging on circadian rhythm range from effects on simple physiological functions to effects on complex cognitive performance, including many psychiatric disorders that influence the well-being of the elderly. In this review, we summarize the effects of aging on morphological, neurochemical, and circadian rhythmic functions coordinated by the main circadian pacemaker, the SCN.

Queueing network-adaptive control of thought rational (QN-ACTR): an integrated cognitive architecture for modelling complex cognitive and multi-task performance

How to computationally model human performance in complex cognitive and multi-task scenarios has become an important yet challenging question for human performance modelling and simulation. This paper reports the work that develops an integrated cognitive architecture for this purpose. The resulting architecture – queueing network-adaptive control of thought rational (QN-ACTR) – is an integration of the QN mathematical architecture and the ACT-R symbolic architecture. This integration allows QN-ACTR to overcome the limitations in each method and model a wider range of tasks. Implemented as a computerised simulation programme, QN-ACTR has been verified in the simulation of 20 typical tasks from the ACT-R literature. The benefits of the integration have been demonstrated in the simulation of 29 transcription typing phenomena, showing its capability in modelling complex cognitive and multi-task scenarios that have not been modelled by either QN or ACT-R.

Knowledge to Go: A Motivational and Dispositional View of Transfer

We synthesize ideas from the foregoing articles in this special issue and from the broader literature on transfer to explore several themes. In many ordinary life circumstances, transfer proceeds easily, but formal learning often shows much less transfer than educators would like, making failure to transfer a focus of investigation. Transfer, like any complex cognitive performance, benefits from motivational and dispositional drivers, an aspect of transfer not much discussed in these articles but inviting attention. Episodes of transfer can be analyzed according to a detect–elect–connect model: detecting a potential relationship with prior learning, electing to pursue it, and working out a fruitful connection. These three “bridges” are somewhat independent; ways in which each of them succeed and fail are detailed, drawing on the contributed articles and the broader literature. Finally, insights from this collection of articles and elsewhere put educators in a position to teach for transfer more effectively, but shifts of mind-set about the nature of knowledge and learning are required.

Sensory displeasure reduces complex cognitive performance in the heat

The aim of this study was to verify that in a hot environment, the subjective state could affect cognitive performance before any increase in core temperature. Eighteen volunteers performed a planning (OTS) and a reaction time task in hot and control environments. Before starting the cognitive assessment, subjects completed the Positive and Negative Affect Schedule (PANAS) and provided subjective measures of thermal comfort and thermal sensation. Our results showed that while simple tasks were not affected, complex cognitive task performance was significantly reduced in the HOT. Furthermore, although subjects responded faster during the complex task (OTS) they took longer to find the correct solution. Within the 15 min of heat exposure, skin temperature (Tskin) significantly increased by ∼3 °C. However, core temperature remained unchanged and there were cortical excitability alterations that could have influenced cognitive performance. Therefore, the increase in Tskin appears to be a sufficient physiological response to alter the subjective state of individuals and impair effective decision-making that could have important consequences in occupational settings.

Could mild hypoxia impair pilot decision making in emergencies?

The decreased pressure in the cabin of a pressurised aircraft (typically equivalent to ~8000 ft) reduces the oxygen level so that the blood oxygen saturation of all occupants falls from >97% (normoxia) at sea-level to below 92% (mild hypoxia). Although exposure to mild hypoxia does not affect well-learned cognitive and motor performance of aircrew, it has been proposed that it can affect the performance of some complex cognitive performance tasks involving multiple demands typical of emergency tasks that may have to be performed by pilots. In order to simulate some of these complex cognitive demands, 25 student volunteers participated in an experiment which assessed performance of complex logical reasoning and and multiple memory tasks before and after 2 hours of exposure to normoxia and mild hypoxia. Performance for the more difficult components of the complex reasoning task, especially involving conflict decisions, were marginally significantly degraded by mild hypoxia. Since the effects were only marginally significant future studies should investigate the effects of mild hypoxia on more subtle complex decision-making tasks.

The Effects of Heat Exposure on Cognitive Performance

Abstract In addition to physical conditioning, successful sporting performance requires a level of perception coupled with efficiency and accuracy in movement. The FIFA World Cup is usually played during the summer months; therefore the aim of this study was to investigate the effects of heat exposure on cognitive performance. Three experiments were performed in an environmental chamber under hot (HOT: 50°C, 30% rH) and control (CON: 24°C, 30% rH) conditions. Exposure time ranged from 15 minutes to 4.5 hours. Subjects performed simple and complex cognitive tasks under different levels of thermal strain. Neuromuscular assessments were performed to assess neural drive and muscular force production. Central (Tcore) and skin (Tskin) temperatures were recorded along with subjective measures of thermal comfort (TC) and thermal sensation (TS). Hyperthermia had no impact upon attention tasks, however, impulsivity increased during sustained attention over prolonged periods. Significant increases in Tcore (>38.30°C) were associated with impaired complex cognitive task performance. The regular application of cold packs to the head limited the detrimental effects of hyperthermia upon short-term memory. However, rapid and substantial variations in Tskin of ∼3°C, independent of changes in Tcore, had similar detrimental effects upon cognitive task performance. Results suggest that reductions in complex cognitive performance with heat exposure occur via a decrement in motor cortical excitability when Tcore increases to ∼38.3°C, but they also originate from an additional cognitive load imposed by thermal strain and the resulting allesthesial Tskin variations; with both these factors acting as competing variables to the cognitive processes. The increase in Tcore with prolonged heat exposure impairs cognitive performance; however applying cold packs to the head can preserve these. Increases in Tskin during brief heat exposures appear to be a sufficient physiological response to alter the emotional state of individuals and impair effective decision-making. Hydration protocols and reducing exercise intensity and load can reduce the physiological strain. Strategies to minimise the ‘thermal shock’ of entering a warm environment should be developed to minimise the impact of subjective feelings of thermal discomfort upon cognitive performance.

The impact of long-term maintenance treatment with buprenorphine on complex psychomotor and cognitive function

Introduction Despite the fact that buprenorphine is effective, well tolerated and due to its pharmacological profile a very safe drug, the impact of long-term buprenorphine substitution therapy on complex psychomotor and cognitive function predicting driving ability is not yet clear. Therefore, a prospective comparison between patients receiving sublingual buprenorphine and a control group of untreated, healthy volunteers was performed. Methods Treated and untreated subjects were matched for age and sex, with three control subjects selected for every buprenorphine patient. Patients using unreported drugs were included in the intention-to-treat (ITT) analysis; the remaining patients were analysed as the per-protocol (PP) group. The test battery comprised the assessment of: performance during stress, visual orientation, concentration, attention, vigilance and reaction time. The primary endpoint was defined as the sum of the relevant scores of the tests after z-transformation of the individual scores. Results 30 patients with sublingual buprenorphine treatment (7.7 ± 3.9 mg per day) were matched to 90 controls. 19 patients were excluded from the PP-analysis because of additional unreported drug intake. Significant non-inferiority could be demonstrated for the PP-group ( p < 0.05) as well as for the ITT-group ( p < 0.001). Conclusion Patients receiving a stable dose of sublingual buprenorphine showed no significant impairment of complex psychomotor or cognitive performance as compared to healthy controls. However intake of illicit drugs as well as the lack of social reliability are major problems in this specific patients group. Despite of the absence of a relevant impact of the drug on driving ability, those patients do not seem to be qualified for getting their driving license.

Neurophysiological and cognitive effects of smoked marijuana in frequent users

Rationale Previously, we reported that acute marijuana intoxication minimally affected complex cognitive performance of daily marijuana smokers. It is possible that the cognitive tests used were insensitive to marijuana-related cognitive effects. Objectives In the current study, electroencephalographic (EEG) signals were recorded as daily marijuana users performed additional tests of immediate working memory and delayed episodic memory, before and after smoking marijuana. Methods Research volunteers (N = 24), who reported smoking ∼ 24 marijuana cigarettes/week, completed this study. Participants completed baseline computerized cognitive tasks, smoked a single marijuana cigarette (0%, 1.8%, or 3.9% ∆ 9-THC w/w), and completed additional cognitive tasks; sessions were separated by at least 72-hours. Cardiovascular and subjective effects were also assessed throughout sessions. Results Overall performance accuracy was not significantly altered by marijuana, although the drug increased response times during task performance and induced a response bias towards labeling “new” words as having been previously seen in the verbal episodic memory task. Marijuana reduced slow wave evoked potential amplitude in the episodic memory task and decreased P300 amplitude and EEG power in the alpha band in the spatial working memory task. Heart rate and “positive” subjective-effect ratings were increased in a ∆ 9-THC concentration-dependent manner. Conclusions Relative to previous findings with infrequent marijuana users, the frequent users in the current study exhibited similar neurophysiological effects but more subtle performance effects. These data emphasize the importance of taking into account the drug-use histories of research participants and examining multiple measures when investigating marijuana-related effects on cognitive functioning.