Levels Of Task Difficulty Research Articles

Decoding go/no-go decisions from eye movements.

Neural activity in brain areas involved in the planning and execution of eye movements predicts the outcome of an upcoming perceptual decision. Many real-world decisions, such as whether to swing at a baseball pitch, are accompanied by characteristic eye-movement behavior. Here we ask whether human eye-movement kinematics can sensitively predict decision outcomes in a go/no-go task requiring rapid interceptive hand movements. Observers (n = 45) viewed a moving target that passed through or missed a designated strike box. Critically, the target disappeared briefly after launch, and observers had to predict the target's trajectory, withholding a hand movement if it missed (no-go) or intercepting inside the strike box (go). We found that go/no-go decisions were reflected in distinct eye-movement responses on a trial-by-trial basis: Eye-position error and targeting-saccade dynamics predicted decision outcome with 76% accuracy across conditions. Model prediction accuracy was related to observers' decision accuracy across different levels of task difficulty and sensory-signal strength. Our findings suggest that eye movements provide a sensitive and continuous readout of internal neural decision-making processes and reflect decision-task requirements in human observers.

Effects of lumbosacral orthosis on dynamical structure of center of pressure fluctuations in patients with non-specific chronic low back pain: A randomized controlled trial

BackgroundA few clinical trials have examined the effect of treatment interventions on postural control in patients with chronic low back pain, all of which have exclusively evaluated postural stability using traditional linear measures of postural sway. However, postural control improvement cannot be determined by exclusively relying on linear measurements, because these parameters provide no information on underlying motor control mechanisms. ObjectiveThis study aimed to compare the effect of using lumbosacral orthoses (LSO) together with routine physical therapy, compared to routine physical therapy alone on postural control, using nonlinear analysis techniques. MethodsForty-four patients with low back pain were randomly allocated to the intervention and control groups. Both groups underwent 8 sessions of physical therapy twice weekly for 4 weeks. The intervention group received LSO in addition to routine physical therapy. Before and after the intervention, non-linear dynamical features of center of pressure fluctuations were assessed during quiet standing at 3 difficulty levels of postural tasks, including eyes open while standing on a rigid surface, eyes closed while standing on a rigid surface, and eyes closed while standing on a foam surface. ResultsThe results of this study showed that a 4-week intervention consisting of LSO and routine physical therapy modalities did not affect the temporal structure of postural sways in patients with low back pain. ConclusionTreatment strategies, such as routine physical therapy modalities or LSO, which exclusively focus on the correction of peripheral mechanics, fail to affect the behavior of the postural control system.

Detection measures for visual inspection of X-ray images of passenger baggage

In visual inspection tasks, such as airport security and medical screening, researchers often use the detection measures d' or A' to analyze detection performance independent of response tendency. However, recent studies that manipulated the frequency of targets (target prevalence) indicate that da with a slope parameter of 0.6 is more valid for such tasks than d' or A'. We investigated the validity of detection measures (d', A', and da) using two experiments. In the first experiment, 31 security officers completed a simulated X-ray baggage inspection task while response tendency was manipulated directly through instruction. The participants knew half of the prohibited items used in the study from training, whereas the other half were novel, thereby establishing two levels of task difficulty. The results demonstrated that for both levels, d' and A' decreased when the criterion became more liberal, whereas da with a slope parameter of 0.6 remained constant. Eye-tracking data indicated that manipulating response tendency affected the decision component of the inspection task rather than search errors. In the second experiment, 124 security officers completed another simulated X-ray baggage inspection task. Receiver operating characteristic (ROC) curves based on confidence ratings provided further support for da, and the estimated slope parameter was 0.5. Consistent with previous findings, our results imply that d' and A' are not valid measures of detection performance in X-ray image inspection. We recommend always calculating da with a slope parameter of 0.5 in addition to d' to avoid potentially wrong conclusions if ROC curves are not available.

Does the Level of Difficulty in Balancing Tasks Affect Haptic Sensitivity Via Light Touch?

ABSTRACT.The purpose of this study was to determine whether the contribution of bimanual light touch varies according to the difficulty level of postural tasks (e.g., vision occlusion, height of support surface). Fourteen healthy young adults each were asked to stand in a tandem position, on a 20-cm height balance beam. Postural tasks included light touch and no touch conditions in two vision conditions, nonvision and full vision. The root mean square of amplitude of oscillation (mediolateral), mean velocity, ellipse area, and path length of the center of pressure revealed that touch conditions reduced sway to a greater extent in the elevated support surface, nonvision condition. Highly unstable balance tasks increase the optimization of light touch and affect the attenuation of postural sway.

Modulation by task-difficulty in the default mode network varies with the complexity of perpetual information during decision making

Modulation by task-difficulty in the default mode network varies with the complexity of perpetual information during decision making

Shared or Distinct Attentional Resources? Confounds in Dual Task Designs, Countermeasures, and Guidelines.

Human information processing is limited by attentional resources. That is, via attentional mechanisms humans select information that is relevant for their goals, and discard other information. While limitations of attentional processing have been investigated extensively in each sensory modality, there is debate as to whether sensory modalities access shared resources, or if instead distinct resources are dedicated to individual sensory modalities. Research addressing this question has used dual task designs, with two tasks performed either in a single sensory modality or in two separate modalities. The rationale is that, if two tasks performed in separate sensory modalities interfere less or not at all compared to two tasks performed in the same sensory modality, then attentional resources are distinct across the sensory modalities. If task interference is equal regardless of whether tasks are performed in separate sensory modalities or the same sensory modality, then attentional resources are shared across the sensory modalities. Due to their complexity, dual task designs face many methodological difficulties. In the present review, we discuss potential confounds and countermeasures. In particular, we discuss 1) compound interference measures to circumvent problems with participants dividing attention unequally across tasks, 2) staircase procedures to match difficulty levels of tasks and counteracting problems with interpreting results, 3) choosing tasks that continuously engage participants to minimize issues arising from task switching, and 4) reducing motor demands to avoid sources of task interference, which are independent of the involved sensory modalities.

Arm Ability Training (AAT) Promotes Dexterity Recovery After a Stroke-a Review of Its Design, Clinical Effectiveness, and the Neurobiology of the Actions.

Arm Ability Training (AAT) has been specifically designed to promote manual dexterity recovery for stroke patients who have mild to moderate arm paresis. The motor control problems that these patients suffer from relate to a lack of efficiency in terms of the sensorimotor integration needed for dexterity. Various sensorimotor arm and hand abilities such as speed of selective movements, the capacity to make precise goal-directed arm movements, coordinated visually guided movements, steadiness, and finger dexterity all contribute to our “dexterity” in daily life. All these abilities are deficient in stroke patients who have mild to moderate paresis causing focal disability. The AAT explicitly and repetitively trains all these sensorimotor abilities at the individual's performance limit with eight different tasks; it further implements various task difficulty levels and integrates augmented feedback in the form of intermittent knowledge of results. The evidence from two randomized controlled trials indicates the clinical effectiveness of the AAT with regard to the promotion of “dexterity” recovery and the reduction of focal disability in stroke patients with mild to moderate arm paresis. In addition, the effects have been shown to be superior to time-equivalent “best conventional therapy.” Further, studies in healthy subjects showed that the AAT induced substantial sensorimotor learning. The observed learning dynamics indicate that different underlying sensorimotor arm and hand abilities are trained. Capacities strengthened by the training can, in part, be used by both arms. Non-invasive brain stimulation experiments and functional magnetic resonance imaging data documented that at an early stage in the training cortical sensorimotor network areas are involved in learning induced by the AAT, yet differentially for the tasks trained. With prolonged training over 2 to 3 weeks, subcortical structures seem to take over. While behavioral similarities in training responses have been observed in healthy volunteers and patients, training-induced functional re-organization in survivors of a subcortical stroke uniquely involved the ipsilesional premotor cortex as an adaptive recruitment of this secondary motor area. Thus, training-induced plasticity in healthy and brain-damaged subjects are not necessarily the same.

N-back training and transfer effects revealed by behavioral responses and EEG.

IntroductionCognitive function performance decreases in older individuals compared to young adults. To curb this decline, cognitive training is applied, but it is not clear whether it improves only the trained task or also other cognitive functions. To investigate this, we considered an N‐back working memory (WM) training task and verified whether it improves both trained WM and untrained cognitive functions.MethodsAs EEG studies have noted task difficulty and age‐related changes in time‐locked EEG responses, called event‐related potentials (ERPs), we focused on the relation between the P300 ERP component, task difficulty level, and behavior response accuracy and reaction time (RT) in young and older healthy adults. We used two groups of young and older healthy participants to assess the effect of N‐back training: cognitive training group (CTG) and passive control group (PCG). Before and after training, cognitive tests were administered to both groups to evaluate transfer effects.ResultsDespite the observed age‐related differences in the P300 ERP component and in terms of RT and accuracy, our findings demonstrate a stronger improvement in the trained task for older CTGs compared to younger CTGs, larger near‐ and far‐transfer effect to WM and fluid intelligence for both younger and older CTGs, and a far‐transfer effect to attention but only for older adults. Significant differences in response accuracy were shown between young and older subjects in spatial memory and attention tests.ConclusionThe application of a WM training is a promising tool for both healthy adults, and in particular for older subjects, as it showed physiological and behavioral differences in cognitive plasticity across life span and evidence of benefits in the trained task and near‐/far‐transfer effects to other cognitive functions.

Changes in Mental Workload and Motor Performance Throughout Multiple Practice Sessions Under Various Levels of Task Difficulty

The allocation of mental workload is critical to maintain cognitive-motor performance under various demands. While mental workload has been investigated during performance, limited efforts have examined it during cognitive-motor learning, while none have concurrently manipulated task difficulty. It is reasonable to surmise that the difficulty level at which a skill is practiced would impact the rate of skill acquisition and also the rate at which mental workload is reduced during learning (relatively slowed for challenging compared to easier tasks). This study aimed to monitor mental workload by assessing cortical dynamics during a task practiced under two difficulty levels over four days while perceived task demand, performance, and electroencephalography (EEG) were collected. As expected, self-reported mental workload was reduced, greater working memory engagement via EEG theta synchrony was observed, and reduced cortical activation, as indexed by progressive EEG alpha synchrony was detected during practice. Task difficulty was positively related to the magnitude of alpha desynchrony and accompanied by elevations in the theta-alpha ratio. Counter to expectation, the absence of an interaction between task difficulty and practice days for both theta and alpha power indicates that the refinement of mental processes throughout learning occurred at a comparable rate for both levels of difficulty. Thus, the assessment of brain dynamics was sensitive to the rate of change of cognitive workload with practice, but not to the degree of difficulty. Future work should consider a broader range of task demands and additional measures of brain processes to further assess this phenomenon.

Modelling decisions of control transitions and target speed regulations in full-range Adaptive Cruise Control based on Risk Allostasis Theory

Adaptive Cruise Control (ACC) and automated vehicles can contribute to reduce traffic congestion and accidents. Recently, an on-road study has shown that drivers may prefer to deactivate full-range ACC when closing in on a slower leader and to overrule it by pressing the gas pedal a few seconds after the activation of the system. Notwithstanding the influence of these control transitions on driver behaviour, a theoretical framework explaining driver decisions to transfer control and to regulate the target speed in full-range ACC is currently missing.This research develops a modelling framework describing the underlying decision-making process of drivers with full-range ACC at an operational level, grounded on Risk Allostasis Theory (RAT). Based on this theory, a driver will choose to resume manual control or to regulate the ACC target speed if its perceived level of risk feeling and task difficulty falls outside the range considered acceptable to maintain the system active. The feeling of risk and task difficulty evaluation is formulated as a generalized ordered probit model with random thresholds, which vary between drivers and within drivers over time. The ACC system state choices are formulated as logit models and the ACC target speed regulations as regression models, in which correlations between system state choices and target speed regulations are captured explicitly. This continuous-discrete choice model framework is able to address interdependencies across drivers’ decisions in terms of causality, unobserved driver characteristics, and state dependency, and to capture inconsistencies in drivers’ decision making that might be caused by human factors.The model was estimated using a dataset collected in an on-road experiment with full-range ACC. The results reveal that driver decisions to resume manual control and to regulate the target speed in full-range ACC can be interpreted based on the RAT. The model can be used to forecast driver response to a driving assistance system that adapts its settings to prevent control transitions while guaranteeing safety and comfort. The model can also be implemented into a microscopic traffic flow simulation to evaluate the impact of ACC on traffic flow efficiency and safety accounting for control transitions and target speed regulations.

A Mechanistic Study of the Association Between Symbolic Approximate Arithmetic Performance and Basic Number Magnitude Processing Based on Task Difficulty.

Two types of number magnitude processing – semantic and spatial – are significantly correlated with children’s arithmetic performance. However, it remains unclear whether these abilities are independent predictors of symbolic approximate arithmetic performance. The current study addressed this question by assessing 86 kindergartners (mean age of 5 years and 7 months) on semantic number processing (number comparison task), spatial number processing (number line estimation task), and symbolic approximate arithmetic performance with different levels of difficulty. The results showed that performance on both tasks of number magnitude processing was significantly correlated with symbolic approximate arithmetic performance, but the strength of these correlations was moderated by the difficulty level of the arithmetic task. The simple symbolic approximate arithmetic task was equally related to both tasks. In contrast, for more difficult symbolic approximate arithmetic tasks, the contribution of number comparison ability was smaller than that of the number line estimation ability. These results indicate that the strength of contribution of the different types of numerical processing depends on the difficulty of the symbolic approximate arithmetic task.

The Role of Task Difficulty in Learning a Visuomotor Skill.

Task difficulty affects the amount of interpretable information from a task, which is thought to interfere with motor learning. However, it is unclear whether task difficulty in itself is a stimulus for motor learning because the experimental evidence is mixed in support of the optimal challenge point framework that predicts one specific level of task difficulty to produce the greatest magnitude of motor learning. We determined the effects of functional task difficulty on motor skill acquisition, retention, and transfer. Healthy young participants (N = 36) learned a mirror star-tracing task at a low, medium, or hard difficulty level defined by the bandwidth of the star. We measured skill acquisition, retention, and transfer to untrained difficulty levels, as well as the perceived mental workload during the task. Task difficulty affected motor performance, but did not affect motor learning and transfer. For the groups that practiced the task at the medium and hard but not at the low difficulty level, initial skill level correlated with the magnitude of learning. The optimal challenge point framework does not capture the complex relationship between task difficulty and motor learning. Previously reported effects of task difficulty on the magnitude of motor learning are probably mediated by perceived mental workload. Task difficulty did not affect the magnitude of visuomotor skill learning but it affected how learning occurred. The data have implications on how athletes learn new motor skills and patients relearn injury-impaired motor skills during rehabilitation.

Good to be stressed? Improved response inhibition and error processing after acute stress in young and older men

While aging and stress are both known to affect cognitive functions, little is known on whether and how age modulates stress effects on executive functions and their neural correlates. The current study investigated the effect of acute stress on response inhibition and error processing and their underlying cortical processes in younger and older healthy men, using EEG. Forty-nine participants (30 young) were stressed with the Trier Social Stress Test (16 young, 9 older) or underwent a friendly control procedure (14 young, 10 older) and subsequently performed a Go/No-Go task with two levels of task difficulty while performance (reaction time, error rate), stimulus-locked (N2, P3) and response-locked (Ne, Pe) ERPs were measured. Previous results on age-related cognitive deficits were replicated, with slower responses and reduced and delayed N2 and P3 components, as well as reduced Ne and Pe components in older participants. Independent of age, acute stress improved response inhibition, reflected in higher accuracy for compatible trials and enhanced inhibition-related components (N2, P3 and N2d, P3d of the difference waves No-Go minus Go), and improved error processing, reflected in enhanced error-related components (Ne, Pe and Ne_d, Pe_d of the difference waves error minus correct trial). Our findings indicate that acute stress leads to a reallocation of cognitive resources, strengthening inhibition and error processing in young and older healthy men to a similar degree. Neural generators of the analyzed ERPs are mainly part of the salience network, which is upregulated immediately after stress. This offers an explanation as to why response inhibition, in contrast to other executive functions, improves after acute stress.

Development and validation of a contextual behavioral distress intolerance task in cigarette smokers

IntroductionDistress intolerance, an individual's perceived or actual inability to withstand negative emotional or physical distress, contributes to the maintenance of smoking. However, there is limited understanding of the contextual factors that impact distress intolerance in general or among smokers specifically. This study aimed to adapt and test a computerized behavioral persistence task that requires re-typing a passage while adhering to specific instructions (Contextual-Frustration Intolerance Typing Task [C-FiTT]). C-FiTT was designed to model contextual factors that influence distress intolerance, negative affect, and smoking urges. MethodDaily smokers (n = 550) were recruited through the use of Qualtrics Panels. Using a 2 × 2 + 1 experimental design, participants were randomly assigned to one of four C-FiTT conditions that crossed task difficulty (low or high difficulty) with passage content (neutral or tobacco withdrawal text), or a neutral control group. ResultsC-FiTT produced an average persistence time of 94.1 ± 114.3 s and 64.7% of participants self-terminated the task. C-FiTT also produced small to medium sized-increases in negative affect and smoking urges. Between-condition comparisons indicated that the high-difficulty C-FiTT produced shorter behavioral persistence, greater self-termination likelihood, and larger increases in negative affect and smoking urges. The combination of high-difficulty and withdrawal content resulted in the shortest persistence time, 100% self-termination rate, and largest increases in negative affect and smoking urges, compared to other conditions ConclusionsFindings provide initial evidence for the validity of C-FiTT in smokers within the context of tobacco withdrawal at low and high levels of task difficulty. Avenues for refinement and use of C-FiTT are discussed.

Effect of reading intervention and task difficulty on orthographic and phonological reading systems in the brain

Children with poor reading skills have differences in brain function when compared to typically-developing readers, and there may also be changes in the brain following reading intervention. However, most functional imaging studies focus on phonological reading tasks with one level of task difficulty. The purpose of this study was to compare good and poor readers on functional magnetic resonance imaging (fMRI) tasks of orthography (spelling) and phonology (rhyming) before and after 3 months of school-based intervention. These tasks were also modulated by task difficulty based on printed word frequency. The results showed that primarily left hemisphere regions were activated for the spelling and rhyming tasks, and poor readers showed a pattern of increased activation in bilateral inferior frontal, bilateral insula, right parietal, and left cerebellum following intervention. Activity in left pars triangularis and right parietal regions were associated with gains in decoding skills. Intervention effects appeared across blocks of easy and difficult words, except for the right parietal cortex. In this region, poor readers had greater activity on the easy word blocks after intervention, which indicates that there was increased recruitment of the right parietal cortex for relatively easy words. These results indicate that effects of intervention may be more evident on phonological tasks in comparison to orthographic tasks, and some of these effects may be modulated by relative task difficulty.

The effect of Balance Exercise Assist Robot (BEAR) to patient after allogenetic hematopoietic stem cell transplantation (allo-HSCT): Preliminary study

Previous studies have shown that patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT) frequently complicate balance dysfunction, with at least 50% experiencing one or more falls during hospitalization. We investigated the effect of Balance Exercise Assist Robot (BEAR) on patients after allo-HSCT, and the correlation between the effect of BEAR and the severity of balance dysfunction before intervention. Fifteen patients, who were allowed to leave the sterile room after allo-HSCT during hospitalization, participated. Mini-Balance Evaluation Systems Test (mini-BESTest), grip power, knee extension strength, 10-m walk test, Timed Up and Go test (TUG), dual-task TUG, functional reach test, Berg balance scale, sub-items of the mini-BESTest, and single-leg standing time were evaluated before and after intervention using BEAR. The participants performed 15 BEAR sessions, 20 minutes per session. The difficulty level of training task was automatically adjusted for each participants by BEAR. We divided into two groups based on pre-intervention Mini-BESTest scores: less than 70% (low group) and 70% or more (high group) and analyzed. Statistical analyses were performed to compare the groups; P < 0.05 indicated statistically significant differences. Informed consent was obtained from all participants before the intervention. There was no significant difference in pre- and post-intervention mini-BESTest in the low group (52.4 ± 15.9 vs. 70.8 ± 18.5) and high group (86.9 ± 12.0 vs. 88.5 ± 13.0). However, change between pre- and post-intervention scores in the low group was greater than the minimally important change of the mini-BESTest. Furthermore, significant improvement was observed between pre- and post-intervention scores for postural response (18.5 ± 22.7 vs. 51.9 ± 32.8), a mini-BESTest sub-item, in the low group. The other pre- and post-intervention outcomes were not significantly different in either group. BEAR was an effective and safe balance training, especially for postural response, in allo-HSCT patients with pre-intervention scores of less than 70% in the mini-BESTest.

Brain-computer interface for workload estimation: Assessment of mental efforts in learning processes

To assess the current mental state of an individual, several monitoring systems have been developed. In this paper, we explore the possibility to exploit information recorded noninvasively from the human cortex to develop a brain-computer interface (BCI) able to estimate brain workload and the mental efforts during a cognitive task. The EEG-based workload classifier presented in this paper combines a power spectral density (PSD) analysis and a statistical criterion. The proposed classifier is applied in the context of distance education and online course platform through two experimental protocols. The first one proposes solving a set of matrices products using pen and paper, while the second one proposes answering problems of logic mathematics on a computer-based learning environment. Experimental results show that the averaged accuracy of distinguishing changes in the theta [4–7 Hz] (θ) band is 79%. For the alpha band [8–11 Hz] (α) the averaged accuracy reached 78%. Based on this classifier, we demonstrate that θ and α powers in central, and posterior sites decrease with the increase in difficulty level of the cognitive task. The accuracy of correct decisions obtained from our results are significantly enhanced while comparing our investigation to some similar works from literature. In the realm of intelligent expert systems, our work results represent a first step to an implementation of an intelligent system for the evaluation of reeducative therapies to be used in physiotherapy centers for children with cognitive disorders as it is the case for Cerebral Palsy.

Alterations in the cortical control of standing posture during varying levels of postural threat and task difficulty.

Cortical excitability increases during the performance of more difficult postural tasks. However, it is possible that changes in postural threat associated with more difficult tasks may in themselves lead to alterations in the neural strategies underlying postural control. Therefore, the purpose of this study was to examine whether changes in postural threat are responsible for the alterations in corticospinal excitability and short-interval intracortical inhibition (SICI) that occur with increasing postural task difficulty. Fourteen adults completed three postural tasks (supported standing, free standing, or standing on an unstable board) at two surface heights (ground level or 3 m above ground). Single- and paired-pulse magnetic stimuli were applied to the motor cortex to compare soleus (SOL) and tibialis anterior (TA) test motor-evoked potentials (MEPs) and SICI between conditions. SOL and TA test MEPs increased from 0.35 ± 0.29 to 0.82 ± 0.41 mV (SOL) and from 0.64 ± 0.51 to 1.96 ± 1.45 mV (TA), respectively, whereas SICI decreased from 52.4 ± 17.2% to 39.6 ± 15.4% (SOL) and from 71.3 ± 17.7% to 50.3 ± 19.9% (TA) with increasing task difficulty. In contrast to the effects of task difficulty, only SOL test MEPs were smaller when participants stood at high (0.49 ± 0.29 mV) compared with low height (0.61 ± 0.40 mV). Because the presence of postural threat did not lead to any additional changes in the excitability of the motor corticospinal pathway and intracortical inhibition with increasing task difficulty, it seems unlikely that alterations in perceived threat are primarily responsible for the neurophysiological changes that are observed with increasing postural task difficulty. NEW & NOTEWORTHY We examined how task difficulty and postural threat influence the cortical control of posture. Results indicated that the motor corticospinal pathway and intracortical inhibition were modulated more by task difficulty than postural threat. Furthermore, because the presence of postural threat during the performance of various postural tasks did not lead to summative changes in motor-evoked potentials, alterations in perceived threat are not responsible for the neurophysiological changes that occur with increasing postural task difficulty.

Subjective Confidence Predicts Information Seeking in Decision Making

There is currently little direct evidence regarding the function of subjective confidence in decision making: The tight correlation between objective accuracy and subjective confidence makes it difficult to distinguish each variable’s unique contribution. Here, we created conditions in a perceptual decision task that were matched in accuracy but differed in subjective evaluation of accuracy by orthogonally varying the strength versus variability of evidence. Confidence was reduced with variable (vs. weak) evidence, even across conditions matched for difficulty. Building on this dissociation, we constructed a paradigm in which participants (N = 20) could choose to seek further information before making their decision. The data provided clear support for the hypothesis that subjective confidence predicts information seeking in decision making: Participants were more likely to sample additional information before giving a response in the condition with low confidence, despite matched accuracy. In a preregistered replication (N = 50), these findings were replicated with increased task difficulty levels.

Real-Time Assessment of the Cross-Task Mental Workload Using Physiological Measures During Anomaly Detection

The ability to detect anomalies in perceived stimuli is critical to a broad range of practical and applied activities involving human operators. In this paper, we propose a real-time physiological-based system to assess the cross-task mental workload during anomaly detection. Forty participants were recruited to detect anomalous images from a set of different distracting images (Task I) and abnormal activities from surveillance videos (Task II). In Task I, the task difficulty levels were manipulated by changing the number of anomalies/distracting stimuli (15, 21, 28, or 36) with and without time constraints (i.e., 4 × 2 = 8 task difficulty levels). Physiological and behavioral data from four task difficulty levels were divided into four categories according to subjective ratings of the mental workload. The support vector machine (SVM) classifiers were trained on these data to predict the mental workload categories of: 1) the same four task difficulty levels (within level); and 2) the other four task difficulty levels in Task I (cross level). Within-level classifications (with an average of 95.29%) were more accurate than cross-level classifications (average of 72.2%), which were much more accurate than random level classifications (25%). In Task II, the same participants monitored one, two, or four video clips simultaneously in accordance with three task difficulty levels. The same physiological signals were processed for real-time recognition of a participant's mental workload after he or she completed each activity detection task. The three-class SVM classifiers were trained on physiological data from Task I to predict the mental workload categories of the Task II (cross task), achieving an overall classification accuracy of 53.83%, compared to a 33.33% accuracy at random. These results are discussed in terms of their implications for developing situation-aware recognition systems of the mental workload and adaptive human-computer interaction platforms.