Mental Load: How Can You Prevent Your Brain From Overheating?
Is it possible to read your emails while keeping your weekend plans in mind and listening to the person on the phone? Welcome to so-called multitasking, which has become a staple of our daily lives thanks to remote work and the rise of digital technology. We may feel like we’re doing two things at once, but in reality, our brain unconsciously shifts its attention very quickly from one task to another. After more than 50 years of scientific research, the term “mental load” has become increasingly common in everyday life and across various professional settings in recent years. But this concept still raises many questions, both regarding its precise definition and how to study or manage it in daily life.
Stéphane Perrey, University of Montpellier
Mental load, also known as mental workload, refers to the amount of mental effort required within a given time frame, which can potentially have consequences for the individual, such as accumulated fatigue or errors in task performance. Consider, for example, the intensive practice of a manual skill, a difficult exam, driving on a busy highway, or searching through a cluttered visual display. These activities draw on perceptual, cognitive, and/or motor processes to produce flexible and adaptive behavior. Engaging, sustaining, and controlling these processes require varying levels of mental effort depending on the circumstances (routine activities versus sudden events). Sometimes, this massive mental effort leads to what scientists call “cognitive overload” or “mental overload.”
A universal definition that is slow to emerge
Researchers are still struggling to propose a universal definition that spans the disciplines concerned with mental load, such as psychology, management, and cognitive science. For some, mental load corresponds to the concept of an individual’s limited capacity (a “reservoir” of attentional resources) to process information. For others, it refers to the management of attentional resources and focuses on the demands of the task at hand. Among the many definitions proposed in the literature, it emerges that mental load can be defined as the amount of effort an individual invests in performing a task, based on their available resources and the characteristics of the task.
In neuroscience, cognitive psychology, and ergonomics (the scientific discipline that studies the relationship between humans and their work), research on mental workload focuses in particular on so-called “safety-critical” applications. These include fields such as the automotive industry, aviation, air traffic control, spaceflight, and defense. In situations where the cognitive cost exceeds available resources, the resulting overload increases the risk of accidents, due to the individual’s difficulty in detecting technical anomalies or warning signals. This is referred to as attentional deafness. This can be the case, for example, for an airplane pilot during a landing or in poor weather conditions. More recently, studies on mental workload have also sparked research interest in the fields of media, human-machine interaction, medical training, sports, and finance.
While laboratory studies have advanced our understanding of brain function during specific tasks, it is important to assess an individual’s performance and cognitive load in the complex work environments encountered in everyday life. This is one of the central themes of neuroergonomics, a discipline dating back to the late20thcentury, which aims to synthesize the approaches and tools used by neuroscience with the practical, field-based methods of ergonomics and engineering. Based on a multidisciplinary approach, neuroergonomics is defined asthe study of the human brain in relation to performance at work and in daily life. One example is the measurement of brain activity in surgeons, for whomincreased mental workload can lead to errors and negatively affect performance.
How Can We Study Mental Load? From Behavioral Responses to Neurophysiological Markers
Just as there are many possible definitions of mental workload, there are many ways to measure it. No single tool or method can provide a complete picture of how an individual responds to a task. Approaches that combine data from multiple sensors or measurements are therefore necessary and can provide more accurate and reliable real-time estimates of mental workload. This is especially true in changing environments (fluctuations in lighting, temperature, etc.) or situations requiring adaptation to the circumstances (illness, technical incidents, etc.).
Self-report questionnaires on perceived mental workload are used to gather individuals’ perceptions while they are performing a task. For example, by incorporating a multidimensional assessment procedure, the NASA-TLX questionnaire provides an overall mental workload score during or after task completion. It is based on a weighted average of the scores (from 0 to 100) on six subjective subscales. These scales are mental demand (level of mental activity), physical demand (level of physical activity), time pressure (sense of pressure to complete the task within a given time frame), performance (level of task goal achievement), effort (amount of effort expended), and frustration (sense of dissatisfaction during task performance).
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Analyzing performance while performing a single task can also help estimate mental workload. For example, more frequent errors or a decrease in information processing speed may indicate a higher mental workload as task demands increase. In the case of a dual cognitive-motor task (talking on the phone while driving, navigating while cycling or walking, etc.), the resulting division of attention can lead to a decline in performance compared to performing each task separately.
In addition, neuroergonomics proposes incorporating objective measures to assess mental workload using various ambulatory techniques in environments that vary over time (workplaces, classrooms, operating rooms, traffic, etc.). For example, eye-tracking analysis can provide insights into mental workload by measuring where an individual directs their attention. Physiological measures, such as heart rate and heart rate variability, electrodermal activity, and even portable brain imaging, can provide specific neurophysiological indicators of mental workload.
In the brain, the prefrontal cortex is a key indicator of mental workload
Mental load is particularly evident in the prefrontal cortex, the area of the brain that has undergone the most significant development in humans over the past few million years. This part of our brain plays a major role in cognitive control, a mechanism for adapting to and overseeing the decision-making process. Cognitive control plays a key role in conflict resolution, error detection, and inhibition, and aims to ensure a sufficient level of performance relative to task demands and unforeseen events, while maintaining an acceptable cognitive cost. Measuring the activation of the prefrontal cortex by observing how much energy—specifically glucose and oxygen—it consumes can provide insight into the amount of resources mobilized to meet the demands of the task. Indeed, difficult tasks or those requiring sustained attention lead to more pronounced activation of the prefrontal cortex and associated brain networks.
This is also the case during strenuous physical activity in complex environments, such as cycling in heavy traffic, where each person may decide to engage differently in the activity after weighing the costs and benefits. In this situation involving both physical and cognitive tasks, the decision regarding speed is cognitively controlled, likely guided by a strategic decision aimed at maximizing benefits relative to costs.
Managing Mental Load
In demanding professional or educational settings, or in other situations such as driving, mental load can fluctuate over time until it reaches a breaking point due to various external and internal factors. How can we cope with the multitude of factors we need to pay attention to?
There are several practical tips that individuals can follow. For one thing, it is often helpful to make a list of all the tasks that need to be done in order to prioritize them. This allows you to create a sequence of tasks to be completed one after another and to set aside non-essential tasks in order to better focus on the work at hand. Each task should align with specific short-term goals (about twenty minutes). It is also important to tailor breaks to the task at hand to effectively manage mental load and reduce distracting interruptions. Finally, it is essential to always allow for adequate recovery time (reading, exercise, etc.).
Applying the principles of neuroergonomics can provide personalized and effective solutions for managing cognitive load. Research on mental workload remains highly relevant, particularly for accounting for individual variability in how people process information and interact with their environment. In this regard, the use of artificial intelligence methods to extract relevant information from multiple combined measurements represents a promising approach for continuously assessing the mental workload of an individual engaged in a task.
Stéphane Perrey, Professor of Exercise Physiology / Integrative Neuroscience, Director of the Research Digital Health in Motion Research Unit, University of Montpellier
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