Mental workload: how can you prevent your brain from overheating?

Is it possible to read your e-mails while keeping your weekend plans in mind and listening to the other person on the phone? Welcome to the so-called multitasking that is part of our daily lives, thanks to telecommuting and the rapid expansion of digital technology at our disposal. We may feel like we're doing two things at once, but in reality our brains unconsciously shift their attention from one task to another very quickly. After more than 50 years of scientific research, the term " mental workload" has gained currency in recent years, both in everyday life and in various professional circles. But the concept still raises many questions, both as to its precise definition and as to how it can be studied and managed on a day-to-day basis.

Stéphane Perrey, University of Montpellier

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Mental load, also known as mental workload, would correspond to a quantity of mental work to be deployed in a given time, and potentially having consequences for the individual, such as accumulated fatigue or errors in task completion. Let's take the example of intensive practice of a manual skill, a difficult exam, driving on a busy freeway or searching through a cluttered visual display. These activities call on perceptual, cognitive and/or motor processes to produce flexible, adaptive behavior. Engaging, maintaining and controlling these processes requires different 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 struggling to emerge

Researchers are still struggling to come up with a universal definition that cuts across the disciplines concerned with mental workload, such as psychology, management and cognitive science. For some, mental load corresponds to the notion of an individual's limited capacity ("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 in hand. Among the many definitions proposed in the literature, mental workload can be defined as the amount of effort invested by the individual in carrying out a task, as a function of the resources available and the characteristics of the task.

In neuroscience, cognitive psychology and ergonomics (the scientific discipline concerned with the relationship between human beings and their work), the study of mental workload is particularly relevant to so-called "safety-critical" applications. These include automotive, aviation, air traffic control, space flight and defense. In situations where the cognitive cost exceeds available resources, the overload produced accentuates the risk of accidents, due to the individual's difficulty in detecting technical anomalies or warning signals. This is known as attentional deafness. This can be the case, for example, for an airplane pilot during a landing or in adverse weather conditions. More recently, studies on mental workload have also attracted research interest in the fields of media, human-computer interaction, medical training, sport and finance.

While laboratory studies have advanced our knowledge of brain functions during a given task, it is important to assess the individual's performance and mental load in the complex work environments encountered in everyday life. This is one of the leitmotifs of neuroergonomics, a discipline that dates back to the end of the 20th century, and aims to achieve a synthesis between the approaches and tools used by neuroscience and the field approach of ergonomics and engineering. Based on a multidisciplinary approach, neuroergonomics is defined as thestudy of the human brain in relation to performance at work and in everyday life. One example is the measurement of brain activity in surgeons, for whomincreased mental workload can lead to errors and adversely affect performance.

How to study mental workload? From behavioral responses to neurophysiological markers

Just as there are many possible definitions of mental workload, so there are many ways of measuring it. No single tool or method can give a complete picture of how an individual reacts to a task. Approaches that combine data from several sensors or measurements are therefore necessary, and can be more accurate and reliable for estimating mental workload in real time. This is all the more the case in changing environments (fluctuations in lighting, temperature...) or contexts requiring adaptation to the situation (discomfort, technical incidents...).

Self-assessment questionnaires of perceived mental workload can be used to collect the perception of individuals during task performance. For example, by incorporating a multidimensional assessment procedure, the NASA-TLX questionnaire provides a global score of mental load during or after task completion. It is based on a weighted average of the scores (from 0 to 100) of six subjective subscales. These scales are mental demand (level of mental activity), physical demand (level of physical activity), temporal demand (feeling of pressure to complete the task within a given timeframe), performance (level of achievement of task objectives), effort (amount of effort involved) and frustration (feeling of dissatisfaction during task completion).

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Analysis of performance on a single task can also help to estimate mental load. For example, more frequent errors or a decrease in information processing speed may indicate a higher mental load if task demands increase. In the case of a dual cognitive-motor task (phoning while driving, orienting while cycling or walking, etc.), the sharing of resources thus created can lead to a drop in performance compared with performing each of the two tasks separately.

In addition, neuroergonomics proposes the integration of objective measurements to assess mental workload, using a number of ambulatory techniques in environments that vary over time (workplaces, classrooms, operating theatres, traffic, etc.). For example, eye-tracking analysis can provide information on mental workload by measuring where an individual directs his or her attention. Physiological measures such as heart rate and variability, electrodermal activity and even portable brain imaging can provide specific neurophysiological indicators of mental workload.

In the brain, the prefrontal cortex is a privileged witness of mental load

Mental workload manifests itself particularly in the prefrontal cortex, the area of the brain that has undergone the greatest development in human beings over the last few million years. This part of our brain is heavily involved in cognitive control, a mechanism for adapting and supervising the decision-making process. Cognitive control is involved in conflict resolution, error detection and inhibition, and aims to guarantee a sufficient level of performance in relation to task demands and unforeseen events, while maintaining an acceptable cognitive cost. Measuring activation of the prefrontal cortex, by observing the extent to which it consumes energy, i.e. glucose and oxygen, can provide information on the quantity of resources mobilized to meet task demands. 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 when demanding physical effort is performed in complex environments, such as a bicycle race in dense traffic, where each individual may decide to engage differently in the exercise after weighing up costs and benefits. In this dual-task situation, both physical and cognitive, the decision to choose speed is cognitively controlled, probably guided by a strategic decision to maximize benefits over costs.

Managing mental workload

In demanding contexts, whether professional or educational, or in other situations such as driving, the mental load can vary over time to the point of overload under the influence of various external and internal factors. How can we cope with the multitude of factors to which we must pay attention?

There are a number of recommendations that can be implemented on an individual level. On the one hand, it is often useful to draw up an overview of all the tasks to be carried out in order to prioritize them. This makes it possible to build up a sequence of tasks to be completed one after the other, and to abandon non-essential tasks in order to better value the work done. Each task should correspond to specific short-term objectives (twenty minutes or so). It's also important to adapt breaks to the task in hand, to effectively regulate mental workload and reduce distracting interruptions. Finally, always allow yourself adequate recovery time (reading, sport, etc.).

Applying the principles of neuroergonomics can provide customized and effective solutions for managing mental workload. Research into mental workload remains extremely relevant, particularly in terms of taking account of individual variability in the way people process information and interact with their environment. In this respect, the use of artificial intelligence methods to extract congruent information from several combined measures represents an interesting avenue for continuously assessing the mental load of an individual engaged in a task.

Stéphane Perrey, University Professor in Exercise Physiology / Integrative Neuroscience, Director of the Research EuroMov Digital Health in Motion Unit, University of Montpellier

This article is republished from The Conversation under a Creative Commons license. Read theoriginal article.