ReviewMental fatigue: Costs and benefits
Introduction
Mental fatigue refers to the feeling that people may experience after or during prolonged periods of cognitive activity. These feelings are very common in everyday modern life and generally involve tiredness or even exhaustion, an aversion to continue with the present activity, and a decrease in the level of commitment to the task at hand (Holding, 1983, Hockey, 1997, Meijman, 2000). In addition, mental fatigue has been associated with impaired cognitive and behavioural performance (e.g. Boksem et al., 2005, Lorist et al., 2005, Van der Linden and Eling, 2006).
Over the past decades, work has changed to a large extent from demanding physical effort, to demanding mental effort. This has resulted in a substantial increase in complaints related to mental fatigue: in the Netherlands, half of the women in the working population complain about being fatigued, while a third of the men report such complaints. Fifteen years ago, only 38% of the women and 24% of the men reported such complaints. A recent survey of the U.S. workforce (Ricci et al., 2007) showed that 38% of workers reported being fatigued. Of these fatigued workers, 66% reported lost productivity time, compared to 26% of workers without fatigue. Ricci and colleagues estimated that lost productivity time from fatigued workers costs employers an excess of a hundred billion dollars annually, compared to non-fatigued workers. On a more personal level, complaints of fatigue can have a profound and negative impact on people's social and occupational life. Moreover, mental fatigue is a common symptom in a large number of chronic medical conditions such as cancer, Human Immunodeficiency Virus, Multiple Sclerosis, Chronic Fatigue Syndrome, Alzheimer's disease, Huntington's disease and Parkinson's disease (see Chaudhuri and Behan, 2000). It is important to realize however, that fatigue as a symptom of disease may involve different biological substrates compared to acute mental fatigue in otherwise healthy people.
Mental fatigue has been shown to result in various deteri,orations in cognitive functioning. Van der Linden et al., 2003a, Van der Linden et al., 2003b, Van der Linden and Eling, 2006 showed that fatigued subjects had difficulties in focusing their attention, planning, and adaptively changing strategies in the face of negative outcomes. Our own work showed that fatigued subjects had difficulties in adequately preparing their responses (Boksem et al., 2006) and had difficulties in sustaining attention and ignoring irrelevant information (i.e. they suffered from increased distractibility; Boksem et al., 2005). In addition, fatigued subjects corrected their mistakes less often and post error performance adjustment was impaired (Lorist et al., 2005, Boksem et al., 2006).
Common sense would dictate that mental fatigue is the direct result of working for a prolonged period of time: the longer one works on a demanding task, the more fatigue one will experience. This, however, has been shown not to be the case. Fatigue may be experienced after working for a relatively short period of time, while working long hours does not always lead to fatigue (Sparks et al., 1997, Park et al., 2001). Indeed, working long hours has been shown not to lead to fatigue at all when the rewards of working (in terms of payment, but also appreciation by peers and co-workers) are perceived as high (Siegrist, 1996, Van der Hulst and Geurts, 2001).
In other words, high workload only results in fatigue when rewards associated with work are low. Here, we will propose a framework for mental fatigue that involves an integrated evaluation of both expected rewards and energetical costs associated with continued performance, resulting in a reduction in motivation and the effort invested in continued performance.
Two complimentary and interacting motivational systems are proposed to result in producing goal directed behaviour: the motivation to obtain rewards and the motivation to avoid harm and punishment. While both rewards and punishments can motivate to engage in activities, both types of motivated behaviour are associated with energetical costs. In the present review, we will propose that the feeling of fatigue may result from the subconscious analyses of cost and benefits to expend energy, or to conserve energy. People will only expend energy on a certain task when (energetical) costs are comparably low and benefits (high reward, low punishment) are comparably high. However, when tasks have to be performed for prolonged periods of time, the amount of energy invested in performance will build up until it eventually outweighs potential rewards, resulting in a decrease in the motivation to work for rewards that fail to be procured. Thus, we propose that the feeling of fatigue corresponds to a drive to abandon behaviour when energetical costs exceed perceived benefits of continued performance.
The purpose of this review is to provide a coherent framework for mental fatigue. Because of this, we inevitably focus more on some aspects of this complex phenomenon that on others. This is especially true for the motivational systems and neural substrates we propose are primarily involved. While we focus on the role the ‘reward system’ of the brain and on the role of the dopamine (DA) neurotransmitter in motivated behaviour, it is certain that other neural structures, neurotransmitters and hormones are also involved. However, by narrowing our focus on these particular aspects of mental fatigue, we are able to present our views on what is a central aspect of this important and complex psychophysiological phenomenon.
Section snippets
Goals
So, what is mental fatigue? This question has proved to be very difficult to answer. Despite its mundane nature, mental fatigue appears to be a highly complex phenomenon that involves changes in mood, information processing and behaviour (Desmond and Hancock, 2001), making it a difficult subject to study. Perhaps asking ourselves the opposite question could clarify matters: what makes us tick? What makes us get out of bed every morning and go to work, to school, or do whatever else is planned
Rewards and punishments
There are at least three psychological components of reward (Berridge and Robinson, 2003, Schultz, 2004). First, the consumption of rewards involves feelings of pleasure (‘liking’). Second, these pleasurable feelings are highly motivating to obtain this reward more often (‘wanting’). Third, in order to do so, one has to learn about the relationships among stimuli and the consequences of actions that led to the procurement of the reward (‘learning’). The obvious benefit of such a reward system
To act or not to act
Despite the importance of the evaluation of potential reward for successful goal directed behaviour, reward seeking activities would only seem to be a part of what constitutes adaptive goal directed behaviour. Rewards always come at a price. To keep with our example: to catch an antelope, the cheetah will have to leave the safety and comfort of its shelter and venture into the open savannah, spending valuable energy. So, to select the best course of action, an organism has to take into account
Mental fatigue: The costs of acting
The fact that our brain can process information on both the potential benefits and the potential costs involved in working in order to reach goals enables it not only to determine whether an expected outcome of behaviour is desirable, it can also determine whether a particular action is actually worth performing (Rushworth et al., 2004). For any action to be worth performing, the desirability of the expected outcome should outweigh the potential energetical costs.
We propose that the feeling of
Mental fatigue and control
As already mentioned in the introduction, there will be a reduced probability that the selection of actions will be controlled by high-level regulatory control processes (Lorist et al., 2000, Meijman, 2000), when people become fatigued. Van der Linden et al., 2003a, Van der Linden et al., 2003b, Van der Linden and Eling, 2006 showed that fatigued subjects had difficulties in focusing their attention, planning, and adaptively changing strategies in the face of negative outcomes. In addition, our
Why fatigue?
Although this seems to suggest that fatigue is only detrimental to performance and goal-directed behaviour, we argue that this is not the case. Instead, we propose that fatigue can best be considered as an adaptive signal that the present behavioural strategy may no longer be the most appropriate, because it continues to demand effort while substantial effort has already been invested and the goal evidently has not yet been achieved. Fatigue may provide the cognitive system with a signal that
Beyond control
Choosing courses of action based on an analysis of costs and benefits is highly adaptive and efficient, but only when one is free to choose between various action alternatives (i.e. the situation is controllable). In everyday life, especially in the work environment, this control over the situation is often lacking. High workload, high demands on cognitive functions, and fixed production quotas limit the possibilities of employees to choose lower effort alternatives when they perceive effort to
Individual differences
Are some more at risk for becoming fatigued than others? Several studies have noted that people with personality characteristics that increase chances of overriding the signal of fatigue are at risk. These personality characteristics include high perfectionism (Magnusson et al., 1996, White and Schweitzer, 2000), high neuroticism (Johnson et al., 1996, Prins et al., 2006) and low extraversion (Prins et al., 2006, Watson et al., 1999). All these personality characteristics relate to the way
Summary
Our environment typically supports multiple goals, associated with different magnitudes of reward. The OFC, BLA and insula have been shown to be primarily involved in coding the expected appetitive and aversive value that each option may provide. This reward-related information may be relayed to the ACC, where these sources of reward information may be integrated to bias behaviour in a particular direction that is predicted to result in the largest reward value.
In addition to information on
Acknowledgments
This work was supported by the Netherlands Organisation for Scientific Research (NWO), as part of the Netherlands concerted research action “Fatigue at Work”.
References (171)
- et al.
Parsing reward
Trends Neurosci.
(2003) - et al.
Effects of mental fatigue on attention: an ERP study
Cogn. Brain Res.
(2005) - et al.
Mental fatigue, motivation and action monitoring
Biol. Psychol.
(2006) - et al.
Parallels between post-polio fatigue and chronic fatigue syndrome: a common pathophysiology?
Am. J. Med.
(1998) - et al.
Effects of excitotoxic lesions of the basolateral amygdala on conditional discrimination learning with primary and conditioned reinforcement
Behav. Brain Res.
(1999) - et al.
Cognitive and emotional influences in anterior cingulate cortex
Trends Cogn. Sci.
(2000) - et al.
Emotion and motivation: the role of the amygdala, ventral striatum, and prefrontal cortex
Neurosci. Biobehav. Rev.
(2002) - et al.
Fatigue and basal ganglia
J. Neurol. Sci.
(2000) - et al.
Fatigue in neurological disorders
Lancet
(2004) - et al.
Efferent projections of infralimbic and prelimbic areas of the medial prefrontal cortex in the Japanese monkey, Macaca fuscata
Brain Res.
(2001)
Functional connectivity with anterior cingulate and orbitofrontal cortices during decision-making
Cogn. Brain Res.
Nucleus accumbens dopamine depletions in rats affect relative response allocation in a novel cost/benefit procedure
Pharmacol. Biochem. Behav.
Glucocorticoids, chronic stress, and obesity
Prog. Brain Res.
Reward, motivation, and reinforcement learning
Neuron
Awareness of muscular force during movement production: an fMRI study
NeuroImage
Job strain, effort-reward imbalance and employee wellbeing: a large-scale cross-sectional study
Soc. Sci. Med.
Intelligence and the frontal lobe: the organization of goal-directed behavior
Cogn. Psychol.
Interactions between the amygdala and ventral striatum in stimulus reward associations — studies using a 2nd-order schedule of sexual reinforcement
Neuroscience
A new view on hypocortisolism
Psychoneuroendocrinology
Effects of intra-accumbens infusions of amphetamine or cis-flupenthixol on sustained attention performance in rats
Behav. Brain Res.
Alcohol and error processing
Trends Neurosci.
Mesolimbocortical and nigrostriatal dopamine responses to salient non-reward events
Neuroscience
Personality dimensions in the chronic fatigue syndrome: a comparison with multiple sclerosis and depression
J. Psychiatr. Res.
Neural predictors of purchases
Neuron
Distinct neural mechanisms of risk and ambiguity: a meta-analysis of decision-making
NeuroImage
The functional neuroanatomy of the human orbitofrontal cortex: evidence from neuroimaging and neuropsychology
Prog. Neurobiol.
The neural basis of financial risk taking
Neuron
Caffeine, fatigue, and cognition
Brain Cogn.
Impaired cognitive control and reduced cingulate activity during mental fatigue
Cogn. Brain Res.
Is perfectionism associated with fatigue?
J. Psychosom. Res.
Cortical pathways to the mammalian amygdala
Prog. Neurobiol.
The concept of allostasis in biology and biomedicine
Horm. Behav.
In search of personality and temperament predictors of chronic fatigue: a prospective study
Pers. Individ. Differ.
Intra-accumbens infusions of antisense oligodeoxynucleotides to one isoform of glutamic acid decarboxylase mRNA, GAD(65), but not to GAD(67), mRNA, impairs sustained attention performance in the rat
Cogn. Brain Res.
Functional neuroanatomy of aversion and its anticipation
NeuroImage
Comparison of neuronal activity in the rostral supplementary and cingulate motor areas during a task with cognitive and motor demands
Eur. J. Neurosci.
Insular cortical ischemia is independently associated with acute stress hyperglycemia
Stroke
Control of response selection by reinforcer value requires interaction of amygdala and orbital prefrontal cortex
J. Neurosci.
Working overtime hours: relations with fatigue, work motivation, and the quality of work
J. Occup. Environ. Med.
Burnout and related factors among HIV AIDS health care workers
Aids Care-Psychological and Socio-Medical Aspects of Aids/Hiv
Topographical organization and relationship with ventral striatal compartments of prefrontal corticostriatal projections in the rat
J. Comp. Neurol.
The debate over dopamine's role in reward: the case for incentive salience
Psychopharmacology
Dorsal anterior cingulate cortex: a role in reward-based decision making
Proc. Natl. Acad. Sci. U. S. A.
Effects of selective excitotoxic lesions of the nucleus accumbens core, anterior cingulate cortex, and central nucleus of the amygdala on autoshaping performance in rats
Behav. Neurosci.
Sensory and premotor connections of the orbital and medial prefrontal cortex of macaque monkeys
J. Comp. Neurol.
Prefrontal cortical–ventral striatal interactions involved in affective modulation of attentional performance: implications for corticostriatal circuit function
J. Neurosci.
Double dissociation of basolateral and central amygdala lesions on the general and outcome-specific forms of pavlovian-instrumental transfer
J. Neurosci.
Regret and its avoidance: a neuroimaging study of choice behavior
Nat. Neurosci.
Involvement of the medial prefrontal cortex–basolateral amygdala pathway in fear related behaviour in rats
Eur. J. Neurosci.
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