DECISIONZZZZZ, DECISIONZZZZZ A wide array of factors can affect the way we make decisions, including time constraints, our mood, the presence of genuine risks or prospect of high losses, or as anyone whos ever encountered a 30-page menu will know simply our capacity to assimilate the information in front of us. Unsurprisingly, when we are tired, it is not just the time it takes us to make certain decisions, but also the quality or accuracy of our decision-making that is compromised compared with when we are well rested. Beyond these basic findings, however, what do we know about how sleep loss affects our everyday decision-making? At the brain level By Claire Coombes, BALPA Human Factors Scientist To begin with, why does sleep deprivation affect our decision-making? It is important to understand that different brain regions support or are integral to different types of cognition, and studies have suggested that some regions are much more affected than others by sleep deprivation. Two such areas are the thalamus and prefrontal cortex, which extend from the middle to the front of the brain. The thalamus is especially important for keeping us alert, and reduced activity in this region after sleep deprivation is linked with degraded alertness and attention. The prefrontal cortex, meanwhile, supports a range of higherorder cognitive processes, such as the ability to maintain and revise plans, control mood, and avoid irrelevant distractions by keeping us focused on the tasks or goals in mind. When we are sleep deprived, there is a greater reduction of activity in the prefrontal cortex, so decisions that rely on the processes normally supported by these areas become increasingly compromised. What is the impact? Its better news for decisions involving well-practised skills or crystallised knowledge. These processes do not appear to rely heavily on the prefrontal cortex, and research suggests that even when were acutely tired we can still show relatively preserved performance on rules-based, critical reasoning and logical, well-practised tasks that are sufficiently interesting or important to engage our brains and dont require long periods of sustained attention. In the operational world, this is probably why routinely practised skills and normal decisions based on standard operating procedures or in familiar scenarios are relatively protected from our fatigue levels, particularly where time is not a constraint. By contrast, decisions that rely heavily on the prefrontal cortex appear to be particularly degraded by sleep loss. These latter divergent thinking skills are considered to be integral to dealing with complex, novel or unpredictable scenarios. Gaps and ongoing questions Most of our understanding of how sleep loss affects decision-making comes from laboratory studies and not the operational world. So it is reasonable to question whether decision-making under controlled circumstances, using unimportant tasks, can ever really reflect the real world, where the consequences of decisions may be life-threatening. The truth is that there are a number of methodological challenges involved with creating experiments on sleep loss and decision-making, which can limit how much we can extrapolate about how people think and behave in real-world contexts. Not much is known about chronic sleep deprivation the type of sleep loss most shift-work schedules bring about and how this affects decision-making, and over what timescales. We also dont have clear answers on what role individual differences or age play in how badly our decisions are affected by our fatigue levels. Brain-imaging studies do seem to have identified the prefrontal cortical areas as being particularly affected by sleep loss, however which, in turn, seems to explain why we see deficits in tasks that rely on thought processes normally supported by those regions. These divergent thought processes appear critical for allowing the brain to cope with decision-making in non-normal or changing scenarios and to act effectively on feedback. As such, the integrity of these functions must be preserved from the effects of fatigue, if we are to make good decisions in a crisis or unfamiliar situation. DIVERGENT THINKING SKILLS AFFECTED BY SLEEP DEPRIVATION be especially degraded by sleep loss. Research has shown that, as participants become progressively more sleep deprived, their ability to produce innovative ideas diminishes and they are more reliant on previous decisions or strategies, regardless of whether they are appropriate. n Information processing ability and avoiding distractions When we are sleep deprived, more time is needed to understand data or integrate information in real time. Our ability to focus our attention is compromised and we can no longer effectively prevent irrelevant visual or auditory distractions from catching our attention. This means that the basic assimilation of incoming information is challenging, and matters are made worse if this information is rapidly changing in a short space of time. The overall effect is that sleep loss makes decisions difficult because we are less able to build a real-time accurate mental picture of what is going on. n Ability to track events, process feedback and shift strategies Sleep loss also degrades our ability to monitor events and update our plans when necessary. For example, various studies have highlighted how sleep-deprived participants begin to lose track of the important tasks or skip over tasks that would have previously required their attention or decisive action. What this means for decision-making is that we become less able to consider or pursue alternative approaches that may be more successful given the latest information. n Ability to think laterally or generate new ideas Exhibiting flexible or original thinking is a further area of thought processing, important to decision-making in unfamiliar or changing situations, that appears to n Risk propensity and ability to appreciate negative consequences Some scientists have suggested that sleepiness alters our ability to appraise risks appropriately or consider the consequences of our actions. The evidence for this is indirect, but compelling. During decisionmaking in the laboratory, sleep deprivation appears to degrade participants ability to weigh up short-term benefits against longer-term penalties and reduce their concern, with negative consequences when the task is framed with high rewards. For more realistic tasks, sleep-deprived drivers have also been found to engage in more risky decisions that do not seem to be accounted for by just bad driving skills, such as increased hazardous overtaking manoeuvres (on lanes that have poor visibility or would require other drivers to move out the way) compared with when well rested. Other research has suggested that our ability to evaluate possible negative consequences from our actions is supported by a key region in the prefrontal cortex. As such, our ability to evaluate risk properly, in terms of appreciating the costs of bad outcomes, is likely to be degraded when we are tired. n Ability to control mood, show insight on our performance and communicate effectively Often, one of the most underappreciated aspects of how sleep-driven fatigue can affect decision-making is just how badly our mood can be affected. The ability to monitor and control our mood effectively appears to depend on the intact functioning of the prefrontal cortex and, hence, theres a real neural basis for why we feel and act very differently. At the individual level, sleep loss compromises our basic interest and motivation to maintain good performance, particularly during continuous, monotonous tasks. From a safety perspective, this growing disinterest coupled with the fact that fatigued individuals may not be aware of their declines in performance presents a real issue, as effective decision-making relies on realistic insight of the situation and a clear idea of whether corrective actions need to be taken. Increasing levels of fatigue have also been linked to feelings of irritability and resignation, longer delays in responses, and a degradation in communication, such as an unwillingness to volunteer information. TECH LOG Sleep loss can affect our everyday decision-making, but surprisingly little is known about why