Ever find yourself exhausted despite not physically working hard?
Whether it is thinking about what to eat, what to wear or remembering to put your phone on charge — from the moment we wake up modern day life is filled with decisions.
Although these simple choices may not feel like strenuous tasks, studies suggest they could be overloading our brains and making us tired all the time.
In fact, by the end of a day filled with seemingly minor cognitive tasks we may find it even harder to make rational decisions, and experts say a build up of a specific brain chemical could be to blame.
Here, MailOnline reveals why decision fatigue really is making us all exhausted.
Although simple choices may not feel like a hard task they could be overloading our brains and making us tired all the time
Researchers have found that after you have made one decision this chemical glutamate just sticks around, builds up and clogs your brain
When we make a decision the brain sends an electric signal between regions of the brain along wire-like structures called neurons.
But in order to send these messages it needs a brain chemical called glutamate, a neurotransmitter.
Researchers have found that after making a decision this chemical glutamate sticks around, building up and essentially clogging the brain, with the effect getting increasingly worse after more and more decisions.
The discovery, from experts at the Paris Brain Institute in France, came after they measured the levels of these brain chemicals in the organ and the affect they had on the performance of challenging tasks.
They focused on a part of the brain called the lateral prefrontal cortex — a part of the brain which tackles difficult tasks and makes decisions.
The 2022 study saw 40 people do memory tasks for six hours while lying in an MRI scanner.
One task included watching sequences of numbers appear on a screen and judging if the current number was the same as the previous one. An easier task was given to 14 people, while a harder one was given to 26.
Glutamate along with eight different brain chemicals were measured at several points during the cognitive exercises.
But curiously at the end of the challenges both groups had the same levels of glutamate in their lateral prefrontal cortex compared to the start of the experiment.
This suggests it’s the quantity of tasks that causes this mental build-up not their difficulty.
Researchers found those taking part in the harder tasks had higher levels of glutamate in their lateral prefrontal cortex compared with the start of the experiment
But researchers noted people doing the harder tasks showed other signs of tiredness, such as dilation of the pupils in their eyes, which wasn’t the case for the group doing the easier task.
The study also looked at how this mental fatigue affects how well people make decisions.
Between the memory tasks researchers gave participants other exercises, such as one where people chose between getting a smaller sum of money straight away or a larger one later.
When people doing the harder memory tasks got more tired, they started accepting a small reward that they would get immediately, but this was not always the case with the other group.
This suggested they were choosing the option that required the least amount of decision making.
Experts at the Paris Brain Institute in France noted that sleep could help rebalance glutamate levels in the brain, but stressed more research is needed.
Other studies have also highlighted that decision fatigue really does impact our ability to think straight.
Experts at the Paris Brain Institute in France noted in the study that sleep could help rebalance glutamate levels in the brain, but stress more research is needed
One 2016 study, published in Chronobiology International revealed people make more rational decisions earlier in the day.
Participants were asked to play a game where they had to accept or reject different economic offers proposed by a virtual participant. They completed this game at both 9am and 5pm.
Researchers observed more cautious decision-making in the morning, while in the evening participants spent less time responding to high-uncertainty offers.
Another 2021 study, published in the Journal of Retailing and Consumer Services surveyed more than 1,000 participants about impulse buying and also found people were more likely to make impulse decisions later in the day.
These both suggest that we make poor decisions later on in the day once our brain is tired.
But there are suggestions that a short rest can help recharge the brain.
According to a 2021 study published in the National Bureau of Economic Research, which looked at decisions made by Major League Baseball umpires, found they had a depletable ‘budget’ of attention.
But after short breaks during a game they were able to replenish these attention budgets.
Study authors said this could be repeated in other work settings and suggested having short breaks during the working day could help people in ‘cognitively-demanding jobs’.
