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.

Zapping the brain could help people who struggle with maths get better at arithmetic. Researchers gave 102 people a set of tricky arithmetic problems, which each involved multiplying a double-digit number by a single-digit number, like 16 x 3 48. Half of the people in the study had their brain zapped with a mild electric current to stimulate their brain cells. People given the brain stimulation, and also tested under more difficult learning conditions, answered the questions in about half the time, compared to people whose brains were not zapped, researchers claim. They reportedly got the answers 52 per cent quicker.

After years of wrestling with the complexities of algebra, fractions and mental arithmetic, some teenagers may be only too keen to dump maths at the earliest opportunity. But a new study suggests that quitting the subject at the age of 16 may have an adverse effect on brain development. Researchers led by the University of Oxford found that adolescents who stuck with maths in their A-levels had higher levels of a brain chemical important for memory, learning and problem-solving. They recruited 87 A-level students to take part in the study and, after scanning their brains, discovered that those who had continued with maths had higher levels of gamma-Aminobutyric acid (GABA) in an area called the prefrontal cortex. The study also found that the students with more GABA were better at solving brain-teasing questions when tested around 19 months later.