Accumulation of ‘toxins’ in brain is why thinking hard is tiring, study suggests

New research suggests that fatigue is a mechanism to preserve the integrity of our brain functioning, Andy Gregory reports

Accumulation of ‘toxins’ in the brain is why thinking hard is tiring, study suggests (Getty/iStock)

Scientists have unearthed new evidence to explain why long periods of thinking intensely can feel as exhausting as physical labour.

According to their theory, this fatigue is caused by an accumulation of potentially toxic substances in the brain.

This build-up – of a chemical called glutamate – in turn alters our control over decision-making, so that we shift toward actions that require no effort or waiting as cognitive fatigue sets in.