That was the opposite of what researchers expected. They had assumed that lazy people’s pre-motor cortices would show less activity when deciding to take action.

“We thought that this might be because their brain structure is less efficient, so it’s more of an effort for apathetic people to turn decisions into actions,” said lead researcher Masud Husain, a professor of neurology and cognitive neuroscience at Oxford University, in a statement. After further investigation, it turned out that people who identified as apathetic had less efficient connections between the anterior cingulate cortex, a part of the brain involved in making decisions and anticipating rewards, and the supplementary motor area, a part of the brain that helps control movement.

“The brain uses around a fifth of the energy you’re burning each day. If it takes more energy to plan an action, it becomes more costly for apathetic people to make actions,” explained Husain. “Their brains have to make more effort.” Husain and his team published their findings in the journal Cerebral Cortex.