Sloth might be one of the seven deadly sins, but lazing about could be a sign of intelligence.
A new study has found a correlation between thinking hard and avoiding physical activity.
Psychology researchers at Florida Gulf Coast University quizzed students on how much they agreed with statements like, "I only think as hard as I have to." Their physical activity was then tracked for a week.
They found students who spent a lot of time thinking were "far less active" during the week than non-thinkers.
But the difference between thinkers and non-thinkers, as they were defined in the study, disappeared at the weekend.
The researchers suspect it's because non-thinkers get bored more easily - as discovered in earlier research - and fill the time with physical activity. Because all the participants in the study were students, it's unlikely to be the result of having to do more physically demanding jobs during the week.
As for the weekend, lead researcher Todd McElroy said more intelligent people would be more aware of the need to get exercise, so could be making up the shortfall where they can.
"Awareness of their tendency to be less active, coupled with an awareness of the cost associated with inactivity, more thoughtful people may then choose to become more active throughout the day."
The research was published overnight in the Journal of Health Psychology.