A new study says there is a powerful effect to believing that you had a restful and full nights sleep, even if you didn't.
The National Institutes of Health studied 164 people and regardless of how the quality of their sleep actually was the night before, one group was randomly told they had above average sleep, the other group told they had below average sleep the night before.
The results showed that the group that thought they were better rested scored higher on simple addition tests. The group that thought they had a rough night sleep scored worse.
Researchers conclude that there is a powerful placebo effect at play here. When you think you are better rested you will perform as if you really are and that mindset sets you up better to tackle the day.