If you want to feel more rested, the key might be exercising mind over matter.

A new study suggests that there is a placebo effect when it comes to perceptions of sleep quality and performance. In other words, if you believe you're exhausted, you're more likely to do shoddy work.

Researchers from Colorado College found that students who were told they had experienced above average deep sleep the night before performed better on tests that measured their attention and memory.

Two studies involved 164 participants who, unbeknownst to them, were assigned to an "above average" sleep quality group, a "below average" sleep quality group, or a control group. Students were connected to a machine they were told would measure their amount of rapid eye movement (REM) stage sleep. 

The next morning they were made to believe that they had either experienced a great night's sleep or a terrible one, based on the data researchers showed them. They also received a five-minute lesson on sleep quality and its impact on cognitive function.

Participants who were told that they experienced a longer-than-average REM sleep performed significantly better on the Paced Auditory Serial Addition Test -- which measures sustained attention and processing speed -- than those who were told they had experienced very little REM sleep.