Nighttime thoughts see light of day: people interpret dreams in ways that affect their waking lives.

Dreams don't just bubble up at night and then evaporate like morning dew once the sun rises. What you dream shapes what you think about your upcoming plans and your closest confidants, especially if nighttime reveries fit with what you already believe, a new report finds.

To see whether people take their dreams seriously, Carey Morewedge of Carnegie Mellon University in Pittsburgh and Michael Norton of Harvard University surveyed students attending universities in India, South Korea and the United States about theories of dream function. In a series of experiments, the researchers also interviewed people in the United States about their interpretations of real and imagined dreams.

People across cultures often assume that dreams contain hidden truths, much as Sigmund Freud posited more than a century ago, Morewedge and Norton report in the February Journal of Personality and Social Psychology. In fact, many people think dreams provide more meaningful information regarding daily affairs than comparable waking thoughts do.

In one experiment, participants reported feeling closer to a friend after imagining a dream in which the friend defended them, versus betrayed them.

"This is very good evidence that dreamed-of actions can result in a self-fulfilling prophecy," says Mark Blagrove of Swansea University in Wales. A person who dreams about a loyal friend may then act in ways that encourage the friend to behave loyally.

The team also found that imagined dreams about communications from God were more meaningful to religious believers than agnostics. Still, agnostics said they'd see more meaning in a dream of God commanding them to do something enjoyable than something unpleasant.

"Our results suggest that the dreams most likely to affect our daily lives and relationships are the dreams that accord with our existing beliefs and desires," Morewedge says.