A study has found that daydreaming is not good for your mood. "Volunteers were unhappier when their thoughts were elsewhere. Statistical tests showed that mind-wandering earlier in the day correlated with a poorer mood later in the day, but not vice versa, suggesting that unhappiness with their current activity wasn't prompting people to mentally escape. Instead, their wandering minds were the cause of their gloom." Psychologist and neuroscientist Lisa Feldman Barrett says the findings 'challenge the foundations of psychology'. Psychologists assume that the mind responds to a stimulus out in the world, but in this study, 'it almost looks like the stimulus is irrelevant.'"