Daydreaming is not just the result of the mind wandering off by accident − people can do it on purpose when they do not find a task challenging. Researchers have shown how there are different types of "zoning out" and that these involve two different cognitive processes.

A study published in Psychological Science looked at intentional and unintentional daydreaming and found the two are caused by different things. They say the finding could have implications for learning by gaining a better understanding of how and why people's attention wanes.

The scientists, from Harvard University, studied 113 students as they completed a computer task. They were asked to tap the spacebar whenever a certain number popped up on the screen.

Half of the students were given a task that featured these numbers appearing in a pattern, so it was easy to predict when to press the spacebar. While the other half did not know when the numbers would appear.

Throughout the task, the volunteers were asked to record whether they were engaged with the task, intentionally started thinking about something else (what to have for dinner, for example), or whether they accidentally started daydreaming.

Was there any difference in daydreams?

Findings showed that the rate of mind wandering was the same for all participants. However, the volunteers with the easier task tended to zone out intentionally, while the group with the difficult challenge daydreamed by accident.

Researchers believe those working on the easier task felt as if they could afford to daydream, as the task did not require their full attention. Those on the hard task had to focus harder to perform well, so if they did end up day dreaming, it was more likely to occur unintentionally.

"These results challenge the common view that all mind wandering is unintentional," said Paul Seli, lead author of the study. "Importantly, this result indicates that intentional and unintentional mind wandering are unique cognitive experiences that sometimes behave differently. In turn, this suggests that researchers ought to distinguish between these two unique subtypes of mind wandering in future work."

The researchers plan to continue analysing both separate types of daydreaming, which they say could lead to uses in everyday life. "We are interested in examining the causes and consequences of unintentional and intentional mind wandering in educational settings," they wrote. "Ultimately, we would like to develop methods with which students can reduce the occurrence of these two unique types of mind wandering so that they can more effectively learn the course material."