Find your mind wandering as you seek the solution to a mental puzzle? Not to worry, experts say.

"Off-task" mental actions including mind-wandering or reminiscing can actually increase brain power when we're faced with perplexing mental tasks.

That flies in the face of previous assumptions that held that the executive control network in our brains, which is focused on external, goal-oriented thinking, had to dominate while internally directed thinking, such as daydreaming, needed to be suppressed when faced with a taxing mental exercise.

"The prevailing view is that activating brain regions referred to as the default network impairs performance on attention-demanding tasks because this network is associated with behaviors such as mind-wandering," says Cornell University neuroscientist Nathan Spreng. "Our study is the first to demonstrate the opposite -- that engaging the default network can also improve performance."

Results suggest the interaction between externally and internally focused neural networks best facilitates complex problem-solving thought, the researchers say.

There's no shortage of studies that seem to suggest activation of the default network interferes with some complex mental tasks, Spreng notes, but in the majority of them the mental activities associated with the default network conflicted with task goals.

Spreng and his colleagues designed an experiment to see if off-task activities, such as reminiscing, could support rather than hinder the goals of the experimental assignment.

The experiment, dubbed "famous faces n-back," tested if accessing long-term memories of famous people, which normally uses default network brain regions, could improve short-term memory performance, which characteristically engages the brain's executive control regions.

In the lab, young adults underwent brain scans while viewing some famous and some anonymous faces in sequence.

They were tasked with identifying whether a face they were currently looking at matched one presented two faces back.

Participants in the experiment were found to be both more accurate and faster at matching famous faces compared to anonymous ones. The improved short-term memory ability was linked with increased activity of the default network -- the "mind wandering" network of the brain.

When the goals of a task aligned with processes normally undertaken by the default network, that network could improve performance on goal-centered tasks, the researchers reported in the Journal of Neuroscience.

"Outside the laboratory, pursuing goals involves processing information filled with personal meaning -- knowledge about past experiences, motivations, future plans and social context," Spreng says. "Our study suggests that the default network and executive control networks dynamically interact to facilitate an ongoing dialogue between the pursuit of external goals and internal meaning."

In other words, it's OK to let your mind wander -- it may take you directly to where you need to be.

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