Ms. Mann’s research has found that daydreaming — an inevitable effect of idleness — “literally makes us more creative, better at problem-solving, better at coming up with creative ideas.” For that to happen, though, total idleness is required.“Let the mind search for its own stimulation,” Ms. Mann said. “That’s when you get the daydreaming and mind wandering, and that’s when you’re more likely to get the creativity.”