People spend almost fifty percent of their time thinking about something other than what they're doing, according to this article in Science Daily. In addition, the magazine reports that the less people focus on the tasks at hand, the less happy they are. The study's conclusion: a wandering mind is not a happy one.
How might this experiment be skewed by a group of writers? Their minds undoubtedly wander a great deal of the time, but those minds are immersed in the act of creation. Is that the same thing as daydreaming or lacking concentration?
The study suggests that the only act which receives a person's full attention is the act of making love (although don't many people say that they enjoy fantasizing during sex?)
The notion that we would be happier if we focused on our tasks is an interesting one. It backs up Camus' existential idea that one need only embrace immediate needs and desires because nothing else ultimately matters.
In an age of multitasking, we have apparently trained ourselves to do our many tasks without giving them much thought. Perhaps be reclaiming our thoughts we can improve the quality of our thinking--but this is where science meets philosophy.