Researchers at the University of Oregon have concluded that the human brain has a built-in limit on the number of discrete thoughts it can entertain at one time. The limit for most individuals is four, according to the research team led by University of Oregon psychology professors Edward Awh and Edward Vogel.

The multitasking cap is not affected by the complexity of one's thoughts. Surprisingly, as many complex concepts can be retained in short-term memory as simple thoughts, the researchers found.