This book chapter from 1977 (with a recent reflection by the author, a professor of psychology and linguistics) discusses the 15-minute rule for getting things done:
Learning to Work
(from the out-of-print book Working it Out)
An excerpt:
Learning to Work

An excerpt:
A related technique:Of course, people laugh when I say fifteen minutes. What can you accomplish in fifteen minutes? Well, more than you would think. Fifteen minutes with no interruptions, no pencil sharpening, no trips to the bathroom, no trips to the kitchen, no telephone calls; fifteen minutes of solid work can be very profitable. I don't plan to stay at fifteen minutes for the rest of my life, but it seemed like a good place to start.
Another point:The basic unit of work in the Pomodoro Technique™ can be split in five simple steps:
The Pomodoro Technique™
- Choose a task to be accomplished
- Set the Pomodoro to 25 minutes (the Pomodoro is the timer)
- Work on the task until the Pomodoro rings, then put a check on your sheet of paper
- Take a short break (5 minutes is OK)
- Every 4 Pomodoros take a longer break
Pseudo-work does not equal work
Here are two facts: (1) I made straight A’s in college. (2) I studied less than most people I know. The same holds true for many of the straight-A students I researched for my book. If this sounds unbelievable, it is probably because you subscribe to the following formula: work accomplished = time spent studying.
The more time you study the more work you accomplish. The more work you accomplish, the better your grades. Ergo, straight A’s imply more work. Right? Then how do you explain me and my interview subjects…
To understand our accomplishment, you must understand the following, more accurate formula:
work accomplished = time spent x intensity of focus
That last factor — intensity of focus — is the key to explaining why straight-A students never seem to embark on the same fatigue-saturated all-night study adventures that most undergrads rely on. Let’s take a specific example. Assume that you have a paper to write. The standard approach is to camp out in the library the day before and work until you finish.
Here’s the problem: even with little breaks, there are only so many consecutive hours of work you can manage before your intensity of focus crashes (in practice, this value is probably close to 2-3 hours for most students). Therefore, most of your time spent working features low focus, increasing the time required to accomplish the task at hand.
The Straight-A Gospels: Pseudo-Work Does Not Equal Work