A similar idea can be seen in the training of health professionals. If a patient or an elderly person has a stain, or gets dirty somehow, that person should be cleaned. Even if it’s only a little spot. If patients stay in that state, they will be less careful themselves in keeping clean. They will tend to feel that it doesn’t matter anymore, it’s already dirty. So their general state of hygiene, self-esteem, and thus health level will start to decline.
The results of this psychological study are applicable in many situations of our daily lives: from the care of our home to the maintenance of our car. But they’re also applicable to our jobs. For example, if you’re a programmer or a project manager, and you allow for a new version to be deployed. But you haven't had it sufficiently tested. Or if you leave that technical “debt” unpaid in the code now —because “we’re in a hurry.” You’d be broadcasting to the whole team the feeling that anything goes. That “it’s enough as it is” and that one can leave quality aside. Sooner or later the phone will ring with complaints from users. Soon we will see a lengthy queue of reported bugs in our queue.
When we apply this theory to software, it’s helpful to explain the term entropy. In physics, entropy is the level of disorder or randomness in a system. Say you see badly indented or commented code. Or a bad choice when naming a variable or some bad design. Fix it as soon as possible or schedule its correction for the near future. Take some sort of action to limit disorder or it will expand. It will create the feeling that any patch or quick fix is valid.
If some code (or thrown-together code) will make your system deteriorate quickly, impeccably written and designed software will have the opposite effect. It will make new programmers avoid breaking something so beautifully built. They will make an effort to put in place the best code they can write. Now you know: make your life and your project easier by fixing broken windows as soon as they appear.
You can find texts like this and many other about how to manage agile projects in my book Agile 101: Practical Project Management (available on Amazon).