An interrupted task or activity is often delayed by 50% or longer and has at least 50% more mistakes than an uninterrupted one. That means that if you’re immersed in a task that usually will take an hour (60 minutes) and someone interrupts you, suddenly your task becomes 90 minutes or longer and will tend to have more mistakes in them.
Here's the reason why: our brains and us takes time to build a certain momentum or state of focus where we can concentrate fully on a task without being/feeling distracted, and once we get into this momentum, we can enjoy a very productive flow, as long as we don't get interrupted.
Productivity momentum or this "flow" can still be disrupted from external input. Interruptions of any sort erases and scrambles your previous optimized brain state and prevent and limit you from re-engaging into that state of flow. When someone interrupts you, it will take you on average 22 minutes to get back to the original task and another 10 minutes to return to your state of productivity flow so that you can concentrate and continue again. Almost 50% of the time you interrupt someone, you actually derail their concentration so much that they don't actually get back to the task immediately even after the interruption ends. You may think that you're just gonna ask that short blurb for a couple of minutes or seconds, but the actual distraction as a result from your interruption can be significantly longer.
20% of interruptions cause people to stop all work on that task for the entire day.
Have you ever been interrupted for a short moment by someone, only to extend that interruption by telling yourself, "now since I've already been interrupted/stopped my momentum, why not I…"
How often has quick questions became long conversations? All these are common experiences, especially so amongst knowledge workers / people (think writers, educators etc) – a seemingly innocent and minor interruption can get you off your focus so much that it may eventually take you hours to get back to the original task…if you get back to it on that day.
Multitasking a.k.a. frequent task switching has also been shown to increase one's stress levels as compared to single handling (managing one task at a time). This means that interrupting others not only hurts their productivity and flow, but it may also cause them mental stress and damage to their health.
Interruptions are much more expensive and damaging that most people realize – one estimated the cost of workplace interruptions to be at USD$ 588,000,000.00 per year in lost productivity for just the US alone.
Well this is possibly a gross underestimated value as it's based purely on wasted productivity hours multiplied by average salary. It doesn't take into consideration the chain of effects as a result of these interruptions, including opportunity costs, lost sales, retrenchment, businesses losing their business edge, decreased ROI in investments, costly mistakes, more sick leave due to increased stress levels etc. It also includes the fact that interruptions may cause some books to never be completed nor published, some businesses never launching and some ideas that never became real.
So the next time you think about "some quick questions" on someone who's productively working on an important task, consider your seemingly innocent question or comment may cause serious consequences, including adding more time to that task to be completed, increasing mental stress, causing mistakes, creating delays and possibly killing the task completely. Even a simple or brief interruption of a complex task can create the mental equivalent of an hour of extra work.
Highly productive people know the importance of working in uninterrupted blocks of time with good focus and concentration, and they take steps to guard against interruption. They wear headphones to limit small talk, closing office doors, cautioning others to not interrupt them unless totally necessary, letting people know when it's good or not good to talk to them, working in different locations, turning off phones and notification services (I know I do this a lot), or by working in different timezones.
Many students love to study late at night, and this is also reflected in the lives of many programmers. One reason is that they're less likely to be interrupted when everyone else is asleep so that their nighttime study or work can be more productive. Online activity such as emails, social media etc also tends to drop significantly late into the night (most of the people sleep).
Yes, socializing is good and fine…but if someone is productively working, don't interrupt them. You can talk to them when they're not engaged.
If you have trouble with people interrupting you more than you'd like, notify them to use the following rule of thumb or similar ones:
When I'm busy working, please don't interrupt me unless what you have to share is so urgent and important that it's worth erasing all the work I've done in the past hour.