Correlating interruptions with productivity

The results? The top 25% were 260% more productive than the bottom quartile!

The lesson here is that interruptions kill software productivity, mirroring Joel Aron's results. Other work has shown it takes the typical developer 15 minutes to get into a state of "flow," where furiously typing fingers create a wide-bandwidth link between the programmer's brain and the computer. Disturb that concentration with an interruption and the link fails. It takes 15 minutes to rebuild that link but, on average, developers are interrupted every 11 minutes.4

Interruptions are the scourge of big projects.

A maxim of software engineering is that functions should be strongly cohesive but only weakly coupled. Development teams invariably act in the opposite manner. The large number of communication channels makes the entire group highly coupled. Project knowledge is distributed in many brains. Joe needs information about an API call. Mary is stuck finding a bug in the interface with Bob's driver. Each jumps up and disturbs a concentrating team member, destroying that person's productivity.