When doing tasks that require continuous thinking, keep out even brief interruptions

Cost: No cost at all. Just close the door, put on headphones, or hang a “Do Not Disturb” sign.
In plain terms: Even a brief interruption lasting 2.8 seconds on average doubles the chance of errors in subsequent steps of a sequential task. An interruption of 4.4 seconds triples that error rate. Field observations also show that it takes an average of 25 minutes to return to the interrupted task, with two other unrelated tasks squeezed in during that time. People who get interrupted do finish tasks faster, but they report higher levels of stress, frustration, effort, and time pressure.
Benefit: On average, a 2.8-second interruption doubles the error rate for sequential tasks, while a 4.4-second interruption triples it. This finding comes from lab experiments. Another study observed 24 office workers (information professionals) in real-world settings. They switched topics every 11 minutes on average, and 57% of those topic switches were interrupted. It took them 25 minutes and 26 seconds on average to get back to the interrupted task, with 2.26 other tasks added in between. A separate experiment with 48 participants showed similar results: interrupted workers completed tasks faster, but reported significantly higher stress, frustration, effort, and time pressure.
Evidence grade: B
Sources:Altmann, Trafton & Hambrick (2014). Momentary interruptions can derail the train of thought. Journal of Experimental Psychology: General. https://doi.org/10.1037/a0030986；Mark, Gonzalez & Harris (2005). No task left behind? Examining the nature of fragmented work. CHI 2005. https://doi.org/10.1145/1054972.1055017；Mark, Gudith & Klocke (2008). The cost of interrupted work: More speed and stress. CHI 2008. https://doi.org/10.1145/1357054.1357072
Notes: The field study mentioned above categorized interruptions into two types: those caused by others approaching the worker, and those initiated by the worker themselves. Simply closing the door blocks only the first type of interruption. To handle the second type, combine this tip with Tip 1 (turn off non-essential notifications) and Tip 5 (batch-process messages).