Multi-tasking is one of the most confusing attempts to increase productivity.
In fact, it usually leads to the opposite effect, that of significant waste of time and effort !
In Jeff Sutherland's Scrum training there is an exercise that proves that multi-tasking is inefficient for 99%+ of people. When I use this exercise in my training I usually find that the self-assumed multi-taskers are the worst and most affected by inefficiency.
There are some people who are good at multi-tasking Read the article Supertaskers and Prof Strayer's long research on this here: https://www.psychologytoday.com/us/articles/201401/meet-the-super-taskers. In summary, if you think you are a great multi-tasker, Strayer suggest you probably are not. It is just that you feel very busy doing lots of things in the same time period, but rarely get things completely 'done'.
I usually cure the multi-tasking problem by training the team together as part of launching the project. However I have seen the behavior in projects I am asked to coach who I have not trained. I usually try to make a charter or agreement with all the team members on what I can and can't do.
Usually the behavior occurs because we don't have a team, what exists is a group of people working on a project or product. Don't confuse a group working together with a team. They are vastly different! Unfortunately most people do not know the difference because they rarely or never are part of a real team. For more on real teams see: www.lc-stars.com/teamwork.html .
The exercise is a simple exercise to write people's names.
Usually there are tables of 7 persons. But 5 or 6 works as well. Groups of 3 or 4 are less useful.
Ask one person to volunteer to act as 'the customer service representative'. They are given a pen and paper to write names.All other people at the table are customers.Explain the rules...In the first round, the customer service rep asks the first person to give one letter of their first name, the next person one letter, and so on until the complete rotation around the table. Then the first person gives the next letter, followed by the next person, and so on. Each time a person is finished giving their name, the state they are 'done' and can skip further rounds. Record the overall time taken. This is the multi-tasking round
In round two, one person spells their first name letter by letter until completely written by the 'customer service rep'. The next person spells their name completely, and so on until everyone is 'done'. This is the single tasking round. Typically it takes 1/3 to /2 the total time of round one.
Review with participants about why the times are different. Ask questions like did participants lose track a bit of where they were in the exercise, e.g. often someone will admit they lost track of their own name. It is important to draw out lessons learned comments and questions.