Do one thing at a time; do not answer messages during meetings
Switching tasks slows responses and increases errors. Frequent users of several media streams had not trained themselves to multitask better; they performed worse on switching tests.
What it takes
Free. Resisting messages during a meeting takes some discipline.
What you may gain
A review found slower responses and more errors after task switching. A separate laboratory study of university students found heavy media multitaskers more susceptible to irrelevant stimuli and irrelevant memories, and worse at switching tasks.
Context & considerations
Switching costs vary greatly by task, so no single percentage is given. Ophir's cross-sectional comparison cannot distinguish whether multitasking weakens attention or people with poorer attention are more inclined to multitask.
Research & references
Monsell (2003). Task switching. Trends in Cognitive Sciences. https://doi.org/10.1016/S1364-6613(03)00028-7 ; Ophir, Nass & Wagner (2009). Cognitive control in media multitaskers. PNAS. https://doi.org/10.1073/pnas.0903620106