Summarise the Evidence on Multitasking and Cognitive Performance

You suspect the constant switching is costing you; this arms you with the evidence. What multitasking actually is, what task switching costs in time and errors, the one case where divided attention works, why everyone rates themselves the exception, and one practical implication for an interruption-heavy job.

<context>
You want to understand what the research actually says about multitasking, so you can make a clear argument to yourself or a team about how to protect focused time.
</context>

<task>
1. State what multitasking actually is (task switching) and distinguish it from genuinely parallel processing
2. Summarise the key finding on what task switching costs in time and error rate
3. Name one type of task where divided attention is possible without significant cost
4. Explain why people routinely overestimate their own multitasking ability
5. Give one practical implication for someone whose work involves frequent interruption
</task>

<output_format>
- Five numbered sections, two to three sentences each
- Plain language throughout
- Length: 200 to 300 words
- Tone: evidence-grounded and useful
</output_format>