Your brain cannot multitask. What it actually does is switch between tasks rapidly — and every switch costs you. Researchers call this a switching cost: a period of 15 to 25 minutes during which your brain is not fully back on the original task. This means that if you check your phone, respond to a message, and return to your work, you are not working at full capacity for almost half an hour. Students who study while watching videos, write assignments while monitoring group chats, or split attention between their work and their notifications are not being efficient. They are training their brains to be shallow — unable to hold a single thought long enough to do anything serious with it.