You can’t multitask. Neither can I.
You can continually interrupt yourself switching from one task to another quite quickly, but you cannot process two pieces of information at once or do two tasks simultaneously.
The more related the tasks the harder it is to switch between the two tasks. If you are watching TV and drinking coffee, those tasks are quite different and so switching between the two is seamless. If the two tasks are related, such as talking on the phone and writing an unrelated report, the switch is more difficult.
The same goes for the complexity of the task. If you are watching TV and drinking coffee, neither takes much brain power. If you are studying for an exam and arguing with your partner, both need large amounts of energy. How did you do on that exam?
Finally, the familiarity with a task makes a difference. If watching TV and drinking coffee is something you do every day, then you need less energy. If you are watching TV and eating rice with chopsticks for the first time, it’s a different story.
So if you want to switch between simple, familiar, unrelated tasks such as watching TV and drinking coffee, then go for it. Other than that, give each task, each person, each conversation your undivided attention. Your relationships will improve and your productivity will sky rocket.