Can humans really successfully multitask? It seems to be a quality parents want to instill in their children, as well as i.e.- teenagers bragging about having music playing, texting, video chatting, all while doing homework, they claim is the best possible atmosphere; for getting their school work done....
"Trying to do two things at once is usually a recipe for doing both badly, according to a long line of research. We’re slower and less accurate when we try to juggle two things."

Generally, it is thought that multi-tasking is just the brain rapidly shifting its focus from one matter to another instead of doing both (or several) things simultaneously. This is very straining and distracting for the brain, and so it ends up doing less well on both tasks than it would if the tasks were done separately.https://www.apa.org/research/action/multitask.aspx

However, there is an interesting article that says there might be more going on that that. The article explains 2 studies done that seem to indicate that our ability to perform a task might depend on the context in which we learnt to perform the task. E.g. " If you’re typing while listening to a conference call, maybe you’re less likely to make mistakes if you were equally distracted when you originally learned to type." 
https://hbr.org/2015/01/the-curious-science-of-when-multitasking-works