I cannot say how many time I've had to debunk the myth of multitasking. Here's a good breakdown for all crowds.
https://goodmenproject.com/guy-talk/smart-people-dont-multitask-fiff/
@arteteco
So the short answer is multitasking doesn't exist: our brains are not paralell processors so we are not able to hold two or more tasks/inputs simulateously. Rather, we are serial or sequential processors, switching (our attention) rapidly back and forth between or among tasks. The research has established that as the frequency of switching, as well as an increase in number of tasks, the quality and efficacy of the outcom are of our efforts deteriorates. That is to say, we perform worse the more we go back and forth between or among multiple things. Memory formation and retention also suffers.
@arteteco
This holds true for your example of walking and listening to a podcast. Walking is largely passive so you're free to redirect your attention to the podcast. However, if you trip or stop at a crossing, your attention shifts away from the podcast and to managing your fall or negotiating the crossing before switching back. In this those moments you've lost attention to and recollection of what is being said in the podcast.
@theodraxis
Thanks, a nice and simple article.
However, a doubt, we are constantly doing more than a thing at a time, how is multitasking defined for the purpose of the studies? Like, I sometimes listen to podcasts while walking or on the bicycle ( or cleaning, or...), and I often read and eat, I mean what are the boundaries between an efficient multitasking and a dangerously inefficient one?