"Associations are representations of events, people, and places
that form when the brain decides to link different kinds of information,
especially if the link is likely to be useful in the future.
The raw material for associations originates primarily
from the five senses but also can be emotional or social cues.
The brain takes several different things into account in deciding
whether to forge these mental connections. For example, if
something provides inputs to two or more senses close together
in time, like the sight, smell, and taste of a cheeseburger,
the brain will almost automatically link the sensations.
In essence, this is our basic learning process.
"

So if anything, multi-tasking would be extremely helpful, if you give all your attention to all of the tasks that you're trying to fulfill.

For example: You just made cupcakes, and you're eating one now. At the same time, you're reading your study book on.. lets say.. physics. So, paying attention to all three senses: The smell of the fresh cupcakes, the taste of the cupcakes, and the information being processed as you read, if you bring the smell of cupcakes with you when you go to a test, you'll be able to remember what you studied as you associate cupcakes with your study material, right?

So, as long as you're paying attention to these senses, smell, touch, taste whatever.. or even paying attention to two study materials at the same time, if you remember their association with each other, the memory will become clearer, and will be in your long term memory?