Photo: supplied by Allen & Unwin / @michaelRock
Like a bright-green file among a stack of brown manila, vivid memories are more accessible to us, neuroscientist Charan Ranganath says.
Dr Ranganath is a professor of psychology and neuroscience and director of the Dynamic Memory Lab at the University of California at Davis.
His book, Why We Remember: The Science of Memory and How It Shapes Us, shines a light on memory and the roles intention, imagination and emotion play in our brain's decision to store certain information.
"Imagine if you open up a filing cabinet, and all of the folders are the same manila colour, you're going to have trouble finding the exact file you're looking for," he told Nine to Noon.
"But if one of them is bright green, and the rest of them are this beige colour, the bright green one's going to be standing out."
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The memories that are going to be easier to pull out are going to be experiences that have vividness and emotional intensity, he said.
"They have the visual details, the sounds, the smells - everything that makes this moment different from everything else."
Distraction is the enemy of memory-forming, he said.
"When we switch from one thing to another - like switching between emails and conversation, or we even think about switching - we lose the thread of what we're doing at any given moment. It pulls us away from all the details of our experience that we want to encode."
This means we end up with "fragmented, blurry memories that are doomed to be forgotten".
That feeling of walking into a room and not knowing why you did is not necessarily a memory problem, he said.
"It's a consequence of the fact that our brain is trying to generate new predictions of things that could happen.
"Once you go to a new room, your brain automatically changes your idea of where you are. And so ... all of a sudden, your brain is trying to pop up all these possibilities for things that could happen in this new space."
To figure out why you came into the kitchen in the first place, you have to mentally time travel, he said, to that previous state your brain was in when decided to leave the lounge and go to the kitchen.
Memories compete, which is why sometimes we temporarily cannot recall the names even of people we know intimately.
"Say, you're trying to pull up the name of one child and you accidentally pull up the name of another child.
"That blocks your ability to see the original child that you're looking for, because these memories are all competing with each other. And once you activate one memory, it starts to win the competition. And it makes it harder to find the one that you're really looking for."
Memorisation depends on planting cues in the mind, he said.
"Use your ability to imagine, to generate cues that will be able to pull up the memory when you need it.
"If I have to remember that today is the day that I'm supposed to take out the trash, I can visualise walking to the house, and then looking at the doorknob and then saying, 'Hey, wait a minute,' and then looking over the trashcan, and then walking over to the bin and taking it out.
"What happens is that when I really come home, and I look at the doorknob, I'm immediately reminded of the fact that I have to take the bin out, because the knob is acting as a reminder."
We knew memory was less sharp as we aged, he said, but advised to never forget the brain is part of the body.
"Things that are going to be good for your body are going to be good for your brain. And the list of these factors is just growing and growing.
"It can be everything from maintaining a healthy diet, getting good sleep, reducing chronic stress.
"We're now learning that even oral hygiene can play a part in that gum disease can accelerate cognitive decline.
"We're starting to realise that [for] people who have hearing problems, that wearing hearing aids can help prevent cognitive decline.
"Point after point after point, we see that the brain is connected to all these parts of your body. And so I really encourage people to take care of [their] physical health as the easiest thing that you can do to significantly reduce your risk of having a memory disorder when you get older."
As for doing crosswords to improve memory, the evidence suggests it would just help you get better at them, he said.
"But I do think being socially engaged can make a big difference. So, if you do crosswords with someone you love, that could be a very good thing to do.
"It's also good to give yourself challenges... As people become more comfortable with, essentially trying to overcome challenges and memory, the better you will do, because you'll just be training yourself in how to be able to recall information when you need it."