Why we remember and forget things

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Our brains only remembers things it thinks are important to us. Photo / 123RF

Memories are a part of us that shape who we are and how we act.

There are some things we want to remember, other experiences we'd rather forget, but Jee Hyun Kim, a behavioural neuroscientist at The Florey Institute of Neuroscience and Mental Health, has discovered we can't control our memories or pick and choose what we store in our brains.

So how does the brain decide what moments in our lives we remember and what moments we forget? Dr Kim said our brain will only record a time in our lives that it thinks is important.

"When something happens, when something feels important or an event triggers a lot of emotion or is visually stimulating, then our brain decides maybe it's something it should keep in mind for the future," she said.

Sometimes humans remember what is perceived as useless information, like lyrics to a song, over something more important, like your mum's birthday.

According to Dr Kim, your brain most likely remembers the song because it is linked to your emotions, more so than a date on the calender.

"We can choose what we think is important but we can't control how we feel about things and what the brain will remember," she said.

According to Dr Kim, while it's difficult for us to control our memories, there is a way it can be done.

"There is some evidence you can control your brain and that's by consciously paying more attention," she said.

"You see people good at remembering names say they consciously pay attention when people introduce themselves.

"Sometimes we don't pay attention externally because we are so self obsessed but if you do listen you can wire your brain to remember something like names."

Dr Kim said not all our memories may be real and we could have fabricated past events in our minds.

"Fabricated memories are quite common and children especially are susceptible to fabrication, especially when someone talks to them about a memory or incident. If what's being said to them sounds right, they can believe that something different happened."

Dr Kim said every time we remembered a moment in our lives, we had to re-encode it back into the brain, which could mix up the message much like a game of Chinese whispers.

"Your memory doesn't just stay frozen in time," she said.

"When the event happened, the memory was encoded in your brain but every time you retrieve the memory you have to re-encode that memory.

"During that window, a memory can be changed and people may not recall the source where the memory came from, like if a friend said something or if they heard it on TV.

"Sometimes people don't remember a time or place correctly."

Dr Kim said memories often changed our behaviour, and what we remembered could influence things we say and do.

"They make us better equipped to seek out things that make us happy and avoid the things that make us unhappy," she said.

When it comes to the brain, Ms Kim is most fascinated by early life memories.

"They are so random for most people and tend to be linked with an emotional event," she said.

"We tend to be quite visual with our memories from an early age. We actually form memories as soon as we are born but we just forget very easily. When I was one I formed memories that I forgot when I was two," she said.

"When we are aged three to four we can collect memories we remember as adults. It's the time our visual perceptions of events are quite good."

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