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Why do we forget things?

6 December 2021

We’ve all had those moments where we can’t quite remember something. Maybe you’ve misplaced your keys, can’t remember someone’s name or just completely forgotten what it was that you were supposed to be doing. A lapse in memory is a common thing, but why does it happen? BBC Bitesize explores how our memories work and why we forget things.

Short-term versus long-term

If you’ve ever spent days revising for an exam only to forget that crucial fact, you might be wondering how that could actually happen.

Dr Liz Coulthard, associate professor in dementia neurology at the University of Bristol, explains that there’s a big difference between our short term and long term memories.

She said: “If you remember things just for a few seconds, like a phone number, you do it almost by rehearsal. You might visually imagine it, or repeat it to yourself. Short-term memory works like that, it’s a loop.

“For longer term memories, they all have to be laid down or stored, so the first thing that happens is they go into an area of the brain called the hippocampus."

If you were to remember the start of a conversation the following day, that is down to a change in your brain structure.

When you form a new memory, your nerve fibres and synapses within the hippocampus are altered. The changing of the synapses is a process known as synaptic plasticity. Once a memory is laid down in your hippocampus, you don’t have to actively remember it or recall it to keep it there.


What happens next isn’t necessarily down to the individual themselves. The memory is strengthened or forgotten in the background, often while we sleep.

Read the full BBC bitesize article


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