Memory types defined

We all know the basic difference between short-term and long-term memory. But why do some memories fade while others remain? Find out what’s happening inside your brain when you start having trouble with memory loss.

In a nutshell

When we talk about memory, we’re mostly referring to long-term memory. These are facts and experiences that we’ve known for days, weeks, months, years, decades or a lifetime. But there’s more to long term memory than meets the eye. For a start there are two different types

1. Conscious memory

This is our memory of facts which can be consciously recalled – that is, we have to think about remembering them. It is sometimes called ‘declarative’ or ‘explicit memory,’ as the information is explicitly stored and ‘declared.’

Science fact: Conscious memories are stored in the temporal cortex after having been encoded or processed in the medial temporal lobe.

Conscious memory can also be divided into two types.

a) Episodic
Episodic memory is our memory of experiences that happened to us personally.
What does that mean? It’s the memory of times, places and emotions of things that happened in our past and which are permanently stored.

b) Semantic
Semantic memory is our memory of specific facts, meanings and concepts that we’ve learnt.
What does that mean? For example, we learn that the capital of France is Paris. This is a fact and one that you may not have any real experience of unless you’ve visited it. It might take a few occasions for us to store the fact in our long-term memory, but once it is there, it’s usually there for good.

2. Unconscious memory

Unconscious memory is our memory of how to do things which we’ve done so often they seem automatic. For example, tying our shoelaces, playing a guitar, riding a bike and even using a knife and fork. We acquire these memories (which are sometimes called ‘implicit’ or ‘procedural memory’) through repetition and practice but they become so ingrained that we don’t consciously think about them anymore when we do them.

Science fact: Procedural memories are encoded and processed in the cerebellum, motor cortex, putamen and caudate nucleus – these are all areas in the brain that are involved with movement and instinctive actions.

So why do we forget things from our long-term memory?

Scientists have several theories about why this happens, here’s the main ones

Decay theory

What it means: Over time, the memory trace that’s formed in your brain when you learn something new might begin to fade and, unless you make a conscious effort to practice or learn the action, it will disappear.

But some psychologists disagree with this theory, believing instead that once you learn something you never forget because ‘it’s just like riding a bike.’ You might be a bit wobbly if you get on a bike after a few decades without practising, but the memory is so ingrained that you will still know how to do it.

Interference theory

What it means: Some memories may compete and interfere with other memories, especially if they’re very similar, which can make it harder to remember them.

Failure to store

What it means: The brain fails to properly encode the memory into your long-term memory. This could be because the brain decided to only remember certain details, and forget others.