AQA GCSE Psychology

Three processes

Everything that is remembered has to go through three processes, and a failure at any one of them is a failure to remember.

Encoding is changing information into a form that memory can hold. The same thing can be encoded in different ways: a phone number can be held as the sound of the digits, as the look of them written down, or as the meaning they carry ("Mum's number"). Storage is holding that encoded information over time, and it is where the different memory stores and their limits matter. Retrieval is getting stored information back out when it is needed, for example when a question asks for it or when a smell brings back an old holiday. Information can be stored and still be unavailable at a particular moment, which is why people say a word is "on the tip of the tongue": the memory is there and the retrieval has failed.

The three are connected in order. Information that was never encoded cannot be stored, and information that was never stored cannot be retrieved, so a student who says "I never took that in" is often describing an encoding problem rather than a storage one.

How memories are encoded and stored

Information reaches memory through the senses, and what is stored differs with the store and the task.

• Sound is the main code in short-term memory, which is why a list of letters that sound alike (such as B, V, P, T) is harder to hold than a list of letters that sound different.
• Meaning is the main code in long-term memory. A person who is asked about a story a few hours later usually remembers what it was about rather than the exact words.
• Pictures and images are also stored. People remember faces and scenes without being able to describe them in words, so visual coding is part of the picture as well.

Long-term memory is not a single lump. It holds several different types of memory, and the differences between them are a way of explaining why one kind of memory can fail while another survives.

Episodic memory

Episodic memory is memory for events and experiences from a person's own life: your last birthday, what you ate for breakfast this morning, the first day at secondary school. An episodic memory is tied to a time and a place, and it is usually recalled with the feelings and surroundings that went with it, so remembering it feels like reliving the event.

Episodic memories are the ones that have to be consciously called up. They are also the ones most likely to be changed over time, because each recall is a chance to rebuild the event slightly differently (Bartlett's theory of reconstructive memory explains how).

Semantic memory

Semantic memory is memory for facts, meanings and general knowledge about the world: that Paris is the capital of France, what the word "photosynthesis" means, how many days there are in a week. Nothing ties it to when or where it was learned. Most people can say that a cat is an animal and has four legs without being able to say when they first learned it.

A semantic memory and an episodic memory can be about the same thing. Knowing that the school leaving date is in July is semantic; remembering the day you walked out of the gates for the last time is episodic.

Procedural memory

Procedural memory is memory for how to do things: riding a bike, tying shoelaces, typing, swimming. It is built up by practice and is used without thinking. A skilled typist cannot easily say where each letter is on the keyboard but their fingers find it straight away, which shows that the knowledge is held in a different way from facts.

Procedural memories are slow to form, because skills need repeating, and they are usually very durable, since a person who has not ridden a bike for ten years can often still do it.

Comparing the three

A practical consequence is that damage or illness can affect one type and leave another. A person with memory loss may forget the events of the last year and still be able to drive, because episodic and procedural memory are held separately.

Why the distinction matters

The three types explain why "memory" cannot be treated as one thing. Revision mostly builds semantic memory (facts and meanings), whereas remembering where you were when you learned something uses episodic memory, and practising a skill such as a maths method builds procedural memory. A study of one type does not automatically say anything about the others, so when a study is described it is worth asking which type of memory it tested. Murdock's word lists test recall of items that have no personal context, while Bartlett's story tests how a meaningful account is rebuilt, and both are covered in the notes that follow.