Information into sensory memory
We are constantly receiving sensory information from the environment:
- Visual information through our eyes.
- Auditory information through our ears.
- Olfactory information through our nose.
- Gustatory information through our mouths.
- Tactile information through our skin.
But we don't actively attend to much of this information!
Data is stored for a very brief period in the sensory store; for example, for up to around 0.5 seconds for visual information and 2 seconds for auditory information.
In the reading below (see Figure 8.2 in the reading), take note of the clever experiment by George Sperling, which was used to measure how long information is held in sensory memory.
Information out of sensory memory
Information in the sensory memory store is either passed on down the line to the short-term store, or it is lost.
Short-term memory
- Short-term memory holds a small amount of information in our consciousness for a short period of time (roughly 20-30 seconds).
- Short-term memory has a limited capacity of "7 plus or minus 2" items (i.e. 5 to 9 items) (Ebbinghaus, 1885; Miller, 1956). This appears consistent across different cultures (e.g. Yu et al., 1985).
- We know this from asking participants to try to memorise and immediately recall sets of stimuli like '71504' (quite easy) or '2753180649' (hard).
- Chunking items can increaase the amount of information held in short-term memory.
- E.g. T H E C A T S A T O N T H E M A T (hard — 17 units to store) vs. THE CAT SAT ON THE MAT (easier — 6 units to store, or maybe just 1!).
Rehearsal
- Information can be held in short-term memory for longer periods if it is rehearsed.
- E.g. when you look up a phone number and repeat it over and over before you ring it.
- Without rehearsal, information is lost — short-term memory needs to make room for new information!
- But if you actively attend to information and rehearse it enough, it will move into long-term memory.
Long-term memory
- Long-term memory can hold information for an indefinite period of time — up to a human lifespan!
- It is seemingly limitless — think about everything you know! Unlike short-term memory, when we store a new piece of information in long-term memory it doesn't "push out" any previously stored memories.
Retrieval
Retrieval is the process of recovering information from long-term memory and bringing it back into short-term memory. It's a little like opening a document on your computer, so you can use and update it.