Sensory memory
Sensory memory is the very first stage of memory. It holds a raw copy of what your senses take in for a fraction of a second to a few seconds. Visual traces last about a quarter of a second, sounds about 3 to 4 seconds. Only what you pay attention to moves on to short-term memory. The rest fades.
In the multi-store model from Atkinson and Shiffrin (1968), sensory memory comes before short-term and long-term memory. It is big but brief. It takes in far more than you can notice, works automatically, and lets almost all of it vanish. Each sense has its own buffer. Iconic memory handles sight, echoic memory handles sound, and haptic memory handles touch.
The classic proof is George Sperling's 1960 experiment. He flashed a grid of 12 letters for a split second. Asked to report all of them, people managed about 4. But when a tone right after the flash told them which single row to report, they could name almost any row. So far more was briefly stored than they could report. After a delay of about one second, that advantage was gone.
The lesson for studying is about attention. Sensory memory catches the whole lecture slide, the voice and your phone buzzing, but only what you attend to gets encoded. Split attention and less of the lecture makes it through. That is why studying with notifications on feels like work but leaves little behind. If it is on your AP Psychology exam, remember the order: sensory memory, then attention, then short-term memory, then encoding into long-term memory.
| Type | Sense | About how long | Example |
|---|---|---|---|
| Iconic memory | Sight | About 0.25 seconds, under 1 second | The light trail when a sparkler is waved in the dark |
| Echoic memory | Hearing | About 3 to 4 seconds | Replaying what someone just said when you were not listening |
| Haptic memory | Touch | About 2 seconds, less studied | Still feeling where a tap on your arm was |
A friend asks Sam a question while he scrolls. He says what? and then answers before she repeats it. His echoic memory held her words for a few seconds, long enough to catch up. In a lecture the same buffer can not save him for long: if he checks messages for 30 seconds, that part of the explanation never reaches short-term memory at all.
- 1Remove the competition. Put your phone out of sight so your attention goes to one source.
- 2Look or listen with a question in mind, so you choose what to attend to.
- 3After each slide or section, pause and say back the key point before moving on.
- 4Use two channels on purpose, like a diagram plus a spoken explanation, instead of two competing things.
- 5Turn what you noticed into retrieval within the day, so it does not stop at short-term memory.