Echoic memory
Echoic memory is auditory sensory memory. It keeps a short echo of what you just heard for about 3 to 4 seconds, long enough to catch the end of a sentence you were not listening to. Ulric Neisser named it in 1967. It lasts longer than iconic memory for images, but anything you do not attend to is gone within seconds.
Speech arrives one sound at a time, so the brain needs a buffer that holds the last few seconds while it works out the words. Echoic memory is that buffer. It is why you can say what? and then answer before the other person repeats the question. Estimates of its length depend on the method, from about one second to around 10 seconds, but 3 to 4 seconds is the usual textbook figure.
Researchers measured it with a sound version of Sperling's letter experiment. In 1972 Christopher Darwin, Michael Turvey and Robert Crowder played items through the left ear, the right ear and both at once, then cued which channel to report. People reported more when cued than when asked for everything, just as with the visual letter grid. Where a sound came from was easier to report than what kind of item it was.
For studying, echoic memory explains why a lecture can feel clear and still leave nothing behind. Every sentence passes through a few seconds of echo. If you are not paying attention, or are busy copying the last slide, it never reaches short-term memory. Notes catch what the echo cannot hold, and reviewing them the same day keeps them from fading over the next days.
| Feature | Echoic memory | Iconic memory |
|---|---|---|
| Sense | Hearing | Sight |
| About how long | 3 to 4 seconds | Well under 1 second |
| Named by | Ulric Neisser, 1967 | Ulric Neisser, 1967 |
| Classic experiment | Darwin, Turvey and Crowder, 1972 | Sperling, 1960 |
| Everyday example | Catching a question right after you said what? | The light trail of a waved sparkler |
In a 90-minute lecture Jana copies every word on the slides and misses what the professor says about why the reaction is reversible. That explanation sat in her echoic memory for a few seconds while her attention was on the slide, then it was gone. The next week she downloads the slides beforehand, writes down only what is said aloud, and spends 15 minutes that evening turning her notes into five questions.
- 1Get the slides before the lecture so you do not have to copy them.
- 2In class, write down what is said that is not on the slides: examples, reasons, hints about the exam.
- 3Use keywords and arrows instead of full sentences, so you keep listening while you write.
- 4The same day, spend 10 to 15 minutes filling gaps and turning the key points into questions.
- 5If the lecture is recorded, go back only to the parts your notes mark as unclear.