by Allison Richmond
The Magic Numbers
Is it possible to increase your short-term memory with practice? In one study, experimenters tested an undergraduate student with normal intelligence and memory abilities. They read him strings of random digits in one-hour sessions over the course of 20 months. At the beginning of the study, he could remember a string of 7 digits, and after over 230 hours of laboratory testing he could remember 79. In addition to this feat, he could recall 80% of the digits he heard at each session as opposed to almost none at the beginning of the study. The student accomplished this through the use of mnemonics, allowing him to use associations already stored in his long-term memory as opposed to using his short-term memory to remember all of the digits.
The student in this study used mainly running times as his mnemonic device, and when he was presented with digits that could not be organized in this way, his performance dropped drastically. Many mnemonic strategies break down long strings of information into smaller, easier to remember chunks. By transforming the information into running times, the student additionally increased his recall capacity because he was a runner, so the information was meaningful to him. In addition to this mnemonic device, the student used a rehearsal procedure which broke the digits down into subgroups in a hierarchical structure.
Although it seemed as if the student’s short-term memory had increased, in fact his performance had improved through the use of mnemonics and hierarchical structures. Through these devices the student was able to recall long strings, without ever holding more than about seven distinct pieces in his short term, or working, memory (Chase, Ericsson & Faloon., 1980)
The theory of the magic number 7 was developed by George Miller in 1956 (as described in Meyers, 2007). He proposed that the short-term memory could hold 7, plus or minus 2, bits of information at once that could be easily recalled. We can remember random digits a little bit better than random letters, but in either case our short-term memory recall is limited, as is our ability to overcome the limit of the magic number 7, as shown in the study described above.
This study suggests that to improve our memory skills we should practice using mnemonic devices and learn to organize material hierarchically. By making information meaningful and relating it to other information or to ourselves, we can encode it in our long-term memory, allowing us to store and retrieve the information readily. This study is strong evidence that the best way to remember something is to relate it back to yourself or to old information. So, next time you’re cramming for a test, try to make associations in addition to simply rehearsing the material.
References
Chase, W. G., Ericsson, A. K. & Faloon, S.. (1980). Acquisition of a Memory Skill. Science, 208, 1181-1182.
Meyers, D. G. (2007). Psychology (8th ed.). Worth Publishers.
