Brown-Peterson procedure

In cognitive psychology, Brown–Peterson task (or Brown–Peterson procedure) refers to a cognitive exercise purposed for testing the limits of working memory capacity. The task is named for two notable experiments published in the 1950s in which it was first documented, the first by John Brown and the second by husband and wife team Lloyd and Margaret Peterson.

The task aims to test the quantity of objects that can be held in working memory while preventing participants from using mnemonics or other memory techniques separate from the working memory to increase recall capacity. In the experiment, participants view a sequence of three-letter constructs called trigrams, and are asked to perform simple algebraic computations such as counting backwards by 3s from 999 between each trigram. A trigram consists of 3 non-morphemic letters, the importance of which is that each letter represents a different independent object to be stored in working memory; therefore, trigrams avoid letter combinations that depict words or common acronyms. The algebraic computations are administered between trigrams to assure the participant isn't using mnemonic strategies to chunk the letters into a single object. Variants of the Brown–Peterson task are still used today, all with the same fundamental concept of administering items for the participant to remember whilst preventing the usage of additional cognitive resources to augment working memory.

The Brown–Peterson task refers to two studies published in the late 1950s that used similar procedures, one in 1958 by John Brown and a second in 1959 by Lloyd and Margaret Peterson.

The first experiment involved 24 psychology students at Indiana University at the time. The examiner proceeded by spelling a random three-letter nonsense syllable and then enunciating immediately afterwards a random three-digit number. The subject would then count backwards by some assigned number, either three or four, from the enunciated number.

After a set interval, a light signal was flashed to prompt the subject to cease verbally counting and to recall the random, three-letter nonsense syllable. The time interval between the enunciation by the examiner of the nonsense syllable (exposure to the syllable) and the signal prompt to the participant was known as the recall interval; the time interval between the signal prompt and the enunciation of the third letter by the participant was known as a latency. In order to maintain reproducibility of results, each participant was tested eight times using each recall interval, which were 3, 6, 9, 12, and 15 seconds. In addition, each nonsense syllable appeared an equal amount of times; the trials were split evenly in terms of counting by either three or four. No successive items contained the same letters, and the time between signal for recall and the next trial was always 15 seconds. In addition, the examiner and participant were instructed to enunciate in rhythm with a 120 BPM metronome, such that two letters or numbers were spoken per second.

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