Is information lost when we do not rehearse it? This is a question that the Peterson and Peterson (1959) experiment wished to answer.
If we recall the multi-store model of memory, devised by Atkinson and Shiffrin in 1968, there are three parts to the memory: the sensory register, the short-term memory, and the long-term memory. Each uses a different method for coding information and varies in duration and capacity.
However, prior to this, in 1959, Lloyd and Margaret Peterson wanted to investigate the duration of the short-term memory through a laboratory experiment. During this period, the separate stores had not been identified, memory was simply seen as short- and long-term memory.
- We will start with a brief recap of the short-term retention meaning.
- After this, we will shift our focus to learn about the Peterson and Peterson (1959) study; this will also cover the method used and Peterson and Peterson's results and conclusions that were found.
- We will finish off with the evaluation of Peterson and Peterson (1959).
The short-term memory system has a limited capacity, freepik.com
Short-term retention – meaning
Short-term memory (STM) is a temporary store that can hold a limited amount of information for a short period.
Short-term retention refers to how long the short-term memory store can hold information.
The STM store needs to retain the memories for long enough so that they can be elaborately rehearsed and moved to the long-term memory (LTM) store. When trying to recall memories stored in the LTM; the information has to first be moved and retained in the STM store.
If you learn something new in class one day, your retention of the information relies on your ability to absorb and retain it. You may remember it for the rest of the day, and then have to revisit the information later in the year. You are refreshing your memory by retrieving the information back into the short-term memory.
Short-term retention can be affected by many factors, such as motivation levels, concentration, injury, and use of social media. As more is discovered about what influences memory, ways to improve our memory have been developed.
Peterson and Peterson (1959)
The aim of the Peterson and Peterson (1959) experiment was to test the duration of STM.
Peterson and Peterson Procedure
The sample pool for the experiment involved 24 psychology students, and the experiment took place in a lab setting.
Trigrams are a material used in psychology research that essentially involves showing participants a combination of three letters that make no logical sense when combined. LTG and BZL are examples of trigrams that may have been used in the study.
The distraction task involves counting backwards in threes or fours from a random number selected by the researcher. The point of this was to prevent the information from being rehearsed and moved to the LTM store.
After completing the distraction task, participants were instructed to recall the trigrams.
A series of trials took place which required participants to recall each after either 3, 6. 9, 12, 15 or 18 seconds for each trigram.
The independent variable was the interval of time between hearing the trigrams and the participant sayings the trigrams (e.g., 3, 6, 9, 12, 15, 18 seconds) and the dependent variable was how accurate the trigrams were recalled.
Remember that the independent variable is the characteristic of the experiment which is manipulated by the researcher, whereas the dependent variable is the one that is being measured in the experiment.
Peterson and Peterson Results
The results of the experiment revealed a trend: the longer that each student had to count backwards (the distraction task), the less accurate they could recall the trigrams.
- 80% of the trigrams were recalled correctly after 3 seconds.
- This fell to 50% after 6 seconds.
- Less than 10% were recalled accurately after an 18-second delay.
The graph shows that participants recalled the trigrams less accurately throughout the time-interval, StudySmarter Original
Peterson and Peterson Conclusion
The study's results indicate that when rehearsal is prevented. As participants more or less could not recall the trigrams after 18 seconds, it can be assumed that the short-term memory has a limited duration of around 18 seconds.
If we are unable to rehearse information, it cannot be passed into the long-term memory, which supports the foundation of the multi-store memory. Information is then lost from the short-term memory through trace decay if there is no rehearsal.
Evaluation of Peterson and Peterson (1959)
Let's discuss the advantages and disadvantages of the Peterson and Peterson (1959) short-term retention study!
Advantages
Use of distraction task: this ensures that the study was measuring what it intended to, the duration of the STM store and not the LTM store. From this, it can be deduced that the study had high internal validity.
Disadvantages
Unable to generalise: The sample pool used for the experiment was a group of 24 psychology students. They all have a similar level of intelligence and are most likely of similar age. When a small sample is used, then it is unlikely to be representative of the wider population, and therefore it is difficult to generalise the Peterson and Peterson results.
Short-term Retention - Key takeaways
- Short-term memory (STM) is a temporary store that can hold a limited amount of information for a short period.
- Short-term retention refers to how long the short-term memory store can hold information.
- The aim of the Peterson and Peterson (1959) experiment was to test the duration of the short-term memory.
- The Peterson and Peterson results revealed that the longer that each student had to complete a distraction task, the less accurate they would be able to recall the trigram.
- As participants more or less could not recall the trigrams after 18 seconds, it can be assumed that the short-term memory has a limited duration of around 18 seconds.
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