Short Term Memory
Short-term memory was sometimes referred to as "primary," "working," or "active" memory, was said to hold a small amount of information for about 20 seconds. Short-term memory can also be described as the capacity for holding a small amount of information in mind in an active, readily available state. The information held in short-term memory may be recently processed sensory input or items recently retrieved from long-term memory or the result of recent mental processing The most important characteristic of a short-term store was that it retains information for a limited amount of time only. Most definitions of short-term memory limit the duration of storage to less than a minute, and in some models as little as 2 seconds.
The Brown-Peterson’s paradigm developed by Brown in 1958 and the Petersons in 1959 tested two hypotheses in what caused forgetting in Short-term memory (STM). The interference theory suggested that the cause of forgetting was the entry of other items into STM. It claimed that strength of information already in STM weaken as new items enters. The decay theory was associated with the length of time in which the information remained in STM; the longer the passage of time, the probability of correct recalling was reduced. In other words, it tested the effects of interference and time limit of STM.
The Brown-Peterson’s paradigm made use of the distracter task to prevent its subjects from rehearsing the letters. When experimented with the paradigm, the subjects had to memorize three short words that were written on an index card for a variable delay with the inclusion of an interfering task. The subjects would hear a three digit number and from there they count the number by three for a period of time. At the end of the interval, subjects were asked to recall the items. Findings suggested that the recall was quite accurate at the short retention intervals but drops rapidly, when the retention interval was approximately 15 to 25 seconds.
Methods
With regards to the Brown Peterson Paradigm, an experiment was conducted using a slightly modified version of the paradigm. The experiment was conducted using 99 participants in
The experiment was conducted to test two hypotheses. Hypothesis number one was that “practice makes perfect” and hypothesis number two was hypothesized as “Fatigue when performing task twice”. In other words, the result should indicate an improved and more accurate result at Time 2 than Time 1 in hypothesis one. On the other hand, hypothesis two should indicate a more accurate result or performance in Time 1 than in Time 2
Results
Table 1
| Repetition Delay | Mean | Std Error |
| 1 1 | 79.628 | 2.066 |
| 2 | 81.818 | 1.870 |
| 3 | 82.390 | 2.166 |
| 2 1 | 92.120 | 1.388 |
| 2 | 90.679 | 1.319 |
| 3 | 87.317 | 1.554 |
The results of Delay experiment, as from above showed, argued in favor of the Brown Peterson Paradigm. The standard error went up as time of delay lengthens. Therefore, conclusion was that the participants were not able to recall as efficiently as time of delay increased from 1 second to 20 seconds.
Table 2
| (I)Delay (J)Delay | Mean Difference (I-J) | Std Error |
| 1 2 | -2.190 | 2.483 |
| 3 | -2.762 | 2.723 |
| 2 1 | 2.190 | 2.483 |
| 3 | -.572 | 2.387 |
| 3 1 | 2.762 | 2.723 |
| 2 | .572 | 2.387 |
Table 3
| (I)Delay (J)Delay | Mean Difference (I-J) | Std Error |
| 1 2 | 1.440 | 1.730 |
| 3 | 4.803 | 1.830 |
| 2 1 | -1.440 | 1.730 |
| 3 | 3.363 | 1.532 |
| 3 1 | -4.803 | 1.830 |
| 2 | -3.363 | 1.532 |
Comparison between Time 1 and Time 2 showed a drop in mean difference and improved standard error. The subjects had actually performed better when tested the second time. The result therefore did not comply with the hypothesis of “Fatigue when performing the task twice”. In other word, it showed a more accurate result or performance in Time 2 than in Time 1, proving that practice do make perfect. Repetition had actually produced better performance or results.
Discussion
Findings from the experiments suggested that time and exposure to a task can affect STM. Repeated exposure to a task can improve a person’s STM, shown in the experiments, was also proven by
Although it was shown that STM was limited by duration of retaining, methods such as chunking can also increase a person’s ability to recall. Ericsson et. al. demonstrated in 1980 that a person was able to increase their recalling ability through the use of chunking. For example, in recalling a phone number, the person usually chunks the digits into three groups. First, the area code (such as 814), then a three-digit chunk (123) and lastly a four-digit chunk (4567). In
Miller, in 1956, summarized evidence that people can remember about 7 chunks in short-term memory tasks. However, that number was meant more as a rough estimate than a real capacity limit. Others have since suggested that there was a more precise capacity limit, but that was only 3 to 5 chunks.
Research by Baddeley et. al. in 1975 had shown that seven number was roughly accurate for college students recalling lists of digits, but memory span varies widely with populations tested and with material. The ability to recall words in order depends on a number of characteristics of the words. Fewer words can be recalled when the words have longer spoken duration.
The working memory model that was developed by Baddeley and Hitch in 1974 led them to propose that the memory we use when working on a task was divided into 2 areas, the visual or acoustic. Visuo-spatial sketch pad deals with visual material and phonological loop deals with auditory material.
When their speech sounds are similar to each other; this is called the phonological similarity effect (Conrad and Hull, 1964). More words can be recalled when the words are highly familiar and/or occur frequently in the language (Pointer and Saint-Aubin, 1996); recall performance is also better when all of the words in a list are taken from a single semantic category (such as sports) than when the words are taken from different categories (Pointer and Saint-Aubin, 1995).
The key concept associated with a short-term memory was that it had a finite capacity, with a time of not more than 30s to the estimates of about 9 varying elements. The average person may only retain about 7±2 different units in his or her short term memory, to be able to improve STM, various methods of techniques had to be applied. The limits to an individual had to really depend on the various situation factors and their conditions. Therefore, general conclusions about STM can rarely be made.
