Short Term Memory
Introduction
Cognitive psychology refers to the scientific study of the processes associated with knowing or the various mental activities. These processes include the acquisition, storing, and use of knowledge at various levels. The field of cognitive psychology covers the entire area of mental activities that are both taking place consciously or unconsciously. Such activities include acts of sensing, perceiving, learning, memory, reasoning, making decisions, and even the unconscious process of dreaming among other notable cognitive events taking at the mental level.
This paper will focus on the concept of memory and information retrieval in the human mind. Over a period, cognitive psychologists have learned that most mental processes that once appeared simple like detecting and responding to external stimuli, are in deed very complex, and sometimes still beyond proper scientific grasp. Ordinarily, the process of responding to stimuli takes fractions of seconds, but sometimes, the duration might be longer (Sternberg, 1969). The key question that remains unanswered is the major process that underpins information retrieval and the duration that they take.
The understanding of these process and the underlying factors will greatly improve the learning processes and detection of neurological malfunctions with no obvious expressions.
Origins of Cognitive psychology
According to Foley (2014), the origin of cognitive psychology dates back to the time of great philosophers such as Plato and Aristotle. The early philosophers wanted to associate a particular section of the body with the process of knowledge acquisition and storage. Most of them thought that knowledge was in the heart whereas others located it in the brain. There were questions on how one comes to know anything, represent information, or carry out the process of decision-making. In 1879 a German scientist, Wilhelm Wundt created the first psychological laboratory at the University of Leipzig in Germany where the first systematic study of psychology started. Wilhelm started by studying mental consciousness by asking people to report their mental processes as they undertook various tasks in their daily activities.
However, most scholars at the time were more concerned with behavioral psychology and most of the cognitive aspects did not receive proper attention for a time. Nevertheless, 1940s and 1950s marked a dramatic revival to the school of cognitive psychology with most scientists making pioneering demonstrations in matters of mental processes. Donald Hebb demonstrated that memory had a biological dimension while George Miller showed that there was a limit to the amount of information one could store in the short term memory (Foley, 2014). Moreover, the pioneering works of Noam Chomsky demonstrated that the process of language acquisition in children relied on certain complex, but internal processes that could extract meanings from the speeches and sounds from their surroundings. All these pioneering works served to stimulate a lot of interest in the study of cognitive psychology, particularly memory.
General Methods of Research
Like most other psychologists, Foley (2014) argues that cognitive psychologists employed several research methods to achieve some of the excellent objectives in their inquiry. Theses methods fall broadly into three basic parts. These include personal reports, measuring of reaction times, measuring of mental activities or other biological factors of importance. One of the important ways of acquiring data for cognitive psychology was through self-reports. Most cognitive psychologists relied entirely on themselves or other closer people for experiments. Most of the experiments took the form of pattern recognition, or recalling words from a list.
The Sternberg Experiment
Historical Factors, Motivations, and Previous Experiments
One of the key topics that have troubled psychologists is the nature of the processes that characterize the interval between stimuli detection and the onset of response. Most cognitive psychologists agree that this process has several stages whose execution directly depends on the success, and completion of the stages preceding it (Sternberg, 1969). Moreover, if this process of stimuli detection to reaction was composed of other components, then the total time one takes to react to a stimulus is the linear sum of the time each component occupying the interval called stimuli-response interval takes.
Experiments employing the use of reaction time dates back to the time Donders who formulated a treatise expanding on the nature of mental processes. Donders subtraction method aimed at isolating each stage of information retrieval in the human memory. The main aim was to study the inherent components that make up the stimuli detection-response interval.
With more researches coming up, several criticisms came against Donders’ use of subtraction method in understanding, and studying mental processes (Sternberg, 1969). Donders experiments of decomposing mental process into analytical stages relied greatly on two assumptions. The first assumption was that elimination or insertion of a stage in the discharge of a task does not affect the execution of other succeeding tasks. However, this was a weakness, as most psychologists argued that altering any particular stage of the mental process affects the other succeeding stages grossly. The second weakness was that the mean reaction times for similar tasks performed in different laboratories differed significantly. Many psychologists argued that the subjects to these experiments were not under proper control of the experimenter.
Theory and Method of Sternberg Experiment
The purpose of Sternberg’s experiment was to study the connection between reaction time and memory load. The method will involve presenting a short collection of items for memorization (Sternberg, 1969). The collection of items should be few enough to fall within the short-term memory. A subject will then have contact with an element; the subject should respond as fast as possible since measuring of reaction time takes place. A comparison of patterns in the reaction times against variation in the number of items in the collection presented follows. The ultimate goal is to determine the connection between reaction time, and the number of items in the collection presented, thus the tasks should be simple, and attract no error.
Sternberg’s experiment, involves very simple tasks. A person views a small collection of items, positive sets, to memorize. In the second stage, the person views one test item that may or may not belong to the original collection. The person should try to respond very fast using yes or no without making mistakes to the elements displayed stating whether they belong to the original set or not. This procedure requires repetition with the number of items varied considerably. An illustration of a sample of this experiment follows below:
Trial 1 Trial 2 Trial 3
Original set (in memory) 2, 5, 3 8, 4, 9, 2, 7 4, 2
Test element
(Is this in the original set) 5 6 4
Correct Response Yes No Yes (Sternberg, 1969).
In Sternberg’s experiment, the main idea is that reaction time increases with increase in the number of items in the collection presented. The experiment is open to individuals with average mental condition. The number of items in the original collection may vary to generate a longer curve. Each participant, however, generates a single curve. The overall experiment is very simple and requires no equipment.
Assumptions and Constraints
Sternberg’s experiment relies heavily on Donder’s theory of subtraction, the concept of insertion, and stage theory that preceded Donder’s experiments (Sternberg, 1969). Both the insertion, and stage theory have their inherent weaknesses, thus Sternberg’s experiment requires refinement in terms of the two theories that supports it. Moreover, the decision to keep elements in the sets at a maximum of six is arbitrary.
Summary of Results
The researcher records the responses and their corresponding time. For most individuals, these responses may be spontaneous; however, the reaction time for each of these differs significantly. The difference in time may be up to half a second, which illustrates that mental introspection may not be accurate. The major discovery that Sternberg made was that reaction time varies with the number of items in the original set. He experimented with original sets containing items ranging from one to six and noted that the reaction time varied according to the elements in the original set.
The major theories and hypothesis in Sternberg’s experiment hold. This is true since an increase in set size increases the reaction time. The reaction time for a set with single item was half a second while that with six items, the reaction time was almost a whole second. Accurate measurements using milliseconds, however, showed that, for every increase in one item in the original set, there was an increase of a bout 40milliseconds in the reaction time (Sternberg, 1969). This implied that any response to a test item required some sort of search in the short-term memory. For a response to occur, one has to compare the test item with every member of the original set in the memory. For a single item in the original set, the response is almost very fast, but for six items, the decision-making time takes longer.
The second discovery was that the mean reaction time for the yes and no responses were nearly the same. For a while, this appeared to negate the idea of searching through some list of items. If an item is in the list, the brain automatically stops after identifying it. Nevertheless, if not, the search goes to the end. This complete search for items not in the original set ensures that actually the item does not occur in the original set by omission. Sternberg explained the approximately equal mean reaction times for yes and no responses using the notion that all the mental searches automatically go to the end for items that are in the original set, and those that are not (Sternberg, 1969). This notion justifies the equal reaction times for both no and yes responses. This second discovery illustrates Sternberg’s ability to observe mental processes, which are not subject to direct observation.
Implications of Sternberg’s Experiment to Future Research
The curves that originate from Sternberg’s results show an increase in the reaction time with increase in the number of elements in the original set presented to the subject (Sternberg, 1969). This rule holds up to six items or fewer as used by Sternberg. Moreover, through extrapolation, one can easily predict the behavior of reaction time with increasing number of element in the set administered. However, in real life, the number of elements in the set cannot increase without bound. Otherwise, reaction time, theoretically, will increase without bound. For practical purposes, there must be an upper bound to the number of elements in the original set. This upper boundary in the number of elements in the original set constitutes the maximum short memory capacity. This requires further research.
Applications of the Sternberg Experiment
There are several applications of Sternberg Experiment. In very recent studies, the experiment assisted in the study of the effect of exposure to harmful chemicals. A sample of factory employees who had traces of harmful mercury in their urine took the tests designed from the Sternberg experiment. The researchers reached a conclusion that the exposure to elements of harmful mercury greatly affected the process of memory search (Sternberg, 1969). In other related studies, some workers had exposure to some harmful solvents in the workplace. The Sternberg Experiment provided a firm basis for evaluating the effects of these chemical exposures to the working memory of workers in question even in the absence of observable damages. Moreover, in the clinical studies, the Sternberg Experiments provides the best evidence for neurological damages resulting from exposure to toxic chemicals even in the absence of observable disturbances in the patients.
Recent Studies in Short Term Memory
There has been continued research in the field of short-term memory. However, the recent researchers rely on the current state of technological advances with most experiments carried out using computer programs (Alvarez & Gavangh, 2008). Experiments that are more recent have focused not only on the ability to retrieve information from the short-term memory, but also on its capacity, which Sternberg never addressed. Furthermore, some studies postulate that there are separate parts of the short-term memory for storing visuals, and verbal materials. Alvarez and Gavangh (2008) wanted to demonstrate the relationship between the capacity of short-term memory and visual information load or number of objects. Cognitive psychologists agree that short-term memory can store a limited number of objects. Sternberg considered this same factor in designing his experiment. Sternberg must have realized that the capacity of short-term memory is limited, and thus created simple sets with fewer numbers of elements, in fact six or less. However, instead of using the simple mathematical objects, this research paper uses complex visuals from shapes, and Macintosh computer to present the shapes to the person taking the experiment. To factor in the cultural dimensions, the study even uses the characters from the Chinese letter system. This offers the study the multi-cultural applicability, and universality that it requires.
In close connection to Sternberg Experiment, this study connects the rate of search to the load of information in the memory. In conclusion, it establishes that with more information load in the memory, the time for search increases, just as in Sternberg Experiment (Alvarez & Gavangh, 2008). Finally, the study establishes the long held thought that short memory can hold a maximum of five objects. However, they argue, the more complex the objects are, the fewer is the number of objects that can be stored. The number stored reduces with complexity of the object.
Conclusion
From the earlier experiment by Saul Sternberg, more concern was on the retrieval time and not on the capacity of the short-term memory. Moreover, Sternberg wanted to provide a manner of observing invisible mental activities. With more advances in the field of technology, there are several ways of monitoring mental activities such computer tomography, and magnetic resonance imaging methods among others. Thus, the use of technology has greatly furthered the cognitive studies and memory in particular. Sternberg decided not to use a set with more than six elements. This directly points to his intuitive thought that the capacity of working memory is limited (Noah, 2008). Studies that are more recent have confirmed Sternberg’s fears by asserting that the short-term memory can only accommodate seven objects with an error of two objects.
References
Sternberg, S. (1969) Memory-scanning: Mental processes revealed by reaction-time experiments. American Scientist vol.57, 421-457.
Alvarez, G. & Gavangh, P. (2008). The capacity of visual short-term memory is set both by visual information load and by number of objects. New York, NY: Harvard University Press.
Foley, A. (2014). Introduction to cognitive psychology. Retrieved from http://www.mrrena.com/misc/cognitive_psychology.php.
Noah, B. (2008). New research on short-term memory. New York, NY: Nova Biomedical Books Publishers.
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