Effect of Auditory and Visual Stimulus on Short-term Memory

Abstract:

The experiment was conducted to investigate the effectiveness between auditory and visual stimuli on short-term memory for learning purposes. 50 subjects were assigned to receive auditory stimulus while another 50 were assigned to receive visual stimulus. After a 4-minute filler task, 1 minute was given to the subjects to recall the passage given. The subjects were tested on their abilities to answer the memory quiz given based on the passage. A z-test was done and that led to the rejection of the null hypothesis. The results showed that the mean memory quiz score for visual memory is 11.36 while the mean memory quiz score for auditory memory is 6.86, concurring with the experimental hypothesis.

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Experimental Hypothesis:

The scores for those who receive visual stimulus will be higher than the scores of those who receive auditory stimulus.

Null Hypothesis:

There will be no significant difference in the scores for both auditory and visual memory as the mean scores for both stimuli are equal.

Research and Rationale:

The objective of this experiment is to investigate the effectiveness between auditory and visual stimulus on short-term memory for learning purposes.

Memory is a neuroplastic process as it deals with the ability of the brain to change its function in response to experience. Memory deals with the ways the changes are stored and subsequently reactivated and retrieved.[1]

The hippocampus plays an integral role in memory. It organizes the formation of the memory image, also known as the engram. The engram is distributed throughout the cerebral cortex, especially in the temporal lobe. It does not lie in the hippocampus. Evidence suggests that the temporary memory storage system is located in the hippocampus while the long-term store is most probably distributed through the cerebral cortex.[2]

Figure 1: The hippocampus gathers incoming information, analyses and organizes it. After that, it sends the information out for storage in the cortex.[2]

Observations are made on humans in whom the hippocampus on each side has been destroyed. Memory loss is experienced for those who have undergone neurosurgical removal of the temporal lobe. This is a treatment for temporal lobe epilepsy. However, if both hippocampi are destroyed, the effect is devastating. The subject no longer has the ability to lay down any record of his experiences even in the recent past.[2]

When something is to be remembered, the memory mechanism involves at least two stages. They are namely the short-term memory, which is a mechanism of information retention for a few minutes and the long-term memory.[2] The retention interval is the period between encoding and retrieval of the memory.[6] Organisation or manipulation of the material held in memory is not entailed for short-term memory.[8] During the few minutes of retention, the information can be consolidated into long-term memory. This is a mechanism to retain information for long periods, sometimes for the remainder of the subject’s life. NMDA receptors and protein synthesis are entailed for the consolidation process.[15] In addition, the transfer of information from the temporary store to long-term store is powerfully promoted by emotional factors.[2]

Evidences show that short-term memory is based on activity in reverberating neuronal circuits. By contrast, long-term memory requires an increase in synaptic efficacy. This may be attained if the synapses grow larger or by some intracellular structural changes in the synaptic regions in the neurons storing the information. To identify the particular structures of the brain related to memory, precise lesions have to be performed in these various structures.[2]

According to the Hebb’s theory, the memories of experiences are stored in the short term by neural activity circulating in closed circuits. These reverberating patterns of the neural activity are vulnerable to disruption. Yet, eventually, they induce structural changes in the involved synapses which proved stable long-term storage.[1] Research suggests that short-term memory is more resistant to extinction than long-term memory.[15] It is said that each time a memory is retrieved from the long-term storage, it is temporarily held in the changeable and unstable short-term memory. Before it is consolidated, the memory is once again susceptible to posttraumatic amnesia.[1] It affects the dynamics of the brain so that sensory feature analysis systems found in different parts of the brain interact with each other.[16]

The mechanism involved in the induction and maintenance of the hippocampus are believed to underlie the fundamental properties of memory and learning. At synapses that exhibit long-term potentiation, the neurotransmitter is glutamate and NMDA type postsynaptic receptors are present. NMDA antagonists block the long-term potentiation. A strong depolarisation of the postsynaptic cell is necessary to unveil the NMDA-operated channels. The simplest way is by activating multiple inputs to the cell. If the postsynaptic element is prevented from depolarisation by a polarising current applied during the period of rapidly repeated stimulation, long-term potentiation can be prevented. The NMDA-operated channels must be activated for this potentiation to be established.[2]

Figure 2: The Baddeley & Hitch model of memory, proposed in 1974.[7] Working memory is the system that is responsible for holding and manipulating information when a wide range of tasks such as reasoning, understanding and learning is performed.[12]

The central executive coordinates the operation of two subsidiary slave systems, the phonological loop deals with speech based information while the sketchpad handles visuo-spatial information. The most important function of the executive processes has to be of selective attention, which is defined as the capacity to focus attention on a stream of information and shutting out irrelevant materials concurrently. It is responsible for the attention control of working memory.[13]

Figure 3: The two primary pathways, namely the dorsal stream (green) and ventral stream (purple), are shown to originate from the primary visual cortex.[9] On the right diagram, the region highlighted in magenta is the primary auditory cortex.[10] Visual stimuli are processed in the visual cortex. It is located in the occipital lobe, which is at the back of the brain.[9] Auditory (sound) information, on the other hand, is processed in the primary auditory cortex in the temporal lobe.[10]

There has been an extensive study by Cohen et al. on the inferiority of auditory recognition memory to visual recognition memory. The subjects in the study were asked to label stimuli received as old or new. Some of the subjects received stimuli in the form of sound clips alone, some through verbal descriptions alone while some received stimuli through matching pictures alone. In addition, some received pairings between pictures and sound clips while the rest received sound clips paired with their respective verbal descriptions. It was found that memory for pictures was significantly better than the rest of the stimuli provided and no notable differences were observed from the remaining conditions. Hence, it is proven than auditory recognition memory is indeed inferior to visual recognition memory.[14]

Furthermore, another study led by Michael A. Cohen in 2011 demonstrated that musicians are equipped with superior auditory recognition memory for both musical and non-musical stimuli as compared to non-musicians. Nevertheless, this advantage did not generalise the visual domain. A number of studies showed that musicians usually outperform non-musicians. In this recent study, the subjects which comprised of both musicians and non-musicians were tested on their auditory and visual memory, using visual objects, familiar music and spoken English. For both groups, visual memory was markedly better than auditory memory. Even though musicians generally have better musical and non-musical auditory memory, the ability to remember sounds is not increased to the levels for visual stimuli. This suggests that the visual domain has a persistent advantage and a fundamental capacity difference exists between auditory and visual recognition memory.[18]

The results from this investigation could assist educators on a better approach to teach students generally. Short-term memory is vital in classrooms as students will need to remember the lesson in order to have a better understanding on the lesson. Sometimes, educators have to skim through the lessons as they have to finish the entire syllabus within a specific period of time. Due to this time constraints, the lessons will be carried out relatively quickly, leaving the students with even less time to understand the lesson. The best teaching style, be it one that relies on auditory or visual stimulus, will enhance the students’ short-term memory and their capabilities to subsequently recall the facts taught during the lessons. In short, educators can decide on which method is more effective in aiding the students to remember better and consequently, understand and learn better. This investigation is carried out to determine which type of teaching approach is more beneficial to the students.

Planning:

Trial 1: Words or Passage

This trial was designed to determine whether subjects should be tested on their capabilities to remember words specifically or main points and the overall content of a certain passage. Even so, the answers for the memory quiz using a passage were all of one word. A group of ten was given 15 words to memorise while another ten were given a short passage to read. Both of the stimuli given were visual and not auditory. After 2 minutes, both groups were required to do a 4-minute filler task which comprised of simple mathematical problems. Then, the first group was asked to write down what they remember while the second group was required to answer a set of questions.

Type of Test

Mean

Words

13

Passage

11

Table 1: The results for the first trial using visual stimulus

The same trial was repeated, substituting visual stimulus with auditory stimulus. Similarly, one group was required to listen to 15 words while the other group was asked to listen to a short passage. After the 4-minute filler task, the subjects were asked to do the same questions as their counterparts during the trial above.

Type of Test

Mean

Words

10

Passage

6

Table 2: The results for the first trial using auditory stimulus

A trend can be observed whereby most subjects tend to remember words at the beginning and at the end of the list more quickly and more efficiently than the ones in the middle. Psychologists link these phenomena to primacy and recency.[3] The primacy effect is a cognitive bias that results from the disproportionate salience of initial stimuli while the recency effect is the cognitive bias whereby there is a disproportionate salience of recent stimuli.[5] This can be used to explain the consistently high scores for the test that only requires subjects to remember words. Hence, it was decided that a suitably short passage of 580 words would be used to prevent the subjects from repeating words at the beginning and at the end of the list as the answers might not be from the those parts of the passage.

Trial 2: Recall versus Recognition

This trial was done to determine if a memory quiz that tests the subjects to recall is more efficient as compared to recognition or otherwise. After spending 2 minutes with the passage, the subjects were asked to do a 4-minute filler task. They were then given multiple choice questions to test them on their abilities to recall. The trial was again repeated, replacing the visual stimulus with an auditory stimulus. The results for both groups on their capabilities to recall was recorded and analysed.

Type of Stimulus

Mean

Visual

15

Auditory

14

Table 3: The results of the second trial for visual and auditory stimulus

Almost all of the subjects managed to get the perfect score during this trial. This seems to show that providing multiple choice questions to the subjects is perhaps not an accurate way to gauge a person’s short-term-memory. The subjects were given an option to guess if they forgot the actual answer and might turn out to get the right answer if they were lucky. It was however noted that a stronger contrast might have been observed if more questions were given. Still, it was finally decided that recognition would be used as my method of conducting the experiment. This way, the subjects would not have the chance to guess and a stark contrast could still be observed from the 15 questions asked.

Trial 3: Duration of Filler Task

This trial was conducted to determine the suitable duration for the filler task to be carried out. The decision had long been made to have a filler task as I would like to provide distractions to prevent the subjects from rehearsing pieces of information in their mind without converting them into short-term memory. The subjects were asked to perform a filler task which consists of simple mathematical questions after spending 2 minutes with the passage given to them.

Duration of Filler Task (minutes)

Mean

2

12

3

11

4

11

5

8

Table 4: The results of the third trial for visual stimulus

This trial was only carried out on subjects who received visual stimuli only. I made an assumption that the effects of the duration of the filler task would be similar as to that of the subjects receiving auditory stimuli. It could be observed from the results above that the mean for the score was relatively constant when the duration of the filler task was from 2 minutes to 4 minutes. A sharp drop was seen when the subjects were required to perform a 5-minute filler task. Thus, I decided to use 4 minutes as the duration for my filler task. It seemed to be long enough to distract the subjects from rehearsing the information but not too long to an extent of causing a conspicuous decay in memory as there was a sharp drop in the mean obtained from the 5-minute filler task trial. The filler task given was a set of simple mathematical questions. Distractions of other sorts such as answering IQ questions were considered at first but rejected later. This was because these questions might be too strenuous for the subjects to handle and might provide too much distraction to the subjects.

Experimental Method:

100 subjects were randomly chosen from a college. They were then divided into two groups of 50. One group was assigned to receive visual stimulus while the other group was assigned to receive auditory stimulus.

At the very beginning of the experiment, the subjects who were going to receive visual stimulus were given three sheets of paper, namely a short passage, the memory quiz which comprises of 15 questions and the mathematical questions intended as a distraction. Their counterparts who would be receiving auditory stimulus were given the exact same materials, however, without the passage.

The first group which received only visual stimulus was asked to only read through the passage once.

The second group which received only auditory stimulus was asked to put on the headphones connected to the computers prepared and to listen to the recording attentively.

The subjects were given another 1 minute as they tried to commit the new pieces of information into short-term memory.

The subjects were then left in a room as the test commenced.

After receiving their respective stimuli, the subjects were required to perform the 4-minute filler task to prevent rehearsal from occurring.

The subjects were then asked to start answering the memory quiz after the 4-minute filler task.

The papers were all collected and the scores obtained by the subjects were recorded and tabulated.

Risk Assessment:

Generally, the entire experiment is rated low-risk. The experiment was conducted in a bright room. Hence, it would be very unlikely to cause any impairment to the subject’s vision. Furthermore, the volume of the recording played over was adjusted to an appropriate level to prevent any impairment of the subjects’ hearing. The subjects were asked to sign consent forms stating that they understood that their results would be used in my scientific investigation. To be fair to them, I preserved the confidentiality of the subjects by keeping their results anonymous. As a precautionary measure, I informed the subjects that the memory quiz was never intended as a way to measure intelligence or the capability of a person’s memory. This was vital as I did not want my subjects to feel any unnecessary stress. In any case, subjects who felt unwell or were unwilling to cooperate were given the choice to withdraw from the experiment.

Observing and Recording:
Results:
Memory quiz scores, x
Visual
Auditory

0

0

0

1

0

0

2

0

0

3

0

0

4

0

4

5

0

10

6

0

14

7

0

9

8

2

4

9

6

3

10

9

2

11

12

2

12

7

0

13

6

0

14

6

1

15

2

1

Total
50
50

Table 5: The results of the memory quiz for visual and auditory stimulus

Interpreting and Evaluation:

The z-test was used to analyse the data statistically. The z-test is used when the sample size is large and when the distribution of the test statistic under the null hypothesis can be approximated by a normal distribution. Since there were 50 samples for each group, the z-test, an extension of a t-test, was chosen.[11]

Number of Samples, n
Mean,
Standard Deviation, I?
Visual, X1

50

11.36

1.797331355

Auditory, X2

50

6.86

2.315253766

Table 6: The basic statistics for the memory quiz scores of visual and auditory stimulus

Hypothesis Test for Two Population Means

H0: I?1 = I?2 (There will be no significant difference in the scores for both auditory and visual memory as the mean scores for both stimuli are equal.)

H1: I?1 > I?2 (The scores for those who receive visual stimulus will be higher than the scores of those who receive auditory stimulus.)

Given the null hypothesis and I?1 = 1.797331355, n1 = 50, I?2 = 2.315253766, n2 = 50

xI„1 – xI„2 ~ N (0, + )

By Central Limit Theorem, the test statistics is:

Z =

According to H0, I?1 = I?2, then in this case I?visual = I?auditory and thus,

Z =

= 10.8562719

a‰? 10.856

According to the Table for the Percentage points of the normal distribution, the 5% (one-tailed) critical value for Z is z = 1.6449. If the calculated value is smaller than the critical value, the null hypothesis, H0 is accepted. However, the calculated z-value is 10.856, which is far greater than the critical value. Therefore, H0 is rejected and the experimental hypothesis, H1 is accepted. There is enough statistical evidence showing that the mean score in memory quiz for those who receive visual stimuli is higher than that for those who receive auditory stimuli.

Graph 1: Comparison between the memory quiz scores for visual and auditory stimulus

Graph 2: Graph showing the comparison between visual and auditory memory in the higher range (Memory quiz score is at least 10). Error Bars using Standard Error are displayed.

Data Analysis:

It is clearly shown for graph 1 that subjects under the visual memory group generally score higher than the subjects under the auditory memory group. This statement is indicated as the memory scores for the visual memory group range from 8 to 15 while the scores for the auditory memory group range from 4 to 15. The mode, which is the memory quiz score with the highest frequency, is 11 for the visual memory group and 6 for the auditory memory group. This depicts that subjects under the visual memory group perform better than their counterparts under the auditory memory group, thus consolidating the theory that visual stimulus is more superior to auditory stimulus on short-term memory.

Under the auditory memory group, no subjects scored higher 13 except for two students, with one scoring 14 while the other getting all the answers correct. These two results are considered as anomalous as most students in their group only managed to score 6 out of 15. They probably have better capabilities to remember the recording, thus aiding them in the memory quiz. Besides, there is also the possibility that they are good listeners and can understand the recording much better compared to the rest of the group. The memory quiz scores for the auditory memory group are normally distributed if the anomalous values are ignored. No notable anomalous results were obtained from the visual memory group. The memory quiz scores for the visual memory group can be said to be normally distributed as a distinct “bell”-shaped is observed.

Graph 2 shows that only a very small number of subjects who received auditory stimulus scored at least 10 out of 15. Only 6 students managed to score at least 10 out of the 15 in the quiz. In terms of percentage, only 12% of the subjects using auditory memory score obtained results of the higher range. On the other hand, 42 out of 50 subjects who received visual stimulus scored at least 10 out of 15, accounting for 84% of those who were assigned with the visual stimulus. Basically, it is shown in graph 2 that visual memory is superior to auditory memory. The difference in percentage between those who scored at least 10 using visual memory and those who used auditory memory is 72%.

There are two explanations behind the superiority of visual recognition memory to auditory recognition memory. Fundamentally, visual objects are different from auditory objects. In their physics or psychophysics, they seem to be more memorable than their auditory counterparts. The other explanation states that visual memory is fundamentally different or bigger than auditory memory. Generally, there may be the lack of capability to remember more than a few auditory objects regardless of how memorable they are, if they are presented one after another in rapid succession. It is hence unlikely auditory objects to be remembered as accurately as visual objects by the same person tested.[14]

In addition, both visual and auditory stimuli are thought to be transformed into auditory subvocalizations.[17] In other words, auditory information will automatically enter the phonological loop if it is perceived and stored as memory. This is not the case for visually presented information as it is not directly stored and has to be first translated into auditory subvocalizations. Therefore, visually presented information may be stored twice, once as auditory code and once as visual code.

Hence, it will be wise to suggest using more visual stimulus to enhance learning among students. This is because the finding clearly proves that providing visual stimulus has a higher efficacy than providing auditory stimulus for learning purposes. Based on the investigation conducted, I strongly recommend educators, be it lecturers or teachers, to incorporate more visual stimulus in their lessons to aid students in remembering better. Relatively, relying on auditory stimulus is not that effective for the educators to convey information to their students.

Evaluation:

100 subjects were involved in this investigation and they were split into two groups of 50. The sample size was considered to be large. A large sample size is essential to increase the validity and reliability of the result as it can minimise the errors within the experiment. As the subjects were all chosen randomly using a random number generator, the subjects involved were considered to represent the A level students in the college. In addition, the subjects were randomly assigned to their respective groups and a consistency of gender was noted among the subjects.

To minimise errors, subjects that felt unwell or were unwilling to participate were replaced. This was again done using a random number generator to make sure that all the subjects in the investigation were randomly selected. All the subjects that were taken into consideration were generally healthy and cooperative throughout the entire investigation.

All of the subjects were of the same age. This is because memory can be variable with age as older people may have a marked reduced efficacy in their memory and may give anomalous results. I specifically made sure that all the subjects involved had band scores that were higher than 8.0 for their IELTS, especially in their listening and reading components. This was to ensure that the subjects had similar proficiencies in the English Language and could understand the article, regardless of whether they were to receive the auditory or visual stimuli. The article was narrated by a native speaker. The participants were debriefed after the experiment and it was found that no problems were encountered in terms of both the content and the narrator’s pronunciation. Subjects with optical aids were allowed to have them on as the inability to see clearly would definitely affect their performance. The experiment was held in a quiet room to avoid any sort of distractions that could affect the subjects from concentrating.

I am aware that this investigation is not free from limitations. However, modifications and several steps were taken to minimise the effects of the limitations on the results. It was impossible to control and determine how each subject chose to memorise the passage and the content. Different methods may have different efficiency in aiding the students to remember better and more. Hence, students who had exceptionally low or high scores were debriefed to find out if their techniques were the reason behind their scores.

An assumption was made that individual variations among all the subjects involved did not have any significant effect on the results of the study. This was because two groups of students were asked to do two different types of memory test. The rationale behind this decision was to test the subjects on the same information. The subjects involved were of the same age and were assumed to have similar learning capabilities as all of them were government-sponsored scholars from the same college.

In short, the results obtained are valid and reliable as there is a large sample size and the whole experiment is controlled with minimum degree of errors.

Further Work:

The subjects chosen may still not be able to represent all the students in the general population as they are all from the same college. Hence, to increase the validity of the results to a higher level, the investigation can be carried out at different colleges to obtain a bigger number of subjects. This will consequently enable the experimental hypothesis to be applied for more students in the general population. A more conclusive study can then be established due to the broader choice of subjects from other colleges.

In addition, the discrepancy between the mean scores for males and females in both memory tests can also be investigated. The memory storage ability between genders can be different and this may have an effect on the results obtained.

Evaluation of Sources:

I have selected a range of sources to aid me in my research. Sources 1, 2, 3 and 4 are books. They are all reviewed by other experts before they are published. Hence, the information found in these books is reliable.

Sources 5, 6, 7, 8, 9, 10 and 11 are all web-based. The information found is up to date as the website is always updated. Vandalism and the addition of false or redundant information are short-lived as any damages are repaired almost instantly.

Sources 12, 13, 14, 15, 16, 17 and 18 are journals. These journals are written by professionals who are highly accredited for their works in their respective fields. The journals contain high level of scientific credibility and have all undergone intensive reviews by equally recognised experts before being published. For example, source 14 is edited and reviewed by Anne Treisman, an expert who is currently in Princeton University.

Conclusion:

Thus, it is shown from this investigation that mean memory quiz score for the subjects who received visual stimulus is 11.36, which is significantly higher than the mean memory quiz score for those who received auditory stimulus, 6.86. The proposed experimental hypothesis is accepted as the z-value obtained is 10.856, way higher than the critical value at a 5% confidence level, 1.6449. A conclusion can hence be established that visual recognition memory is indeed superior to auditory recognition memory. Visual stimulus can definitely aid learning and information retention more efficiently than auditory stimulus.

Appendix 1:
Passage on Sleep[4]

Sleep is an alteration of consciousness during which there is decreased electrical activity in the cerebral cortex and from which a person can be aroused. Two main stages of sleep are non-REM and REM. REM is an acronym for rapid eye movement. During non-REM sleep, sometimes called normal sleep, metabolic rate decreases, breathing slows, and blood pressure decreases. Slower-frequency, higher-amplitude waves (theta and delta waves) are characteristic of non-REM sleep. This is electrical activity is thought to be generated spontaneously by the cerebral cortex when it is not driven by impulses from other parts of the brain.

Every 90 minutes or so, a sleeping person enters the REM stage for a time. During the stage (about 20% of total sleep time), the eyes move about rapidly beneath the closed but fluttering lids. Brain waves change to a desynchronized pattern. Everyone dreams, especially during REM sleep. PET scans of sleeping subjects indicate that during REM sleep, blood flow in the frontal lobes is reduced. In contrast, blood flow increases in areas that produce visual scenes and emotion. During REM sleep, neurons in the RAS release the neurotransmitter norepinephrine, which stimulates heightened activity in certain regions of the brain.

Using rats, researchers have demonstrated that stimulation of the preoptic nucleus of the hypothalamus results in non-REM sleep. The preoptic nucleus is located near the suprachiasmatic nucleus, the most important of the body’s biological clocks. The suprachiasmatic nucleus receives information about the duration of light and dark from the retina of the eye and apparently transmits this information to the preoptic nucleus.

Melatonin, a hormone released by the pineal gland, also plays a role in regulating the sleep-wake cycle. The suprachiasmatic nucleus signals the pineal gland above light and dark. This gland secretes up to 10 times as much melationin during darkness as during daylight. The fatigue and decreased physical and mental performance referred to as jet lag occur when we fly to a different time zone where the body is no longer synchronized with the light-dark cycle.

The raphe nuclei in the brain stem (lower pons and medulla) appear important in producing REM sleep. Many neurons that project from the raphe nuclei release serotonin, a neurotransmitter involved in sleep. After many hours of activity, the sl

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