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Effect of Chewing Gum on Working Memory Performance

Effect of Chewing Gum on Working Memory Performance

This experiment was designed to investigate the effect of chewing gum on working memory performance. A total of sixty subjects were divided two groups of thirty, namely the gum-chewing group and the no-gum group. They were required to read an article of 473 words within a time limit of 4 minutes. After that, they were asked to complete a memory quiz consisting of fifteen questions relating to the article and their scores were recorded. Subjects in the gum-chewing group chewed gum throughout the entire session whereas no chewing behaviour was performed by subjects in the no-gum group. It was found that the gum-chewing group achieved overall better performance in the memory quiz, with a mean score of 10.43; while the mean score for the no-gum group was 8.80. Statistical analysis using a z-test showed that the calculated z-value was higher than the critical value at 5% confidence level. This led to a supportive conclusion that chewing gum enhances working memory performance, concurring to the experimental hypothesis.

Null Hypothesis

There is no significant difference in the memory quiz scores for both the gum-chewing group and no-gum group.

Experimental Hypothesis

The mean memory quiz score for the gum-chewing group is higher compared to the no-gum group.

Research and Rationale

The aim of this experiment is to investigate the effect of chewing gum on working memory performance, thus evaluating whether chewing gum enhances working memory performance.

Memory is the ability to retain and recall information and past experiences in the human brain. It involves three processes: ¹

Encoding: Acquiring information and creating a memory trace

Storage : As a result of encoding, some information is stored within the memory

system for later use

Retrieval: Recovering or extracting stored information from the memory system

Figure 1: The Working Memory Model as proposed by Alan Baddeley. ²

Working memory refers to a system that enables temporary storage of the intermediate products of cognition and supports transformation of those products. It is critical in the performance of complex cognitive tasks that involve reasoning, comprehension and general learning – such as answering questions based on an article. ³

Alan Baddeley proposed a model of working memory as an alternative model of short term memory. He suggested that instead of all information going into one single store (as proposed by the multi-store model), there are different systems for different types of information (Figure 1).

Research identified that working memory involves the interaction of the prefrontal cortex with a network of other cerebral cortical areas in the brain. The prefrontal cortex that supports executive functions is highly activated during the encoding, retaining and retrieval of specific types of perceptual information. ⁴

Figure 2: The specific parts of the brain involved in memory. ⁵

A study by Takada and Miyamoto, 2004 revealed from functional magnetic resonance imaging (fMRI) that forebrain regions are being activated during gum chewing. Their results suggested that prefrontal cortex activation during mastication may contribute to higher cognitive information processing. ⁹

Figure 3: Activation revealed during gum chewing. Left and right sides represent left and right hemispheres, respectively. The centre represents an overhead view.

Wilkinson et al. provided the first evidence that chewing sugar-free gum can improve episodic memory and working memory. There was a significant effect on both immediate and delayed word recall, with more words being recalled in the chewing condition compared with the quiet control condition. ⁷ Results from Baker et al. supported the findings of Wilkinson et al. for word list learning.⁸

The main components of chewing gum include gum base, sweeteners, softeners, flavourings and colourings. The biggest difference between sugared gum and sugar-free gum is the sweetener used; where sugared gum primarily uses glucose whereas sugar-free gum uses sugar substitutes called polyols. Xylitol, sorbitol and maltitol are the most common types of polyols. ⁶ There is speculation that enhanced memory performance is due to the ingredients in the gum itself.

However, many studies ¹â° , ¹¹ that employed fairly sophisticated control conditions to prevent the possible influence of glucose, taste or odour; have indicated that improvement in certain cognitive functions is related to the act of mastication itself rather than being an effect of the caloric or nutritional value from gum sweeteners and additives.

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Dr Andrew Scholey (2004), of the human cognitive neuroscience unit at the University of Northumbria led a research study and found that people who chewed sugar-free gum throughout tests of both long-term and short-term memory produced significantly better scores than people who did not. The tests included questions relating to short-term memory, such as recalling words and pictures; and working memory, for example the ability to retain a person’s phone number. ¹â° For my investigation, the memory quiz score acquired by a subject will serve as an indication of his or her working memory performance.

The outcome from this investigation could benefit the process of learning as the idea of working memory is very important in acquiring knowledge. For instance, students could chew gum while studying to facilitate better retention. In a classroom setting, working memory is critical for students in remembering facts and important contents of a lesson. Hence, teachers could be advised to reverse school policies against chewing gum. Students might also be encouraged to chew gum during exams as this would lead to enhanced mental functioning associated with learning, thereby resulting in improved academic performance. The abovementioned could be quite practical as chewing gum is widely available and relatively affordable.


Several trial experiments were conducted to determine the suitability of the methods and to modify the investigational procedures. Different subjects were used in different trial experiments.

Trial 1: Length of Passage

This trial experiment was designed to find out the most appropriate length of passage to be used in the memory tests. A sample of twelve subjects was taken and they were divided into three groups of four each. The subjects in the first group were given a passage of 198 words, those in the second group given a passage containing 473 words and the remaining subjects in the third group given a passage of 874 words. All the passages were adapted from the same article which was going to be used in the actual investigation. After reading the passage once, the subjects were required to complete a memory quiz consisting of fifteen questions related to their respective passages.

Length of passage

Memory quiz performance of subjects in respective groups

Group 1

Group 2

Group 3

Mean score

Mean percentage


Mean score

Mean percentage


Mean score

Mean percentage











Table 1: Results of the first trial experiment.

Based on the trial results, it is shown that subjects in group 1 who studied the short passage of 198 words yielded almost perfect performance in the memory quiz. On the other hand, subjects in group 3 hardly answered half of the questions correctly. They complained that the given passage was too long and faced difficulty having to remember too much factual information. Hence, I decided to use the moderately long passage of 473 words so as to yield ideal results in the actual investigation.

Trial 2: Setting a Time Limit

This trial was done to determine the necessity of a time limit and thus the suitable duration for studying the passage. Three subjects were asked to read the given passage of 473 words while trying to commit important facts and figures to memory. The time taken for each subject to finish studying the passage once was recorded using a digital stopwatch.


Time taken to finish studying the passage once (minutes)







Table 2: Results of the second trial experiment.

The mean time taken to finish studying the passage once was 3.52 minutes. It is shown here that all the subjects managed to complete this reading task in less than 4 minutes. Thus, I decided to employ a time limit of 4 minutes in my actual investigation as it seemed sufficient, even for slower readers, to retain important details from the passage. Setting a time limit here is critical as it is a good guarantee of fairness in the leaning process.

On the other hand, I decided not to set a time limit during the memory quiz itself. This is to eliminate the factor of stress as subjects will be compelled to complete the quiz in a limited time frame. Without a time limit, the subjects can recall the information properly. Hence, optimum performance can be achieved and any possibility of unreliability can be reduced.

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Trial 3: Necessity of Filler task

The purpose of this trial is to determine whether a filler task is necessary after being presented with information before proceeding to the memory quiz. Four subjects took part in this trial, where two subjects were asked to perform a filler task consisting of simple mathematical problems and the remaining two without having to.


Mean memory quiz score

With filler task


Without filler task


Table 3: Results of the third trial experiment.

The results from this trial indicate that the mean memory quiz score of the subjects without the filler task was slightly higher and it was noted from the subjects’ answer sheets that the last few questions regarding the last part of the passage were answered correctly. Subjects will tend to recall better the last few pieces of information from the passage. Therefore, a filler task is required to reduce the recency effect. “The recency effect, in psychology, is a cognitive bias that results from disproportionate salience of recent stimuli or observations.”¹² Seven simple mathematical problems were chosen as filler tasks to distract the subjects temporarily and prevent rehearsal.

All the above trials were carried out while the subjects chewed gum, since I have assumed that the effect of the factors investigated are the same for both gum-chewing condition and no-gum condition; as suggested by the null hypothesis.

The chewing gum administered was Wrigley’s Extra White Sugar-free Gum – Peppermint. I chose to use sugar-free gum in my investigations so as to control for the possible influence of glucose. Glucose in sugared gum serves as a primary source of energy for the brain and it is proven that its availability influences psychological processes. Sugar-free gum is preferred over sugared gum as it doesn’t contribute to tooth decay and has a much lower calorific value. Moreover, most of the researches in documented scientific journals employed the use of sugar-free gum.

The administered one-page printed passage ¹âµ (Appendix) entitled “AFRICA” was acquired from the website This passage was chosen because it is clear, concise and contains a lot of information which can be asked in a memory quiz. In this particular investigation, fifteen simple questions (Appendix) predominantly about names and figures were designed and the answers could be readily obtained from the passage. This methodology was employed instead of simple words or image recall because this mimics the real life situation in a classroom or an exam setting where students are bound to either receive or recall a great deal of information in rapid succession.

The manipulated variable in this investigation is the action of gum-chewing while the memory quiz score is the responding variable. The constant variables in this investigation include the type of chewing gum administered, age of subjects, their level of education, the part of a day as well as the environmental conditions during the conduct of the investigation, and the proportion of gender in each group. All the tests were conducted in the morning in empty classrooms and the numbers of male and female subjects were equal in both gum-chewing group and no-gum group, specifically 15.

Experimental Method

A random sample of sixty subjects aged 20 was selected from the registered A-level students in my college using a random number generator. The subjects were divided into two groups of thirty, namely the gum-chewing group and the no-gum group.

All the subjects received three sheets of paper beforehand. One sheet contained the article, the other with the filler task of seven simple mathematical questions, and the last one with the memory quiz consisting of fifteen questions.

Each subject in the gum-chewing group was provided with a piece of sugar-free gum. Prior to undergoing the following procedures, they were required to chew the gum for a period of three minutes to allow the body to acclimatise.

Each subject was left alone and seated at a desk in a quiet classroom with fluorescent lighting.

Next, all the subjects in both groups received uniform instructions to carefully study the printed article within a time limit of 4 minutes and try to commit important information to memory. The gum-chewing subjects continued to chew gum in a constant and natural rhythm throughout the entire session until the end of the memory quiz. No chewing behaviour was performed by the subjects in the no-gum group.

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Immediately after that, the subjects were asked to complete the filler task.

After the retention interval, the subjects were required to do the memory quiz without a time limit.

The quiz papers were collected and the score for each subject from each group was recorded. The pieces of chewed gum were wrapped in tissue paper before being discarded into the bin.

Risk Assessment

Prior to the experiment, the subjects were informed that the memory test was not testing a person’s intelligence or memory power as would be done in a more complete memory test. This was to prevent unnecessary stress. The subjects were debriefed that the data would be used in a scientific investigation and informed consent was obtained so as to gain permission to use their results.

To preserve the confidentiality of the subjects, their results were kept anonymous. At the same time, they were also asked not to disclose any information regarding the test to anyone who had not taken it.

In any case, subjects experiencing any medical and dental problems; or suffer mint allergy were asked to withdraw. The risk of sorbitol inducing a laxative effect had been considered, but this is a very rare occurrence. All the subjects were strictly instructed not to swallow the piece of gum.

All in all, the experimental procedure was ranked low-risk.

Statistical Analysis and Interpretations

A z-test was employed to demonstrate the statistical data by testing the null hypothesis, which states that the two groups will have the same mean. It is a statistical test that compares between two means to determine whether there is a significant difference. The test is selected whereby the population standard deviation is known and normal distribution is applied. The sample size must also be large (n ≥ 30).

Number of samples, n

Mean, x̄

Standard deviation, σ

Gum-chewing group, X₁




No-gum group, Xâ‚‚




Table 5: The basic statistics for the memory quiz scores of both groups.

Hypothesis Test for Two Population Means

H0: μ1 = μ2 (The mean scores in both groups are equal)

H₁: μ1 > μ2 (The mean scores in the gum-chewing group is greater than that in the no-gum


Given the null hypothesis and σ₁ =2.201262264, n₁ =30, σ₂ =1.777638883, n₂ =30

x̄₁ – xÌ„â‚‚~N (0, + )

By Central Limit Theorem, the test statistics is:

Z =

Since under H0: μ1 = μ2 then in this case μgum-chewing = μno-gum and thus

Z =



According to the table for the Percentage Points of the Normal Distribution, the 5% (one-tailed) critical value for Z is z=1.6449 so this calculated value is significant. Z =3.1554 is higher than the critical value of 1.6449. The null hypothesis, H0 is rejected and the experimental hypothesis is accepted. This proves that the mean score in memory quiz for the gum-chewing group is higher than that for the no-gum group.

The z-test demonstrated that subjects who chewed gum at both learning and recall phases were associated with superior working memory compared to those in the no-gum group. At 5% probability level, the value of z=3.1554 was higher than the critical value of 1.6449. This indicates that the probability of the results of both groups being significantly different is more than 95%, with the mean of the gum-chewing group being greater than that of its counterpart. The probability that the results occurred by coincidence and chance is less than 5%. This supports the experimental hypothesis that chewing gum can enhance working memory, whereby the scores in memory quiz will be generally higher under gum-chewing conditions compared to no-gum conditions. This is broadly consistent with the findings of the aforementioned study done by Wilkinson et. al ⁷ and Scholey (2004) ¹â° .

Data Analysis and Evaluation

Graph 2 shows that the modes of the no-gum group and gum-chewing group are 9 and 10 respectively. It also illustrates that there was a greater number of people who could achieve a score of 11 and above in the gum-chewing group as compared to those in the no-gum group (15 versus 5). 2 people in the gum-chewing group attained a score of 14 in the memory quiz while there were none from the no-gum group. This clearly suggests that chewing gum had some effect in the improvement of their scores.

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However, in the gum-chewing group, there is one subject whose score is exceptionally low, which is 4. This anomalous result could probably be due to the subject being tired or sleep deprived. Besides, the subject might have felt stressed when placed alone in an empty classroom and hence performed below par.

Similarly, in the no-gum group, one subject achieved a score of 13 which is much greater than the mean score in that particular group. One possible reason for this anomaly is that the subject could be a much better learner than others so he could easily recall information from the passage.

As aforementioned in the study by Takada and Miyamoto, there is a possibility of activation of neural circuits shared by chewing and memory formation. Another study by Hirano et al. examined the effects of chewing gum (without odour and taste components) on neuronal activities in the brain during a working memory task using fMRI. There were increased blood-oxygen-level dependence (BOLD) signals in the prefrontal cortex, precuneus, thalamus, hippocampus and inferior parietal lobe during the tasks, thereby further suggesting that chewing gum may accelerate the process of working memory. ¹³

Another explanation is that chewing gum raises the heartbeat. According to both studies done by Wilkinson et al. ⁷ and Scholey (2004) ¹â°, the participants’ heart rates were significantly higher in the chewing condition than in quiet controls. This would have resulted in increased delivery of oxygen to the brain, thus leading to enhanced memory performance.

Additionally, chewing may promote the release of insulin which could influence memory via central mechanisms. “When you chew, the body releases insulin, which is probably a conditioned response that occurs in anticipation of a meal. We know the brain contains receptors for insulin, molecular docking points that bind onto the insulin molecule. Although their function isn’t well known, we know they are fairly densely packed in the hippocampus which is crucial for memory,” Scholey says.¹â´ Besides, the released insulin can also take up glucose in the blood to provide energy for the brain.


A large sample of 30 subjects for each group was taken, giving representative data which reduced the likelihood of inconsistent results and gave enough replicates to support the conclusion (ignoring the anomalies). In addition, the random process of selecting the subjects and assigning them to groups with consistency in sex differences helped to improve reliability.

All the subjects were of the same age, which is 20 years old. This is because aging could affect memory, as older people might have reduced effectiveness in their memory power. Furthermore, the subjects possessed the same level of education with a similar degree of English proficiency; hence able to understand the article well. As it appears that the effectiveness of learning could be variable throughout the day, all the tests were conducted in the morning only whereby the subjects were fresh in mind. The experiment was carried out in an empty classroom which provided a perfectly quiet environment, as distractions could have affected the subjects’ performance.

In order to minimise the degree of error, uncontrolled variables were kept to a minimum. For instance, subjects with less than 5 hours of sleep the night before were not considered for this investigation as lack of sleep could influence memory performance. All the subjects were ensured to have taken breakfast before participating in the memory test so that they had enough energy and alertness.

Consequently, the outcome of the experiment is considered valid and reliable.

Limitations and Modifications

There were a few limitations in this study. First of all, different individuals have varying memory power and capacity. The assumption made in this study is that the individual variations amongst the subjects between both groups did not affect the results of the study. The modification that could be made here is to have the same subject perform the memory test under both gum-chewing and no-gum conditions, provided that different testing materials are used. These materials must also then be closely similar in terms of length and information.

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Furthermore, it was impossible to control how each subject chose to memorise the information from the passage, as different techniques may have yielded different degrees of encoding into memory and thus producing different results. Some subjects who practised speed reading, or skimming and scanning for important information, had extra rehearsal time. The aim of the filler task was to prevent the effect of rehearsal; but in practice this would be very difficult to control. The subjects may be consciously or subconsciously repeating the information in their mind while performing the filler task.

In addition, the subjects may not represent the true population of general college-aged students although they selection of subjects was random. This is due to the limited availability of subjects, and they are only from one particular college. Thus, the investigation could be modified by employing a larger sample size which consists of subjects from other colleges.

Evaluation of Sources

I have selected a range of sources to be used in my research. Sources 1 and 3 are psychological texts by experts and are credible sources as their contents have been reviewed by other experts prior to publication.

Sources 7, 8, 9, 10, 11 and 13 are scientific journals that have a high level of scientific credibility, as they were written by well-known professionals in their respective field. These researches are cited by other sources, and this proves that their research must have been accepted by the scientific community and is very reliable.

Source 2 is a website written by an author who received a Master’s degree in Educational Psychology, thus the information can be trusted.

Source 4 is a helpful primer on the brain and nervous system, which serves as a basis to neuroscience. Its validity and reliability is ensured as it is published by the Society of Neuroscience, the world’s largest organization of scientists and physicians who study the brain and nervous system.

Source 5 is from Scholarpedia, a peer-reviewed open-access encyclopaedia written by scholars from all around the world. It could be regarded reliable as it is constantly updated from time to time.

Source 6 is considered accurate as it is a unique dental website contributed by professional and academic dentists.

Source 12 is a site written to provide an up-to-date, authoritative statement of knowledge, theory and practice in the psychology field; hence factual accuracy can be ensured.

Source 14 is an online newspaper article (BBC) with guaranteed validity.

Source 15 is a website that provides resources for free printable English worksheets, whereby the worksheets are continuously being tested and refined in a classroom setting in order to maximize their comprehensibility and fluidity.


There is evidence from my study that the performance under gum-chewing condition is significantly better than that under the no-gum condition, as it can be seen that the mean memory quiz score of 10.43 for the gum-chewing group is higher than that of 8.80 for the no-gum group. The z-value calculated from the statistical test, 3.1554, is higher than the critical value at 5% confidence level; therefore the experimental hypothesis proposed is accepted. This leads to a supportive conclusion that chewing gum enhances working memory performance.



Africa is the second-largest continent after Asia. It also has the second-largest population after Asia. About one billion people live in Africa. That is almost 15% of the world’s population. There are currently 54 countries on the continent of Africa, when including island countries and the Western Sahara. The number of countries sometimes changes because many of the countries were made by colonial powers. Colonial powers are countries that made colonies in Africa when it was first being discovered by outsiders.

There are about 2,000 different languages in Africa. Most of the languages belong to one of four large language groups. The four large language groups are Afro-Asiatic, Nilo-Saharan, Niger-Congo, and the Khoisan languages. People also speak some non-African languages in Africa. About 20% of the population speaks Arabic, mostly in northern Africa. About 10% speak Swahili, mostly in south-eastern Africa. Many people also speak English, French, and Portuguese. One African country, Nigeria, has 250 different languages!

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There are many different tribes and cultures in Africa. For example, there are the Ashanti people. They live in Ghana. They are famous for their beautiful Kente cloth. Kente cloth can be of different colors. Ashanti people wear clothing made of Kente cloth for important events. There are also the Madinka people. They live in West Africa – mostly in Senegal, Gambia, and Guinea-Bissau. The Madinka people are famous for their music. They tell their history with music.

Most scientists think that the first humans came from Africa. The first written information in Africa comes from Egypt at around 3300 B.C.E. (B.C.E. means Before the Common Era, or before the year “0”). Egypt is one of the oldest African civilizations. At that time, Egypt traded with Phoenicia, which is now Lebanon, and includes parts of Israel, Palestine, and Syria. Egypt was discovered by the ancient Greeks, who were the first Europeans to go to Africa.

Many African countries became free after World War II. Some countries became free in a peaceful way. Some countries had to fight to be free. The time after colonial rule is commonly referred to as “post-colonial Africa.” Post-colonial Africa has had some very big problems. After the colonial powers left, there were problems with government. Between 1960 and 1980, there were 70 coups (pronounced “koo”). A coup is the overthrow of a government. There were 13 presidential assassinations. That means 13 African presidents were murdered. In the 1970s, there was a huge famine in Ethiopia. A famine is a time of little or no food.

People visit Africa because the landscape is beautiful. There are many animals in Africa. Many tourists visit Kruger National Park in South Africa. The park has 517 species of birds! The park also has 147 species of mammals. The park even has webcams so people can watch the animals using their computer.

Memory quiz

About one billion people live in Africa, which is almost ___% of the world population.

How many countries are there on the continent of Africa?

There are about ____ different languages in Africa.

About 20% of the population (mostly in northern Africa) speaks _____.

Which African country has 250 different languages?

The Ashanti people are famous for their beautiful Kente ____.

The Madinka people are famous for their music, where they tell their _____ with music.

The first written information in Africa comes from Egypt at around _____ B.C.E.

Egypt was discovered by the ancient _____.

Many African countries became free after _______.

What is a coup?

How many presidential assassinations were there?

In the 1970s, there was a huge famine in _____.

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