Effect of Caffeine on an Individual's Cognitive Performance

3년 전

Effect of Caffeine on an Individual's Cognitive Performance

Caffeine is a psychoactive drug that stimulates the central nervous system and affects the consumer in multiple different ways. Students were split into three groups, one consumed a drink consisting of 100% of the allocated caffeine, one consumed 50% of the allocated caffeine, and the last had no caffeine. Each of the groups then had to complete specific cognitive tests - Reaction Time (RT) analysis and Stroop Tests (ST) - to show the effect of the caffeine on their brains.

The aim of the investigation was to test the hypothesis, ‘The higher the dosage of caffeine absorbed by the body, the faster cognitive functions in brain work, decreasing time needed to react to stimuli and increasing scores on the Stroop Test’.
30 minutes after the participants drank their respective drinks, they had to complete several tests to find out how caffeine affected their cognitive performance. The first test was the Reaction Test (RT), where participants had watched a computer screen and had to tap the screen when it changed color.

The second test was the Stroop Test. It tested the participants’ cognitive performance and ability. It also required attention and concentration.

Using the quantitative data derived from the tests, the experiment will determine the psychological effects of caffeine, in controlled amounts, on the brain. In conclusion of the investigation, the data will be presented in graphs in a detailed summary which will display the RT and ST results.


The independent variable of the investigation was the percentage of caffeine in the cola consumed by the participants. The dependent variable in the investigation were the scores obtained through the ST and the RT tests completed by participants. Various variables needed to remain constant throughout the investigation as to insure the accuracy of the results. Some of these constant variables include the amount cola consumed, waiting time and the method of measuring and briefing the tests.
The results derived from the investigation are summarized in tables and charts below. These results are in the form of quantitative quantitative data answer the hypothesis; “The higher the dosage of caffeine absorbed by the body, the faster cognitive functions in brain work, decreasing time needed to react to stimuli and increasing scores on the Stroop Test”.
Table 1: Summary of RT Scores.
Group 1: 0% Caffeine Group 2: 50% Caffeine Group 3: 100% Caffeine

Average Reaction Time (seconds) 0.46 0.38 0.45

This data shows the average reaction times for each group. From the graph, it is visible that the group which consumed half strength cola had the longest reaction time this was proceeded by the full strength cola group. Between the two, the full-strength cola group only showed a 0.01 second quicker reaction time. However out of the three groups, the decaffeinated group had the quickest reaction time; presenting a 0.08 second difference from the slowest group. This means that the lower the caffeine consumed, the quicker the response time.

Table 2: Summary of ST Scores
Group 1: 0% Caffeine Group 2: 50% Caffeine Group 3: 100% Caffeine

Average Stroop Test Score 22.14 22.5 21.99

The ST tested the participant’s ability to distinguish between useful and irrelevant information and then say the correct answer out loud. The final score represents how fast participants were able to complete the test. The ST was designed to test the participant’s cognitive performance and would be an appropriate test to use to test the research hypothesis. Group 3, the 100% caffeine group, reported the fastest reaction time, supporting the research hypothesis. However, group 2, the 50% caffeinated group, scored the slowest average time. This somewhat contradicts the hypothesis because the relationship between an increase in caffeine and improved cognitive performance.

These findings show that caffeine does have an effect on cognitive performance. The RT results show that Group 2, the group which had 50% caffeinated drinks, had the fastest reaction time. They reported an average score of 0.38 seconds. Group 3, the 100% caffeine drink group, had the second fastest reaction time, at 0.45 seconds. Group 1, who drank decaffeinated drink, had the slowest average reaction time, at 0.46 seconds.
Suprisingly, group 3 did not score the fastest average reaction time. The explanation for this outcome is that caffeine in the Cola influences the release of the neurotransmitter dopamine, which activates the pleasure centres of the brain. As a result, group 3 participants felt happy and excited, which distracted them from being alert and focused on the test.
The Stroop Test was used because it was an effective way of testing a subject’s attention and executive function, giving a picture of their overall cognitive performance when combined with the RT data. ooIn this test, group 3 reported the fastest reaction time. The caffeine had effectively increased cognitive performance, as reflected by the ST results. Group 3, the 100% caffeine group, scored the fastest average time in the ST. This is most likely because the caffeine simulated the participant’s senses, allowing them to interpret visual information and speak it out loud faster than other groups. It can be concluded this group had the sharpest attention and executive function, meaning that they were able to better sort out meaningful information from distracting information.
A possible explanation for the 50% caffeine group scoring the slowest time is that the decaffeinated group had participants with great natural cognitive performance and were able to perform better than the 50% caffeine group.

A strength of the investigation was the large number of participants. This contributed to the reliability of the final results because any random errors which may have occurred were minimized.
Participants were not told which caffeine group they were placed in order to prevent biased results.
A strength of the investigation and its results is the numerous repetitions over a substantial number of years. This allowed for conclusive generalisations to be made specifically for the 16-17 age group.
Ethically, this study was very sound due to a number of precautions which were taken. Such as the provision of sufficient briefing of the purposes and aim of the study to subjects, consent to voluntary participation was signed. In addition, the subjects’ right to withdraw from the study for any or no reason and also their right to confidentiality was upheld.
A systematic error which the investigation encountered was explaining the ST. The test was difficult to explain. In order to improve the reliability of the investigation’s results, more tests should be conducted by the participants so that more information is gained and can be compared.
Furthermore, when the participants were reading the words out loud, the classroom became noisy, which was a distracting environment for the participants to be tested in. This external simuli had a negative effect on the participants’ cognitive performance. If the investigation is to be repeated, an ideal environment for the participants to be tested in is in a quiet room where participants cannot be distracted by external stimuli. Each participant should be allocated a separate room so that they aren’t distracted by each other speaking the words out loud.
Random errors which occurred during the testing stage of the investigation include a miscalculation of the average scores and participants misreading the score on their laptops. There were instances where participants altered their scores in order to look good among friends when they compared results.
However, these random errors are minimized because of the large number of participants who took part in the investigation.
The investigation’s findings show that caffeine has varying effects on a consumer. There are many variables which contribute to caffeine’s effectiveness in enhancing cognitive performance, such as how well their cognitive performance already is, how well an individual can utilize the stimulant to perform better and how tolerant they are to the effects of caffeine.
The average scores for both tests were very close, proving that there is no distinguishable improvement which caffeine gives to a consumer.
Hence, the investigation has disproved the hypothesis, ‘The higher the dosage of caffeine absorbed by the body, the faster cognitive functions in brain work, decreasing time needed to react to stimuli and increasing scores on the Stroop Test’ because caffeine has a different effect on everyone, because everyone has unique traits, caffeine tolerance levels and natural cognitive performance.

Word Count: 1424

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it does not matter if it has good or bad effects, I will continue taking my 2 liters of coffee daily with a lot of sugar whenever there is