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Effects of Caffeine and Sex Differences on Memory


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This study was conducted to determine the effect caffeine has on memory recall and verify whether or not there are sex differences. Though there are different types of memory, this study focuses on free immediate recall. Caffeine has been proven to cause alertness, help some forms of memory, and impede other types of memory. It was hypothesized that caffeine would improve memory, and that males would score better than females on the memory tasks regardless of caffeine consumption. Participants were run in a blind study where they had no previous knowledge of whether they are ingesting actual caffeine pills or placebos. Recall memory was tested using a basic word list. The results were consistent with previous research in that caffeine helps boost certain types of memory. However, there were no sex differences in memory recall found. There still is a need for further research on sex differences, caffeine's effects, and the varying types of memory because of potential relationships between these variables.

Effects of Caffeine and Sex Differences on Memory

Caffeine can be found in many different food items that are commonly consumed. Some of them are: chocolate, coffee, soda, and other food products. When most people think of caffeine they associate it with hyperactive behavior or a liquid that heightens attention and alertness. It is increasingly becoming the most used psychoactive substance in America (Majithia 2008). According to New Scientist magazine, 90% of Americans consume caffeine on a daily basis (Lovett 2005). It is mostly recognized as a mild central nervous system stimulant, but because its ability to produce cholinergic stimulation, it may lead to higher cognitive functioning. This can be associated with memory (Riedel 1995). Even though that is an apparent characteristic, there has been very little conclusive evidence about the affect caffeine has on memory. Not many studies have performed an extensive study that that test all types of memory, but have rather made small steps on general ideas about caffeine.

Everyday we reach into the databases and files in our brain to retrieve memories and we also put in new files when we create new memories. Occasionally, someone might misplace their keys or forget the name of the classmate that sat next to them in their high school graduation. There are many different types of memory that are active when we decide to try and remember things. Some diseases such as Alzheimer's potentially affect memory to the point where the body doesn't even remember how to function. This is when people realize that memory is more important when there are problems retrieving simple memories. Memory can be broken up into to two general types: short term memory and long term memory. Short-term memory is considered to be working memory. Then again long-term memory can be broken again down to two types: explicit and implicit (Posit Science 2010) . Implicit is what is used unconsciously in our thought and flows without effort. Explicit memory is more conscious and associative. It synonymous with memories that are linked together. There is a study that found that woman may perform better on short term memory tasks, but it only used 6 subjects and may have not reflected an actual population (Zwyguizen-Doorenbos 1990). The results may have been inflated. After

Some people in high stress situations with constraint on time, use caffeine as a means to stay awake and begin to substitute caffeine and other diuretics for sleep, but this may not be the best choice. A study done by Mednick, Cai, Kanady & Drummond (2008) found results that concluded that caffeine may not be an appropriate substitute for naps or a full night's sleep because it actually can impair motor memory and has only short term effects. This study did in fact conduct an experiment that measured multiple types of memory. They measured declarative verbal memory, procedural motor skills, and perceptual learning. They expressed the idea that caffeine restrict tasks containing explicit information (Mednick 2008). Most Then again, another study by Koppelstaetter (2010) and colleagues found results that showed that caffeine may in fact boost activity in regions of the brain associated with attention and short term memory. Perhaps only certain types of memory benefit from caffeine when it's at its peak levels in the brain. We initially thought that the form that the individual would ingest would cause differences in the affect of the caffeine on memory. We found that previous research suggests that no matter the form ingested, the caffeine would still reach the bloodstream and eventually affect the brain (Dye 2007). The only difference between a pill containing caffeine and a liquid containing caffeine would be that the pill requires the outside sugar capsule to dissolve which may or may not take more time, but we will assume that they do.

According to one study, because caffeine is an antagonist to adenosinergic mechanisms, which are associated with sleep and suppressing arousal, it neutralized the effect of sleep loss (Dielkelmann et al., 2008). This supports the idea that caffeine is helpful in retrieving memories better than with the absence of caffeine. Findings such as these give light to the idea that caffeine may help individuals perform at their optimal level. In concordance with our literature of interest, we predicted that there will be a significant difference between memory recall scores from those taking caffeine and men will have generally higher scores than women.



We recruited participants by sending mass emails to all psychology students currently available. Additionally, we put up flyers around UAB's campus. As an incentive to participate, we offered extra credit in a psychology class of their choice to those who complete the study. Prior to the study, we received department approval for the extra credit. A total of 40 participants were selected to participate in the study. The participants were moderate caffeine consumers and had no history of chronic disease. Before participation, participants were asked to not consume any alcohol 24 hours before the study and to get at least 8 hours of sleep. Along with these requests, we asked participants to not ingest extra caffeine outside of this study during the day of the memory testing.

Research Design

We used a blind study so that participants wouldn't know if they were taking caffeine or the actual placebo in order to produce results that didn't reflect other mental processes such as motivation. We planned on using a factorial design with 2 independent variables. Those variables would be gender/sex and caffeine dosage (200 mg vs. 0 mg). The dependent variable would be the resulting memory recall score. We divided the participants into groups of 10 for each group: males taking sugar pills, males taking caffeine, females taking sugar pills, and females taking caffeine. We decided that the participants should swallow the pills down with the assistance of water versus another type of drink so that there will not be a change in chemistry of the pill or any added effects. Initially, we had considered using liquid caffeine, but decided with the varying amounts of caffeine in different drinks that the pill would so much easier to administer. In order to not confuse results, we will label the container with a number to ensure that we don't record results incorrectly.

To lower the mortality rate, we offered incentives for the completion of the study. To limit the practice and potential improvement of recall memory before the actual memory test, we only tested the participants once. We took several steps to eliminate bias from our study results. We picked a neutral day and time of the week to eliminate the time of day factor influencing results. We also had participants get an adequate amount of sleep (at least 8 hours) and had them abstain from alcohol consumption. It should be noted that all researchers participating were trained not to show much emotion while administering the caffeine or providing the word list or blank sheet of paper. This creates an environment where the emotions of the researcher will not cause the participants to feel uncomfortable during the study.


The basic memory recall test design was identical in form to one used by Soo-ampon et al. (2004). Everyone participating is familiarized with what is required of them for the study. Two groups of 20 would be separated and put into two different rooms in order to eliminate crowding. The environment for the study was UAB classrooms decorated in neutral colors to minimize distraction. Essentially, there were no bright colors in either room and they could house a capacity of about 25-30 students each. Once entering the room, participants were given a caffeine pill or sugar pill and the researchers recorded each individual's name and type of pill while also hiding the identity of which pill the subject would ingest. After a period of precisely 25 minutes, monitored by a timer, participants are asked to be seated around the room and researchers presented participants with a sheet of paper. In order to ensure no cheating between participants, we sat them at least 5 feet apart so this wouldn't interfere with the ending results. On the sheet of paper, there were 20 nouns listed on the page. Only 10 of the words are high frequency words that appear frequently in English materials. The other 10 words are low frequency words that appear less frequently in English materials. These words were arranged in a random order. The researchers give the participants only 2 minutes to study the list of words. After time is up, researchers replace the word list with a blank sheet of paper and writing utensils. Participants are given 2 minutes to write down as many of the words that they can remember from the word list given to them previously.

Statistical Analysis

The scoring for the immediate recall test was based on the number of words correctly recalled. Spelling errors weren't taken into account. If the meaning of the word was altered by a spelling error, then the word would not be scored as correct. Also, if the form of the word changed, then it would not count either. The possible score could range from 0-20. In order to analyze the data we collected, we used a 2 x 2 factorial ANOVA using the SPSS program. We wanted to be able to detect any effects of the two main variables, plus any interaction effects of the variables: gender/sex and caffeine administered.


The results weren't entirely consistent with the hypothesis. There was a significant difference in those taking caffeine, but there was no difference in scores between males and females. With an alpha level of <.0001, the factorial ANOVA test showed a significant difference between those who ingested 200mg of caffeine and those who took the sugar pill [Table 1]. According to the calculated means, those who took caffeine (M=17.1, S.D=1.02) scored generally higher than those who just took a sugar pill (M=12.9, S.D=1.12) [Table 2; Figure 1]. When it came to the variable gender/sex, there was no significant difference.


The findings show that caffeine may not actually give any advantage to men, but produce the same results across gender and sex. Talk about possible implications of your findings -such as recommending caffeine consumption to help boost memory on simple tasks or any other implications you can think of.

There were particular limitations to the results. We did not test participants that reflected the entire population. We used only psychology students ranging in age from 17- 23 and also the location of the participants was limited to Alabama, which is considered to generally be more rural than an urban area. Results should be interpreted cautiously because another population of people might produce different results. Such a small sample size could have possibly limited the generalizability of the study also.

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