The objective of this study is to find out whether caffeine has an effect of Short term memory and Attention. The study involves 1 IV which is Caffeine with 3 levels (Water, Tea and Coffee) and 2 DVs which are (Short Term Memory and Attention). Participants will be undergraduates from James Cook University undergoing their Psychology Degree and participating for credit points for their allocated Statistics module, a minimum number of 158 participants are required to take part in an Attentional Blink Test followed by a Sternberg Task. The results are expected to reflect significant effects that caffeine have on Short Term Memory and Attention.
Keywords: Caffeine, Attentional Blink Test, Stenberg Task
Introduction: Effects of Caffeine on Short Term Memory and Attention
Today, approximately 80% of the world’s population consumes caffeinated products daily. The demand of these beverages is widely due to the positive effects caffeine has on the body and mind (Melanie, Heckman, Jorgeweil ; Demejia, 2010).
There are 3 variables that will be measured and incorporated in this study; they are caffeine, short-term memory and attention. Short-term memory is often used interchangeably with working memory; it is also the extent of recollection of a specific item or memory. Attention is the ability to be vigilant against external stimuli and distractions that could result in failures to perform an intended action (Olivers, 2008). Caffeine can be found mostly in coffee and tea with a scientific name of trimethylxanthine. An adult is advised to consume within 400 milligrams (mg) of caffeine a day or the amount of four cups of brewed coffee (Melanie, Heckman, Jorgeweil ; Demejia, 2010).
In a study by Oei and Hartley (2005), participants were tasked to attempt a signal detection and memory scanning task while consuming caffeinated or decaffeinated coffee. Results reflected that overall participants who have ingested caffeinated coffee do perform better in both memory and attention task. However in another study the findings do not agree with the positive effects of caffeine. The state of over-arousal is congruent with the anxiety levels of the individual. Although caffeine has observable effects on the nervous systems its effects supports no substantial evidence supports the retrieval and memory (McLellan, Caldwell ; Lieberman, 2016).
Research on the potentials of caffeine absorption has help researchers understand the potential role of age-related GABA in cognitive decline. Although consumption of pharmaceutical drugs or dietary supplements such as caffeine should maintain cognition of an adult to a certain extent, with age a higher dosage will be required to achieve a certain degree of cognition sustenance (Nashiro, Sakaki, Braskie ; Mather, 2017). Another research done by Mitchell; Ericksen (2011) explains the effects of social factors in relation to caffeine consumption. They address factors such as age, alcohol, brand of caffeine products, efficacy, gender and the current health state are hard to take into account in any research that measures cognition as a variable. Interestingly, it was concluded that younger participants found the “energy kick” more accepting while consuming caffeinated products than older participants. Thus it was described that if a study aims to measure how caffeine affects cognition its best to use a younger population for the study.
An attention blink task is stimulated through the use of sensory processing. It explains the method as the presentation of rapid serial visual representation where stimuli such as letters or numbers appear successively between 6-20 items per second. However, claims by Olivere ; Meeter (2008) this method lacks the assessment on attention. According to the boost and bounce theory, the brain processes are aroused by perceptual features such as its shape, colour and orientation, As stimuli are presented, attention reaction is defined by is influenced by those stimuli that appears as defining attributes about it. The more features a stimuli portray, the better the effect on attention. As Attention blink task reflects only stimuli with a few features such as length of items display and alphabets or numbers it is argued as an instrument that lacks its measurement effect to record attention processing.
The Sternberg task is a tool for studying short-term memory in experimental psychology, the task consists of a set of items using the “List Length” manipulation. This is to test the memory encoded during the first phase of the trial and retained the memory in order to respond to a final probe item. Probe judgments consist of (an item of the trial memory set) or negative (not an item of the memory set). However, Corbin ; Marquer (2013) conducted an analyses and define this test was as accurate in measuring memory as it claims. According to them the Sternberg’s paradigm appears to be a verbal working memory task assessor as this task seems to address more of recognition than a recall condition.
The aim of this research is to investigate the effects of caffeine intake on short-term memory and attention. The drink beverages provided are of 3 different products milk, plain water and coffee. As research on caffeine in related to attention and memory were indecisive in many research. This experiment will investigate the effects of Caffeine in regards to short-term memory and attention on JCU undergraduates whom derive from a younger population. The Sternberg Search task will be used to test for short-term memory while the Attention Blink test will be used to test for attention. Two hypotheses will be investigated in this experiment which is based on previous research:
There will be a significant difference between the Caffeine intake group as compared to the milk and plain water group in the results of the short-term memory task.
There will be a significant difference between the Caffeine intake group as compared to the milk and plain water group in the results of the attention task.
An a priori power analysis was conducted using G*Power 3.1 to determine the sample size. With a power of .80, an effect size of .25 and ? = .05, the required sample size obtained was n= 158. Purposive sampling will be used to recruit participants through James Cook University’s Research Participation programme targeting students currently enrolled in the degree of Psychological Science aged 18-30. Prospective participants would be enrolled in psychology core subjects allowing students to obtain credit points (i.e. PY1101, PY1102, PY2103 and PY2107). Participants will be awarded 8 credit points.
Participants will be asked to fill in a consent form to provide their consent to participate in the experiment. They will be required to provide their student ID number and signature for the allocation of credit points after participating in the experiment. Reference numbers will be given to each participant to maintain their anonymity.
To operationalize caffeine levels, three types of beverages will be used: coffee, milk and water. Participants given water will be known as the control group while other participants given milk or coffee will be known as low and high caffeine groups respectively.
News Telecast Audio
A CNN news telecast audio with duration of 10 minutes will be played and participants will be asked to write down the details they can remember from the news audio. This task will act as a distractor to disguise the true nature of the experiment and allow the effects of caffeine to take effect.
Sternberg Search Task
The Sternberg Search task will be used to measure short-term memory span and administered through the use of the Coglab software. Each trial contains a set of either 1, 3, or 5 numbers presented on the computer screen for 1.2, 3.6 and 6 seconds respectively. A probe item or a number will be shown on the screen 1-3 seconds after the presentation of a trial and participants will be instructed to recall if the probe item appeared was shown in the trial. A total of 60 trials will be presented in this task and the duration is 40 minutes. Short-term memory is defined as the number of correct detections of the probe item.
Attention Blink Task
The Attention Blink task will be used to measure attention and administered through the use of the Coglab software. Each trial contains a sequence of 19 letters and participants are tasked to spot the probe item, either a letter “K” or “J”, appeared in the sequence. The letters are presented sequentially 100 milliseconds each and participants will enter their response after the sequence is completed. A total of 60 trials will be presented and the estimated duration is 35 minutes. Attention is defined as the number of correct detections of the probe item.
Prospective participants for this experiment will book a time slot via the James Cook University SONA system and they will take part in the experiment in a computer lab. Prior to participating in the experiment, participants will be presented with an information sheet (See Appendix A) and a consent form to indicate their consent (See Appendix B). Participants will be provided with a covered cup of beverage containing coffee, milk or water and asked to consume the beverage. After consuming the beverage, participants will be asked to put on the headsets provided and the news audio telecast will be played. Participants will then be asked to write down the details of the new telecast on a sheet of paper. The next task presented will be the Sternberg Search task and participants will be provided with instructions on the computer screen before commencing the task (See Appendix C). The second task is the Attention Blink task which will commence immediately after participants have read the instructions (See Appendix D). The results of the experiment will be recorded through the Coglab software and entered into the SPSS software.
The experiment contains one independent variable, caffeine levels, with 3 levels (Coffee, Milk and Water) and two independent variables, attention and short-term memory. Therefore, the MANOVA analysis will be used to analyse the results. The use of this analysis will reduce the Type 1 error as compared to the use of multiple ANOVA analyses and make comparisons across the 3 levels of the independent variables and the dependent variables. Also, the MANOVA analysis will explore how the patterns of the dependent variable vary from each level of the independent variable.
Prior to the MANOVA analysis, several assumptions need to be met. First, the Shapiro-Wilk test will be used to determine multivariate normality in the 2 dependent variables. To meet this assumption, the Shapiro-Wilk test must not achieve significance. To test the absence of multivariate outliers, the mahalanobis and cook’s distances will be tested through regression. The maximum value of the mahalanobis distance will be obtained from the residual statistics table and compared to the critical value based on the number of dependent variables which is 2. If the value of the mahalanobis distance exceeds the critical value, multivariate outliers are present in the data and must be removed. The presence of univariate outliers need to be tested through the use of box plots for each group of the independent variables for the 2 dependent variables. To test the assumption of homogeneity of covariance, the Box’s test will be used. The Box’s test should not achieve significance for the assumption of homogeneity of covariance to be met. To test the assumption of linearity, a scatterplot matrix will be used to test the presence of a linear relationship between the 2 dependent variables. This assumption is met when the values are displayed in a linear way. To test the absence of multicollinearity, a Pearson’s correlation will be used. The r value should not be above .80 as values above .80 will indicate the presence of multicollinearity.
The Wilk’s lambda test statistic will be used for the interpretation of the independent variable on the 2 dependent variables if all the assumptions above are met. If the assumptions are violated, the Pillai’s trace test statistic will be used. If the results achieve significance on any or both of the dependent variables, the results will be analysed with separate univariate ANOVA tests. Prior to conducting these tests, the Levene’s test will be used to analyse the homogeneity of variance for each dependent variable. The Levene’s test should not be significant prior to conducting the separate univariate ANOVA tests. After identifying the dependent variable which reach significance, pairwise comparisons will be used to analyse the effects of each level of the independent variable on the dependent variables which reach significance.
Significant differences found in the MANOVA analysis indicate that caffeine has an effect on either or both of the dependent variables, attention and short-term memory. Separate univariate ANOVAs will be conducted to identify the dependent variable or variables that caffeine has an impact on. Pairwise comparisons will then be used to analyse the individual levels of caffeine on the dependent variables which obtain significance. However, separate ANOVAs and pairwise comparisons will be used only if significant differences are found. Findings from this research will provide insight into how caffeine affects the brain mechanisms responsible for attention span and short-term memory. As attention and short-term memory are required in studying school materials, these findings could shed light on how caffeine consumption affects studying habits and their exam performance over time.
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