Abstract
The Stroop effect involves demonstrating a longer reaction time inherent in performing a more complicated task. The effects of conflict processing on reaction time is thought to be significant; the higher the level of conflict processing, the longer it takes for someone to react to that conflict. The current study measures response times based on four different exercises involving the reading of numbers and row length. The third exercise includes two levels of complexity (counting and number identification), as opposed to a single level of complexity with the remaining exercises. Eight pairs of subjects are tested for reaction time based on these exercises. The Stroop effect is measured using mean reaction times to each sheet, and the t-tests for each comparison are calculated. According to the results, response time grows measurably longer when the level of complexity increases.
Introduction
Cognitive conflict processing involves the selection of one stimulus among competing stimuli, requiring the ability to selectively attend to particular features in an environment. The Stroop effect is an experiment that is intended to determine one's ability to ignore conflicting stimuli while focusing on one single targeted dimension (Henkin et al., 2010). The Stroop effect measures the response and reaction times of subjects. It is one of the most extensively studied phenomena in cognitive neuroscience (Henkin et al., 2010). The Stroop effect is mostly used to study conflict processing in visual modalities, though there is some auditory modality data provided (Henkin et al., 2010).
The overall component of Stroop effects are the conflict between informationt hat is taken from linguistic parts of a stimulus, and the perceptual component that corresponds with it (Pothos & Tapper, 2009). Emotional Stroop tasks are used to determine conflicts between emotional states and visual stimuli; the primary approach stems from elementary associative learning processes between elements. This type of conflict determines just how much reaction time is affected by the emotional response to a certain color or visual stimulus. In emotional Stroop tests more so than other types of tests, the associations between the emotional cue and the target are made automatic more quickly (Pothos & Tapper, 2009).
One incongruity that arises within emotional Stroop tests is the presence of inconsistent findings, which can stem from differing effects of stimulus valence and arousal (Dresler et al., 2009). It has been determined that the level of arousal is the primary source of emotional interference, and not the valence of the emotional stimuli; the more arousing the stimuli, the greater the level of interference. When considering the level of anxiety someone undergoes during cognitive conflict processing, it has been made clear that response time decreases with the greater level of anxiety experienced by the subject (Dresler et al., 2009).
Working memory load is the amount of total information that can be carried by a human mind at one time. The level of WM load possessed by a human being can determine their baseline level of reaction time. Distractor processing is the ability for the human mind to deal with and work through distracting or conflicting stimuli; these are known as Stroop stimuli (Gao et al., 2007).
In order for people to figure out what action needs to be performed regarding an object or event, information has to be gathered on the object that is to be reacted against. Its size, speed, color, trajectory and the like are factored into the object before taking an action, which leads to the response time humans typically experience. The more complicated a cognitive process is, especially combining certain sets of information (such as color, order, and number), the longer the reaction time (Luo et al., 2010).
Method
The goal of the experiment was to determine whether pairs of individuals would perform cognitive conflict processing at longer times, depending on the difficulty of the stimuli. 16 participants were selected for this experiment, consisting of 11 females and 5 males. The mean age of the participants was 20.8 years, with a standard deviation of 4.1.
Each participant was tested in pairs, with the two participants entering a room with the researcher. Four sheets were provided to the participants one at a time, each with a different activity. In Sheet 1, the participants were asked to say aloud the number in each row as quickly as they can; the first sheet contains single numbers, one to a row. Sheet 2 consisted of differing rows of plus symbols; the participants were asked to count aloud the number of plus symbols in each row. Sheet 3 consisted of rows of the same number, all in varying lengths; the participants were to count aloud the number of digits in each row - this sheet carried the greatest level of complexity. Sheet 4 consisted of the same exercise as Sheet 3, but the numbers in each row corresponded to the number of digits in each row.
The amount of time it took for each participant to verbally state the number of rows was recorded with a stopwatch; the results were then subjected to t-tests, comparing two of the tests at a time to determine mean reaction times. The dependent and independent samples were the third sheet (the most complex one) and the remaining sheets, respectively. As Sheet 3 presented a greater level of cognitive conflict, the goal was to see if this sheet gave participants greater difficulty than the rest.
Results
When all participants finished with all four sheets, the reaction times were compiled and averaged. According to the results, the longest reaction time given was in Sheet 3, with a mean reaction time of 18.5 seconds, with a standard deviation of 3.7; Sheet 3 had a mean reaction time of 13.3 seconds, with a standard deviation of 2.8, Sheet 4 had a 13.2 second reaction time (standard deviation 3.1), and Sheet 1 has an 11 second reaction time (standard deviation 2.1).
A 1-tailed t-test was conducted with an alpha of .05, each test comparing the mean reaction times of two of these sheets. The t-statistic for each comparison reveals the differences between the average means of both sheets, and the statistical significance of each comparison was made. Statistically significant comparisons (p < .05) include those of Sheet 1 versus Sheet 3 (M = 3.26 sec, p = .03), Sheet 2 versus Sheet 3 (M = 3.22, p = .04), and Sheet 3 versus Sheet 4 (M = 3.31, p = .04) - all related to Sheet 3. Statistically insignificant results include comparisons of Sheet 1 versus Sheet 2 (M = 1.34, p = .06), Sheet 1 versus Sheet 4 (M = 1.32, p = .07), and Sheet 2 versus Sheet 4 (M = 1.12, p = .08)
Discussion
Given the longest reaction time being that of Sheet 3, which combined sets of numbers which were different than the number of digits within the row (ex. two 1s in a row, three 2s, etc.), it is clear that, given a greater level of complexity, participants had longer reaction times. In the other sheets, which included only one level of sophistication (listing off numbers or groups of matching symbols), the reaction times were much shorter. Sheet 1, with a simple listing of numbers, showed the lowest level of sophistication, and therefore carried the shortest reaction time as an exercise.
Because of the Stroop effect, the rows consisting of numbers which did not correspond to the actual number of digits in the row created that added level of sophistication that took the brain longer to process. The difference between number and group of digits created a conflict within the brain that needed more time to process. In the comparisons of different exercises, the biggest differences in mean reaction time were between Sheet 3 and any of the other exercise sheets, which were also the most statistically significant.
This results support the hypothesis of the current study, which is that cognitive conflict processing becomes more time-intensive when the conflict involves a greater level of sophistication. In essence, the more difficult something is to process, the more time is spent processing it. This is the essence of the Stroop effect - reaction times increase when tasks are more complicated - and it was proven correct in this study. The implications of this study provide further evidence of the cognitive toll that more sophisticated conflicts carry in reaction and processing time.
References
Chunming, L., Lupianez, J., Xiaolan, F., & Xuchu, W. (2010). Spatial Stroop and spatial orienting: the role of onset versus offset cues. Psychological Research, 74(3), 277-290.
Dresler, T., Meriau, K., Heekeren, H. R., & der Meer, E. v. (2009). Emotional Stroop task: effect of word arousal and subject anxiety on emotional interference. Psychological Research, 73(3), 364-371.
Henkin, Y., Yaar-Soffer, Y., Gilat, S., & Muchnik, C. (2010). Auditory Conflict Processing: Behavioral and Electrophysiologic Manifestations of the Stroop Effect. Journal of the American Academy of Audiology, 21(7), 474-486.
Pothos, E., & Tapper, K. (2010). Inducing a Stroop Effect. Applied Cognitive Psychology, 24(7), 1021-1033.
Quanying, G., Zhe, C., & Russell, P. (2007). Working Memory Load and the Stroop Interference Effect. New Zealand Journal of Psychology, 36(3), 146-153.
