The Stroop Effect Part 1
Can you ignore incongruent information ?
Analyze a classic experiment in psychology with this dataset based on the original 1935 paper by John Ridley Stroop. Activities from Stroop’s original datasets are spread across 3 separate activities, it is recommended that you complete them in sequential order to get the most out of them.
Part 1 - How does color interference affect reading time?
Part 2 - How does word interference affect reading time?
Part 3 - How does practice influence interference?
Background
Try reading out loud the words written on the left and then try it on the right. Notice a difference? Did you find yourself taking longer to say words on one of the sides? If so, you weren’t alone in feeling impeded due to the Stroop effect!
The Stroop effect refers to a phenomenon in which our response time is delayed by incongruent stimuli. For example, in the task above, one’s ability to read the words or name the ink color in which the word is printed on the right side is hampered due to the presence of conflicting information, either due to a mismatch between the font color and the color that word represents. This effect is thought to be a result of our internalization of an existing relationship between a word and its associated visual representation and is hypothesized to occur because of how we learn and process naming colors as opposed to reading words. Although psychologist John Ridley Stroop was not the first to detect such an effect, he developed one of the most effective and replicable sets of tests to study it in an elegant study first published in 1935 (full text can be found here).
While there is no general agreement on the underlying cause of this effect, the Stroop test has played a critical role in psychological research and clinical psychology. This is because of its capacity to reveal how the brain processes information and the extent to which individuals can override their instinctual fast thinking which causes them to rely on the learned association of words and their visual representation. The test is often used to measure a person’s selective attention capacity and skills, processing speed, and (alongside other tests) executive function difficulties due to ADHD, anxiety, depression and even traumatic brain injury. Typically with these tests, psychologists predict that if an individual’s executive functioning is not strong, they are likely to take longer to process incongruent stimuli because of their inability to inhibit interference due to known automatic associations between two stimuli.
In the first part of the study Stroop conducted, he wanted to test whether the presence of conflicting visual stimuli (colors that are not indicated by words) impedes our ability to process information correctly. The dataset below has been recreated from the reported summary statistics in Stroop’s iconic 1935 paper. Try analyzing the data below on your own and compare your interpretations to what Stroop found in his study.
Dataset
This data is recreated from his first experiment, with participation from 70 college undergraduate students (14 men and 56 women). He recorded the time it took participants to read the names of colors from a list printed only in black ink (RCNb), and then recorded the time it took them to read names of colors from a list regardless of the color of ink they were printed in (RCNd).
When reading the names of colors from the RCNd list, participants were allowed to re-read the names if an error was made in reading the names, and was included in the total time to read. (This time delay is called color interference).
Variables
Participant ID: A unique ID given to each participant. This variable is categorized as info and will not be analyzed.
Sex: This categorical variable indicates whether the participant was male (M) or a female (F)
Participant’s Year of Study : This categorical variable indicates whether the participant was in undergraduate (1st-4th Year) or Graduate school
Treatment: This categorical variable is the type of word list that participants will have to read in a given experiment. Variables include reading color names printed in black ink (RCNb) or reading color names written in ink printed in a color different from the one written (RCNd).
Time to Read (sec): This numeric variable is thetime it took for a participant to read the associated word list, measured in seconds.
Activity
1) State the question that Stroop asked, below:
2) What was Stroop’s hypothesis of this experiment?
3) What variables would you need to explore the question? State your prediction of those variables below:
Big Question 1: Is the data ______
Make a graph to determine the distribution of the reading time look like when testing for interference. Make a histogram and paste it here:
5) Add descriptive statistics of box and whisker, and include your new graph below:
6) What does the box and whisker tell us about the distribution of this dataset?
Big Question 2: Does the interference of different colors seem to affect the average ability of the participants to read the words?
7) Display a dot plot of reading time against the two treatments by putting treatment as x-variable and Time to Read as y-variable. Include your new graph below:
8) Find the mean and 95% confidence intervals by adding descriptive statistics for the graph in #7. Screenshot and include this new graph below:
9) Based on this graph, does color interference seem to affect reading time?
Big Question 3: Do males and females differ in their performance on the Stroop test?
10) Explore this question by grouping data by the Z- variable to indicate the gender of the participants. Keeping the same graph from #8, make sex your z-variable, and paste your graph below. (Continue to include the mean and 95% CIs)
11) Based on this graph and statistical analysis, how does sex affect the outcome of time to read when color interference is present?
Take it further:
12) What statistical test would you use to test if color interference had a significant role in affecting reading time regardless of the gender of the participants? Explain why?
13) Using the appropriate graph-driven hypothesis test - report your results in the table below and explain your inference regarding the strength of color interference in reading.
*Teachers can request an answer key through the form below.