Exploring the Stroop Effect Part of: Inquiry Science with Dartmouth (a new program!) Developed by: Sergey Fogelson and Rick Schluntz Adapted from: http://www.ithaca.edu/faculty/stephens/stroopi.html Overview Mental operations can come into conflict with each other. For example, it is exceedingly difficult to both remember a list of 15 words and count backwards from 500 in multiples of 7. This is because distinct mental processes (remembering, computing a number) can share mental resources. This lesson explores a similar kind of mental conflict directly, by replicating a famous psychological effect discovered by John Ridley Stroop. Science Standards (NH Science Curriculum Frameworks) S 7-8: 2 Students demonstrate their understanding of PICTING AND HYPOTHESIZING by Predicting results (evidence) that support the hypothesis. Proposing a hypothesis based upon a scientific concept or principle, observation, or experience that identifies the relationship among variables. S 7-8: 4 Students demonstrate their ability to CONDUCT EXPERIMENTS by Accurately quantifying observations using appropriate measurement tools. S 7-8: 6 Students demonstrate their ability to ANALYZE DATA by Identifying, considering and addressing experimental errors (e.g., errors in experimental design, errors in data collection procedures) Identifying limitations and/or sources of error within the experimental design. Using color, texture, symbols and other graphic strategies to clarify trends/patterns within a representation. S7-8:7 Students demonstrate their ability to EXPLAIN DATA by Using scientific concepts, models, and terminology to report results, discuss relationships, and propose new explanations. Generating alternative explanations. Documenting and explaining changes in experimental design. Sharing conclusion/summary with appropriate audience beyond the research group. Using mathematical analysis as an integral component of the conclusion. Using technology to collect, quantify, organize, and store observations (e.g., use of probe). S57-8:5 Students demonstrate their ability to REPRESENT DATA by Representing independent variable on the X axis and dependent variable on the Y axis. Determining a scale for a diagram that is appropriate to the task.
Focus Question Are all colors processed in the same way by the human eye and visual system? Objectives Through this lesson, students will: Predict how quickly they can read a given list of words. Perform an experiment to establish relationships between naming a color and automatically reading a presented word. Background The Stroop effect was first described in 1935 by John Ridley Stroop. Generally, the Stroop effect refers to the difficulty observers have in eliminating meaningful but conflicting information from a task, even when that information is irrelevant or counterproductive in that task. The Stroop effect can manifest as either interference, that is, when one mental operation degrades the performance of another, or as facilitation, that is, when one mental operation enhances the performance of another. The focus of this lesson is exploring conditions under which both interference and facilitation can occur. Materials (for 6 groups of 3 students) 6 timing devices (phone, watch, stopwatch, etc.) 3 lists of words per group (congruent, incongruent, control) 1 Data sheet per group Preparation In this experiment, every group member will be tested on all of the word lists twice (right side up and upside down). Make sure that the current group member being tested doesn t know which list will be shown to him/her (and whether the list will be presented right-side up or upside down). Procedure 1. Have one group member be in charge of timing the current group member being tested while the other member presents the current word list to the current subject. 2. Notify the member being tested that his/her task is to name the color that the words are written in as quickly as possible without making any mistakes. 3. Present the subject with one of the lists and immediately begin timing. 4. Record their time and note whether any mistakes in naming were made. 5. Continue in the same way with all other word lists and across other subjects. Make sure that word lists have been presented in the correct orientation (right side up) and upside down to all group members. 6. Students should then first calculate mean color naming times from all the raw data for each of the three lists. These means can then be combined in different ways to investigate whether facilitation and interference occurred. 7. To calculate Stroop Interference: Stroop Interference(right side up) = RTincongruent(right side up) RTControl(right side up) 8. To calculate Stroop Facilitation: Stroop Facilitation(right side up) = RTCongruent(right side up) RTControl(right side up)
9. You can also determine whether the Stroop effect is made smaller by making the words difficult to read: Stroop Interference(upside down) = RTIncongruent(upside down) Rtcontrol(upside down) Stroop Facilitation(upside down)= RTCongruent(upside down) RTControl(upside down) 10. Now you can determine whether the effect decreases when you interfere with the automatic reading of words (Is the second group of numbers smaller than the first?) Additional Information The classic demonstration of the Stroop effect is produced when one tries to name the color of the ink in which a word is printed when the word itself is the name of a color other than that of the ink. Typically, one is slower in this situation than if the word is not a color term. This form of Stroop interference is thought to be evidence for the automatic nature of reading. Automatic in this context refers to an activity, such as reading, that is so well learned that it is occurs even when one attempts to suppress it. The interference probably arises when different words in the mental lexicon representing the color terms are activated by both the words and the ink color and compete with one another, slowing the overt response.
CONGRUENT
INCONGRUENT
CONTROL DOG BOAT CHAIR WINDOW FAN FART KIDS TRAY BOTTLE FENCE TOY SPORT
Exploring the Stroop Effect Data Sheet Experimental Data: Right-Side-Up Control Congruent Incongruent Time(s) # Errs Time(s) # Errs Time (s) # Errs S 1 S 2 S 3 MEA N Stroop Interference = RTincongruent RTControl = Did Stroop Interference occur (>0 = yes; <0=no)? Stroop Facilitation = RTCongruent RTControl = Did Stroop Facilitation occur (<0 = yes;>0=no)? Experimental Data: Upside-Down Control Congruent Incongruent Time(s) # Errs Time(s) # Errs Time (s) # Errs S 1 S 2 S 3 MEA N Stroop Interference = RTincongruent RTControl = Did Stroop Interference occur?
Stroop Facilitation = RTCongruent RTControl = Did Stroop Facilitation occur? Interference Right Side Up Interference Upside Down: Facilitation Right Side Up Facilitation Upside Down: QUESTIONS: Did making the words more difficult to read (by putting them upside down) affect Facilitation and Interference equally? Please describe. Given these results, describe what you think interference is. Given these results, describe what you think facilitation is. Describe what happened during the experiment to you and to your other group members; did any of the lists seem harder to recite than the others? Speculate why.
EXTENDING YOUR RESULTS: How much variation was there among subjects within your group? Across all of the groups in class? What relationship seems to exist between word meaning and word color? Can this kind of effect be replicated with other stimuli? Can an auditory Stroop effect be created? What are the differences between facilitation and interference? What may be causing them in your mind?