What happened
You classified ink colors across congruent, neutral, and incongruent trials. Your interference cost, incongruent minus congruent reaction time, is your personal Stroop effect, the time your executive system needed to overrule the automatic reading response.
Why it happened
Word reading reaches the response system faster than color naming. On incongruent trials both pathways activate conflicting responses; the anterior cingulate detects the conflict and recruits prefrontal control to bias processing toward the task-relevant feature. That arbitration takes time.
Experimental design
Research protocol
Within-subjects repeated measures; color-word Stroop task
- Independent variable (IV)
- Stimulus congruency (congruent, neutral, incongruent word–ink pairings)
- Dependent variable(s) (DV)
- Reaction time (ms) to name ink color
- Response accuracy
- Stroop interference score (RT_incongruent − RT_congruent or − RT_neutral)
- Measured constructs
- Inhibitory controlProcessing speedExecutive attention
- Operational definitions
Stroop interference
Slowing (and errors) when ink color conflicts with the word's meaning
Automaticity
Overlearned reading proceeds without deliberate control, competing with color naming
Response conflict
Simultaneous activation of incompatible response tendencies
- Key terms
Stroop effect
Classic interference when naming ink color of incongruent color words (Stroop, 1935).
Anterior cingulate cortex (ACC)
Conflict monitoring region engaged when competing responses are co-activated.
Dorsolateral prefrontal cortex (DLPFC)
Implements top-down biasing toward task-relevant dimensions (color, not word).
The original experiment
Year
1935
Researchers
John Ridley Stroop
Sample
70 undergraduates across three experiments
Key finding
Naming ink colors of incongruent words took 74% longer than naming solid color patches.
Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18(6), 643–662.
Where this shows up in the world
Clinical assessment of ADHD, addiction, and frontal-lobe function
The emotional Stroop probes attentional bias in anxiety and PTSD
Design lesson: never make a label fight its own appearance
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