Numerical Stroop Task
The Numerical Stroop Task is a cognitive control experiment that measures your ability to focus on relevant information while ignoring irrelevant distractors.
Frequently Asked Questions
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What is the Numerical Stroop task?
The Numerical Stroop task measures the size congruency effect. You must judge which number is physically larger, ignoring its value.
How does a trial work?
On each trial, two numbers appear. Press A if the left number is physically larger, L if the right number is physically larger.
What feedback do I get?
After each response, you will see feedback indicating if you were correct or not.
Show Details
Size Congruency Effect (Numerical Stroop)
The numerical Stroop task is a great and popular task. Officially, it is called the Size Congruency Effect. The effect was first described by Besner and Coltheart (1979). Another nice early study on the effect was by Henik and Tzelgov (1982). There is a good review by Reike and Schwarz (2017).
Example: In this study, subjects were asked to judge which of two digits (e.g., 3 5) was larger either in physical or in numerical size… (size congruity effect).
In short, you are repeatedly shown a pair of numbers. One is physically larger than the other. You need to figure out which one is the physically larger of the pair. If the left one is larger, you press the A key (which is left on the keyboard) and if the right one is larger, you press the L key (which is right on the keyboard).
This can be confusing, because a number can be numerically smaller, yet physically larger. Look at the image below to see some examples.
The difference between how fast you respond in congruent and incongruent trials is the Size Congruency Effect.
The Numerical Stroop Task Vs Original Stroop Task
Similar to the "real" Stroop task, you respond to stimuli that are sometimes containing "confusing information".
Here is a comparison of the two:
| Condition | Congruent (Straightforward) | Incongruent (Confusing) |
|---|---|---|
| Numerical Stroop | 48 | 93 |
| Original Stroop | GREEN | BLUE |
In the Original Stroop task, the color word "GREEN" and "BLUE" represent congruent and incongruent conditions respectively.
| Numerical Stroop | Original Stroop | |
|---|---|---|
| Stimuli | Numbers | Colour Words |
| Task | Look which number is physically larger | Look what the ink color of a word is |
| Congruent (Straightforward) | The smaller number is lower in value than higher value | The ink color and word meaning are the same |
| Incongruent (Confusing) | The smaller number is higher in value than smaller number | The ink color and word meaning do not match |
References
- Henik, A., & Tzelgov, J. (1982). Is three greater than five: The relation between physical and semantic size in comparison tasks. Memory & Cognition, 10(4), 389-395. 10.3758/BF03202431
- Besner, D., & Coltheart, M. (1979). Ideographic and alphabetic processing in skilled reading of English. Neuropsychologia, 17, 467–72.
- Bowman, K.A. (2020). Response Time modeling for the size congruity effect: Early vs. late interaction. https://psyarxiv.com/2j7qz/
- Reike, D., Schwarz, W. Exploring the origin of the number-size congruency effect: Sensitivity or response bias?. Attention, Perception, & Psychophysics, 79, 383–88 (2017).
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About This Experiment
This experiment is an educational adaptation for demonstration purposes. It is not a clinical diagnostic tool. Results reflect your performance in this specific session and should not be interpreted as an assessment of your cognitive abilities.
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