Variable Tempo Stroop
— Experimental
A browser-based Stroop colour-naming task that accelerates across four blocks. As the inter-stimulus interval shrinks from 1000 ms to 250 ms, three novel within-person constructs capture whether your ability to override word-reading holds up under speed pressure. Clearly labelled experimental: validated constructs, novel operationalization without published norms. Free with a free account.
What the task measures
The classic Stroop effect (Stroop 1935) is the extra time and errors incurred when the ink colour of a colour word conflicts with the word itself: reading “RED” in green ink is slower than reading “GREEN” in green ink. This well-replicated phenomenon reflects the automatic capture of word-reading processes that must be overridden to name the ink colour (MacLeod 1991).
The Variable Tempo Stroop extends the classic design by administering the task across four blocks with a shrinking inter-stimulus interval — the rest period between one response and the next stimulus. As the ISI compresses from 1000 ms to 700, 450, and 250 ms, the cognitive system has progressively less time to reset before the next conflict appears.
From your trials we compute three constructs, all within-person (no population comparison):
- Tempo Amplification Ratio (TAR) — Stroop interference at the fastest block divided by interference at the slowest block. TAR > 1 means your inhibitory cost grew under time pressure; TAR = 1 means it stayed stable.
- Dynamic Inhibition (DI) — the least-squares slope of interference across tempo ranks. A steep positive slope means each tempo step added substantially more conflict cost.
- Executive Flexibility (EF) — accuracy at the fastest block as a percentage of accuracy at the slowest block. Near 100 % means you held your error rate; lower values mean the fastest tempo exceeded your error-monitoring capacity.
A high TAR combined with a steep DI and low EF suggests that structural inhibitory capacity, rather than executive flexibility, is the limiting factor when responding under temporal pressure.
Why “experimental”?
The task is clearly marked experimental for three specific reasons:
- Novel operationalization. The TAR, DI, and EF constructs as defined here — using this four-level ISI schedule and these formulas — have not appeared in peer-reviewed validation studies. The conceptual logic is grounded in established inhibition theory, but the specific metrics are unpublished.
- No normative data. No published reference sample has been run on this exact design, so no percentile or T-score can be reported without fabrication. Every figure is within-person only.
- ISI schedule is designed, not validated. The four ISI values (1000 / 700 / 450 / 250 ms) were chosen from first principles to span a meaningful tempo range; they were not taken from a published validated protocol.
The classic Stroop effect itself is not experimental — it is among the most robust findings in cognitive psychology. What is experimental is this particular tempo-manipulation design and its derived indices.
Common questions
What is the Stroop effect?
Named after J. R. Stroop (1935), the Stroop effect is the interference that arises when the word “RED” is printed in green ink and you must name the ink colour: the automatic habit of reading the word competes with the deliberate task of naming the colour. Typical interference in healthy adults is 50–200 ms depending on design, response method, and pacing.
What do the response keys mean?
The task uses four home-row keys — D for Red, F for Green, J for Blue, K for Yellow. The word and ink colour are always one of these four. Your job is to press the key that matches the ink colour, ignoring what the word says.
Why does the task get faster between blocks?
The inter-stimulus interval (ISI) is the blank gap between your response and the next fixation cross. A shorter ISI means you have less time to prepare for the next trial. Comparing your Stroop interference across the four ISI levels is the core manipulation of the task.
Is this suitable for clinical use?
No. This task is experimental research instrumentation. It produces within-person descriptive indices without validated clinical cutoffs. Do not use results for clinical assessment, diagnosis, or treatment decisions.
Is it really free?
Yes. The task is free to take with a free account. Create one in under a minute and your results appear immediately after completion.