The Stroop Effect and Other Sneaky Brain Games

Having been associated for long with Vikram A. Sarabhai Community Science Centre (VASCSC), the pioneering science centre in the country, I always source STEM education materials and kits from them.

A few weeks ago, we received one such package I had ordered. The wonderful thing about VASCSC material is that they don’t let an inch of space go to waste. So the large envelope in which the kit came was also printed with any number of science games and puzzles.

The one that my 6 year old grand daughter and I really had fun with was the Stroop Effect.

It was all giggles as she held out the sheet with a bunch of words and asked me to look at them.  The word “RED” was written in bright blue ink. She asked me to say the colour, not the word..

“Red!” I said instinctively.

“No!” she giggled. “It’s blue ! You have to say the colour of the ink!”

Oh.

And just like that, we stumbled headfirst into the Stroop Effect—a clever little quirk of our brains first identified by psychologist John Ridley Stroop in 1935. Stroop, an American psychologist conducted a series of studies as part of his PhD research. He was fascinated by how automatic processes—like reading—can interfere with other tasks, such as identifying colours. In his now-famous experiment, he showed that when colour words (like “red” or “green”) were printed in mismatched ink colours, people took longer to name the ink colour. This delay, or interference, revealed something profound about how our brains handle conflicting information.

So what is the Stroop Effect?

The classic version of the Stroop test asks you to name the colour of the ink in which a different colour name is written. Like the word “Green” printed in red ink. Sounds simple, right? But our brains are wired to read words so automatically that it slows us down, or even trips us up, when the word and the ink colour don’t match.

This interference between what we read and what we see is a fascinating peek into how our minds juggle competing bits of information.

Why does it matter?

What seems like a party trick actually has deeper implications. Psychologists use the Stroop test to study attention, processing speed, and cognitive control. In clinical settings, it helps assess brain injuries, dementia, and even ADHD. The longer it takes for a person to respond correctly, the more it can reveal about how their brain is functioning.

But even beyond labs and clinics, understanding the Stroop Effect has very real applications.

Take driving, for instance. Ever noticed how highway signs use simple fonts and colours? Imagine if a stop sign said “Go” in red letters—confusing, right? Designers rely on principles like those revealed by the Stroop Effect to make sure our brains process the right cue first.

It’s not just colours and words

Once you start noticing, these mental speed bumps are everywhere. Consider this: we all know that when we try rubbing our stomach with one hand and patting our head with the other, we run into hilarious situations. It is tricky, because your brain is trying to coordinate two conflicting patterns of movement. That’s a bit like motor interference, another cousin in the Stroop family.

Or think of the McGurk Effect, where what you see affects what you hear. If a video shows someone saying “ga,” but the sound is “ba,” your brain may hear “da.” Vision wins over sound, just like reading wins over colour in the Stroop test.

And then there is change blindness—when something in a visual scene changes, and we don’t notice because our attention is elsewhere. Magicians depend a lot on this trick, as also UX designers, who try to guide user attention in websites and apps using visual cues.

A lesson in humility

For me, discovering the Stroop Effect was a gentle reminder that our brains, for all their wonder, are not infallible. They’re predictably imperfect, prone to biases and blind spots. Well, that makes life more exciting!

–Meena

Image: Venderbilt University site