The word says one thing; the ink says another
The Stroop effect is the interference that can make naming a colour slower when a printed word names a different colour.
Imagine RED printed in blue ink. The task is to say “blue”, ignoring the word. A perfectly familiar word has suddenly become an unhelpful neighbour.
A simple task became a classic experiment
In his 1935 study, J. Ridley Stroop asked 100 students to name ink colours while ignoring conflicting colour words. He also timed them naming coloured squares.
On average, naming colours took much longer with the conflicting words. The task was not simply to read a colourful page: the instruction changed which information mattered.
Reading can intrude on another job
A familiar written word can bring its spoken name to mind while you are trying to name the ink. Those competing responses help explain the awkward pause.
Researchers study this as part of selective attention: following one feature while ignoring another. The exact processes behind the interference are still debated.
One mix-up is not a verdict on your brain
Two experiments published in 2017 found interference both when participants spoke colour names and when they pressed keys. Other distraction patterns differed between the tasks, showing that the details matter.
This small illustration is not an intelligence or medical test. For another surprise involving familiar things, discover why recognising a logo does not guarantee remembering its details.