Stroop Effect Experiments

The Stroop effect experiments, first reported by John Ridley Stroop in his 1935 doctoral dissertation, demonstrated that naming the ink color of a word takes measurably longer when the word itself names a different color, such as the word red printed in green ink, than when the word and its ink color agree or the stimulus is a plain colored block. Stroop's central studies compared the time taken to read color names printed in black ink, read color names printed in mismatched ink colors, and name the colors of plain colored patches, finding that incongruent color words interfered sharply with naming speed while congruent or neutral stimuli did not. Stroop interpreted the effect as evidence that reading a familiar word is a highly practiced, largely automatic process that a slower, more effortful task such as naming an ink color cannot suppress. The Stroop task became one of the most widely used measures in cognitive psychology and neuropsychology for studying selective attention, automaticity and cognitive control, and countless variants of the original color-word design remain in active use in laboratories today.