The Stroop effect is a psychological phenomenon that demonstrates the interference between cognitive processes. It occurs when the name of a color is printed in a color that differs from the name itself, such as the word "red" printed in blue ink. Participants are typically slower to name the color of the ink than when the word and color match. This effect highlights the challenges of selective attention and cognitive control. The Stroop test is often used in psychological research to study these processes, revealing how automatic responses can conflict with controlled responses, leading to slower reaction times and increased errors.