The Stroop Effect
In his historic study, Stroop found that reading names of colors interfered with individuals’ ability to name the ink color the word was printed in when the two differed (i.e., the word “BLUE” written in red ink) (1935). However, the basis of this phenomenon can be traced back to Cattell who found that naming colors and pictures took twice as long to accomplish than reading the word these colors or pictures represented (1886). He concluded that this was due to reading being an automatic process while identifying colors or pictures requires a conscious effort (Cattell, 1886). MacLeod (1991) reflects that it was Cattell’s work which strongly influenced future psychologist including Stroop.
In his experiment, Stroop investigated how the reaction time to name colors increased when it conflicted with the automatic process of reading. He broke down his experiment into three parts. In the first, he tested how reading the name of a color printed in a different ink color (i.e., BLUE) differed from reading the name of a color printed in black ink (i.e., BLUE). The difference between the name of the color and the ink color it was printed in caused a slight interference resulting in an increased reaction time of 2.3 seconds (Stroop, 1935).
In the second part of his experiment, Stroop (1935) looked at reaction time differences between naming the color of solid blocks (i.e., ■ ■ ■ ■ ■) versus naming the color of the ink not the name of the color (i.e., responding “RED” for BLUE). He found that participants required 74% more time to name the color of the ink when it did not agree with the name of the color (Stroop, 1935). Stroop concluded that it was the interference between the automatic process of reading the names of the colored words and the conscious process of naming the ink color which created such a difference in reaction times (1935).
In the third and final part of his experiment, Stroop (1935) examined how practice could impact reaction times. Over a two week period, participants practiced various tasks which used colored words, names of colors and colored blocks. It was found that practice decreased reaction time when naming ink color when it conflicted with the name of the color (i.e., answering “RED” for BLUE) and that such interference could disappear if newly established (Stroop, 1935). The second discovery during this part of the experiment was that reaction times for reading the name of the color and naming the ink color were almost equal at the end of the practice period (Stroop, 1935). Even though this resulted in a significant increase in reaction time for reading the name of the color (i.e., saying “BLUE” for BLUE), Stroop concluded that this equaling of reaction times signified that the interference between the automated process of reading and the conscious process of naming the ink color could disappear with practice (1935).
Over the years, several experiments and tests have been devised to study how...