You may have heard of the Stroop effect, and you may have even seen it demonstrated. But can the Stroop effect itself be manipulated? This short demo may show that it can.
In case you’re not familiar with the effect, it occurs when you try to say the color a word is printed in, while the word itself names a color (so if you see “RED” you should say “green.”) Try it with these short lists. Remember, say the color the word is PRINTED in, not the color named by the word.
Which column was most difficult? Let’s make this a poll:
The basic Stroop effect predicts that Columns 2 and 3 will be much harder than Column 1, since reading the name of a different color makes it more difficult for us to say the color of the letters. But if we’ve replicated a nuance of the effect here, Column 3 should be more difficult than Column 2. Why? It’s a process called “negative priming.” In Column 3, the color of the letters in a word is named in the word above it (“Black” is printed in purple, “Red”is printed in black, and so on).
Normally when we’re “primed” with a word or an image, it’s easier to produce that word or related words later on (so “detective” might help us remember “police” in a list like “cat, airplane, telephone, police, museum”). But in our example above, priming actually acts the opposite way, and makes the task more difficult.
A 1989 study led by Stephen Tipper (who first observed the negative priming effect) suggested that children might actually have a different response to negative primes than adults: the effect appeared to be much smaller in children. But in 2004, Verena Pritchard and Ewald Neumann found no difference in negative priming in children versus adults. Which study was correct?
To get to the bottom of the matter, Pritchard and Neumann conducted a much larger study of 244 individuals, in five separate groups ranging from 5 to 25 years old. The experimenters went into classrooms and tested kids using flash cards with lists of eleven words much like the example above. Each card had just one list, which was either a standard Stroop task like in Column 2 of our example, or a negative priming task like Column 3. The experimenter timed the respondents and tracked their number of errors. Here’s a first look at the results:
The green bars show reaction times (for each word) with the standard Stroop task. The yellow bars show the reaction times when negative priming is used. For every age group, the reaction times are significantly longer with negative priming. Indeed, the difference between the Stroop reaction times and the negative priming times is significantly larger for younger kids than for adults!
What’s going on here? This is the opposite of what Tipper’s team found. Pritchard and Neumann point out that young kids are generally slower to react, so when you properly account for that by taking a logarithm of their reaction times, there’s no difference between the scores for children and adults. Everyone they tested responded the same to negative primes, it’s just that adults do the task faster.
Now arguably kids may just not be as good at reading as adults, which somehow might affect the results of this study. So in a new experiment, Pritchard and Neumann repeated the test using colored blobs instead of words:
This time the task was simply to name the color of the centered blob while ignoring the two flanking blobs. Once again, the same result was found: Both kids and adults experience negative priming, and there’s no significant difference between the effect for kids and adults.
So while adults most definitely are better at the Stroop task than kids, negative priming affects kids and adults equally. Pritchard and Neumann believe this means that there’s a different cognitive mechanism for negative priming versus the self-disciplined inhibition response required for the Stroop task. Negative priming may be a relatively automatic function, while inhibiting the urge to just read the word instead of naming its color may be a more conscious process.
Verena E. Pritchard, Ewald Neumann (2009). Avoiding the potential pitfalls of using negative priming tasks in developmental studies: Assessing inhibitory control in children, adolescents, and adults. Developmental Psychology, 45 (1), 272-283 DOI: 10.1037/a0014168