Introduction/objective. – In a sample of 171 participants aged 6 to 18, the present investigation assessed the changes in the size of the Stroop effect with age, and its relationship with the development of expectancies.
Method. – Experiment 1 consisted in four separated tasks, involving naming print colors or reading color words in either a purely neutral or mixed incongruent/neutral condition. Experiment 2 examined changes in the effect of expectation on color naming and word reading processes with age. We manipulated the stimulus set size (from three to seven different neutral stimuli to name or read per condition) in a neutral word-reading and a neutral color-naming task.
Results. – As expected, color naming and word reading develop with age, as revealed by decreased response times. More surprisingly, the magnitude of the Stroop effect was similar across age groups. No reversed Stroop effects were observed (Experiment 1). Moreover, increasing the number of different colors to be named slowed color-naming, but did not impact word reading latencies (Experiment 2).
Conclusion. – A reduction of the cost associated with increasing neutral stimulus set size with age was also observed, revealing the development of expectation processes. The regression analysis linking the data of the two experiments confirmed the impact of expectancies on color-naming but not on word reading. The analysis also supported the idea that the Stroop effect is in part due to expectation.