The lateralized stroop: a meta-analysis and its implications for models of semantic processing.

Area of Science:

• Cognitive Psychology
• Neuroscience
• Human Brain Function

Background:

• The prevailing theory suggests greater Stroop interference in the left hemisphere (LH) due to its verbal processing advantage.
• However, empirical data often shows no significant difference in Stroop interference magnitude between the left hemisphere (LH) and right hemisphere (RH).
• This aligns with findings in lateralized semantic priming research.

Purpose of the Study:

• To conduct a meta-analysis of lateralized Stroop experiments.
• To determine if the LH produces significantly more interference than the RH.
• To investigate hemispheric differences in Stroop interference magnitude.

Main Methods:

• A meta-analysis was performed on a subset of lateralized Stroop experiments.
• Exclusionary criteria were applied, resulting in 19 included studies.
• Effect sizes for differential interference were calculated, with 26 estimates included.

Main Results:

• The overall effect size (d+=.06) indicated no significant difference in Stroop interference magnitude between the hemispheres.
• The LH interference effect (d+=.73) and RH interference effect (d+=.67) were both significant when examined independently.
• Hemispheric asymmetry in Stroop interference was not supported by this meta-analysis.

Conclusions:

• There is no significant difference in the magnitude of Stroop interference between the left and right hemispheres.
• Both hemispheres exhibit significant within-hemisphere interference effects.
• Findings challenge the prevailing speed of processing account for Stroop lateralization and are discussed in relation to lateralized semantic priming.