The locus of interference in the Simon effect: an ERP study

Area of Science:

• Cognitive Neuroscience
• Psychology
• Human Motor Control

Background:

• The Simon effect is a well-documented phenomenon in cognitive psychology.
• It demonstrates how irrelevant spatial information can influence response selection.
• Understanding its underlying neural mechanisms is crucial for cognitive models.

Purpose of the Study:

• To investigate the neural basis of the Simon effect using electroencephalography (EEG).
• To differentiate between perceptual and response interference accounts of the Simon effect.
• To examine the utility of the lateralized readiness potential (LRP) in studying the Simon effect.

Main Methods:

• Experiment 1: Visual stimuli presented laterally, requiring left/right hand responses.
• Experiment 2: Distractor added to the non-target side.
• Experiment 3: Stimuli presented on the vertical meridian to avoid lateralization confounds.
• EEG recordings, focusing on P300 latency and Lateralized Readiness Potential (LRP).

Main Results:

• Spatial S-R incompatibility delayed P300 latency in Experiments 1 and 2, supporting perceptual interference.
• Lateralized stimuli in Experiments 1 and 2 obscured early LRP development.
• Experiment 3 revealed LRP signs of incorrect response preparation in incompatible trials, supporting response interference.

Conclusions:

• Both perceptual and response interference mechanisms likely contribute to the Simon effect.
• The LRP can provide insights into response interference when confounds are minimized.
• This study refines our understanding of the cognitive and neural processes underlying the Simon effect.