The Simon effect and its reversal studied with event-related potentials

Area of Science:

• Cognitive Psychology
• Neuroscience
• Human Factors

Background:

• The Simon effect is a well-documented phenomenon in cognitive psychology.
• It describes slower reaction times (RT) when stimulus and response locations are incongruent.
• Previous research has explored various explanations for the Simon effect and its potential reversal.

Purpose of the Study:

• To investigate the Simon effect and its reversal using neurophysiological measures.
• To examine the role of stimulus-response (S-R) mapping in modulating the Simon effect.
• To differentiate between stimulus evaluation and response selection processes using P300 latency and motor-related potentials.

Main Methods:

• Participants performed a task involving color stimuli and randomly changing color-labeled response keys.
• Two S-R mapping conditions were employed: same-color and alternate-color key presses.
• Behavioral measures (RT), P300 latency, and motor-related potentials were recorded.

Main Results:

• A standard Simon effect was observed in the same-color mapping condition.
• A reverse Simon effect occurred in the alternate-color mapping condition, challenging existing explanations.
• P300 latencies mirrored RT patterns, indicating involvement in response selection, not stimulus evaluation.
• Motor-related potentials suggested response activation influenced by stimulus location, supporting response-interference theories.

Conclusions:

• The Simon effect and its reversal are significantly influenced by S-R mapping instructions.
• P300 latency appears to reflect response selection processes rather than stimulus evaluation duration.
• Findings support response-interference models for explaining the Simon effect and its variations.