Exploring handedness asymmetries in the Simon effect

Area of Science:

• Cognitive Psychology
• Human Factors
• Neuroscience

Background:

• The Simon effect demonstrates faster reaction times (RTs) for spatially corresponding stimulus-response pairings.
• An asymmetry in the Simon effect is often observed, with larger effects for stimuli on the dominant hand's side.
• The underlying cause of this asymmetry (hand dominance vs. conceptual spatial codes) requires further investigation.

Purpose of the Study:

• To replicate and examine the nature of the Simon effect asymmetry.
• To differentiate between hand dominance and conceptual spatial codes as drivers of the asymmetry.
• To determine if the asymmetric pattern is specific to spatial stimuli.

Main Methods:

• Compared manual key-presses (left/right) with vocal responses ('left'/'right').
• Assessed the Simon effect using spatially located squares versus centered words ('Left'/'Right').
• Conducted a second experiment with non-visible hands and response boxes to control for visual cues.

Main Results:

• The Simon effect asymmetry was replicated specifically for spatial stimulus-manual response tasks.
• A general dominant-hand reaction time advantage was observed, independent of the Simon effect.
• This dominant-hand advantage explained the apparent asymmetry by comparing RTs from different hands.

Conclusions:

• The Simon effect asymmetry in manual tasks is primarily driven by hand dominance, not general spatial coding.
• The observed asymmetry is specific to tasks involving spatial stimuli and manual responses.
• A dominant-hand reaction time advantage influences the interpretation of Simon effect data.