Implicit response-irrelevant number information triggers the SNARC effect: evidence using a neural overlap paradigm

Area of Science:

• Cognitive Psychology
• Neuroscience
• Numerical Cognition

Background:

• The spatial-numerical association of response codes (SNARC) and numerical distance effect (NDE) suggest number activates spatial representations.
• Existing evidence primarily stems from tasks explicitly involving number symbols or magnitude judgments.

Purpose of the Study:

• To investigate if implicit, task-irrelevant numerosity information can activate spatial number representations.
• To explore this using the neural overlap paradigm with nonsymbolic and auditory number stimuli.

Main Methods:

• Four experiments were conducted using the neural overlap paradigm.
• Participants judged color or orientation of stimuli, while implicitly processing numerosity from visual arrays or auditory numbers.
• SNARC effects were measured in relation to task-irrelevant numerical information.

Main Results:

• SNARC effects were observed exclusively in orientation judgment tasks, irrespective of stimulus modality (visual or auditory).
• Stronger SNARC effects were found for smaller numbers (1-4) compared to larger numbers (6-9).
• This indicates quantity extraction occurs but is not precise across the entire number range.

Conclusions:

• Overlap in parietal processing between numerical and orientation information likely underlies the observed SNARC effects.
• Implicit numerical information, even when task-irrelevant, can influence spatial representations.
• The findings suggest a non-uniform precision in quantity extraction across different number ranges.