Hemispheric Lateralization of Arithmetic Facts and Magnitude Processing for Two-Digit Numbers

Area of Science:

• Cognitive Neuroscience
• Neuropsychology
• Human Brain Function

Background:

• The human brain exhibits functional asymmetry (laterality) across cognitive domains.
• Numerical cognition processing may involve both bilateral and unilateral mechanisms.
• Retrieval of arithmetic facts is hypothesized to be left-hemisphere lateralized.

Purpose of the Study:

• To evaluate the claim of left-hemisphere lateralization for arithmetic fact retrieval.
• To investigate hemispheric processing asymmetries for multiplicatively related number triplets.
• To examine if right-hemisphere-only transmission offers an advantage over left-hemisphere transmission.

Main Methods:

• Healthy participants (n=23) performed a number bisection task with multiplicatively related triplets (e.g., 12_16_20).
• Stimulus presentation was lateralized to assess hemispheric processing advantages.
• A control task evaluated processing of incompatible number pairs across visual hemifields.

Main Results:

• The multiplicativity effect in the number bisection task was replicated.
• No significant hemispheric processing asymmetries were observed for multiplicative items.
• A control task showed no increased processing disadvantage for incompatible number pairs with lateralized presentation.

Conclusions:

• The hypothesis of left-hemisphere lateralization for arithmetic fact retrieval was not supported in this task.
• Participants likely used verbal working memory for number triplets, allowing interhemispheric communication.
• Lateralized presentation effects may be more apparent in simpler tasks or earlier processing stages.