When numbers get heavy: is the mental number line exclusively numerical?

Area of Science:

• Cognitive Psychology
• Neuroscience
• Human-Computer Interaction

Background:

• The mental number line, characterized by left-to-right orientation of increasing numerical values, is often cited as evidence for a unique spatial-numerical link.
• However, left-to-right orientation extends to other dimensions, suggesting a general magnitude system where different magnitudes share neural and conceptual resources.

Purpose of the Study:

• To investigate the nature of information represented along the mental number line.
• To determine if the mental number line exclusively represents numerical magnitudes or can accommodate non-numerical ones.

Main Methods:

• Participants performed the Spatial-Numerical Association of Response Codes (SNARC) task.
• The SNARC task involved participants responding to numerical stimuli presented spatially.
• Participants sometimes wore wrist weights to manipulate perceived magnitude associated with left/right sides.

Main Results:

• Weighting the left wrist, linking less weight to the left and more to the right, disrupted the typical left-to-right orientation of the mental number line.
• This manipulation eliminated the behavioral trace of the spatial-numerical association for numbers.
• Findings indicate that the mental number line can simultaneously represent numerical and non-numerical magnitudes.

Conclusions:

• The mental number line does not exclusively represent numerical information.
• Spatial organization on the mental number line reflects a shared representational currency (more/less relations) across different magnitude dimensions.
• This suggests a dynamic integration of magnitude dimensions rather than a unique spatial-numerical system.