Number, size, and space associated in a common system by distinct mechanisms

Area of Science:

• Cognitive Psychology
• Neuroscience
• Magnitude Representation

Background:

• The spatial numerical association of response codes (SNARC) effect links small numbers to left responses and large numbers to right responses.
• The size congruity effect (SCE) shows faster responses when numerical value and physical size are congruent.
• Previous research suggested SNARC and SCE are independent under explicit processing.

Purpose of the Study:

• To investigate the interplay between number, size, and spatial representations.
• To determine if common or distinct mechanisms underlie these associations.
• To examine these effects using an implicit parity judgment task.

Main Methods:

• Implicit parity judgment task.
• Manipulation of numerical value and physical size.
• Measurement of response times and accuracy.
• Analysis of SNARC and SCE interactions.

Main Results:

• The SNARC effect, SCE, and a SNARC-like effect (size-space mapping) were all observed.
• A significant interaction revealed the SNARC effect was larger in SCE-congruent trials.
• SCE was primarily present in SNARC-compatible trials, but number-space mapping (SNARC) dominated incongruent trials.

Conclusions:

• Number, size, and space share overlapping yet distinct neural mechanisms.
• These findings support the A Theory of Magnitude (ATOM) regarding a generalized magnitude system.
• Implicit processing reveals complex interactions between numerical, size, and spatial information.