Interaction between space and number representations during motor preparation in manual aiming

Area of Science:

• Cognitive Psychology
• Neuroscience
• Human Motor Control

Background:

• Evidence suggests a spatial component in number magnitude representation, with smaller numbers linked to the left and larger numbers to the right.
• The 'mental number line' theory posits an orientation from left (small numbers) to right (large numbers) in spatial representation.

Purpose of the Study:

• To investigate whether the spatial-numerical association arises from a continuous or categorical mapping.
• To examine the influence of number magnitude and spatial location on motor planning and execution.

Main Methods:

• Measured reaction times (RTs), movement times (MTs), spatial accuracy, and endpoint pressure during manual aiming tasks.
• Subjects reached with the right hand towards visual digit targets presented at various horizontal locations.
• A GO/NO-GO task ensured processing of digit parity (odd/even).

Main Results:

• Movement times, accuracy, and pressure showed no digit-related effects.
• Reaction times were shorter for smaller digits, irrespective of target location.
• An interaction between target location and number magnitude was observed, with RTs shortest when magnitude and location were congruent.

Conclusions:

• Motor preparation is influenced by both direct number magnitude activation and the congruity between number magnitude and spatial location.
• Findings support a continuous mapping model between mental number representation and physical space.