The left-digit bias in two-dimensional manual pointing.

Area of Science:

• Cognitive Psychology
• Human Perception
• Numerical Cognition

Background:

• The left-digit bias (LDB) influences numerical comparisons, making numbers with identical leading digits seem closer.
• Previous research established LDB in nonspatial and number-to-position tasks.

Purpose of the Study:

• To investigate the motoric effects of LDB in spatial localization tasks.
• To determine if LDB influences angular measures of number representation in circular space.
• To examine the role of visual feedback in LDB manifestation during spatial localization.

Main Methods:

• Participants localized spoken numbers (1-12.5) on a clock-face arrangement.
• Spatial localization was measured using angular responses in circular space.
• The task was conducted with and without visual feedback to assess its influence.

Main Results:

• A significant left-digit bias was observed, with numbers sharing the same leading digit localized closer together angularly.
• This effect persisted regardless of the presence or absence of visual feedback.
• LDB manifested as a compression of decimal targets towards the lower boundary of their respective digit categories.

Conclusions:

• The left-digit bias robustly impacts spatial localization, extending its influence to angular measures.
• Findings suggest cognitive, rather than perceptual, origins for LDB.
• The bias is characterized by an overweighting of leading digits, compressing numerical representations towards lower same-digit boundaries.