Pseudoneglect for the bisection of mental number lines

Loftus, Andrea M., Nicholls, Michael E. R., Mattingley, Jason, Chapman, Heidi L. and Bradshaw, John L. (2009) Pseudoneglect for the bisection of mental number lines. The Quarterly Journal of Experimental Psychology, 62 5: 925-945. doi:10.1080/17470210802305318

Author Loftus, Andrea M.
Nicholls, Michael E. R.
Mattingley, Jason
Chapman, Heidi L.
Bradshaw, John L.
Title Pseudoneglect for the bisection of mental number lines
Journal name The Quarterly Journal of Experimental Psychology   Check publisher's open access policy
ISSN 1747-0218
Publication date 2009-01-01
Year available 2009
Sub-type Article (original research)
DOI 10.1080/17470210802305318
Open Access Status
Volume 62
Issue 5
Start page 925
End page 945
Total pages 21
Place of publication Hove, E. Sussex, United Kingdom
Publisher Psychology Press
Language eng
Abstract Patients with unilateral neglect of the left side bisect physical lines to the right whereas individuals with an intact brain bisect lines slightly to the left (pseudoneglect). Similarly, for mental number lines, which are arranged in a left-to-right ascending sequence, neglect patients bisect to the right. This study determined whether individuals with an intact brain show pseudoneglect for mental number lines. In Experiment 1, participants were presented with visual number triplets (e.g., 16, 36, 55) and determined whether the numerical distance was greater on the left or right side of the inner number. Despite changing the spatial configuration of the stimuli, or their temporal order, the numerical length on the left was consistently overestimated. The fact that the bias was unaffected by physical stimulus changes demonstrates that the bias is based on a mental representation. The leftward bias was also observed for sets of negative numbers (Experiment 2)—demonstrating not only that the number line extends into negative space but also that the bias is not the result of an arithmetic distortion caused by logarithmic scaling. The leftward bias could be caused by a rounding-down effect. Using numbers that were prone to large or small rounding-down errors, Experiment 3 showed no effect of rounding down. The task demands were changed in Experiment 4 so that participants determined whether the inner number was the true arithmetic centre or not. Participants mistook inner numbers shifted to the left to be the true numerical centre—reflecting leftward overestimation. The task was applied to 3 patients with right parietal damage with severe, moderate, or no spatial neglect (Experiment 5). A rightward bias was observed, which depended on the severity of neglect symptoms. Together, the data demonstrate a reliable and robust leftward bias for mental number line bisection, which reverses in clinical neglect. The bias mirrors pseudoneglect for physical lines and most likely reflects an expansion of the space occupied by lower numbers on the left side of the line and a contraction of space for higher numbers located on the right.
Keyword Number line
Mental space
Number representation
Line bisection
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Queensland Brain Institute Publications
ERA 2012 Admin Only
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 34 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 34 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Thu, 20 Oct 2011, 03:10:58 EST by Debra McMurtrie on behalf of Queensland Brain Institute