Arm dominance is an emergent effect of practice executing complex trajectory shapes required by tools and objects
- 1Department of Neurology, David Geffen School of Medicine, University of California
- 2Departments of Neurology, Neuroscience, and Physical Medicine and Rehabilitation, School of Medicine, Johns Hopkins University
- 3Santa Fe Institute
Abstract
Limb dominance is a human behavioral characteristic with many cultural, practical, scientific and clinical implications. Yet why the dominant limb performs better across a range of motor skill-requiring tasks remains unanswered. Is it because of an intrinsic hemispheric advantage or instead is it the result of life-long practice with the dominant side? We tested these alternatives using two tasks. The first was 3D reaching with either an inertial challenge or the need to use a stick-like tool. The second required participants to write with their dominant and non-dominant elbows. We applied a novel geometric analysis to quantify movement-trajectory shape. We show that (1) tool-use unmasks markedly inferior control in the non-dominant arm, and this is because tools impose the need to generate unfamiliarly shaped movement trajectories; and (2) there is no general dominant limb motor control advantage, only task-specific experience or practice. These results reframe dominance as predominantly about learned control of tool kinematics rather than baseline asymmetry in control of limb dynamics.
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BibTeX
@article{arac2026dominance,
title = {{Arm dominance is an emergent effect of practice executing complex trajectory shapes required by tools and objects}},
author = {Ahmet Arac and Nicolas Y. H. Jeong Lee and John W. Krakauer},
journal = {Proceedings of the National Academy of Sciences},
year = {2026},
month = jun,
doi = {10.1073/pnas.2601569123},
url = {https://doi.org/10.1073/pnas.2601569123},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Arm dominance is an emergent effect of practice executing complex trajectory shapes required by tools and objects
AU - Ahmet Arac
AU - Nicolas Y. H. Jeong Lee
AU - John W. Krakauer
PY - 2026
DA - 2026/06/30
JO - Proceedings of the National Academy of Sciences
DO - 10.1073/pnas.2601569123
UR - https://doi.org/10.1073/pnas.2601569123
AB - Limb dominance is a human behavioral characteristic with many cultural, practical, scientific and clinical implications. Yet why the dominant limb performs better across a range of motor skill-requiring tasks remains unanswered. Is it because of an intrinsic hemispheric advantage or instead is it the result of life-long practice with the dominant side? We tested these alternatives using two tasks. The first was 3D reaching with either an inertial challenge or the need to use a stick-like tool. The second required participants to write with their dominant and non-dominant elbows. We applied a novel geometric analysis to quantify movement-trajectory shape. We show that (1) tool-use unmasks markedly inferior control in the non-dominant arm, and this is because tools impose the need to generate unfamiliarly shaped movement trajectories; and (2) there is no general dominant limb motor control advantage, only task-specific experience or practice. These results reframe dominance as predominantly about learned control of tool kinematics rather than baseline asymmetry in control of limb dynamics.
SN - 0027-8424
SN - 1091-6490
ER -