Handedness is an important indicator of the brain’s functional lateralization, yet it is mainly assessed using subjective self-report inventories that are prone to ceiling effects and heavily skewed distributions. Here, we propose a rapid behavioral metric for identifying hand dominance based on the variability of circular index finger movements measured by a touch-sensitive smartphone screen. By quantifying the trajectory’s variability using shape similarity analysis, we show that the index finger of the dominant hand exhibits significantly smaller movement variability than the non-dominant one.
In a study of 116 participants, this behavioral marker agreed with Edinburgh Handedness Inventory (EHI)-defined handedness in 94% of participants using eight seconds of movement data. Unlike the heavily skewed J-shaped distribution characteristic of the EHI, the difference in movement variability between the left and right fingers is approximately normally distributed. This provides a tool to quantify the degree of motor lateralization, offering a rapid behavioral method for identifying handedness using an accessible device.
The authors thank Ayako Hoshi for helping with the data collection and NTT, Inc. for funding the work. The authors thank NTT, Inc. for funding the work. Communication Science Laboratories, NTT, Inc., 3-1 Morinosato Wakamiya, Atsugi, 243-0198, Kanagawa, Japan Atsushi Takagi, Seiji Matsumura, Hiroaki Gomi & Naotoshi Abekawa Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku City, 169-0072, Tokyo, Japan The authors declare no competing interests.
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Takagi, A., Matsumura, S., Gomi, H. et al. Rapid identification of handedness via motor variability of circular finger movements. Sci Rep (2026). https://doi.org/10.1038/s41598-026-71085-1 DOI: https://doi.org/10.1038/s41598-026-71085-1
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