Integrating spatial and temporal metrics in smartphone-based finger tapping test: Insights into motor performance...

The Finger Tapping Test (FTT) is a classical tool for assessing motor timing. While traditionally limited to temporal measures, smartphone-based versions enable simultaneous recording of both temporal and spatial parameters, opening new opportunities for digital phenotyping of motor behavior. We aimed to characterize the temporal evolution of both temporal and spatial metrics during a 30-second smartphone-based FTT.

Eighty healthy adults performed the FTT with both hands using a custom smartphone application. We quantified number of taps, intertap interval, total displacement, and elliptical area across six consecutive 5-second intervals. Friedman's ANOVA and Kendall's W were applied to assess time-dependent changes and effect sizes.

Temporal parameters were sensitive to fatigue: tap count and total displacement decreased, while intertap interval increased across blocks. In contrast, the elliptical area remained stable, indicating preserved spatial control despite temporal deterioration. The largest effect size was found for intertap interval, particularly among female participants (Kendall's W = 0.8).

Unlike traditional FTT implementations that capture only timing, our smartphone-based approach integrates spatial metrics, revealing a dissociation between temporal fatigue and spatial stability during repetitive tapping.

These findings demonstrate the added value of spatial metrics in digital motor assessments, highlighting the potential of smartphone-based FTT as a scalable and low-cost tool for behavioral neuroscience. By bridging temporal and spatial domains, this approach advances methodological innovation in motor performance analysis and paves the way for applications in both research and clinical populations.