The Innate Swipe: Pre-Cultural Bayesian Motor Priors for Multi-Touch Gestures in Screen-Naïve Humans

The multi-touch gesture set—the horizontal swipe, pinch-to-zoom, tap, and edge-drag—is universally treated as a designed convention that users acquire through exposure. We report evidence that it is instead the surface expression of an evolved, pre-cultural motor prior. Using a $\text{Platonic slab}$—a responsive capacitive surface that renders no user interface—we elicited gestures in response to non-verbal prompts from four cohorts, including screen-naïve neonates ($n=41$) and consenting screen-naïve adults ($n=28$). Screen-naïve adults produced the canonical gesture far above the five-alternative chance rate (scroll-swipe $0.71$, pinch-to-zoom $0.66$, tap-select $0.58$; all $p<10^{-6}$) and were well-calibrated in the Tetlock sense (Brier $0.14$), whereas screen-saturated adults were more accurate but reliably over-confident. Fitting an innateness temperature $\beta$ yields $\hat{\beta }=3.9$ (95% CI $[3.1,4.8]$) on the responsive slab but only $0.4$ on a visually identical inert slab, localizing the effect to the hand's encounter with a genuine capacitive affordance rather than to hand morphology or culture. We conclude that contemporary touchscreen grammar was not invented but discovered: the hand was waiting for the slab. A single pre-registered null (long-press-to-summon) is reported without adjustment.