Early braille reading as an exploratory procedure: Perceptual sensitivity to numerosity and cell content

Braille readers must learn to encode braille symbols via active exploratory touch. The former may be novel, but the latter is an extant exploratory skill. We investigated naive, blindfolded sighted participants' scanning of braille text at different speeds, in order to measure their perceptual sensitivity to braille cell numerosity differences and changes in the interior content of target cells. Slower finger velocities lead to greater perceptual sensitivity —itself not remarkable— but this heightened sensitivity necessarily comes from finger velocities that increasingly fluctuate between acceleration and deceleration. We revisit considerations of perceptual constancy, texture and movement kinematics.