In this presentation, Octavio Pardo-Virto will review multiple traditional theories on letter perception by complimenting them with the most relevant findings in the field of psychophysics and our visual system. These findings are very well known to the legibility research community but less common in type design literature. Pardo-Virto will explain the blurry mechanisms of perception in visual channels; from a physiological aspect to how we identify and read letters. This will provide a better understanding of the value in different design strategies focused on enhancing the legibility of typefaces. This presentation will walk through a new framework to approach legibility research studies that’s not based on letterforms, but in our visual frequency perception, using variable fonts and bayesian experimental methods.