The perception of rhythmic figures relies upon the mechanism of categorical perception: the tendency for the human perceptual system to perceive the infinite variety of rhythmic nuances with reference to a small number of prototypical rhythmic patterns that serve as reference structures. The subproject examines the common assumption that these reference structures are defined by very simple integer durational ratios across cultures, above all 1:1 (a perfectly even rhythm) and 1:2 (the prototypical uneven rhythm). The main method used involves test subjects listening to simple rhythms while tapping along on a small percussion instrument. The systematic deviations between what they hear and how they tap along during this process provide information about the participants’ perceptual prototypes. The subproject involves participants in Mali, Bulgaria, Bolivia, Germany, USA and several other countries.