Sound to meaning correspondences in spoken language are assumed to be largely arbitrary. However, research has identified a number of exceptions to the arbitrariness assumption. In particular, non-arbitrary mappings between sound and shape, the bouba/kiki effect, have been documented across diverse languages and both children and adults are sensitive to this type of sound symbolic mapping. The cognitive basis for the associations between nonword labels and particular shapes remains poorly understood making it difficult to predict how findings generalize beyond the limited stimuli tested. To identify systematic bases for sound-to-shape mappings, we collected ratings of roundedness and pointedness for a large database of pseudowords. We find that attributes of both consonants and vowels are systematically related to judged shape meanings of pseudowords, and offer hypotheses as to the cognitive mechanisms underlying the observed patterns.