This paper attempts to improve the understanding of shape-sound symbolism by isolating the phonological features of the pseudo-words used in the experiments and the graphic features of the figures matched with them. In a first section, it analyses the classic maluma-takete effect from both an articulatory and acoustical point of view, showing that it is determined by several phonological features operating simultaneously. In a second section, two new experiments are presented to isolate, first, vowels and consonants and, second, the consonant features of [voicing], [manner of articulation], [nasality] and [place of articulation] in relation to the graphic features of {acuity}, {continuity}, {curvature}, {regularity}, and {density}. The main result is that each phonological feature shows a different pattern of correlations with the graphic features, determined by its subtle phono-articulatory and phono-acoustic structure.