  In this work, we attempt to capture patterns of co-occurrence across vowel
systems and at the same time figure out the nature of the force leading to the
emergence of such patterns. For this purpose we define a weighted network where
the vowels are the nodes and an edge between two nodes (read vowels) signify
their co-occurrence likelihood over the vowel inventories. Through this network
we identify communities of vowels, which essentially reflect their patterns of
co-occurrence across languages. We observe that in the assortative vowel
communities the constituent nodes (read vowels) are largely uncorrelated in
terms of their features and show that they are formed based on the principle of
maximal perceptual contrast. However, in the rest of the communities, strong
correlations are reflected among the constituent vowels with respect to their
features indicating that it is the principle of feature economy that binds them
together. We validate the above observations by proposing a quantitative
measure of perceptual contrast as well as feature economy and subsequently
comparing the results obtained due to these quantifications with those where we
assume that the vowel inventories had evolved just by chance.
