  Electronic communication records provide detailed information about temporal
aspects of human interaction. Previous studies have shown that individuals'
communication patterns have complex temporal structure, and that this structure
has system-wide effects. In this paper we use mobile phone records to show that
interaction patterns involving multiple individuals have non-trivial temporal
structure that cannot be deduced from a network presentation where only
interaction frequencies are taken into account. We apply a recently introduced
method, temporal motifs, to identify interaction patterns in a temporal network
where nodes have additional attributes such as gender and age. We then develop
a null model that allows identifying differences between various types of nodes
so that these differences are independent of the network based on interaction
frequencies. We find gender-related differences in communication patters, and
show the existence of temporal homophily, the tendency of similar individuals
to participate in interaction patterns beyond what would be expected on the
basis of the network structure alone. We also show that temporal patterns
differ between dense and sparse parts of the network. Because this result is
independent of edge weights, it can be considered as an extension of
Granovetter's hypothesis to temporal networks.
