  In contrast to long-term relationships, far less is known about the temporal
evolution of transient relationships, although these constitute a substantial
fraction of people's communication networks. Previous literature suggests that
ratings of relationship emotional intensity decay gradually until the
relationship ends. Using mobile phone data from three countries (US, UK, and
Italy), we demonstrate that the volume of communication between ego and its
transient alters does not display such a systematic decay, instead showing a
lack of any dominant trends. This means that the communication volume of egos
to groups of similar transient alters is stable. We show that alters with
longer lifetimes in ego's network receive more calls, with the lifetime of the
relationship being predictable from call volume within the first few weeks of
first contact. This is observed across all three countries, which include
samples of egos at different life stages. The relation between early call
volume and lifetime is consistent with the suggestion that individuals
initially engage with a new alter so as to evaluate their potential as a tie in
terms of homophily.
