  Taking informed decisions, namely acting rationally, is an individual
attitude of paramount relevance in nature and human societies. In this work, we
study how rationality spreads in a community. To this end, through an
agent-based model, we analyse the dynamics of a population whose individuals,
endowed with a rational attitude controlled by a numerical parameter, play a
simple game. The latter consists of multiple strategies, each associated with a
given reward. The proposed model is then used as a benchmark for studying the
behaviour of Bitcoin users, inferred by analysing transactions recorded in the
Blockchain. Remarkably, a population undergoing a sharp transition from
irrational to rational attitudes shows a behavioural pattern similar to that of
Bitcoin users, whose rationality showed up as soon as their cryptocurrency
became worth just a few cents (USD). To conclude, a behavioural analysis that
relies on an entropy measure combined with a simple agent-based model allows us
to detect the rise of rationality across a community. Although further
investigations are essential to corroborate our results, we deem the proposed
approach could also get used for studying other social phenomena and
behaviours.
