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To communicate with other intelligent life a civilization has to develope some sort of technology. If again we consider the Earth's case, this happened for humans but not, for example, for dolphins. The factor $f_c$ measures the fraction of civilizations that develop communicative technology. As intelligence and curiosity seem to go hand-in-hand, it seems conceivable that all intelligent lifeforms might evolve towards a technological form. $f_c = 1$  \cite{nishimichi_testing_2014}  \href{http://en.wikipedia.org/wiki/Fermi_paradox}{Fermi}  \href{http://en.wikipedia.org/wiki/Rare_Earth_Hypothesis}{Rare %\href{http://en.wikipedia.org/wiki/Fermi_paradox}{Fermi}  %\href{http://en.wikipedia.org/wiki/Rare_Earth_Hypothesis}{Rare  Earth}