We demonstrate and discuss the process of gaining information and show an example in which some specific way of gaining information about an object results in the Tsallis–and not the Shannon–form of entropy.

Examples of joint probability distributions are studied in terms of Tsallis’ nonextensive statistics both for correlated and uncorrelated variables, in particular it is explicitely shown how correlations in the system can make Tsallis entropy additive and that the effective nonextensivity...