The efficiency of Gaussian adaptation relies on the theory of information due to Claude E. Shannon (see information content). When an event occurs with probability "P", then the information −log("P") may be achieved. For instance, if the mean fitness is "P", the information gained for each individual selected for survival will be −log("P") – on the average - and the work/time needed to get the information is proportional to 1/"P". Thus, if efficiency, E, is defined as information divided by the work/time needed to get it we have: