Psychohistory is a term coined by
Isaac Asimov in his
Foundation Series. The character
Hari Seldon, a
mathematician, develops this branch of
mathematics. It is basically a statistical analysis of the past and based on this information it becomes possible to
predict the future.
Originally we are led to believe that this new technique can only be used to predict very large changes in humanity. As the series progresses we find that it gets refined to be able to predict even individuals. (IIRC)
From Foundation by Isaac Asimov:
...Gaal Dornick, using nonmathematical concepts, has defined psychohistory to be that branch of mathematics which deals with the reactions of human conglomerates to fixed social and economic stimuli...
...Implicit in all these definitions is the assumption that the human conglomerate being dealt with is sufficiently large for valid statistical treatment. The necessary size of such a conglomerate my be determined by Seldon's First Theorem which...
...A further necessary assumption is that the human conglomerate be itself unaware of psychohistoric analysis in order that its reactions be truly random...
The basis of all valid psychohistory lies in the development of the Seldon Functions which exhibit properties congruent to those of such social and economic forces as...
-- Encyclopedia Galactica