Jean-Gabriel De Tarde or Gabriel Tarde in short (12 March 1843, Sarlat-la-Can*da, Dordogne -- 13 May 1904, Paris) French sociologist, criminologist and social psychologist who conceived sociology as based on small psychological interactions among individuals (much as if it were chemistry), the fundamental forces being imitation and innovation. Among the concepts that Tarde initiated were the group mind (taken up and developed by Gustave Le Bon, and sometimes advanced to explain so-called herd behaviour or crowd psychology), and economic psychology, where he anticipated a number of modern developments.
Tarde
Gustave Le Bon