<P> Because political science is essentially a study of human behaviour, in all aspects of politics, observations in controlled environments are often challenging to reproduce or duplicate, though experimental methods are increasingly common (see experimental political science). Citing this difficulty, former American Political Science Association President Lawrence Lowell once said "We are limited by the impossibility of experiment . Politics is an observational, not an experimental science ." Because of this, political scientists have historically observed political elites, institutions, and individual or group behaviour in order to identify patterns, draw generalizations, and build theories of politics . </P> <P> Like all social sciences, political science faces the difficulty of observing human actors that can only be partially observed and who have the capacity for making conscious choices unlike other subjects such as non-human organisms in biology or inanimate objects as in physics . Despite the complexities, contemporary political science has progressed by adopting a variety of methods and theoretical approaches to understanding politics and methodological pluralism is a defining feature of contemporary political science . </P> <P> The advent of political science as a university discipline was marked by the creation of university departments and chairs with the title of political science arising in the late 19th century . In fact, the designation "political scientist" is typically for those with a doctorate in the field, but can also apply to those with a master's in the subject . Integrating political studies of the past into a unified discipline is ongoing, and the history of political science has provided a rich field for the growth of both normative and positive political science, with each part of the discipline sharing some historical predecessors . The American Political Science Association was founded in 1903 and the American Political Science Review was founded in 1906 in an effort to distinguish the study of politics from economics and other social phenomena . To date, the American Political Science Review is the leading journal in Political Science research . </P> <P> In the 1950s and the 1960s, a behavioural revolution stressing the systematic and rigorously scientific study of individual and group behaviour swept the discipline . A focus on studying political behaviour, rather than institutions or interpretation of legal texts, characterized early behavioural political science, including work by Robert Dahl, Philip Converse, and in the collaboration between sociologist Paul Lazarsfeld and public opinion scholar Bernard Berelson . </P>

Who began the systematic study of political science