A contested concept basically refers to an idea or belief that is consistently challenged by various experts in a field.
A volatile variable is any changeable condition that often exists in a chaotic and uncontrolled environment. In politics, fluctuating interest rates, persistent budget deficits, and continuous political instability may represent uncontrolled environments where variable conditions lead to unpredictable outcomes.
Rotten reproducibility refers to difficulties in recreating or evaluating the results of prior experiments.
How do contested concepts, volatile variables and rotten reproducibility separate political science from the natural or hard sciences?
There are five factors which separate the hard sciences (chemistry, biology, physics, etc) from political science:
1)Clearly defined terminology
In the hard sciences, experts agree on definitions of key terms and important concepts. On the other hand, it is often difficult to achieve uniformity of purpose in an environment where key ideas or concepts are consistently challenged (contested). This is especially true in comparative politics where experts across different cultures and political persuasions may disagree vehemently on working definitions of civil rights and economic progress.
In the hard sciences, important measurements are set in stone. For example, the density of a substance will always constitute a relationship between the mass of the substance and its volume (D=m/v), while Newton's law of Universal Gravitation is calculated as
F = G m 1 m 2 / r 2
where G is the Universal Gravitational Constant (6.67x10-11 N.m2/kg2), r is the distance between two objects, and m is the mass.
In political science, it is difficult to quantify abstract concepts such as national mood or happiness in conclusive and accurate terms.
3)Highly controlled conditions.
This is probably the most important factor which distinguishes the hard sciences from political science. Experts in the hard sciences pride themselves on their ability to control intrinsic factors which will determine the outcome of any experiment. Political scientists cannot make such claims because they cannot control political climates and environments ( the concept of volatile variability).
Growth regression analysis shows that changing political factors often affect national stability and progress. For example, in countries where fundamental rights and civil liberties are assured, there often exists a corresponding vibrancy in economic activity. Countries with highly unstable political environments often report lower private sector-driven economic growth. However, because political environments can be extremely volatile (due to political variables such as civil war and political corruption), it is difficult to predict the outcomes of any experimental efforts to bring about change.
In the hard sciences, scientists across cultures can easily duplicate or reproduce the results of previous experiments. This isn't the case in political science. In fact, political scientists have long decried the lack of data sets and sufficient quantitative information to evaluate past analyses.
5)Predictability and testability.
In most hard sciences, scientists can predict future outcomes based on present data. This does not hold true for the soft sciences at all. For example, there still remains considerable difficulty in predicting the outcome of presidential elections based on economic factors. Theories abound, but no concrete data exists to back up individual assertions. Read about it here:
Models Based on ‘Fundamentals’ Have Failed at Predicting Presidential Elections.