The aim of research is always to disprove rather than prove a hypothesis. It is very easy to prove a hypothesis wrong, but near enough impossible to prove it correct.
For example, if I were to create a hypothesis that all crows in the world are black, to prove it correct I would need to have had to have known for a fact that I had seen every crow in the world as proof. However to prove my hypothesis incorrect all I would have to do would be see one non-black crow. This is known as falsifiability. Here is an article on the famous philosopher Karl Popper’s definition of falsifiability (http://www.stephenjaygould.org/ctrl/popper_falsification.html)
All research can ever aim to do is falsify a theory. That’s why we create null hypothesis, which are the opposite of what we’re aiming to find (eg, when aiming to find a difference between the effects of two treatment conditions, the null hypothesis would be that there is no difference). Although disproving our null hypothesis does not necessarily mean that our hypothesis must then be true, it helps bring us one step closer to that aim.
Once enough congruent research findings are brought together to create enough evidence to convince people that a new theory is more accurate than the predominantly held belief then there is a “paradigm shift” which is when the new theory becomes the most widely held belief.
In conclusion no, you can’t ever conclusively prove a research hypothesis, but you can disprove opposing theories or null hypothesis to strengthen your argument.
kfh1991 
Is it always true that you cannot prove a hypothesis? In psychology yes, but two hydrogen atoms and an oxygen atom is pretty much universal. I know that this is a chemistry example but science is science in my eyes, as psychology is just as important as any other science.
So surely psychology will soon be able to have a more provable basis? or are than any parts that are provable?
Absolutely not, I disagree with this. We are discussing two completely different science areas here. The natural sciences are behaving in such away that they are devoid of option or deviation from norms, in that case we can safely assume that water will always contain a base of two hydrogen atoms bonded to one oxygen. Animals, in which I include human life, are able to make choices and deviate from social norms in that the 7 billion people on the planet could all choose to behave differently. We have already identified a huge amount of individual differences between people and across time and cultures and it is for this reason that I believe we will never be able to produce a universal truth for human behaviour; people are individual and behave oddly and no two people behave in the same way, unlike the molecular structure of water.
I love the fact that this is one of the only blogs I have read that acknowledges the importance of the failure to reject a null hypothesis! The basis of this failure produces the best scope for improving and modifying our theories. It is only when we are forced to question our theory that we are able to change it. The process of accepting the null hypothesis allows us to question the foundation of a theory including the variables we are testing and also the research methods that we employ to test the theory in the first place. The failure to reject the null will, or at least has the potential to question whether we have paired the correct variables together and present weaknesses in research that can improve the basis for the research of other scientists. A failure to reject the null is not a failure at all – it is simply part of scientific exploration.
What you’ve briefly described “all crows in the world are black…seen every crow in the world” is deductive reasoning, where we assume because we’ve seen 50 instances of an event it will happen again (http://matt.colorado.edu/teaching/highcog/fall8/j99.pdf). However this is not true because all it takes is one instance where the crow isn’t black to disprove the theory. Despite this researchers consistently use this reasoning as evidence for their theories. We can never fully prove a hypothesis; we can only suggest that a theory is very probable (http://www.usca.edu/polisci/apls301/Text/Chapter%208.%20Hypotheses.htm).
Pingback: Homework for my TA – Week 8/9 « psucd3
Pingback: Comments for marking week 9 | psud77