Psychology is unique among other medical sciences in that it cannot ask test participants to like, prefer or support something. As such a vast body of psychological studies are purely observational and can find correlation but not causation.
For example if there is a link between self-awareness and empathy, how to test if being more empathetic increases self-awareness, being more self-aware increases empathy, or, let's say, level of some hormone control both and they are otherwise independent of each other?
Let's compare those two situations:
- A study found that people who eat a lot of sugar are fat. How researchers can test whether a) eating sugar makes people fat b) being fat makes people eat more sugar or c) both sugar consumption and body fat are influenced by the same external factor?
- A study found that people who like yellow color are more likely to be psychopaths. How researchers can test whether a) liking yellow turns people into psychopaths b) being a psychopath makes people like yellow c) being a psychopath and liking yellow are both influenced by the same external factor?
In first scenario the answer is easy - split test subjects into two groups, force one group to restrict sugar intake and monitor their weight, help second group lose weight and monitor their sugar intake.
In second - I cannot find the answer. Because psychology generally concerns itself with what people are as opposed to what they do, the standard approach in medicine described above cannot be utilized. Researchers can't force someone to like yellow, neither can they turn someone into a psychopath.
When researchers find a statistical correlation between character traits or preferences, how do they test whether there is a causal relationship between those characteristic, if traits cannot be adjusted?