In psychology (and many other fields as well) the variables are very fuzzy which complicates things as well. It's not just a correlation-vs-causation/causation-

In psychology (and many other fields as well) the variables are very fuzzy which complicates things as well. It's not just a correlation-vs-causation/causation-from-correlations issue, it's also often an issue of even knowing whether one thing is really distinct from another, and if so, how. This complicates experimental designs also, for what it's worth, in that it can be difficult to determine what a manipulation is acting on, and whether it's acting on what you intend it to. This is in part why there's such a huge interest in mediation modeling, although you're back to the misspecification issue. It's difficult to know what you don't know.