Prediction trees is still by far the biggest game-changer I have ever found for understanding, predicting, and healing people - both myself and others.
Prediction trees was the biggest broadening my empathy and compassion, because asking "what prediction trees would make this make sense?" is (in principle) a purely deterministic process which is guaranteed to eventually reach at least one sympathetic angle on why someone is a certain way or did something.
Ever struggle to see how a behavior or reaction could be rational? Prediction trees. If it's not obviously rational, and it's not obviously naturally selected rational game theory (either at the individual level or only for the benefit of a cooperating collective), prediction trees always makes this tractable and generates at least one possible answer ("if you had such and such life experience, this and this would be predictive of that, and if you have enough probability of that, it's rational to react that way").
Ever struggle to understand why you feel a certain way? Prediction trees, probably. Again, always yields at least one possible answer. The only problem is that sometimes the actual causes are "you have an untreated medical/physical issue", so merely generating a possible answer isn't enough. But prediction trees lets you prune and weigh possible answers - where before you might've needed to just directionlessly shrug, you now can just use actual logical inference to compare the likelihood of forming a given prediction tree, how you could get a given prediction tree from lossy optimization of a better prediction tree, the feasibility/complexity of a given tree, and so on.
Ever struggle to change how you feel or react to better match your values or what you think is rational? Prediction trees, sometimes (either unblocks the change, or reveals some way it's not as values-aligned or rational as you thought).