The point of science is to establish connections between objects. The point of philosophy is to establish connections between affect and affect, and subject and subject. The error of scientism is precisely in trying to treat subjects as objects.
In philosophy, broadly understood (which here could easily also mean both psychology and sociology), introspection can yield useful information, since the subject of action–the human affective domain–is coterminous with the subject doing the introspecting, with the salient question being the extent of congruence between that person’s affective environment, and that of others.