Since I know many people on here are very savvy about psychology and psychiatry, I thought I would GroupThink-source a question I have. I am working on a paper on non-human primate personalities, but I would like to make a sidenote about human psychology. The question is as follows: I know there is a strand/strands of Psychology or Psychiatry that believes everything people do is for a reason - some (sometimes unconsciously) self-perceived benefit to the individual - , even if the behaviour is seemingly irrational or destructive. However, I have no idea what this strand might be called, and google came up with existential questions and generic weirdness. (To give a tiny bit of context, in the pertinent section I am discussing anti-social behaviours and how they are frequently marginalized and dismissed as maladaptive and abnormal.)

Any and all leads would be appreciated!