Yes,you are probably correct in suspecting more complexity in such opposite ends of the spectrum as anhedonia at one end and pleasure at the other. Good wishes with your research, my simple starting points would be around survival, basic drives, and Maslow's hierarchy of needs, together with some sociological observations. Also those philosophical and religious movement or individuals who might tend to practise at the extremes. Occam's razor also would be a guide. ie at the extremes there is mostly pathology.
Getting a bit out of my depth here, Good journey, anyhow.
