Morningness and Eveningness - yes these are real words

My wife is writing a paper on sleep timings in older adults and it has sparked a bit of debate at Fortress Macdonald.  It seems that sleep like many other things in the world of Psychology is divided by the old nature vs nurture chesnut, or in this case biological vs sociological.
Maybe it is the Physics in the background or reading one too many books on Zen, but I have long held the belief that if there were two directly opposing schools of thought on any given topic, each with good research and plenty of erudite proponents then the only logical conclusion one could draw is that they are both correct.  Like Dick Vitale's Epiphany in Wave Theory 101 - It's Duality BAYBEE!!!
It seems this argument of mine has become a little tiring on the ears at our place but I'm going to see what I can dig up to convince the boss.  I suspect I'll be getting the boss into a bit of Fuzzy Thinking, and try to convince her to see beyond the dodgy tie-dye new-age cover...