[PeterisP]

Sure you can, you just need to make an appropriate study - e.g. if you compare how similar are the expressed interests in identical twins vs nonidentical twins vs ordinary siblings vs nonrelated children adopted as babies (who all share the same environment), then you can measure the nature/nurture split; if the interests of identical twins are just as similar as siblings, then that's evidence that interests are determined solely by nurture, but if identical twins have significantly more similar interests than genetically nonidentical twins (which IMHO was the case, but I'm not going to look for the studies) then that would be evidence that at least part of these differences are innate.