Makes sense and agreed totally but with caveats.
just anecdotal, but in the old days when less lines were available, grey and texas rat snakes, then black rats then lighter colours were more calmer respectively based on lightness. Records of that time will support that.
However, That’s lust anecdotal and based on limited information that was available at that time. So does not mean was was true.
And also was probably based on the limited and particular lines avaluable at those early times.
Also sounds a bit racist which i am against. So I prefer to think about it as particular lines and not the amount of melanin.
Until we have more information and quantity of research at least its just anecdotal from those old times.
That only shows that we can not ‘prove’ anything with little information.
As a note, I used to breed for feeding response and calmness. regardless of morph, that calmness like any trait can be selectively breed for.