Griesbach wrote in his first canon:
Brevior lectio, nisi testium vetustorum et gravium auctoritate penitus destituatur, praeferenda est verbosiori. Librarii enim multo proniores ad addendum fuerunt, quam ad omittendum.
'A shorter reading, unless it stands completely without the support of ancient and important witnesses, is to be preferred to a more verbose one. Copyists were much more inclined to add than to omit.'
My question is this: what was the basis on which Griesbach maintained that copyists were far more likely to add than to omit? Was it simply his impression, and if so on the basis of how many manuscripts and variant readings? Had there been work on scribal habits within the editing of Classical texts at the time? Or is it rather simply a statement of what Griesbach thought to be intrinsically more likely?