I just watched an acquaintance (who shall be called the "Giftee") open a Christmas gift, and I am appalled by her selfishly casual actions. The Giftee opened the gift, twisted her lips, and then tossed it aside. Her lack of gratitude was compounded by eye rolling and the comment that, "that's the small cheap one, isn't it? The new one is better." Mind you, this came from someone who didn't even have one of the item in the first place! On top of that, I happen to know that the Giver scrimped and sacrificed in order to provide the carefully selected gift in response to something the callous Giftee had long lusted after.
Needless to say, the Giftee is NOT a Mamaknologist.
My mother, also known as The Mother Of All Knowledge (or at least that's who I thought she was when I was growing up), would have frowned on this. Why? In the first place, no gift is ever owed. A gift is given freely and openly, with no thought of reward or personal gain attached. As such, my mother would tell you, grace and thankfulness are the obligation of any Giftee -- because nobody was forced or otherwise obligated to think kindly of you. Secondly, as every Mamaknologist knows, it costs nothing to say, "thank you," in response to thoughtfulness.
Finally, my mother and both my grandmothers, along with an endless line of other wise women would remind you that (open your bible, please...) 1 Thessalonians 5:18 advises us, "In every thing give thanks: for this is the will of God in Christ Jesus concerning you."