Why is it that some elderly are totally void of positive feelings, but when it comes to negative feelings and comments, they become very expressive?

Yes, my mother is the same... most of the time. She has lost her "cooth" so to speak. She says things out loud and it is sometimes very embarrassing. I just tell her that was not nice... and remind her that she taught me not to say things like that. Haha!

Some people are just like that and it is extremely hard to be around them. I live in a family where a couple of them have those tendencies: very critical of things and other people (even the driver in the car next to us); impatient to their own benefit; seemingly angry with the world (which in truth they probably are). I've come to accept it although perhaps I'm the one who needs counseling. I also see it as a means of control of their environment . . . you are so involved in their attitudes you don't have a chance to have an opinion of your own (no would you wish to express them because that might start a fight!). Hang in there, she's not going to change. Just remember that you are a person, too, with your own feeling and attitudes. Perhaps should not be around her so much if that's at all possible.

Maybe she's depressed. Maybe she's got dementia. It's been my experience that very often a dementia diagnosis doesn't happen as a result of a routine doctor visit unless the patient is really quite impaired. In the early to mid stages, the family really needs to speak up and tell the doctor (preferably in a letter) about the behaviors they've noted so the doctor knows to look for it.
I think that even when doctors do see the early signs, they don't want to alarm or depress the patient. Imagine having to tell someone who's still pretty aware that they are losing their mind and there's nothing that can be done about it! Once the doctor knows the family is on board (meaning accompanying the patient to visits, the patient signing off that the doctor can speak to family members...) they can discuss your parent's status with you.

Do what you can and then let it go. It just causes us pain to resist something we can't change. Ignore bad behavior as much as possible and reward positive behavior (if any). To dwell on what we feel SHOULD be, to expect things to change or become fair, all this just puts our own minds in a negative place. We have to use inner resources and not give away our own power to anyone else. Good luck and God bless.

Its funny in a way but it seems like at the assisted living place my mother is in that they all get a kick out of being unhappy and complaining. It almost seems like they are in high school and being annoyed with everything is the "in" thing to do. I don't quite get it.
However, last night at family night when there was a slight problem with dinner I saw how some of the adult children there acted (those visiting) and was not surprised as the negative outlook on everything apparently runs in some families.

A good neuro-psych evaluation is in order, since it is obvious her happy circuits are not working. Talk to her primary physician about a referral .