How long do cats remember places and people? I will leave the house in the next months for half a year or so. Will my cat remember me when I get back?
Cats do remember places and people, although where/who they remember, and for how long, is variable (just like humans).
There's been some research on feline short-term memory, but I could find less information on long-term memory.
This article is rather poorly referenced, but does make some statements about long-term memory that it claims are research-based:
Researchers have discovered that there is not much difference between how a cat, a human, or another animal's brain utilizes certain cues to assist in the creation of short and long-term memories. A cat's brain functioning has been compared to that of a two to three year old child and, when compared to a dog, a cat's memory is almost 200 times more retentive. Without repeated and reinforced training, a dog's memory span is about 5 minutes. Cats, on the other hand, averaged about 16 hours, only IF the activity benefited THEM.
A cat's long-term memories are directly related to experiencing pleasure (benefit) or displeasure (pain, fear or threat). For example, it takes a long time and a lot of patience to gain the trust of an abused or neglected cat. If they suffered physical or mental abuse from a man or child, then they will associate that memory with all men and all children. The same holds true for positive experiences. Every time a cat receives affection, praise, or a treat for doing a specific activity, it is logged into their memory as "a good thing" and they will continue to use it to their benefit.
The inevitable anecdotes
I believe that I've experienced cats remembering me years after we have had prolonged interactions. One example is a roommate of mine that I lived with about 10 years ago. His cat is not generally friendly, but we got along very well, and I was one of the few people the cat would actively seek out (i.e. he would climb in my lap and sit there while I pet him). After my friend moved out, there were periods of 1-2 years in between my visits to his new home, and when I would come over, his cat would still come and climb in my lap for petting. Over times, my visits have unfortunately become less frequent (I moved out of the area), and while the cat still seems to remember me, he is not as friendly to me as he used to be.
Here is a video of someone who claims to have been reunited with their cat over a year after her cat left home and roamed the neighborhood as a feral cat:
The internet is littered with similar claims. There is also a host of unreferenced claims about feline memory that I won't include here.
However, it is pretty certain that your cat will remember you after 6 months if you interact with the cat on a regular basis.
Whether the cat is happy to see you (at first) will be another story... ours tend to seem mad at us when we come back after leaving for a few days, and we get the "cold shoulder" for the first day or so :)
My cats were away from me for 8 months. The first day they were nervous about the new surroundings (one more than the other) but they didn't seem frightened of me. Within one day they were playing together and doing familiar happy things like rolling on their backs. Purring and tails high as a kite bumping heads with everything. They even gave kisses on day two. They slept most of the day but enjoyed the Florida breeze from the patio. By 10pm on day two they were play chasing each other and interacting with me in familiar individual ways. They slept next to us and laid in our laps all day long. They will remember you.
My cat is currently staying with my parents - the first time he has stayed with them in their new (5 years) house. He has chosen to sleep by the side of a bookshelf that he was born on 14.5 years ago in their old house. Has he remembered something about the shelf, or perhaps the smell of my Mum's study in the new house is the same as the old house? Whatever, I find it amazing!
I know cats have memory. I've known many cats in my life and often have observed that they "remember" me. I've seen this by cats acting a particular way to me versus other people. I knew this one cat in particular ("Maggie"), for most of her 22 year life (though I only had her for the last 7-8 years).
She would enjoy going into this ritual game/battle with me (and no one would see her do it with other people). She would get up on a surface that had cloth on it (like a bed, but sometimes a couch) and would furiously paw at it with her front paws. This would be my queue to pet her very fast on her sides, then she would flop over on her side and the game would begin.
My objective was to touch her whiskers or tummy and her objective was to bite me before I did this (she pulled her punches so she never broke the skin). She did this after one of the early times I met her and always did it with me, even though sometimes it was months or a year before I saw her again.
I'd agree with the statement that just like people their memories are variable. They tend to remember people and how the people treated them rather well.
I have a cat that is not friendly at all and takes a long time to warm up to anyone. I had a live-in boyfriend and after quite some time we broke up and didn't see each other for over a year. We were then reunited and his first time back in the house, my unfriendly cat was all over him as if he had never left. Your cats will remember you.
We bought a pitch black cat and after two weeks got a friend for her also pitch black...Chloe and Zoë. After about two months both kittens went missing, we think they were playing outside and a dog chased them and they got lost. After 5 months we gave up hope and the kids starred accepting the worst, they died. We are in the process of moving to the country and this morning while having coffee in comes Zoë! Crying moaning and very thin with a big cut on her upper leg. She came into the house straight away no hesitation. She wanted attention from me straight away. I was so excited it took me a few minutes to recognize if its Zoë or Chloe..Zoë was smaller with only a few white hairs on her chest. Its almost 7 months later and she came back. She was only living with us for just over 3 months so yes, if you treat your animal well they remember and will return! Wish she could tell us what happened. :)
I think this answer relies highly on what you are talking about. There is, of course, the obvious distinction between positive and negative things (extreme things are likely better remembered than moderate things). I am more interested in more subtle distinctions: specifically, between the 5 senses. I hypothesize that cats remember a human for a long time not by he looks, or even by how he sounds or acts. I think that the cat may remember a human purely by scent. It is advantageous for a cat, and any other hunting animal, to remember scents for a long time, for obvious reasons. In fact, any animal, really, should be good at remembering scents, as they must be able to identify and trace pheromones, as well as identify and trace animal tracks.