My father believed that he could dowse. I was a young teenager when I realized that I could not repeat my hits without external cues. In other words, let's say you felt that you detected water at one spot. Naturally, if you walked over that same track, you would expect the same hit if dowsing were real. But, of course, you already know where you got the hit so, not surprisingly, you do. However, if you are blindfolded and go over the same track, your ability to repeat the hit only works as well as you can estimate your position. If you are led around by someone first so that you don't know your starting position then your hits will be random. My father talked about an occasion when a construction crew was digging but couldn't find a buried line. Naturally, it isn't good when you accidentally tear out buried gas or water lines while digging so this was important. But they couldn't find it. My father then dowsed it and the line was where he indicated. I doubt my father had any special ability. My guess would be that he was able to mentally connect two points above ground and estimate where the line was likely to be.
I used to have a Manx cat. The rounded head, arched back, stocky body, dense underfur, and lack of a tail are classic Manx characteristics. You can see that even in December 2002, my wife took enough medications to require a pill organizer. My wife had congestive heart failure and this caused severe chest pains at times. This was initially controlled with nitroglycerin pills. However, when they got worse in 2005, I had to give her liquid morphine. The thing is that she wouldn't always tell me when she was having chest pains and she was very good at hiding it. However, I noticed that my cat which was usually on or near my wife's hospital bed would act agitated so then I knew when my wife was having chest pains. I have no idea how my cat could detect this but I'm quite certain that she was not psychic. It might have been smell because people tend to sweat more when they are in pain or it might have been her breathing or perhaps both. After my wife died, I wouldn't let the cat on my bed while I was sleeping. However, when I woke up in the morning, she would jump up on the bed. I noticed that she waited right next to the bed where she couldn't see me. Yet, even if I didn't move, she jumped up on the bed right after I woke up. My best guess would be that there was a change in the sound of my breathing that would tell her that I was awake.
Some people have claimed that their dogs are psychic and can tell when they are coming home. I've even seen some casual experiments that tended to confirm this. Yet, when more controlled testing was done, this mysterious ability disappeared. Naturally, if you like the idea that your dog is psychic then you tend to favor less controlled experiments that don't disprove your beliefs. Higher up on the delusion scale would be people who believe that they are pet psychics. This was never more clear than on one episode of The Dog Whisperer where Cesar worked with a woman who insisted that she was a pet psychic and could tell what the dog was thinking. She kept up a steady monologue of what she claimed were the dogs thoughts. Oddly enough though, she was completely unable to either predict or modify the dog's behavior despite what she claimed was her deep understanding of the dog. She got it wrong again and again and again but that didn't dent her belief that she could tell what her dog was thinking.
Seeing an unexplained result does happen from time to time. Thinking that this could be an example of something paranormal is also not an uncommon belief. This usually doesn't hurt anything. However, someone cannot insist that their beliefs are based on solid proof while carefully avoiding rigorous testing that could potentially disprove their beliefs.