Watching tropical fish swimming about in a tank is a peculiarly calming experience - which is perhaps why they're so often to be seen in dentists' surgeries.

It might also help to explain why people who keep fish are the happiest and most contented breed of pet owner.

According to a new study by psychologist Professor Richard Wiseman, pet choice is often a good indication of personality.

Dog owners tend to be cheerful, while cat lovers are dependable and emotionally sensitive. Reptile fanciers are independent - and have no sense of humour.

But no one is happier than a keeper of fish, according to the professor's research.

They stand out as the most contented of individuals - and almost 60 per cent are convinced that their fishy friends have a personality and sense of humour.

Worcester Aquatic Centre manager Dave Preece said he thought there was something to the findings. He says: "Keeping fish is a relaxing hobby and you get a lot from it when you get it right. The fish have different behavioural habits - but whether it's a personality I don't know. Some fish are very active and some are quite slow moving.

"A lot of the marine fish are brightly coloured which is why people choose them. There are some more drab looking fish, such as the blenny and gobies, but they are very interesting and I suppose you can say they do have more personality.

"You can sit and watch a fish tank for hours. There is something transfixing about it."

More than 2,000 owners were invited to give details about both their own and their pets' personalities via a psychological questionnaire posted on a website.

Analysing the results revealed that different kinds of people chose to have different types of pet.

In many cases, owners believed they and their animal companions were psychologically similar.

Dogs and dog owners emerged as cheerful, playful and fun-loving, while cat owners regarded both themselves and their pets as emotional and sensitive.

Winner of last year's Worcester News Pet Idol competition, Katie Lettley and her cat Tip Toes, agreed.

Katie says: "For me it is true. I do think that my cats understand me. I have a T-shirt that my friend designed for me and it says Only My Cat Understands Me on it, which I think is right.

"If I cry for some reason, Tip Toes is there and will stay with me. It is like they know. I show an emotion and they seem to react to it."

The study also says that pets' personalities often mirror those of their owners - and Katie agrees.

"You can rely on them. I like to think that I am reliable too," she says.

Alison Richardson, from Droitwich, has owned her dog, Dibley, since she was 13.

Alison, a veterinary nurse in Kidderminster, says it was owning her dog that made her realise what she wanted to do in life.

"If you have a strong bond with your animal then I think the animals do become quite similar to you. We both have a nice nature," she says.

"I think that pets adjust to their owners and they become similar to them. If you are an active person then the dog is also quite active. And if you are laid back then they are as well. They do adjust to you."