Since cats first got their adorable claws into us about 9,500 years ago, humans have had a love affair with felines.

Today more than 80 million cats reside in U.S. homes, with an estimated three cats for every dog on the planet. Yet there's still a lot we don't know about our feline friends—including what they think of their owners.

John Bradshaw is a cat-behavior expert at the University of Bristol and the author of the new book Cat Sense. After observing pet cats for several years, he's come to an intriguing conclusion: They don't really understand us the way dogs do.

Bradshaw recently shared some of his insights with National Geographic.

How did you get into cat behavior?

For the first 20 years of my career I studied olfactory [smell] behavior in invertebrates. I've always been fascinated by this other world that animals live in—primarily of odor, which is dogs' primary sense. So in the early 1980s I started working on dog behavior. [Later] I very quickly became fascinated with cats, and what their idea of the world is compared to the one we have.

What do you do in your research?

A lot of observation—watching groups of cats to see how they interact with one another and deducing their social structure. [I watch] cats in colonies that are free-ranging, and in animal shelters where quite a number will be housed together—you get interesting dynamics [when new cats are introduced].

I've also done slightly more manipulative things, such as studying the way cats play with toys, or testing cat [behaviors] at different times of the day. [I also observe] relationships with owners, interviewing them and giving them questionnaires to find out how they perceive their cats.

Why did you conclude that cats don't "get us" the way dogs do?

There's been a lot of research with dogs and how dogs interact with people. [It's] become very clear that dogs perceive us as being different than themselves: As soon as they see a human, they change their behavior. The way a dog plays with a human is completely different from [the way it plays] with a dog.

We've yet to discover anything about cat behavior that suggests they have a separate box they put us in when they're socializing with us. They obviously know we're bigger than them, but they don't seem to have adapted their social behavior much. Putting their tails up in the air, rubbing around our legs, and sitting beside us and grooming us are exactly what cats do to each other. 

I've read articles where you've said cats think of us as big, stupid cats. Is that accurate?

No. In the book [I say] that cats behave toward us in a way that's indistinguishable from [how] they would act toward other cats. They do think we're clumsy: Not many cats trip over people, but we trip over cats.

But I don't think they think of us as being dumb and stupid, since cats don't rub on another cat that's inferior to them. 

Can we discover what cats really think about us?

More research needs to be done. [It's] not an area that's received sufficient attention. [Cats are] not wild animals, so ecologists [might think], 'Well they're not really animals at all.'

What has been most surprising to you in your research?

How stressed a lot of pet cats can be without their owners realizing it, and how much it affects the quality of their mental lives and their health. Cats don't [always] get on with other cats, [and people don't realize] how much that can stress them out. Other than routine visits, the most common reason cats are taken to vets is because of a wound sustained in a fight with another cat.

[More cats are mysteriously getting] dermatitis and cystitis [inflammation of the bladder] and it's becoming abundantly clear that these medical problems are made worse by psychological stress. [For instance], inflammation of the bladder wall is linked to stress hormones in the blood.

One solution is to examine the cat's social lifestyle, instead of pumping it full of drugs. [For example, that could mean making sure] two cats that [don't get along] live at opposite ends of the house. Quite often the whole problem goes away.

I have a few questions from cat owners on Facebook. First, why might a cat yowl when it's by itself in a room?

Cats learn specifically how their owners react when they make particular noises. So if the cat thinks, 'I want to get my owner from the other room,' it works to vocalize. They use straightforward learning.

Why do some cats treat one human member of the household differently?

They're much smarter than we give them credit for: They learn what works with what person. They know if [one member of the family] is prone to get up at 4 a.m. and give them some treats.

Why do cats knead us?

They are using behavior that they would use toward their mother—all the behavior they show toward us is derived in some way from the mother-kitten relationship. The kitten learns to raise its tail, rub on its mother, and knead and purr. Grooming is what mothers do back to kittens.

So they're using bits of behavior already in their repertoire to communicate with us. There aren't very many behaviors—maybe half a dozen. 

Can you train cats?

Yes. Cats can learn what they're not supposed to do. If your cat has developed a habit [of jumping up on the kitchen table], there are limited ways to prevent it.

You could use a spring-loaded toy, so when a cat jumps up on something, the toy goes bang and up in the air—the cat doesn't like that and jumps down. Another reasonably benign [strategy] is to use a child's water pistol. But make sure the cat doesn't realize you've got it. Cats don't forgive, and once they realize a person is causing them anxiety or hurt, they keep away.

What do you want owners to know about their cats?

Acknowledge that cats are sociable animals to a point, but not sociable to the extent that dogs are. A lot of people who have one cat decide they would like to have another cat, thinking two cats are twice as much fun. But the cats may not see it that way.

The simple message I would like to get across is if you do want to have more than one cat, go about it in a careful way—and be prepared to give up on it if it doesn't work.

There are very few surprises that will startle you more than discovering a lump or bump on your dog. As your hand wanders over your canine pal in affectionate scratching or petting, your fingers just may chance upon a lump that “was not there before." 

It will scare the biscuits out of you ... GUARANTEED!  With that nagging "C" word drifting about the back of your mind, your first fear is that your dog might have cancer. Setting in motion your search for an answer as to what this lump is you make a quick trip to the I hope that lump isn't serious.

"How long has this been here?" the veterinarian asks. "Just found it yesterday, doctor," you respond.

"Let’s see if we can find any others," says the doctor as experienced and sensitive hands work the dog over.  Sure enough, "Here’s another one just like it!" says the doctor as she places your hand right over the small, round, moveable soft mass under the skin of the dog’s flank.

"I think these are what we call Lipomas, just fat deposits under the skin. They are very common and usually present no problems," says the doctor. Your relief at hearing the good news is cut short as the doctor continues …

"However, we honestly do not know what these lumps truly are unless we examine some cells under the microscope. So I’d suggest that we do a simple needle biopsy, place some cells on a slide and send the slides to a veterinary pathologist for a definite diagnosis."

The doctor in this case is being thorough and careful. How true it is that a definitive diagnosis of "what it is" simply cannot be made without microscopic examination of the lump’s cells. A veterinary specialist in pathology is the final authority and judge when it comes to shedding light on these lumps and bumps that we too often find on our canine pals.

The lipoma is one of the most commonly encountered lumps seen by veterinarians during a physical exam. These soft, rounded, non-painful masses, usually present just under the skin but occasionally arising from connective tissues deep between muscles, are generally benign. That is, they stay in one place, do not invade surrounding tissues and do no metastasize to other areas of the body. They grow to a certain size and just sit there in the tissues and behave themselves.

Most lipomas do not have to be removed. Occasionally, though, lipomas will continue to grow into huge fat deposits that are a discomfort to the dog and present a surgical challenge to remove. And even more rarely, some lipomas will be malignant and spread throughout the dog’s body. 

Is it a tumor?
And therein lies the true challenge in dealing with lumps and bumps on dogs -- we simply cannot predict with 100% accuracy just what any of these foreigners will do. So we do the best we can by removing them when indicated or keeping a close guard over them so that at the first sign of change they can be removed.

Not every lump or bump on your dog will be a tumor. Some superficial bumps are due simply to plugged oil glands in the skin, called sebaceous cysts. Skin cysts can be composed of dead cells or even sweat or clear fluid; these often rupture on their own, heal, and are never seen again. Others become chronically irritated or infected, and should be removed and then checked by a pathologist just to be sure of what they are. Some breeds, especially the Cocker Spaniel, are prone to developing sebaceous cysts. 

And yes, the sebaceous glands in the skin do occasionally develop into tumors called sebaceous adenomas.  According to Richard Dubielzig, DVM, of the University of Wisconsin, School of Veterinary Medicine, "Probably the most commonly biopsied lump from dog skin is a sebaceous adenoma. This does not mean it is the most commonly occurring growth, just that it is most commonly biopsied." Fortunately this type of skin growth rarely presents trouble after being surgically removed. 

So how are you to know which lumps and bumps are dangerous and which can be left alone? Truthfully, you are really only guessing without getting the pathologist involved. Most veterinarians take a conservative approach to the common lipomas and remove them if they are growing rapidly or are located in a sensitive area.

However, caution needs to be observed because even the common lipoma has an invasive form called an infiltrative lipoma. For example, when a nasty looking, reddened, rapidly growing mass is detected growing on the gum aggressive action is indicated.  Also, keep in mind that not all lumps and bumps are cancerous, and some are fairly innocent and do not warrant immediate surgery.

Types of Lumps and Bumps

Non-cancerous lumps
Cysts, warts, infected hair follicles, hematomas (blood blisters) and others do cause concern and can create discomfort for the dog, though non-cancerous lumps have less health impact than cancerous growths.

Cancerous lumps
Cancerous growths can be either malignant or benign, and occasionally even share characteristics of both.  Malignant lumps tend to spread rapidly and can metastasize to other areas of the body. Benign growths tend to stay in the place of origin and do not metastasize; however they can grow to huge proportions (see such an example of inoperable tumor pictured on the right).

Mammary gland tumors, mast cell tumors, cutaneous lymphosarcoma, malignant melanoma, fibrosarcoma and many other types of tumors with truly scary names command respect and diligent attention on the part of dog owners and veterinarians.

Diagnosis
Below are the most common methods of finding out "what it is" …

Impression Smears

Some ulcerated masses lend themselves to easy cell collection and identification by having a glass microscope slide pressed against the raw surface of the mass. The collected cells are dried and sent to a pathologist for staining and diagnosis. Sometimes the attending veterinarian will be able to make a diagnosis via the smear; otherwise, a specialist in veterinary pathology will be the authority regarding tumor type and stage of malignancy.

Needle Biopsy

Many lumps can be analyzed via a needle biopsy rather than by total excision. A needle biopsy is performed by inserting a sterile needle into the lump, pulling back on the plunger, and "vacuuming" in cells from the lump. The collected cells are smeared onto a glass slide for pathological examination. Usually the patient isn’t even aware of the procedure. Total excision of the mass is attempted if the class of tumor identified warrants surgery.

Radiography & Ultrasound

 X-ray and ultrasound evaluations are generally reserved for collecting evidence of internal masses. Most lipomas are superficial and reside under the skin or skeletal muscles. There are other lumps that can be palpated by the veterinarian via manual examination that may require spread of cancer internally (ie., metastasis).

CT Scans

Superficial lumps and bumps do not require that CT Scans be done, so this procedure is usually reserved for internal organ analysis. If a superficial malignant tumor is diagnosed, however, a CT Scan can be helpful in determining if metastasis to deeper areas of the body has occurred.