How "Pet-tie" Are Dogs? What About Goldfish and Lizards?

Do pet prototypes undercut the unconditional love theory of pet-keeping?

Posted Dec 05, 2017

Stop……Before reading any further, think of a bird. Now, picture it in your mind.

I am fairly sure you did not come up with a mental image of an ostrich. When I asked my wife to quickly think of a bird, she thought of a cardinal. I suspect your bird was probably like hers – a smallish flying animal with feathers and wings, a creature that resembles a robin or a sparrow. That's because they are more “birdy” than ostriches. Cognitive psychologists call examples that typify a category prototypes.  For instance, when people are asked to think of a tool, they are more likely to say a screwdriver than an awl.

Photo by Dmitry Maslow/123rf
Source: Photo by Dmitry Maslow/123rf
What about the concept “pet?” Samantha Strazanac and I investigated our prototypes of pets, and the results shed light on the theory that we keep pets because they provide us with unconditional love. The study also offers a new approach to examining cultural differences in our relationships with companion animals.

Humans keep all kinds of animals as pets. My veterinarian pal Joe once confessed to me that when he was a kid his favorite pet was a crayfish. Mine was a white duck named Murphy who followed me around like a puppy. Unusual pets are more common than you may think. According to a 2012 report by the American Veterinary Medical Association, there are 83 million “specialty/exotic” companion animals in American households. This is considerably more than the 70 million dogs and 74 million cats living in our homes. Most of the animals in the specialty/exotic pet category were fish and – surprisingly – chickens. Yet Americans also live with 3.2 million pet rabbits, 2.3 million pet turtles, 1.2 million pet snakes, and a million pet lizards.

The Pet Prototype Scale

But should you have a pet boa constrictor? As discussed in this New York Times article, our shifting pet prototypes sometimes raise ethical issues.To investigate the extent people think of different species as prototypical pets, Samantha and I developed the Pet Prototype Scale.  Here are the instructions. 

“When people are asked to think of the word “bird”, they usually think of something like a robin rather than a penguin or an ostrich. We would like to know the types of animals that come to mind when you think of the word “pet.” Please indicate on a 0 to 4 scale the degree that each animal comes to mind when you think of the word “pet.” 

The instructions were followed by a list of 19 animals ranging from dogs and cats to tarantulas and tigers. The subjects first rated each species on a scale from 0 (not at all pet-like) to 4 (perfectly exemplifies the word pet). Then they indicated how much they would like to have each animal as a personal pet, also on a 0 to 4 scale.

In this first stab at assessing pet prototypes, we gave our scale to a convenience sample of 91 college students. 

Our Pet Prototypes

The results were intriguing. This graph shows the percent of respondents who said members of the various species “perfectly typify” their concept of a pet.  

Graph by Hal Herzog
Source: Graph by Hal Herzog

Here are some of the findings.

  • The Obvious. Some of the results were what you would expect.  For example, all the subjects agreed that dogs were perfect pet prototypes, and 94% agreed that cats were perfect pet exemplars.  As we anticipated, hardly any of the respondents thought that a tiger exemplified a pet (despite the fact that there are over 3,000 pet tigers living in the United States).  
  • The Surprises. There were also some surprises. A century ago, caged birds were the most popular pet in America. Yet most of our subjects did not feel that parrots and parakeets exemplified "petness." As Jenny Vermilya argued in this guest post, our views of horses are also changing. Nearly half of the subjects thought of horses as prototypical pets. And nearly one out of three respondents rated hermit crabs high on our pet scale. (We were dismayed that 14% of the subjects thought of monkeys as prototypical pets.)  
  • Pet Prototype versus Wanting One. Not surprisingly, the average prototype scores of the species were correlated with their “I want one as a pet” scores. But, as this graph shows, with the exception of dogs, there
    Graph by Hal Herzog
    Source: Graph by Hal Herzog
    were impressive mismatches between prototype scores of an animal and whether people would want one for a pet. Hamsters, for example, scored high on the Prototype Scale, but low on the “I want one for a pet” measure. Disconnects between thinking of an animal as a pet and wanting one as a pet even held true for creatures like cats and goldfish.
  • Sex Differences. Men and women did not differ in the degree that they thought of the species as prototypical pets. The sexes were, however, different in some of the types of animals they would personally like to live with. Women were more interested than men in owning a cat or a rabbit. Men, on the other hand, were more likely to want a pet snake. Go figure.

Undercutting the “Unconditional Love” Theory of Pet-Keeping?

We think our study, if replicated with a larger and more representative sample, undercuts the popular “unconditional love” theory of why humans keep pets. While dogs (and occasionally cats) might shower their owners with unconditional love, this is not true of goldfish and hamsters. Yet even though they do not provide their owners with the undying affection of puppies and kittens, most of our subjects said goldfish and hamsters perfectly embodied the concept of a pet. 

The Pet Prototype Scale also offers an avenue into investigating a neglected aspect of human-animal relationships – how attitudes towards pets vary across cultures. Not many Americans would rate bugs high on the scale. Yet grasshoppers and giant beetles are popular pets in Japan. Indeed, as described in this post, Korean researchers even found that elderly people who took care of pet crickets were less depressed and mentally sharper than individuals in a no-pet control group. In Malaysia, among many Shafi’i Muslims, dogs are not considered pets. They are regarded as “unclean,” and according to religious laws, dogs should not even be touched.

The Next Step?

We hope this preliminary study will encourage other researchers to investigate conceptions of what it means to be a pet. So, if you are an investigator who might be interested in pet prototypes, drop me an e-mail (, and I will send you a copy of the scale. 


American Veterinary Medical Association (2012). U.S. Pet Ownership and Demographics Sourcebook. Schaumburg, IL. American Veterinary Medical Association.