All dog lovers know that their pets in older age aren't the same as they were as puppies, but owners often can't pinpoint the exact personality changes brought on by the passage of time.
A study published Wednesday in Scientific Reports attempts to map out those changes and finds that there are some personality traits — such as attraction to novel experiences, the desire to explore and the urge to run around — that seem to change for most dogs with age.
"Similar to humans, dog personality is both stable and malleable," said the study's lead author, Borbála Turcsán, a research fellow at Eötvös Loránd University in Budapest, Hungary. "Dogs that are active and curious when young will remain active and curious when they get old, but only compared to other dogs. A dog's personality changes over time, and, on average, every dog becomes less active and less curious as they age."
To study how dogs' personalities might change with time, Turcsán and her colleagues recruited 217 border collies who were participants in the Clever Dog Database in Vienna. The dogs' ages at the beginning of the study were 6 months to 15 years old.
At the outset, the dogs were evaluated using a series of tests known as the Vienna Dog Personality Test. Four years later, the researchers invited dogs that were still alive, along with their owners, back to the lab for retesting. Thirty-seven dogs (and their owners) showed up.
Included in the tests were:
Exploration test: Dogs were allowed to explore a room and the different objects in it for one minute while the owner stood in the middle of the room ignoring the dog.
Frustration test: The experimenter swung a large piece of sausage on a string in front of the dog's nose, just out of reach, for one minute.
Novel object test: The dog encountered a self-moving toy that made a sound and had one minute to interact with it.
Ball playing test: The owner threw a tennis ball three times and encouraged the dog to retrieve it.
Obedience test: The owner gave the dog four basic commands — sit, lie down, stay and come — while the experimenter was trying to distract the dog with rustling noises.
Problem-solving test: The owner showed the dog how to remove the lid of a bin to get a piece of sausage from it, and then the dog had one minute to remove the lid and get the food.
When the researchers compared the dogs, they found that the most active and curious ones in the first test were still the most active and curious ones four years later but that individually they were less active and curious than they had been.
Overall, the researchers found that the dogs' attentiveness and ability to solve problems changed a lot during life, improving up until about 6 years of age and then remaining stable. The novelty-seeking trait didn't change much in early life, but then, when the dogs were 3, their curiosity about novel objects and situations started to decline.
The dogs' ability to tolerate frustration remained the same during their lives, as did their desire to socialize. But their activity levels decreased continuously as they got older. "The age of the dog was the strongest predictor of the dogs' level of calmness," Turcsán said.
The study was interesting, but it wasn't terribly surprising, said Dr. Katherine Houpt, professor emeritus at the Cornell University College of Veterinary Medicine. "Something that was surprising to me is that dogs don't seem to get particularly more intolerant of frustration as they get older," Houpt said.
The study's findings may not apply equally to all breeds, Houpt said. "They used the smartest breed to study, and [the downward trends], when it comes to diminution and novelty-seeking, might be different with beagles, for example."
There was some good news for dog owners, Houpt said.
"Dogs get less active with age, and that should give hope to the people who have puppies that are too active," Houpt said. "And while they become less oriented to problem-solving and novelty-seeking as they get older, they remain obedient and social, which is probably the most important thing for owners."