A human's best friend is a dog, but that's not always reciprocated.
Some of our canine pets are colloquially called "ball junkies" because they have an addictive-like attitude toward their toys. They choose to play tug-of-war or fetch over eating or interacting with others, and they'll keep messing around with their favorite objects, even if they are exhausted or injured.
Researchers at the University of Bern in Switzerland are now drawing comparisons between the 'excessive toy motivation' of some domestic dogs and human addictions to gambling or internet gaming.
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Unlike those for substance addiction, there are very few animal models that are useful for studying behavioral addictions. In humans, these are sometimes defined by a repeated failure to resist a rewarding act, despite longer-term harm to the individual or others.
The domestic dog is the only accepted species apart from us that displays addictive-like behavior spontaneously, and while that doesn't mean they officially exhibit addictive behaviors, there are parallels that scientists want to explore.
To start the research off, veterinarian behaviorist Alja Mazzini and colleagues surveyed the owners of 56 male and 49 female dogs. Thirty-three of the dogs exhibited addictive-like behaviors toward their toys in experiments.
These canines fixated on their toy, displaying 'cravings'. They also showed a lack of interest in alternative toys, and made persistent efforts to access their favorite even when it was put out of reach – a sign of poor self-control. They preferred the toy over a food puzzle or interacting with their owner.
In their survey responses, participants with toy-addicted dogs said their pets required more and more play to become satisfied. Many also agreed with the statement that "If I did not counteract this tendency, my dog would be a ball junkie."
According to their owners, most of these toy-addicted pets would continue to play despite detrimental consequences.
"This suggests that some dogs may fulfill the criterion of continuing the addictive-like behavior despite adverse consequences in real life, even if this could not be demonstrated in the behavior test," explain the authors.
Just as online gaming can bring humans joy, playing with toys can bring dogs joy. But problems can arise when the play becomes excessive, and it seems that some dogs are vulnerable to developing harmful compulsions toward their favorite objects.
"Subsequent research endeavors should seek to correlate individual differences in addictive-like behavior in dogs with characteristics associated with addictive behaviors in humans," the authors conclude, "such as high impulsivity, impaired reversal learning, heightened perseveration, and delayed extinction of previously rewarded responses."
The study was published in Scientific Reports.