Researchers have found interesting similarities between the behavior of overweight dogs and personality traits associated with obesity in humans.
Obesity, a significant health issue in both humans and dogs, is attributed largely to genetic predisposition, reproductive status, and diet and exercise. Researchers in Europe recently evaluated the behavior of overweight dogs in comparison with personality traits associated with obesity in humans and identified some interesting similarities.
Ninety-one healthy adult pet dogs of breeds prone to obesity (beagle, golden retriever, Labrador retriever) and not prone to obesity (border collie, Mudi) were evaluated and videotaped for later evaluation and behavior coding. Evaluations included 10 trials of 2 experimental tests.
The first test was a 2-way object choice test in which a low-value (low-incentive) food option was always available for reward in a bowl (the trial included a pretrial training phase in which dogs were trained to always expect this low-quality reward at a certain location); a second bowl contained either a high-choice food item or no food item. The 2 bowls were placed on the floor simultaneously and dogs had to choose 1. This experiment measured their tendency either to maximize reward intake regardless of the quality of the reward or to more readily give up on the low-quality food choice once they learned that a higher-quality reward was present.
The second experiment was the cognitive bias test, in which a pretrial training phase consistently presented a bowl in a specific “rewarded” or “nonrewarded” location. In the training phase, the bowl was placed in an ambiguous location halfway between the rewarded and nonrewarded locations used in the training phase and alternated between reward and nonreward contents. The latency (time) between releasing the dog and when it reached the bowl was measured, and dogs were allowed a maximum of 30 seconds to reach the bowl. This provided an assessment of their food responsiveness.
Results and Discussion
Sixty-six dogs completed all 20 trials and were used in the analyses. A treatment effect was noted, in that over the course of the trials, dogs chose faster in successive trials in which a reward was present, as opposed to the empty alternative. For the 2-way object choice test, significantly more dogs completed all 20 trials when the bowl contained a high-quality food item (P < .001); however, endurance (whether dogs completed all 20 trials) was not influenced by body condition or breed. Overweight dogs and beagles were less likely to choose the bowl in the reward location (eg, consistent but low-quality reward) if the bowl in the alternate location contained a high-quality food item, indicating that they were more likely to give up on the lower-quality food item (the authors speculated possible correspondence to a lack of perseverance identified in obese human subjects). For the cognitive bias test, overweight dogs reached the ambiguous bowl and the nonrewarded bowl with a lower probability than the normal weight dogs (P = .026 and P = .008, respectively), again perhaps indicating a lack of perseverance.
Overall, overweight dogs attempted to maximize the intake of high-quality food, which is similar to obese humans who also show a bias toward high-calorie food choices. Obese dogs also hesitated when faced with an ambiguous reward outcome. Outcomes were not associated reliably with breed, except in the case of the beagle, whose patterns of behavior and motivation matched those of obese dogs.
Dr. Packer is an associate professor of neurology/neurosurgery at Colorado State University College of Veterinary Medicine and Biomedical Sciences in Fort Collins, and is board certified in neurology by the American College of Veterinary Internal Medicine. She is active in clinical and didactic training of veterinary students and residents and has developed a comparative neuro-oncology research program at Colorado State University.