Journal Scan: Punitive training makes dogs pessimistic
A recent veterinary behavior study shows that aversive training methods can negatively impact the welfare of dogs.
Aversive methods for training dogs have prompted much debate over whether they compromise animal welfare. While previous studies have corroborated the link, a recent review of the literature revealed study methodologies that were insufficient for drawing practical conclusions: Many relied solely on surveys, studied only subpopulations like police and laboratory dogs, zeroed in on shock-collar training to the exclusion of other training techniques, or examined short-term effects but failed to explore long-term welfare indicators as well.
A recent study, by contrast, evaluated both the short- and long-term effects of positive and negative reinforcement on companion dog welfare.1 Behavioral and physiologic data were collected to assess short-term effects, and decision-making tasks were employed to evaluate long-term consequences. An understanding of how different training methods impact canine welfare can lead to the establishment of training protocols that lessen dogs' stress and safeguard their wellbeing.
What researchers did
Investigators at the Abel Salazar Biomedical Sciences Institute recruited 92 dogs, all around 2 years old, from three punishment-based (“aversive group”) and four reward-based (“reward group”) dog training schools in the metropolitan area of Porto, Portugal.
A short-term welfare assessment incorporated video recordings of three training sessions and six saliva samples (three post-training and three at-home baseline collections). The videos were analyzed for frequency of stress-related behaviors, such as crouching and yawning. In the saliva samples, cortisol concentrations were measured.
A long-term welfare assessment utilized a spatial cognitive bias task: The dogs were trained to associate one side of the room with a bowl containing a sausage treat (“positive”), and the other side of the room with an empty bowl (“negative”). Then the researchers conducted three trials placing an empty bowl at sequentially different locations-near the positive bowl, near the negative bowl, and exactly between the two-and timed how quickly each dog reached the edge of the bowl in search of sausage. The scientists hypothesized that the speed at which each dog approached the bowls (approach time) would negatively correlate with the animal's degree of pessimism.
What they found
Short-term welfare indicators-negative behavior and elevated cortisol levels-were more prevalent in the aversive group. Videos of training sessions showed a significantly higher frequency of stress-related behaviors-turning the body, moving away, crouching, yawning, salivating and lip-licking-in the aversive group than in the reward group. Investigators also found a strong positive relationship between the number of stress-related behaviors a particular dog exhibited and the number of aversive stimuli used in that dog's training school.
Analysis of training-elicited changes in salivary cortisol concentration revealed a significant difference between groups: Dogs from the aversive group experienced an average rise in salivary cortisol concentration of 0.10 µg/dl after training, while dogs from the reward group had no significant changes in post-training cortisol. Furthermore, the average differences in cortisol concentrations positively correlated with the number of aversive methods used in training.
In the long-term welfare (cognitive bias) testing, there were no statistically significant differences in approach time between groups for the near-negative and near-positive bowls, but there were significant differences for the centrally placed (most ambiguous) bowl, with dogs from the aversive group taking longer to approach the bowl than dogs from the reward group. The research team also found a positive correlation between the number of aversive stimuli used at a dog's training school and the time that dog took to reach the central bowl.
What it means
This empirical study looking at both short- and long-term effects of aversive and reward-based training on overall welfare of companion dogs revealed that those trained using punishment-based methods manifested reduced welfare compared with their reward-based counterparts. They displayed more stress-related behavioral and postural stress responses during their training sessions and higher post-training cortisol levels.
In the cognitive bias tasks, thought to measure long-term consequences of aversive training, dogs from punishment-based programs exhibited decision-making that modeled a more pessimist mindset. Investigators also found that the higher the frequency of punishments used in training, the greater the impact on overall welfare of the dogs. They concluded that, effectiveness aside, if reward-based training methods are better for canine welfare than aversive methods, dog owners and handlers should integrate more of this methodology into training.
1. Vieira de Castro AC, Fuchs D, Pastur S, et al. Does training method matter?: Evidence for the negative impact of aversive-based methods on companion dog welfare. bioRxiv 2019:1-34.
Dr. Joan Capuzzi is a small animal veterinarian and journalist based in the Philadelphia area.