Do dogs prefer your praise or food?

Does your dog really love you is it simply using you to get food? That's one of the questions scientists at Emory University have been attempting to answer.

A new small-scale study published in the journal Social, Cognitive and Affective Neuroscience, suggests that, given the choice, many dogs would prefer praise from their owners rather than food. The study is one of the first of its kind to combine neural-imaging data with behavioural experiments in order to examine the reward preference systems at work in the canine brain.

"We are trying to understand the basis of the dog-human bond and whether it's mainly about food, or about the relationship itself," says Gregory Berns, a neuroscientist who heads up the Dog Project at Emory University's Psychology Department and lead author of the research.

"Out of the 13 dogs that completed the study, we found that most of them either preferred praise from their owners over food, or they appeared to like both equally. Only two of the dogs were real chowhounds, showing a strong preference for the food."

Traditional scientific thought regarding dogs can be traced back to the famous experiments into classical conditioning which were conducted by Ivan Pavlov in the early 1900s. Pavlov trained dogs to associate a particular stimulus with food. He then demonstrated that if the dogs were presented with the stimulus, they would start salivating purely in anticipation of the food, even if there was none present.

"One theory about dogs is that they are primarily Pavlovian machines: They just want food and their owners are simply the means to get it," Berns says. "Another, more current, view of their behaviour is that dogs value human contact in and of itself."

The latest study was the first to train dogs to enter an fMRI scanner voluntarily and remain inside without being restrained or sedated as the scans took place. The latest research built on the Dog Project's previous work which identified a region of the canine brain – known as the ventral caudate region – as a key reward centre. They found that this reward centre responds more strongly to the scents of familiar humans than it does to those of unknown humans and even to the scents of other dogs.

In the latest study, the dogs were trained to associate three different objects with different outcomes: A toy truck was associated with a food reward; a toy knight with praise by the owner; and a hairbrush was associated with no reward, acting as a control.

The dogs were then shown these three objects while inside an fMRI machine, undergoing 32 trials for each while their neural activity was recorded.

Not surprisingly, all of the dogs showed more preference – signalled by stronger neural activation – for the stimuli which were associated with rewards rather than no reward, although their responses differed. Nine of the canines displayed similar levels of neural activation for the food stimulus and the praise stimulus, while two dogs showed more activity for the food stimulus.

Afterwards, the dogs then underwent a behavioural experiment: Each dog was placed in a room with a basic Y-shaped maze, where one path of the maze led to a food reward and the other to the dog's owner. The dogs were released into the maze and allowed to choose one of the paths. If the dog came to the owner, they were praised.

"We found that the caudate response of each dog in the first experiment correlated with their choices in the second experiment," Berns says. "Dogs are individuals and their neurological profiles fit the behavioural choices they make. Most of the dogs alternated between food and owner, but the dogs with the strongest neural response to praise chose to go to their owners 80 to 90 percent of the time. It shows the importance of social reward and praise to dogs. It may be analogous to how we humans feel when someone praises us."

Using the results of the latest experiment, the team at the Dog Project will be able to conduct more complicated research into the canine brain. A study is currently underway which is examining the ways dogs process and understand human language.

"Dogs are hypersocial with humans," Berns says, "and their integration into human ecology makes dogs a unique model for studying cross-species social bonding."