Various types of data stemming from observational studies to more controlled behavioral and noninvasive neuroimaging projects clearly show that dogs experience rich and deep emotional lives. Among those conducting detailed neuroimaging research on dogs who have a choice of whether or not to participate in the studies, Emory University professor Dr. Gregory Berns and his research team have published many papers detailing what dogs' brains are doing in different social situations. Their findings have been summarized in his book called What It's Like to Be a Dog: And Other Adventures in Animal Neuroscience and in an interview I conducted with Dr. Berns about his groundbreaking research (please also see "Decoding the dog's mind with awake neuroimaging"). More information about the importance of non-invasive brain imaging also can be found in "How Dogs View the World: Brain Scans Tell Us What They See."

Source: Damedeeso, free images Dreamstime

While there are numerous stories, many of which reside in my email inbox, suggesting dogs feel , it was only a few years ago that a study by Christine Harris and Caroline Prouvost of the University of California in San Diego called "Jealousy in Dogs" was published in the open-access journal PLOS ONE in which they showed that dogs do experience what we call jealousy in humans. I've written about the details and significance of this carefully done project in an essay titled "Dogs Know When They've Been Dissed, and Don't Like It a Bit." The authors concluded that jealousy occurs in species other than humans—and that much more comparative research is needed. I agree with their conclusion, and also that more research needs to be conducted on this topic.

Dogs and their wild relatives are prototype mammals among whom one would expect jealousy to evolve as an adaptation to the social milieu in which they live. I'm sure I'm not alone in having observed behavior patterns suggesting jealousy among wild coyotes and wolves, for example, and I also feel certain that other researchers have seen similar behavior patterns in other wild animals.

Brain imaging and jealousy in dogs

A new study conducted by Dr. Peter Cook and his colleagues called "Jealousy in dogs? Evidence from brain imaging" has recently been published in the journal called Animal Sentience and nicely follows up on Drs. Harris and Prouvost's work. It is available online so here are a few snippets to whet your for more. Dr. Cook and his team studied 13 dogs who voluntarily partook in this research project and who entered into a scanner and remained calm. Their brains were scanned in three different situations: dog gets food; fake-dog gets food; and food is deposited in a bucket. The researchers looked at activity of the dogs' amygdala, using as a measure of jealousy. Of course, dogs (and other animals) might also feel and display jealousy without being visibly assertive or aggressive (also see), so this needs to be taken into account because it's possible this study was too narrowly focused on a single set of behavior patterns and other forms of jealousy wouldn't be detected. However, using aggression as a measure in this particular study is a good beginning and a relatively straightforward way of getting a handle on the relationship between overt behavior and brain activity in a situation where one would expect jealousy to be displayed.

The results of this study are extremely interesting. Specifically, the awake-fMRIs showed a significant relationship between amygdala activity and dog-directed aggression. The researchers write, "In 13 domestic dogs cooperatively scanned with awake-fMRI, aggressive temperament was positively correlated with bilateral amygdala activation when viewing their caregivers providing food to a realistic-looking fake-dog relative to dropping the food in a bucket." The dogs' behavior was explained as a possible indication of jealousy. However, they also note, "From both human and non-human studies, activation in the amygdala has been linked with a range of affective states, including , anger, , and even jealousy. As such, amygdala activation should not be equated with specific emotions; it should be more broadly interpreted as a neurobiological indicator of high arousal. Depending on the context, such arousal may serve as a prelude to overt aggressive behavior (LeDoux, 2003)."

The practical side of neuroimaging studies

There's also a very useful potential practical (applied) side to this important research. The researchers also discovered that the amygdala response in dogs who displayed aggression habituated with repeated exposures to the situation that caused it, so it's possible that repeated exposures to that specific situation might help to reduce or to eliminate dog-dog aggression. They also point out that there might be behavioral correlates of amygdala activation, perhaps facial expressions, body postures, gaits, or vocalizations, for example, that could be used to predict when dogs are likely to engage in aggressive interactions. Having useful predictors of when aggression is increasingly likely would be a wonderful way to decrease or to eliminate aggressive encounters that often result in people surrendering their dogs.

While we surely need more research on the emotional lives of dogs and other animals, I was especially pleased to learn more about the basis of jealousy and also how neuroimaging could potentially lead to interventions in dog-dog/human aggression that could help to curtail these sorts of interactions.

Please stand by for further discussions of non-invasive research on the neural bases of nonhuman emotions. As we learn more about what causes dogs to experience different emotions and their neural correlates, these data could help us develop better connections with our canine companions. Shared emotions can function as "social glue" that contributes to the development and maintenance of reciprocal social bonds among individuals, including those that form between nonhumans and humans (Su, et al.). As such, they and we could benefit from a deeper appreciation and understanding of what they're feeling, and it would be a win-win for all concerned.