Dogs have long been man’s best friends for a good reason. While the origin of the human-dog relationship is not definitively known, estimates date back to 15,000-30,000 years ago when wolves began moving closer to hunter-gatherer societies to scavenge for leftover meat. Since then, wolves have been selectively bred, undergoing significant evolutionary changes to morph into the hundreds of domestic dog breeds we celebrate today.
While dogs cannot talk–at least not in the traditional sense–owners know exactly what their dogs are saying at all times. For example, when your dog pricks his ears, he is probably curious about something; when he rolls onto his back, he wants to play. However, what if I told you that as we recognize our dogs’ needs and wants, dogs seem able to assess our own? In more ways than one, dogs cognitively evolved to be in tune with humans. Regarding reading our moods and understanding human communication, dogs have an extraordinary gift that others in the animal kingdom remain unparalleled.
1. Reading Facial Expressions and Emotions
Nato the Rottweiler was visiting the park with his owner when an older man came and sat down at a nearby bench. Nato had never met the man before, but he insisted on approaching the stranger and sat calmly beside him, wagging his tail and licking the stranger’s hands. After talking to the older man, Nato’s owner found out that he was in mourning after having just lost his dog. It seemed almost as though Nato had sensed that the old man was sad and went out of his way to comfort him.
Stories such as Nato’s are not uncommon. A mounting body of evidence suggests that dogs can evaluate human emotions. In a series of famous studies, researchers presented dogs with human faces displaying varying emotions—from happy and playful to angry and sad—paired with sounds that matched or did not match the positive and negative facial expressions. Similarly to infants, dogs looked longer during trials where the faces and audio pairings did not align, suggesting they can use cross-modal information to evaluate the states of humans and can readily differentiate between positive and negative emotions (Yong & Ruffman, 2016; Hagley, 2012; Albuquerque et al., 2016).
Not only can dogs read our emotions, but they also seem affected by our emotional states. Dogs are, for example, highly receptive to human crying. Just like humans, dogs show higher stress hormone levels and faster heart rates when listening to sounds of babies crying compared to sounds of babies babbling or white noise (Yong & Ruffman, 2014) and to human and dogs’ whining compared to non-emotional sounds (Huber et al., 2017). Dogs tend to approach humans who cry more often than humans who are humming, even if the person is a stranger (Custance & Mayer, 2012). During trials where a human cried behind a closed door, dogs tended to quickly open the door to reach and comfort the human (Sanford, Burt, & Meyers-Manor, 2018). These results reflect dogs’ capacity to recognize human sadness and distress and respond empathetically.
2. Following Communicative Gestures
Gesturing is an essential non-verbal communication in which humans use physical bodily actions instead of language to convey an intended message. Examples include waving to greet someone or nodding as a sign of confirmation. In humans, an understanding of gestural communication emerges between the ages of about 9-12 months, representing a cognitive milestone in their communicative development.
Scientific evidence suggests that our canine counterparts might be equally skilled in comprehending human communicative gestures. Miklósi et al. (1998) observed that dogs could successfully use gestural cues to locate hidden food. Using an object choice task, experimenters hid food in one of two bowls and performed one of five predetermined gestures–pointing, bowing, nodding, head-turning, or glancing–in the direction of the baited bowl. Dogs could integrate these cues to inform their decisions and overwhelmingly select the bowl suggested by the human actor. These results have been replicated by many researchers (Hare & Tomasello, 1999; Soproni et al., 2002; Agnetta et al., 2000) even in puppies as young as 6-9 weeks and stray dogs with limited prior human experience, suggesting that dogs need not require extensive training to understand and use human cues, but seem to do so automatically (Virányi et al., 2008; Riedel et al., 2008; Bray et al., 2021). This video shows puppies successfully integrating communication cues to locate hidden food.
Due to their remarkable capacity to “read” human gestures and body language, dogs have become one of the world’s most popular service animals. In addition to their roles as hunters, herders, and detectors, dogs are often trained as helpers for people with emotional or physical disabilities and ailments. Their propensity for understanding external cues makes dogs highly trainable, and dogs may assist in a wide variety of tasks ranging from guiding people with vision impairments and retrieving items for people with mobility issues to signaling certain sounds to people who might be deaf or hearing impaired.
3. Understanding Intentions
Based on the above literature, it seems evident that dogs know how to interpret human gestures to make informed decisions, such as which bowl to choose during an object choice task. However, dogs must first understand that gestures mean something to use human gestures. When humans point, we are pointing to something or someone; when we look in a specific direction, we are (usually) not just staring out into space; our gaze is directed toward something in particular. In other words, when humans act, we do so with a goal. Most actions are not random but instead are intentional. An understanding of intentional action is a complex cognitive feat demonstrated by relatively few non-human animals, but it seems to be a fundamental ability underlying social development in human infants. New evidence suggests that this understanding may also be present in dogs.
In a landmark study performed by Marshall-Pescini et al. (2014), dogs were tested to see if they had different expectations for humans versus nonhumans–here, they used a black box–to interact with an object. During habituation trials, dogs were acclimated to either the human or non-human agent as they interacted with one of two objects placed at a distance away from each other. These trials were followed by a test phase, where agents interacted with the same object as during the habituation but in a different position or a different object in the habituation object’s original position. It turns out that dogs showed a similar response pattern to infants, whereby they tended to look longer when humans chose to interact with a new object, as opposed to the same object in a new location. These findings imply that dogs associate human reaching actions as oriented towards an object, not a location. There were no differences in the looking times for the inanimate agent, likely because the dogs did not extend their beliefs of intentional, object-directed action to the black box.
While dogs may not grasp every spoken word or phrase, owners are onto something when they claim their dog knows what they are saying. As implied by the Marshall-Pescini et al. study, dogs seem to understand something fundamental about our nature that often goes unnoticed by many other animals. Our millennia-long coevolution has enabled dogs to learn the nuances of human behaviors. Dogs have developed the remarkable capacity to recognize our physical and emotional states and act on them accordingly. So, the next time you wonder if your dog knows you’re sad–or happy or angry or feeling lively and ready to play–remember that your dog has evolved to do so.