Interactions between dogs and people as well as dogs and other dogs have become an area of intense research focus in recent years. This is true partly because people like to watch their own dogs and partly because, given their evolutionary (and possible co-evolutionary) history with us, dogs' brains and neurodevelopment patterns may be excellent models for humans.
What exactly are social signals?
Inherent in all studies of communication is this tenet: The currency of social interaction is information, and the more accurate the information, the better. Accurate information facilitates risk assessment, and risk assessment affects how we decide to spend our time and other currencies.
The tool that provides access to this desired information is the social signal, which can be visual, tactile, auditory or olfactory. Cues and signals differ—cues provide information (for example, the sun rose) but exist for reasons other than providing that information. Signals are usually defined as actions or structures that benefit an individual by altering the behavior of others around that individual as a result of the information provided.1 Social signals open and close discussions, specify the types of interactions (e.g. play or fight), reveal how well participants know each other and generally determine the quality of the interaction.
Sending and receiving signals
Individuals sending signals do so because it benefits them. The choice and timing of the signal are determined by context: patterns of signals are not random, and using them in an inappropriate circumstance won't help and may hurt the signaler. This is one way we recognize behavioral pathology—the signal is given in a context where it is not needed or in an intensity or frequency that does not match the ongoing social situation.
Those receiving the signal, the receivers, alter their behaviors when the signal carries information indicating that there is value to them in behavioral change—for example, dog No. 1 growls upon dog No. 2's approach; dog No. 2 withdraws rather than be bitten. Reliability of a signal can be gauged by rarity, repeated pattern and redundancy. Even within one signaling system—let's say visual signaling—congruence of the signals given by the tail, ears, eyes, mouth and overall posture all lead to enhanced reliability. If a vocal signal (e.g. a whine) reinforces an understanding of the signaler's state, such redundancy has made the message of the signal clear.
Who's appeasing whom?
It has become increasingly common among people who own dogs to talk about their dog "appeasing" them. Descriptions of dog to dog behavior are frequently couched in terms of who "appeased" whom. Unfortunately, what we've given up in behavioral information may have far more value than what's provided by the "appeasement" label. So how accurate is such labeling, and does it have a role in how we talk about dogs?
Appeasement signals have been said to advertise peaceful intentions and are thought to be present only when such information is relevant—for example, in situations when fighting may establish, even temporarily, a hierarchy, pecking order or other social rule that avoids injury or death.2
What does it mean?
In a general sense, the word appease is associated with a couple of definitions that apply to the canine appeasement discussion:
(1) to please someone or make him or her less angry by giving or saying something desired
(2) to make a pain or a problem less troubling; to bring to a state of peace, quiet or calm.
More specifically, appeasement behaviors in dogs have been defined in an additional two ways:
3) postures and attitudes exhibited by a dog to calm himself or herself and others in situations of potential conflict3
4) signals such as yawning, moving in an arch, lifting a paw, licking the lips, laying down and looking away4 that occur in agonistic encounters and that decrease the probability of the agonistic behavior continuing at the same or a higher level.
Examining behavior patterns
The dogs' responses were grouped in three categories: redirected and social approach behavior (sniffing or licking the floor or playing with inanimate objects), displacement activity (yawning, stretching) and appeasement gestures (flicking the tongue, lifting the paw). Freezing and withdrawing—passive and active behavioral responses to an uncomfortable situation, respectively—were also noted but not included in the three main categories. The behavioral data were analyzed along with cardiac response data (heart rate and heart rate variability) obtained from a Polar Systems heart monitor.
Analyzing the results
Appeasement gestures (flicking the tongue, licking the paw) differed statistically in duration and frequency among the sequences (see Table 2) and were primarily seen during the paw and muzzle test sequences. Displacement activities also differed significantly among the test sequences and were highest during the shoulder, ground and tail sequences. Dogs showed redirected behavior for a longer period of time and more frequently if being petted on the shoulder, chest, paw and tail. Heart rate differed significantly among the test sequences and was highest during the muzzle, neck and collar sequences.
The authors concluded that being petted on the head, shoulder or paw resulted in the dogs' initiating an increasing number of appeasement gestures and redirected behaviors and engaging in them for longer durations. Simply put—where you choose to pet a dog matters.
Petting dogs and holding them around the head (neck, muzzle or collar) resulted in an increased standard deviation of normal-to-normal R-R intervals (SDNN), indicating that both sympathetic and the parasympathetic effects on heart rate were affected by location of petting. Dogs manipulated in such regions may feel more entrapped and less able to make behavioral choices. Furthermore, appeasement gestures (lifting a paw, looking or moving away, licking the lips) were positively correlated with heart rate, some of which might be due to the motor activity involved in these behaviors.
In this case, the appeasement gestures exhibited by these dogs in relation to the SDNN and heart rate measures are more in line with definition 4 above: signals, such as yawning and licking the lips, may decrease the probability of an agonistic behavior continuing. However, appeasement gestures also were negatively associated with root mean square of successive heartbeat interval differences (RMSSD) and RMSSD/SDNN ratio, suggesting that the lower the vagal tone and sympathovagal balance (reduced vagal tone and balance are thought to be markers of increased stress), the more common the appeasement gestures. If these gestures are more common when stress levels are higher, definition 3—postures and attitudes exhibited by a dog to calm himself and others—may be more appropriate. This explanation may especially fit if the change in vagal tone was associated with dogs tolerating gestures they disliked, as the authors suggest.
Do true appeasement signals exist?
At least two of the four common definitions of appeasement may fit responses of dogs in controlled situations established to cause stress or anxiety. The behaviors identified most consistently as appeasement behaviors in such research (lifting a paw, looking or moving away, licking the lips)4,8 are all commonly reported stress- and anxiety-related behaviors.
Ethological definitions of these behaviors routinely characterize them as intention movements, withdrawal from social interaction indicators, and indicators of uncertainty, respectively.7 Such descriptions may be more unbiased than a label such as "appeasement gesture," especially when in a controlled study these behaviors are associated with such a complex physiological profile. However, in the restrictive context of this careful study, there is a pattern of relatively narrow behavioral responses and activity that appears to meet two of the four definitions of appeasement. In this study, one could justify the carefully restricted use, as do the authors.
But should we in the world at large accept that appeasement is driving all canine behaviors and accept the term as a descriptor of canine behavior in the absence of more nuanced information? Absolutely not. We can see in Table 1 the wide number of possibly co-varying responses that are part of any anxiety, stress or distress response.
The message from all of these studies is that patterns of co-variation of all behavioral, physiological and neurochemical responses matter, and the context in which they are exhibited is key. If we can start to think this way, we may be able to figure out how to measure and compare individual responses in a practical way that allows us to anticipate when certain interactions or situations will change a dog's behavior in ways injurious to the dog. And that would be priceless.
Dr. Karen L. Overall is a researcher, editor of The Journal of Veterinary Behavior: Clinical Applications and Research, and author of more than 100 publications, dozens of chapters and a new book, The Manual of Clinical Behavioral Medicine for Dogs and Cats.
1. Maynard Smith J, Harper DGC. Animal signals: models and terminology. J Theor Biol 1995;177:305-311.
2. Hasson O. Emotional tears as biological signals. Evol Psychol 2009;7:363-370.
3. Rugaas T. On talking terms with dogs: calming signals. Wenatchee, Wash. Dogwise Publishing, 1997.
4. Pastore C, Pirrone F, Balzarotti F, et al. Evaluation of physiological and behavioral stress-dependent parameters in agility dogs. J Vet Behav: Clin Appl Res 2011;6:188-194.
5. Wosegien A, Lamprecht J. Nodding: an appeasement behaviour of pigeons (Columba livia). Behaviour 1989;108:44-56.
6. Koolhaas JM, Korte SM, De Boer SF, et al. Coping styles in animals: current status in behavior and stress-physiology. Neurosci Biobehav Rev 1999;23:925-935.
7. Overall KL. Manual of clinical behavioral medicine. St. Louis, Mo. Elsevier, 2013.
8. Kuhne F, Hö ler JC, Struwe R. Behavioral and cardiac responses by dogs to physical human-dog contact. J Vet Behav: Clin Appl Res 2014. [In press]