Let me paint a picture I have witnessed a thousand times. A three-year-old rescue, a Kelpie-mix named "Blue," is walking with his owner. It’s 5:00 PM. The street is busy. Blue’s owner, well-meaning, is holding the leash in a white-knuckled grip, anticipating the school bus that arrives every day at 5:02 PM.
Blue, a creature of exquisite sensory attunement, is not just walking; he is processing a data-storm. He smells the anxiety-sweat on his owner’s palm (a change in chemosignal). He feels the micro-tension in the leash. His ears are flicking, tracking the rumble of distant traffic, the high-pitched shout of a child, and the jingle of a dog tag two blocks away. His cortisol, already elevated from a noisy morning, is simmering. He is in a state I call high allostatic load—the cumulative, physiological wear and tear of chronic stress.
At 5:02 PM, the bus turns the corner. The squeal of its brakes is a high-frequency assault. The "whoosh" of the air brake is a sudden, novel pressure-change.
In the next 80 milliseconds—faster than a conscious thought—a signal from Blue's thalamus (the brain's sensory relay station) splits. One signal takes a high-speed, synaptic super-highway directly to his amygdala, the core of his Primal Mind. This "low road" signal is crude. It doesn't say, "a yellow bus is stopping"; it says, "THREAT! LOUD! SUDDEN! DANGER!"
The amygdala hijacks the system. It screams "FIRE!" to the brainstem (specifically the Periaqueductal Gray), which instantly triggers a reflexive motor pattern: freeze. For 500 milliseconds, Blue is a statue. His owner, missing the cue, pulls the leash: "Come on, Blue." That pull, combined with the amygdala's signal, forces the next reflexive option: fight.
Blue explodes. He hits the end of the leash, barking, lunging, spinning, and growling. His owner yells, "Blue, NO! Bad dog!" The owner is embarrassed, angry, and afraid. They see a "bad, aggressive, dominant" dog.
I see something else entirely. I see a dog whose Primal Mind—a reflexive, emotional, survival-based system—has completely hijacked its Cognitive Mind, the thinking, learning, decision-making system. The owner is punishing a physiological reflex as if it were a malicious choice This is the catastrophic misdiagnosis, and it is the single greatest obstacle to resolving canine behavioral problems. If we are to have any hope of helping these dogs, we must stop judging the behavior and start understanding the biology.
The Catastrophic Misdiagnosis: Why Labels Ruin Dogs
In our human world, we are obsessed with labels. "Aggressive" is the most damning of all. This single word is a death sentence, both figuratively and, all too often, literally. It fuels breed-specific legislation (BSL), it's the justification for inhumane training methods, and it's the final, tragic reason cited in shelters before euthanasia.
The problem is that the label is almost always wrong. What the average person calls "aggression" is, in the vast majority of cases, reactivity.
Let me be unequivocally clear: reactivity and aggression are not the same. They may look identical—the barking, the lunging, the growling, the snapping—but the underlying neurobiology is a world apart.
Reactivity is a symptom of emotional overflow. It is a panic attack. It is an involuntary, reflexive outburst from a nervous system that is overwhelmed and has lost access to its "thinking" centers. It is driven by the Primal Mind.
Aggression is a strategy. It is a learned, purposeful, and often cognitively-driven behavior intended to achieve a specific outcome: create space, acquire a resource, or stop a perceived threat. It is driven by the Cognitive Mind.
Conflating these two is like mistaking a sneeze for a spoken threat. One is an uncontrollable reflex; the other is an act of intention. When we punish a reactive dog for its outburst, we are, in neurological terms, punishing a dog for being terrified. We are pouring gasoline on its emotional fire.
The result? We amplify the fear, destroy trust, and, in a tragic, self-fulfilling prophecy, teach the dog that the world is indeed a terrifying place where it must fight to survive. We are the ones who, through this profound misunderstanding, create true aggression.
The Dual Architecture: The Primal Mind vs. The Cognitive Mind
To understand this, you must visualize the dog's brain as a house with two separate security systems. One is an ancient, hard-wired, trip-wire system that locks down the house. The other is a modern, smart-tech system that analyzes data, checks cameras, and makes an informed decision.
When a trigger appears, both systems get the alert. The one that "wins" dictates the dog's behavior.
The 'Primal Mind' (LeDoux's "Low Road")
This is the ancient trip-wire. It is the survival-at-all-costs system, a network dominated by the limbic system, particularly the amygdala. The pathway, as mapped by neuroscientist Joseph LeDoux in his foundational work on fear, is one of raw, terrifying speed:
Sensory Input (e.g., sound of bus) -> Thalamus (Relay Station) -> Amygdala (Threat Detector)
Speed Over Accuracy: This is the "low road." It is a fast, crude, "quick and dirty" signal. It has very few synaptic connections, meaning it's incredibly fast (milliseconds).
No Context: The signal bypasses the thinking, contextualizing parts of the brain. The amygdala doesn't know what the trigger is, only that its sensory profile (loud, sudden, high-frequency) matches a "threat" template.
The Hijack: The amygdala’s job is not to feel, but to act. It instantly activates the Hypothalamic-Pituitary-Adrenal (HPA) axis (the body's stress-hormone cascade) and signals the Periaqueductal Gray (PAG) in the brainstem.
The 4 Fs: The PAG is the command center for the "Four Fs" of survival: Freeze, Fight, Flight, or Fiddle (appeasement/flirt). These are not conscious choices; they are reflexive, pre-programmed motor patterns. When a dog is "reactive," they are trapped in this Primal Mind pathway. They are not choosing to lunge and bark; their amygdala and brainstem are running a defensive program before their thinking brain has even received the full data packet.
The 'Cognitive Mind' (LeDoux's "High Road")
This is the modern, smart-tech system. It is the "thinking brain," centered in the Prefrontal Cortex (PFC). Its pathway is slower, more deliberate, and built for analysis.
Sensory Input -> Thalamus -> Sensory Cortex -> Hippocampus -> Prefrontal Cortex (PFC) -> Amygdala
Analysis: The signal is sent from the thalamus to the sensory cortex ("What is this sound, exactly?").
Context: It's then sent to the hippocampus ("Where have I heard this before? Oh, this is the 5:02 PM bus. Nothing bad happened the last 20 times.").
Decision: The data goes to the PFC, the brain's CEO. The PFC integrates all this information and makes a "top-down" executive decision: "This is a known, non-threatening event."
The Brake: The PFC then sends an inhibitory (calming) signal to the amygdala, telling it to stand down. This is the neurobiological "brake." A well-regulated dog is a dog whose Cognitive Mind (PFC) can effectively receive data, analyze it, and apply the "brake" to the Primal Mind's (amygdala's) impulse before an explosion occurs.
A reactive dog is a dog whose "brake line" has been cut. The Primal Mind's signal wins the race every single time, long before the Cognitive Mind can intervene.
The Neurochemistry of Reactivity: Living in Allostatic Load
Why is the Primal Mind's brake line cut? The answer is chemistry. A reactive dog is not just "badly trained"; it is, in many cases, physiologically compromised.
When the Primal Mind's alarm is pulled, it floods the body with a potent chemical cocktail via the Sympathetic Nervous System (SNS), the body's "go" pedal.
Epinephrine (Adrenaline): The "sprint" hormone. Injected directly into the bloodstream by the adrenal glands, it provides immediate, explosive energy for fight or flight. It's the lunge, the surge of power.
Norepinephrine (Noradrenaline): The "vigilance" hormone. As a neurotransmitter in the brain, it dials up sensory acuity to 11. The dog's hearing becomes sharper, its pupils dilate, and it becomes "stuck" on the trigger, unable to disengage.
Cortisol (Glucocorticoids): The "marathon" hormone. This is the one that truly explains reactivity. When the hypothalamus signals the pituitary, which signals the adrenal glands (the HPA axis), cortisol is released. While adrenaline is gone in minutes, cortisol can stay in the system for hours.
Now, imagine a dog like Blue. He lives in a noisy apartment. His owners are stressed. He gets one walk a day on a busy street. He is constantly exposed to micro-triggers that activate his HPA axis. He never fully returns to a baseline state of calm.
This chronic, low-level activation leads to a state known as Allostatic Load (a concept pioneered by Bruce McEwen). It is the cumulative "wear and tear" on the body from chronic stress.
This is what high allostatic load does to the brain's architecture, and it's devastating:
It Strengthens the Primal Mind: Chronic cortisol increases the dendritic density in the amygdala. This is a terrifying concept: stress physically strengthens the brain's fear center, making it more sensitive and more likely to fire.
It Damages the Cognitive Mind: Simultaneously, chronic cortisol is neurotoxic to the hippocampus and prefrontal cortex. It actually atrophies (shrinks) dendrites in these areas.
This is the vicious cycle: Chronic stress physically strengthens the Primal Mind (the accelerator) while simultaneously damaging the Cognitive Mind (the brake).
The dog isn't just "overreacting"; its brain has been physically changed by stress, leaving it with a hyper-sensitive accelerator and a failing brake system.
The Neuroscience of Aggression: A Learned, Instrumental Strategy
If reactivity is a Primal Mind hijack, true aggression is a learned strategy, a plan, executed by the Cognitive Mind. It may have been born from fear, but it has "graduated" into a conscious (or at least, learned) tool. This is the domain of operant conditioning, or instrumental learning. The dog's brain, a highly efficient survival machine, learns one simple rule: behavior that works gets repeated.
This learning is governed by the Cognitive Mind (PFC) and then "stamped in" as a habit by a different brain structure: the basal ganglia.
Let's trace the development of learned aggression:
The First Event (The Reactive Outburst): A dog, in a state of Primal Mind panic, has a reactive outburst. A strange man is walking too close, the dog explodes, and the man (naturally) backs away.
The "Aha!" Moment (Negative Reinforcement): The dog's Cognitive Mind (PFC) logs this. The behavior (lunging/barking) led to the consequence (the scary man disappeared). This is negative reinforcement: the removal of an unpleasant thing reinforces the behavior that preceded it.
The "Habit" Forms (The Basal Ganglia): The dog tries this again. It works. The PFC, having confirmed the strategy, "outsources" this pattern to the basal ganglia (specifically the dorsal striatum), the brain's habit-formation center.
The "Off-Ramp" is Built: A new, efficient neural pathway is now formed: Trigger (Man) -> Basal Ganglia (Run 'Aggression' Program) -> Consequence (Man Leaves). This behavior is now instrumental. It has a purpose. It's a tool. This is why aggressive dogs often look "calmer" and more "focused" than reactive dogs. The reactive dog is chaos; it's a "scream." The aggressive dog is focused; it's a "threat." It is executing a learned, efficient motor program, often with minimal emotional overflow, to achieve a calculated result.
This is also why resource guarding (aggression over food, toys, or space) is a classic example of Cognitive Mind aggression. It is a highly successful strategy (driven by positive reinforcement: "I growl, I get to keep the bone") that the dog's PFC and basal ganglia have deemed effective.
The Tragic Slide: How Reactivity Becomes Aggression
Here is the most critical and dangerous part of the equation: reactivity and aggression are not always separate. There is a dark, well-worn path between them. This is how the Primal Mind's reflex teaches the Cognitive Mind a strategy.
This "slide" is built on two core neurological principles:
Hebbian's Law (1949): "Neurons that fire together, wire together." Every single time your dog has a reactive outburst, that Thalamus -> Amygdala (Primal Mind) pathway is activated. The neurons fire. And the connection between them becomes stronger, faster, and more myelinated. The dog is, in effect, practicing its panic. Each outburst makes the next one easier to trigger.
Behavioral Kindling (Goddard, 1969): This is a term borrowed from epilepsy research. If you give a rat a tiny, sub-convulsive electrical jolt to its amygdala once a day, for the first few days, nothing happens. But after two weeks, that same, tiny jolt will produce a full-blown grand mal seizure. The amygdala has become "kindled," or hyper-sensitized. This is exactly what happens with behavioral reactivity. Each reactive outburst is a "behavioral seizure" that "kindles" the Primal Mind, lowering the threshold for the next explosion.
This is the tragic slide, step-by-step:
A dog is in high allostatic load (chronic stress).
This lowers the threshold for a Primal Mind hijack (reactivity).
The dog has a reactive outburst at a trigger (e.g., another dog).
The trigger's owner, understandably, pulls their dog away.
The reactive dog's Cognitive Mind and Basal Ganglia immediately learn the connection: "My explosion... made the threat go away."
This sequence is repeated. The Primal Mind pathway gets stronger (Hebbian's Law/Kindling), making outbursts more frequent. And the Cognitive Mind's lesson gets stronger (Negative Reinforcement).
One day, the dog sees a trigger. But this time, it doesn't wait for the Primal Mind to panic. The Cognitive Mind proactively and intentionally deploys the lunge-and-bark strategy because it has learned that this is the most effective way to control its environment.
The dog has "graduated." What began as a terrifying, involuntary reflex has now become a confident, voluntary strategy. We, through mismanagement and misunderstanding, have allowed the dog's brain to learn that aggression works.
The Unspoken Variable: The Handler's Nervous System
Now, we must discuss the most uncomfortable truth in all of dog training. The dog is not on the end of the leash alone. There is a human attached, and that human is a walking, breathing part of the dog's neurobiology.
I cannot overstate this: You are your dog's external nervous system.
Dogs are not just watching our body language; they are sensing our internal physiological state. This is not "woo-woo"; this is hard science.
Emotional Contagion - Limbic Resonance (Interoceptive Attunement): Dogs are masters of interoceptive attunement. A groundbreaking 2014 study by Yong & Ruffman found that when dogs were exposed to the sound of a human infant crying, their cortisol levels rose significantly, mirroring the stress response of a human. They catch our stress.
Long-Term Stress Synchronization: It gets deeper. A 2019 study by Sundman et al. in Scientific Reports made a stunning discovery. They measured long-term cortisol levels in the hair of dogs and their owners. They found that the dogs' cortisol levels directly mirrored the cortisol levels of their owners. This effect was so strong that it was not influenced by the dog's activity level, but by the owner's personality (specifically, high levels of neuroticism). Your chronic stress becomes your dog's chronic stress.
Chemosensory Confirmation: When you are anxious, your body releases stress chemosignals (pheromones) in your sweat. To a dog—a creature whose primary sense is olfaction—your anxiety is not a vague "vibe." It is a loud, specific, chemical smell that screams, "DANGER IS PRESENT."
Let's revisit the "neuroceptive feedback loop" I mentioned in the prologue. This is how the handler unwittingly causes the explosion:
Trigger Appears (e.g., another dog).
Handler's Primal Mind Fires: The handler's own amygdala fires, anticipating a "bad" reaction.
Handler's Physiology Changes: Their heart rate variability (HRV) flatlines. Their breath becomes shallow (SNS activation). Their body releases stress chemosignals.
The Leash: They tighten their grip. The leash is not a tool; it is a neuro-cable transmitting your SNS activation directly to the dog's highly-sensitive tactile receptors.
The Dog's Confirmation: The dog senses all of this: the smell of your fear, the tension on the leash, the change in your breathing. To the dog, this is objective, empirical proof that the approaching trigger is, in fact, a mortal threat.
The Explosion: The dog's Primal Mind, now justified and amplified by its handler's panic, explodes with a force it might not have otherwise. The handler then says, "See! I knew he would react." They fail to see that they were the co-author of the entire event. You cannot teach a dog to have a calm Cognitive Mind if you are trapped in your own Primal Mind.
Intervention: A Dual-Pronged Neurological Strategy
We are not just "training a behavior." We are performing neuro-sculpting. We are physically changing the dog's brain. And because the causes are different, the solutions must be.
You cannot "correct" a Primal Mind panic. You must rewire it.
You cannot "punish" a Cognitive Mind strategy. You must reroute it.
Prerequisite For All: Management & Decompression
Before any "training" can begin, you must do two things:
Management (Starve the Bad Pathway): Management is not "giving up." It is the non-negotiable first step. You must arrange the dog's life so it cannot rehearse the problem behavior. Every time the dog explodes, Hebbian's Law fires, and the "bad" pathway gets stronger. You must starve that pathway.
Examples: Window film so the dog can't see the mailman. Walking at 5:00 AM instead of 5:00 PM. Using baby gates or crates. A properly conditioned basket muzzle, which is a safety tool, not a punishment.
Decompression (Lower the Allostatic Load):You cannot teach a brain that is drowning in cortisol. You must lower the allostatic load by activating the Parasympathetic Nervous System (PNS)—the "rest and digest" system.
Examples: "Sniffaris" (long, meandering walks on a long line, letting the dog sniff everything). Scent work games. Puzzle toys. Chewing. These activities are clinically proven to lower cortisol and release calming neurotransmitters like acetylcholine. This is the only way to get the brain into a state where it can learn.
Example Protocol 1: Rewiring the 'Primal Mind' (Treating Reactivity)
Goal: Change the dog's emotional response (CER) to the trigger. We must teach the Primal Mind that the trigger is no longer a threat.
The Tools: Systematic Desensitization (DS) and Counter-Conditioning (CC).
The Process:
DS: We find the dog's sub-threshold distance—the "learning zone" where they can see the trigger, but are not yet hijacked by their Primal Mind. (For my students I refer here to my Critical Circle of Stress vs. Confidence) This is the state where the Cognitive Mind is still online.
CC: From this safe distance, we pair the appearance of the trigger with a high-value, dopamine-releasing reward (e.g., chicken, liver).
The Neuroscience: This is brilliant, targeted neuro-sculpting.
Trigger (Bus) -> High-Value Food
We are using the mesolimbic pathway (the brain's "reward" or "seeking" system, driven by dopamine) to overwrite the amygdala's fear response.
Dopamine is a powerful neuromodulator that facilitates neuroplasticity (the brain's ability to change).
With repetition, the amygdala's association is literally rewired. The trigger (bus) no longer predicts fear (cortisol); it now predicts food (dopamine). The Primal Mind's alarm is disarmed.
Example Protocol 2: Rerouting the 'Cognitive Mind' (Treating Aggression)
This is where we must address the inevitable question: "But what about punishment? What do I do when my dog does the aggressive behavior?"
This is the most misunderstood concept in all of training. In clinical science, "punishment" is not about retribution; it is simply a consequence that makes a behavior less likely to occur.
The trap everyone falls into is confusing Positive Punishment (+P) with Negative Punishment (-P). My entire methodology is built on understanding the profound and dangerous neurological difference between the two, especially when dealing with aggression.
The Neurological Fallacy of 'Traditional' Punishment (+P)
Positive Punishment involves adding an aversive to stop a behavior. This is the "punishment" most people think of: a leash correction, a prong-collar pop, a shock collar, or a harsh "NO!"In severe aggression cases, I never recommend this. The reason is neurological, not emotional.
It Activates the 'Primal Mind': Aggression, even when it has become a learned Cognitive Mind strategy, still has its roots in the Primal Mind's threat-detection system (the amygdala). Applying a painful or frightening stimulus instantly activates this system.
It Floods the Brain with Cortisol: The pop, shock, or yell is a new threat. This triggers a defensive-threat response, flooding the dog's brain with epinephrine and cortisol.
It Shuts Down the 'Cognitive Mind': Here is the fatal flaw: The prefrontal cortex (PFC)—your 'Cognitive Mind'—is the first thing to go offline during a Primal Mind hijack.
You are trying to run a protocol that requires the dog's thinking Cognitive Mind to make a choice. But the very tool you're using (Positive Punishment) shuts that part of the brain down.
It's like trying to teach a frustrated and angry student a complex math problem by screaming in their face. You will get a stress response (freezing, fleeing, or fighting back), but you will never get learning. You may suppress the behavior in the short term, but you have massively increased the dog's allostatic load (chronic stress) and simply confirmed its belief that the trigger (the other dog) leads to a painful, frightening experience. You have made the underlying problem worse.
The Scientific 'Punishment': How We Reroute a Failed Choice (-P)
This is the answer. This is how we "punish" the aggression scientifically, without the neurological fallout. Negative Punishment (-P) involves removing a desired reinforcer to stop a behavior. Our protocol for aggression is therefore a two-part equation: We use Differential Reinforcement (DRA) to make the new behavior wildly profitable, and we use Negative Punishment (-P) to make the old aggressive behavior completely unprofitable.
Example Protocol 2: Rerouting the 'Cognitive Mind' (DRA + Negative Punishment)
Goal: Teach the Cognitive Mind that the new behavior (the "Look") is highly profitable, and the old behavior (the aggression) is completely unprofitable.
Tools: DRA (the "paycheck") and Negative Punishment (the "failure").
The Process in Action:
Fluency First: We proactively teach the dog a new, simple, alternative behavior away from any triggers. We build fluency in this "job" (e.g., a "Look," "Touch," or "Find It") until it is fast and automatic.
The Setup: We put the dog in a managed situation with its trigger (e.g., another dog at a 100-foot distance). We have our high-value "paycheck" (rewards, food, toy, etc) ready.
The Choice: The instant the dog sees the trigger, before it can run the old aggression program, we cue the new behavior ("Look!").
The Two Scenarios: At this moment, the dog's Cognitive Mind makes a choice. We must have a plan for both outcomes.
Scenario A (The Dog CHOOSES Correctly): The dog's Cognitive Mind inhibits the old pattern and performs the "Look" (or other new job).
Consequence (The "Paycheck"): An avalanche of high-value reinforcement (R+). We deliver the paycheck. The new neural highway (Trigger -> Look -> Reward) is strengthened. We have just made this new choice more valuable.
Scenario B (The Dog CHOOSES Incorrectly): The dog ignores our cue and instead "chooses" its old, learned aggressive strategy. It fixates, stiffens, but has not shown the "full" behavior yet.
Consequence (The "Punishment"): We calmly and immediately apply Negative Punishment (-P).
How: We use the leash not for a "correction," but as a simple tool. We calmly turn 180 degrees and walk away. We do not pull, yank, or scold. We simply remove.
What was removed?
The opportunity to engage with the trigger.
The reinforcement of "winning" or "controlling" the situation.
The forward motion and the handler's engagement.
The aggressive behavior failed. It produced nothing. It cost the dog the one thing it wanted, which was to interact with (or drive off) the trigger.
The Neuroscience of This Protocol:
This two-part strategy is neurologically brilliant.
In Scenario A (the correct choice), we use DRA to flood the new pathway with dopamine, making it a highly rewarding, "seeking" behavior.
In Scenario B (the incorrect choice), we use -P. Because we remained calm and did not introduce a threat, we did not activate the dog's Primal Mind. The dog's Cognitive Mind remains online and is able to register the consequence: "My new 'Look' strategy produces a jackpot. My old 'aggression' strategy produces nothing and makes the trigger go away and I lose my forward momentum. It is an inefficient, failed behavior."
We are simultaneously making the new behavior incredibly valuable and making the old behavior completely worthless. That is how you scientifically, safely, and effectively "punish" and reroute severe aggression.
My Final Thoughts
When you stand at the end of that leash, your dog erupting in a storm of noise and fury, you have a choice. You can see a "bad dog" who is defying you, or you can see a dog whose Primal Mind is screaming for help.
You can see a dog who is "dominant," or you can see a dog whose Cognitive Mind has learned a desperate, maladaptive strategy to feel safe in a world it cannot control.
Behavior is not morality. It is biology.
Aggression and reactivity are not a failure of the dog's character. They are a sign of imbalance—a signal of a nervous system trying, and failing, to find equilibrium. Our task as trainers, and as owners is not to condemn, but to translate. Stop punishing the smoke detector. Look for the fire. Is it a real fire (a true threat)? Or is the detector just broken, drowning in the "smoke" of chronic cortisol? When we trade emotional labels for biological understanding, we trade frustration for empathy. We stop blaming the dog for a neurology it did not ask for and start helping it build new, healthier pathways.
You cannot teach a dog to be calm if you do not embody calm. You are their external regulator. Your breath is their anchor. Your calm Cognitive Mind is the "brake" they are missing. That is the only path from chaos to clarity. That is not magic. That is science. And that is the foundation of our work together.
Bart de Gols - Copyright 2025
Reference List
Goddard, G. V. (1969). The development of epileptic seizures through brain stimulation at low intensity. Annals of the New York Academy of Sciences, 163(1), 323-341. (Relating to the concept of Kindling).
Hebb, D. O. (1949). The Organization of Behavior: A Neuropsychological Theory. New York: Wiley & Sons. (Relating to Hebbian's Law: "Neurons that fire together, wire together").
LeDoux, J. E. (1996). The Emotional Brain: The Mysterious Underpinnings of Emotional Life. New York: Simon & Schuster. (Foundation for the "high road" and "low road" fear pathways).
LeDoux, J. E. (2012). Rethinking the Emotional Brain. Neuron, 73(4), 653-676. (Refining the role of the amygdala in threat detection vs. subjective fear).
McEwen, B. S., & Stellar, E. (1993). Stress and the individual. Mechanisms leading to disease. Archives of Internal Medicine, 153(18), 2093-2101. (Foundation for "Allostatic Load").
Sundman, A. S., van den Berg, L., &... Roth, L. S. V. (2019). Long-term stress levels are synchronized in dogs and their owners. Scientific Reports, 9(1), 7391. (Evidence for interspecies cortisol synchronization).
Wolpe, J. (1958). Psychotherapy by Reciprocal Inhibition. Stanford, CA: Stanford University Press. (Foundation for systematic desensitization and counter-conditioning).
Yong, M. H., & Ruffman, T. (2014). Emotional contagion: Dogs and humans show a similar physiological response to human infant crying. Behavioural Processes, 108, 155-165. (Evidence for interspecies emotional contagion and cortisol response).