There have been more than a few times when I've been at a pet sitting/dog walking meet and greet with an owner of a certain personality type and I have realized that the pets are going to be so much easier to deal with when the owner isn't around. I will fully admit that we prefer to work with animals and often times I have been at a meet and greet where I need to tell the owner to bring the energy down or to let me interact with their pet but I just can't bring myself to do it. From my recent studies of dog training and learning theory I understand this is part of operant conditioning and I am expecting a negative outcome to my assertion of my authority and so I do nothing and the pet remains an issue during the meet and greet and I leave and curse myself for not asserting my authority in a situation I know perfectly well how to handle.
It makes perfect sense that our moods would affect our pets. This 2012 article from Psychology Today highlights the fact that emotions are contagious. With this being the case it makes perfect sense that our vertebrate mammal pet friends would also be affected by our moods. If we are nervous then they will likely be nervous. Think about the reinforcement this would give to a dog with any type of territorial aggression and the cycle of bad behavior and reinforcement their human's emotions could create. This is of course an extreme example and most of the pets we meet that end up a little nervous are ones that jump on us. They jump up, we turn away to ignore them and not reward the behavior, and their people grab at their collar or in some other way to get them off of us. For the dog they jumped up, got rewarded, and learned that jumping on strangers gets them that reward. But at the same time their people are no nervous with them around strangers and they are getting mixed signals. Jumping on strangers gets them attention but now their people are nervous around strangers and that makes them nervous.
This is one of those behaviors where it would be much easier for us if we could talk to our pets. Let them know that people coming to visit is a good thing but we just don't want you jumping up on them as a greeting.
I have also met people that give the correction before any action has occurred, and believe me we can sense the nervous energy as well. So here I am attempting to work with a nervous dog which means I'm on the floor at his or her level, avoiding eye contact, with my back or side towards him or her. slowly the dog approaches and sniffs me. It eventually decides to come closer and I reach for an introductory touch along it's side. As I reach for him or her the owner takes in breath ready to utter a no and the dog hears this and feels the energy and either skitters away or sometimes snaps. Now all the progress I'd made is gone.
With cats this is manifested in a much different way. This BBC article highlights a study that cats can sense our emotions. While nervous dogs can become fearful dogs and then biting dogs a nervous cat even if it hisses and swats will run and hide. I have had few aggressive cats at meet and greets. Most of the cats that are deemed nervous just run and hide. It is important to note there is a huge difference between a nervous house cat and a semi-feral cat someone has made a pet. Cats that have had trauma in their past often attache to one or two people and will have nothing to do with anyone else. This is a lot different than a house cat that is nervous around strangers and runs and hides, and we won't know the difference until we are alone in the house with the cat and see if it decides to come out. We can sit still and silent for as long as we like for a semi-feral traumatized cat and they will never come near us but for a cat that is friendly with it's owner and nervous around strangers we can quickly become friends.
Animals might even be better at sensing our moods than other people as all our communication with them is of the non-verbal variety and remember dogs especially are olfactory creatures and our emotions have scents that they can pick up. This is why the number one thing to do when approached by any angry animal is to remain calm. The old saying the dogs can smell fear exists for a reason. but they can also smell and sense your nervous energy, happiness, sadness, and all emotions in between.