Imagine…
You are a very sociable person. You were raised in a large family. You love your fellow humans. But suddenly you find yourself in a new home. No more humans. None. Your family is the strange animals that care for you. Pigglepigs. They don’t behave like humans. Their behaviour is a complete mystery to you. They don’t talk to you in any kind of language you can understand – just a load of noises which make no sense. Worse, from that day for weeks, you don’t see, let alone meet, another human. You miss them desperately! But you get along OK. The Pigglepigs are kind, albeit bossy. Then one day, out on a walk with your Pigglepig family, you see on the horizon not just ONE human being, but a whole bunch of them! You can’t contain yourself. You charge over to them, laughing excitedly and generally making something of an idiot of yourself as you shout ‘HI! HI! OMG! People! Who are you?’ You hug and kiss a couple before they are aware you are on top of them. But the third one is ready for you – and pushes you away angrily. After all – you are a complete stranger. You have not only ignored all the social niceties of a proper greeting – you HUGGED him?? He gets cross. At least the others just move away and put up with your nonsense. But the one that got angry – he’s not prepared to let it go. He’s a bad-tempered old bugger with a dodgy hip; he can’t evade you and it hurts. You nearly had him over! He gets hold of you and shouts at you to ‘stop!’ Suddenly all your enthusiasm evaporates. You are frightened. You had never met anyone as grumpy as that before and you were only trying to be friendly, and you hadn’t seen a fellow human being in WEEKS.

Your Pigglepig family gallops up and intervenes to stop things getting out of hand. “It’s OK!” says Dad Pigglepig. “He’s friendly!” They are angry with the grumpy old man who’d told you off so aggressively. Then they turn round and tell you off too. But what for you really don’t know. You did just want to be friends! All very stressful. No chance for apologies. No making up between you and the humans you were so desperate to make friends with. Everyone is angry or upset. You hadn’t been able to stay around and make friends with any of them and worse, there was the shock of finding out that some people are horrible. A poor encounter on every level.
We can easily see how a young dog might be set up to make bad mistakes when encounters with other dogs are mismanaged by us humans, or he is allowed to behave in a way that upsets other dogs. The dog barking and lunging with either excitement or frustration on the end of the lead; the grumpy old man as he reacts sharply, and aggressively, to stop other dogs from hurting him or being knocked over. Both might be labelled as “reactive”, but they have very different motivations; potentially very different outcomes in the long term.