Why Puppies Do What They Do: The Science Behind Puppy Behaviour
Updated: Nov 5
One minute your puppy is curled up on your lap, and the next they're biting your sleeve, chewing the table leg and tearing round the kitchen. It can look completely random, but it isn't. Every puppy I've ever trained has had a totally different personality, even within the same breed, but almost everything they do comes down to their age, their instincts and what's been rewarded. Once you can see that, it's much easier to know what to do.
THE SHORT ANSWER
Puppies do what they do for three main reasons: their brain and body are still developing, they're following instincts like chewing, chasing and exploring with their mouths, and they repeat whatever gets them something they want. Biting, chewing, zoomies, jumping up and "forgetting" training are normal stages, not defiance. Tiredness and overexcitement make all of them worse. Plenty of sleep, a steady routine, and rewarding the behaviour you'd like to see shape a puppy into a calm adult dog.
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Their brain is still growing
The parts of a puppy's brain that handle self-control and calming down are some of the last to mature. So a puppy can know a cue in the kitchen and seem to forget it in the garden, or go from calm to wild in seconds. They're not ignoring you. They just can't manage that much yet.
That's also why short training sessions and plenty of sleep matter so much. Young puppies need around 18 to 20 hours of sleep a day. Read more about why puppies need more sleep than training.
Instinct vs learned behaviour
Some behaviours come built in: chewing, sniffing, chasing moving things, picking things up, and using their mouths in play. You can't switch these off, but you can give them an outlet, like toys, chews and sniffing games.
Other behaviours are learned. If jumping up gets attention, your puppy jumps more. If sitting gets attention, they sit more. Every interaction is teaching your puppy something.
Why puppies bite and mouth
Puppies explore and play with their mouths. They also bite more when they're overtired, overexcited or teething. Mouthing is how they learn bite inhibition, a soft mouth for life. Here's how puppies learn bite inhibition.
Why puppies chew everything
Chewing eases sore teething gums, it's calming, and it's how puppies find out what things are. Teething runs from about 12 weeks to six or seven months. Read why puppies chew everything.
Why puppies get the zoomies
Zoomies are a burst of energy, often in the evening or after a bath, a poo or a busy day. Short zoomies are normal. Frantic ones that come with biting usually mean your puppy is overtired and needs help to settle.
Why puppies seem to forget training
Puppies don't generalise well. "Sit" in the kitchen and "sit" in the park feel like different things to them. Practise in lots of places, starting easy. Some training wobbles again in adolescence, from around six months, which is normal too.
Fear periods
Many puppies go through a phase where things they were fine with suddenly worry them, often around 8 to 11 weeks and again in adolescence. Go at their pace, let them watch from a distance, and pair new things with treats. Pushing a worried puppy closer usually makes the fear bigger.
How to shape behaviour that lasts
Reward what you like, straight away
Manage the environment so mistakes are hard to make
Give instincts an outlet: chews, sniffing, safe chase games
Protect sleep and keep a steady routine
Keep training short and fun
Stay calm. Telling off adds worry, not understanding
RENEE'S TIP
When your puppy does something you don't like, ask two questions: what are they getting out of it, and are they tired? The answer usually tells you what to change.
QUICK CHECK
ā Their brain is still growing
ā Instincts need an outlet
ā What gets rewarded gets repeated
ā Tiredness makes everything worse
ā Reward the behaviour you want
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FAQs
Why do puppies do what they do?
Because of their developing brain, natural instincts, and what's been rewarded. Most puppy behaviour is normal for their age.
Why does my puppy go crazy in the evening?
Evening zoomies are common, especially when puppies are overtired. Help them settle with a chew and a nap.
Why does my puppy forget their training?
Puppies don't generalise well, so a cue learned in one room needs practising in others. Adolescence can bring wobbles too.
Is my puppy being naughty on purpose?
No. Puppies repeat what works for them and are still learning self-control. They aren't being spiteful.
How do I change my puppy's behaviour?
Reward what you like, manage the environment, give instincts an outlet, protect sleep and keep training short.
ABOUT THE AUTHOR
Renee Patience Ā· National Dog Trainer of the Year 2025
Founder and head trainer of Paws Academy, with more than 30 years training dogs and a Level 6 Diploma in Applied Canine Behaviour. Renee has competed in agility, obedience and heelwork to music across the UK, including at Crufts and Olympia, has appeared on CBBC, and is the author of the Modern Training Guides and the Modern Breed Handbook series. Pictured with her boxer, Kookie.
