Dogs come in all shapes and sizes - the UK Kennel Club recognises 221 different pedigree dogs, from Affenpinscher to Yorkshire Terrier (there are sadly no dog breeds starting with the letter ‘z’!).
Then there are all manner of crossbreeds, from so-called ‘designer dogs’ to lovable mongrels.
Each has its own list of positive and negative attributes, and it’s important to take plenty of time to think about what breed will fit into your lifestyle the best - for instance a smaller dog if you live in a flat, or a hypoallergenic dog if the mere mention of dog hair makes you think about sneezing.
There is even scientific research to guide you, in particular psychologist Stanley Coren’s groundbreaking book The Intelligence of Dogs.
One thing worth considering is that some types of dog are more likely to be aggressive than others.
Before they were domesticated, dogs had to fight for everything from food to territory – so signs of aggression were essential to their survival.
Many of these has been bred out to create the perfect family dogs we know today, but other retain the wilder characteristics.
There can be good reason for this – for example for those used as service or guard dogs – but prospective owners should be aware that this is the case before choosing to welcome a certain dog into their homes.
It should also be said that individual dogs may display attributes that are unusual for their breed, and all dogs have the potential to be aggressive in certain situations.
That said, here are the 24 breeds of dog most and least likely to show signs of aggression.
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17. Golden Retriever
What's true of the Labrador Retriever is also usually true of close cousin the Golden Retriever. That's certainly true when it comes to levels of aggression. Other than enjoying a nibble of their owners when teething, this is a dog whose main emotion is love and devotion. | AFP via Getty Images
18. Bernese Mountain Dog
It would be a pretty big problem if the enormous Bernese Mountain Dog was an aggressive breed - thankfully they are another breed of monumental dog who are gentle giants. They are particularly gentle with children and make wonderful family pets - as long as you have enough room and enough cash to pay for all that food! | Getty Images
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19. Cavalier King Charles Spaniels
As puppies, you could be forgiven for mistaking a Cavalier King Charles Spaniels for a cuddly stuffed toy. If treated well they present about the same level of danger to humans. | Hans Lucas/AFP via Getty Images
20. Havanese
A more diminuative pup that doesn't suffer from the 'small dog syndrome' that often leads to aggression is the Havanese. These dogs were originally bred in Cuba and just like to snuggle up with their owner. If they aren't able to they may get a little grumpy, but never aggressive. | AFP via Getty Images