By Paul Rincon
BBC News science reporter, in Washington DC
Dogs show huge differences in personality, according to a US scientist who has developed a test to assess canine character.
Pets should be matched with their owners on the basis of similar personalities
Dr Sam Gosling, of the University of Texas, rates the dogs on four key traits with positive and negative extremes.
He adds that his work suggests pets should be matched with owners who have similar personalities.
The work was presented at a major science conference in Washington DC.
"We used approaches used to assess human personality and applied them to dogs," said Dr Gosling.
"You do find personality differences between breeds. Indeed, many have been bred on that basis. But you also find enormous [personality] differences within the breeds themselves."
Dr Gosling first asked pet owners to rate their pet on the four personality traits and then asked strangers to rate the animals on the same characteristics.
The four dog personality factors were energy levels, affection-aggression, anxiety-calmness and intelligence-stupidity.
Anxiety-calmness was assessed by studying a dog's reaction as its owner walked away with another dog.
The ability to retrieve a biscuit from beneath a cup was used as a measure of intelligence.
These traits were adapted from the five-factor model; used to assess human personality.
And the University of Texas psychologist is a firm believer that pets should be matched with their owners on the basis of similar personalities.
The ability to retrieve a biscuit from beneath a cup was used as a measure of intelligence
"If you can make a breed-based judgment that's fine. But you can also do behavioural tests. And one of the places that are very interested in this are dog homes.
"They have very high incentives to find out what these animals are like and how well-matched they are to their owners."
The results were presented to the annual meeting of the American Association for the Advancement of Science.