London - Pet dogs can understand far more words than many of their owners give them credit for.
Though most will react to "walkies", "sit" or "fetch", a new study shows that their language comprehension is far wider.
They can identify slight variations such as "hid" and "had" and recognise the same word said in a variety of accents.
When a team led by the University of Sussex played 70 dogs four different people saying the same word and a fifth saying a slightly different one, the first and last voices provoked the most interest.
Lead author Dr Holly Root-Gutteridge said: "Dogs probably gained the ability to distinguish between the growls of other dogs to work out their size, and then they started paying attention to our language after we domesticated them. I actually know dogs that can respond to 75 different commands."
The results, published in the journal Biology Letters, follow the death this year of Chaser, a border collie trained by her owner, retired US psychologist Dr John Pilley, to recognise 1 022 differently named toys.
The study of 42 dogs also found dogs can tell the difference between regional accents.
Researchers played recordings of four different people saying the same word to the pets and then followed it up with a word that sounded slightly different.
Words were played through speakers as said by both men and women.
The dogs responded strongly to the first voice, by looking at the speaker, turning their head towards it or raising their ears for three seconds on average.
As different people repeated the same word, the attention span of the dogs dwindled.
But when the word being said was altered, from "hood" to "had" for example, the pets reverted to the original response, proving they recognised it as a new command.
Scientists say their findings suggest dogs can recognise short words as being the same when spoken by different people, including commands.
The average dog is thought to understand around 160 words.