The way dogs have come to understand the nuances of human language is impressive for an animal that doesn't speak words.
Just a fraction of a second after we say a word, dogs can respond to it. They are able to understand the tone of our voice.
A new study shows that the average dog can respond to 89 words or phrases, which is more than our own. Roughly half of these are commands, like'sit' or'stay', but some general words, like 'wait' and 'treat', are also understood.
The most learned dogs were found to respond to over 200 specific words, which is roughly equivalent to the vocabulary of a two-year-old human child.
Dogs seem to respond to certain words in a specific and consistent way, which suggests they have some level of language comprehension.
The findings are based on an established vocabulary checklist used by parents to assess a human infant's vocabulary. It was given to 165 owners of dogs, including canines from a range of breed types.
Breed type, work status, and the age of the dog's owner did not seem to have an effect on the size of the dog's vocabulary.
"Based on owner reports, dogs seem to vary greatly not only in the number but also in the kinds of words to which they purportedly respond," the authors write.
In 2004, researchers reported on a border collie named Rico who had learned to retrieve over 200 items, including stuffed toys and balls.
A border collie who had been training for three years had a toy vocabulary of over 1,000 words.
What about your average dog?
The authors of the current study used an online survey to have dog owners report how their pet responded to 172 words.
There's a chance that the owners will underestimate their pet's understanding. The research shows that parents are better at understanding their child than a trained observer, so the same may apply to their pets.
The method of giving dog owners a fixed list of words to work through ensures that a pet owner doesn't forget to test some words, as might have happened in previous studies on canine vocabulary that came up with an average doggy lexicon about three times smaller.
Dog owners were asked to rate their dog's response to certain words and phrases on a scale of 0 to five.
A score of zero meant their dog never responded to a word or phrase. A score of five points meant that the dog would often do even when the words were said in different locations, in different tones, and by different people.
There were ten words or phrases that were specifically recognized by more than 90 percent of the dogs.
Only a few dogs could respond to phrases and words like 'whisper', 'loud', 'antler', as well as names for the dog walker, the doggy daycare, or the kennel.
Pet owners had the chance to add more words and phrases to the established vocabulary list. The owners who added the most commands, nouns or verbs were more likely to have professionally trained dogs or dogs that were good at learning quickly.
Professional dogs, like those trained for the military, the police force, or search and rescue, have 1.5 times the vocabulary of dogs without this career training.
The authors of the study didn't have enough dogs from each breed to figure out if certain dogs are better at learning words than others, but they did show significant variations in their word-learning abilities.
The owners of herding dogs and toy-companion dogs believed their dogs responded to more words than the owners of terriers, sporting-gun dogs, companion dogs, and other breed dogs.
The authors say that the research is exploratory and that conclusions about the ability of certain dog types to respond to human language is premature.
The findings of the current study come with limitations because of how subjective it can be to interpret dog behavior.
There is a chance that the dogs in the survey were incorporating human gestures and other contextual information into their understanding of certain words. A completely untrained dog could have a lower vocabulary than a dog that had received basic training.
The research highlights a potential way for scientists to measure dog responses to language in the future.
This tool could one day allow us to identify which words are most likely to be responded to by which dogs.
The authors conclude that the tool could become an efficient, effective, and economical research instrument for mapping out some of their competences and perhaps help predict early the potential of individual dogs for various professions.
Applied Animal Behaviour Science published the study.
