Dogs’ brains don’t process the difference between two words that differ by only a single sound, a study has found. This is similar to how children process words at around 14 months, and could explain why dogs only learn a small number of words over the course of their life.
Researchers at the Eötvös Loránd University, Budapest studied the brain activity in dogs using a non-invasive electroencephalography (EEG). They chose dogs without any particular training, and secured electrodes to their heads with tape.
The researchers then played a recording of words dogs knew, similar-sounding nonsense words and nonsense words that sound completely different, and recorded the dogs’ response to these words.
The brain activity showed that the dogs could distinguish between words they know and nonsense words in around 200 milliseconds, a similar timescale to humans.
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They also found that while dogs do have an exceptional ability to process sounds, they don’t differentiate between words they know (e.g. ‘sit’) and nonsense words that differ by only a single sound (e.g. ‘sut’). This puts their processing ability around that of a one-year-old child.
However, the researchers believe that this is not because of the limits of their intelligence, but because they don’t pay attention to all of the sounds in a word.
“Similarly to the case of human infants, we speculate that the similarity of dogs’ brain activity for instruction words they know and for similar nonsense words reflects not perceptual constraints but attentional and processing biases,” explained Dr Attila Andics, principal investigator of the MTA-ELTE ‘Lendület’ Neuroethology of Communication Research Group.
“Dogs might not attend to all details of speech sound when they listen to words.”
Between 14 and 20 months of age, human infants learn to pay attention to the differences between similar-sounding words, and their vocabulary rapidly expands. However, dogs never learn this skill, the study suggests, and so on average they only learn 165 words over their lifetime, despite spending their whole lives in a family surrounded by human speech.
Reader Q&A: Why do dogs tilt their head when you speak to them?
Asked by: Toby Graham, Shrewsbury
A dog’s range of hearing is wider than ours but not as accurate. Perking their ears up while tilting their heads helps them pinpoint where noises are coming from more quickly. It also helps them to hear and interpret the tone of our voices, and pick out familiar words such as ‘walkies’.
Dog behaviour expert Dr Stanley Coren believes that dogs with shorter muzzles tilt their heads less because they have a better view of our facial expressions and are therefore not so reliant on their ears to understand us.