"Speak slower human, come on!"

The evolution of human-dog communication
Vocal communication between dogs and humans has evolved to be highly effective, shaped by the needs of both species.

While humans adjust their speech to accommodate dogs’ capacities, dogs have developed a sensitivity to human speech cues, even without prior exposure.

Dogs’ vocalizations (or speech, you could say) differ from human speech in rhythm, often operating at a slower rate. These vocal rhythms align with the dog’s neural processing, which is more tuned to lower-frequency sounds than humans.

Now, scientists have made brainwave measurements on both dogs and humans to compare their brainwaves when communicating with each other.

The study
The study used EEG in both species to measure brain processes in response to speech stimuli. EEG (Electroencephalography) is a test that measures electrical activity in the brain using small sensors placed on the scalp. It records brain wave patterns.

Dogs were exposed to command words (e.g., "sit," "come"), while researchers observed their responses. Humans, on the other hand, listened to streams of words and gave feedback on how clear and understandable they found the speech.

It was found that both species did neural tracking of speech. Neural tracking of speech refers to the brain’s ability to follow and process the rhythms and patterns of speech sounds. As someone listens, the brain tracks the rhythm and patterns of the speech, helping with understanding words, meaning, and speaker intent. This process is crucial for speech comprehension.

There were differences, though: humans showed better tracking in syllables, while dogs primarily tracked in words. This suggests that humans track speech at the syllable level, while dogs focus on word-level tracking.

The research showed that as speech rate increased, both human and dog brain activity decreased, indicating that faster speech impairs comprehension.

Interestingly, the way dogs respond to human speech suggested that human vocal production has adapted to match dogs’ auditory capacities. This finding supports the hypothesis that human speech evolved to be more comprehensible to dogs, indicating a co-evolution of communication patterns.

So, how do you help your dog understand you?
Dogs’ vocal (dog-talk) rhythm is slower than humans, with their natural vocalization rate centered around 2 Hz. This slower rhythm is consistent with the vocalization system of other non-human animals.

The study proposes that this slow rhythm may be the best for human-to-dog communication, with humans adjusting speech rate to align more closely with the dog's auditory system, enhancing effective communication.

In conclusion, this study shows that dogs and humans process sound patterns differently over time, highlighting unique ways their brains handle speech and vocal cues.

Humans may have adapted their speech to better align with dogs’ neural capabilities, potentially strengthening interspecies communication. Bottom line: "Speak slower, human"!

About the scientific paper:

First author: Eloïse C Déaux, Switzerland/France
Published: PLos Biology, October 2024
Link to paper: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002789