Dogs Process Spoken Words Using Two-Tiered Brain Hierarchy

Like humans, dogs process intonation and word meaning in separate brain regions.

Posted Aug 03, 2020

Kamille Sampaio/Pexels
Source: Kamille Sampaio/Pexels

A new fMRI brain imaging study of dogs shows that their brains process spoken words in hierarchical ways that are surprisingly similar to how the human brain uses a two-tiered hierarchy to process spoken words. These findings (Gábor et al., 2020) were published on August 3 in Scientific Reports.

This study was conducted by researchers at Eötvös Loránd University in Hungary. The cohort included 12 pet dogs between the ages of 2 to 10 years old from three different breeds. There were six border collies, five golden retrievers, and one German shepherd. Of note: The dogs who participate in this ongoing "Family Dog Project" research initiative are not harmed in any way during their brain scans.

"Emotional prosody" is a term used by the researchers to describe the emotive feelings associated with different inflections used in dog-directed speech. In general, people tend to use a higher-pitched tone that is similar to baby talk when praising a dog (e.g., "Such a good boy!").

How does the two-step process of analyzing spoken words happen in a dog brain? First, subcortical regions in a dog's brain pick up the intonation of speech and infer if the tone is positive, negative, or neutral. Second, cortical areas of the dog's auditory cortex interpret the denotation and meaning of a spoken word or command, such as "sit."

How did the scientists get the dogs to stay still in the fMRI? The dogs used for this experiment had been trained to lay motionless for up to about eight minutes, but each experiment lasted for a shorter duration.

While the awake dogs laid motionless in the fMRI, the researchers observed how their brains responded to three different Hungarian words of praise: azaz ("that's it"), ügyes ("clever"), and jól van ("well done") that were spoken repeatedly by a dog trainer who flipped between using positive or neutral intonation.

Then, the dogs had their brains scanned while listening to random "meaningless" conjunction words such as akár ("as if"), olyan ("such"), and mégsem ("yet"). These conjunction words were also said repeatedly using positive or neutral intonation. Conjunction words were used in the second part of this experiment because they're usually woven into everyday speech and aren't associated with any specific context nor do they have lexical meaning to dogs.

By comparing how the dog brain responded to hearing "praise words" vs. "meaningless words" spoken with a positive or neutral intonation, the researchers were able to identify speech processing hierarchy in the dog brain. As the authors explain: 

"Our findings suggest that dogs, similarly to humans, process emotional prosodic cues in spoken words at lower levels (subcortical and near-primary cortical regions, reflected in both short-term and long-term adaptation effects) and lexical information at higher levels (near-primary and secondary auditory cortical regions, reflected in long-term adaptation effects) of the auditory processing hierarchy. Prosody processing was thus subcortically independent of lexical cues, prosody influenced lexical processing in a near-primary cortical region and, finally, lexical processing was independent of prosodic cues in a secondary auditory cortical region."

This two-minute YouTube video recaps the significance of this research on "Speech Processing Hierarchy in the Dog Brain."

"Although speech processing in humans is unique in many aspects, this study revealed exciting similarities between us and a speechless species. The similarity does not imply, however, that this hierarchy evolved for speech processing" senior author Attila Andics said in a news release. "Instead, the hierarchy following intonation and word meaning processing reported here and also in humans may reflect a more general, not speech-specific processing principle."

This research suggests that subcortical brain regions typically analyze simpler, emotionally-loaded cues held in the intonation of spoken words in both the dog brain and the human brain. On the flip side, more complex and learned lexicons (i.e., words with meaning) appear to be analyzed in higher-ordered cortical regions of the dog brain. "What our results really shed light on is that human speech processing may also follow this more basic, more general hierarchy," Andics concluded.

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Anna Gábor, Márta Gácsi, Dóra Szabó, Ádám Miklósi, Enikő Kubinyi, and Attila Andics. "Multilevel fMRIAdaptation for Spoken Word Processing in the Awake Dog Brain." Scientific Reports (First published: August 03, 2020) DOI: 10.1038/s41598-020-68821-6