Amazing stuff!
I always believed that dogs do not have a good eyesight. "Dogs have lower visual acuity than humans, averaging around 20/75 vision, meaning a dog must be 20 feet away to see an object as clearly as a human can from 75 feet away. While they lack fine detail and full color spectrums, they excel at detecting motion and seeing in dim light." (Google Search)
"In a new study, researchers trained a group of family dogs to lie still inside an MRI machine while showing them pictures of strangers with either happy or neutral expressions. Images of smiling human faces consistently lit up the temporal cortex and caudate nucleus, which are regions of the brain associated with reward and other functions like learning and emotion.
In a second experiment, the researchers showed dogs pictures of people displaying happiness, fear, anger, and sadness.
Analysis of the animals’ brain activity revealed distinct patterns separating fear from anger and sadness, suggesting that dogs can tell the difference between certain negative facial expressions. “Our results suggest that dogs’ brains can differentiate between some facial expressions as distinct categories, rather than merely detecting that one expression is more positive or negative than another,” ..."
From the highlights and abstract:
"Highlights
• Happy human faces elicit right frontotemporal-caudate responses in dogs
• Dog brain response patterns distinguish happiness from negative facial expressions
• Whole-brain response patterns differentiate some pairs of negative facial expressions
• Dog brains represent human facial expressions beyond positive-negative valence
Summary
Dogs can distinguish human facial expressions, particularly happiness, yet brain processes remain unclear.
Using fMRI, we conducted two experiments in awake pet dogs.
In Experiment 1 (n = 8), happy faces elicited a stronger response than neutral faces in a right temporal cluster extending to the caudate nucleus, including the rostral Sylvian gyrus.
In Experiment 2 (n = 12), dogs viewed faces expressing happiness, anger, fear, or sadness.
Using the Experiment 1 cluster as a region of interest, a machine-learning classifier distinguished happiness from each negative facial expression, but not between negative pairs, showing differential BOLD responsiveness to happy faces.
Whole-brain representational similarity analyses revealed activity patterns differentiating angry vs. fearful faces (right mid ectosylvian and left splenial gyri) and sad vs. fearful faces (right rostral suprasylvian gyrus) but not angry vs. sad faces.
This provides direct evidence that dog brains can distinguish between two negative facial expressions."
Dogs can tell if you’re angry, scared, or sad "Our canine companions may really understand what we're going through, new study suggests"
Dog brain representations of human facial expressions: Encoding happiness and differentiating specific negative expressions (open access)
Figure 1 Functional localizer for happy human faces > neutral human faces (n = 8)
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