Researchers at Emory University in Atlanta, Georgia, trained more than a dozen dogs to cope with noisy magnetic resonance imaging (MRI) scanners.
This allowed scientists to get clear images of canine brains because the animals had not been sedated.
Initial analysis suggested the bond between dog and owner may go further than a need for security and food and extend to emotions comparable to human affection, scientists said.
"We can really begin to understand what a dog is thinking [using a scanner] rather than infer it from their behaviour," said neuroscientist Gregory Berns.
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"I thought that if military dogs can be trained to work in dangerous areas and jump out of helicopters then surely we could train them to sit still inside an MRI scanner," Berns said.
Using hand signals to indicate the dogs were about to receive a food treat, Berns and his team showed that the caudate nucleus, a part of the brain associated with positive emotions, was similar in dogs and humans.
Researchers will now analyse brain scans from dogs offered treats by strangers and machines.
"We hope to show that they love us for things far beyond food, basically the same things that humans love us for. Things like social comfort and social bonds," Berns said.