People care about whether cats really do understand and pay attention to their owners," says Vonk. "Our work shows that they may not be as indifferent as people accuse them of being."
Domestic cats first appeared around 10,000 years ago
It may have taken so long to discover cats' emotional intelligence because their responses are rather subtle. As well as obviously "positive" actions like purring or rubbing, Galvan and Vonk noticed that the cats adopted certain body positions, and ear and tail movements, that are associated with contentedness.
In contrast, scientists have known for several years that dogs respond differently to happy and angry faces. That is at least partly because their responses are more obvious. A 2011 study showed that dogs will actively avoid someone who appears angry, rather than just changing their body language.
The difference between dogs' and cats' responses to human emotions could be rooted in prehistory.