[DailyMail] The researchers, from Vanderbilt University in Nashville, Tennessee, say the number of neurons in an animal's cerebral cortex is a hallmark of intelligence.The cortex is the largest layer of the brain and is associated with a range of complex behavioural characteristics.
Researchers found that dogs possess around 530 million cortical neurons, while cats only have around 250 million.
By comparison, a human brain houses around 16 billion cortical neurons.
'I believe the absolute number of neurons an animal has, especially in the cerebral cortex, determines the richness of their internal mental state and their ability to predict what is about to happen in their environment based on past experience,' study lead author Dr Herculano-Houzel told Vanderbilt University's news site.
The researchers applied their intelligence theory to several carnivorous species, and found that bigger brains do not necessarily mean more cortical neurons.