The brain of P. lujiatunensis is well known, a 2007 study published on the anatomy and functionality of three specimens all clearly of the species. Generally thought until the study, the brain of Psittacosaurus would have been similar to other ceratosians with low Encephalization Quotients. Russell & Zhao (1996) believed “the small brain size of psittacosaurs implies a very restrictive behavioural repertoire relative to that of modern mammals of similar body size”. However, the 2007 study disposed of this misbelief, finding the brain more advanced. Generally negative allometry for brain size with development in vertebrates, but it was shown that in Psittacosaurus this was not true. The EQ score for P. lujiatunensis is 0.31, significantly higher than genera such as Triceratops