Dolphins have been declared the world's second most intelligent creatures after humans, with scientists suggesting they are so bright that they should be treated as 'non-human persons. It has become clear that they are 'cultural' animals. meaning that new types of behaviour can quickly he picked up by one dolphin from another. They have distinct personalities, a strong sense of self, and can think about the future. Studies on dolphin behaviour have highlighted that their communications are similar to those of humans and that they are brighter than chimpanzees. These claims are backed up by anatomical research showing that dolphin brains have many key features associated with high intelligence. Researchers argue that it is morally unacceptable to keep such intelligent animals in amusement parks, or to kill them for food or by accident when fishing.
The term 'backed up in the extract can be replaced with_____.