Even if we did think that animals were less intelligent than humans beings they should be protected by rights  Babies and individuals with learning disabilities may lack intelligence, a sense of justice and the ability to conceive of their future. We ensure that babies and the learning disabled are protected by rights and therefore these factors cannot be criteria by which to exclude a being from the rights system. Therefore, even if animals are not as advanced as human beings they should be protected by rights. An inability to know what's going on might make being experimented on etc even more frightening and damaging for an animal that it may be for a human being.