There are 2 main theories for the comparison of animal intelligence: A phylogenetic based approach: since the time of aritotle people have tried to organise the animal kingdom into a sequence of intelligence or “scala naturae” great chain of being. What has now become known as the phylogenetic scale of intelligence is based upon Darwins theory of evolution as laid out in his on the origin of the species 1859. As intelligence serves an adaptive purpose it is a reasonable assumption that the more evolved an animal is the more intelligent it will be. For instance we evolved from homo-sapiens around 100,000 years ago and we are much more intelligent than them. However this had been proven not to be the case. In fact evolution encourages tree like not linear organisation of organisms and their characteristics. As gould said 1996 our species is a “tiny twig on the floridly aborescent bush of life” Evolution provides an example of the diversity of a species, it does not provide any grounds for ranking animals according to their intelligence. An alternative approach to comparing animal intelligence is the niche specific theory of intelligence. This theory argues that animals have different environmental pressures and that is reflected in their intellectual ability for example a bird has excellent navigation skills and a dog has an excellent sense of smell. However there are also common evolutionary pressures which all species share such as food illness learning. The underlying mechanisms for learning which foods to avoid is the same in all animals so this theory is also a shite way to explain the distribution of intelligence.
The main problem when comparing species intellects is how to define a test which is a fair test. All animals differ in their intellectual abilities and are better at some things than others so how can we define a test which tests them equally. There have been 4 main ways provided: Adaptation to the environment:
Many believe that the defining characteristic of intelligence is that it enables animals to behave adaptively. Barnett 1970 proposed “intelligence here means the ability to adapt behaviour to circumstances”. Therefore one way to compare animals intelligence is to look at how well adapted they are to their environment. However this measure of intelligence is very weak, it is not fair to compare different environments. This also implies that if an animal swapped environments they would become less intelligent.
Another method proposed for comparing animals intelligence is by comparing brain size. The brain is the organ responsible for intelligence and therefore it might be reasonable to expect animals with larger brains to have greater capacity for intelligence. However we would expect humans to be at the top and we are not because other animals have much larger bodies which need larger brains to control basic activities such as respiration and digestion. Therefore the method of comparing brain size to body weight has been proposed however this would put birds above humans also rendering it wrong. Jerrison 1973 however introduced a more complex ratio based on log scaling using a ratio o 2/3. This is called the encephalisaton quotient and does position man at the top. However there are still problems to be encountered with this method as well. Brains are not just for intellectual activity they are mainly used for basic processes like respiration and digestion so measure of brain size is contaminated. Brain weight is also affected by neural density and ventricular capacity which are not necessarily mean more intelligence. To overcome these problems it has been suggested that we focus on the measurement of the neocortex as this is the part of the brain which is particularly well developed in humans and therefore it has been argued that a large neocortex reflects advanced...