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 What is 'intelligence'? The best definition for the word, which would apply across different species, is 'the capacity for learning'. How is it possible to measure that capacity? The first intelligence tests for humans were developed in 1905, but these early tests were more an assessment of a person's education - it tested what they had learnt rather than their potential for learning. Although modern IQ (Intelligence Quotient) tests are greatly improved, there is still some difficulty in simply translating the questions for people from different cultures. Translating for another species is an entirely different matter. Even if you just take a few examples of behaviour from across the animal kingdom it becomes apparent that 'intelligence' is not simple. Some animals have a very great capacity for learning only in one specific area, or can perform mental tasks which humans are unable to do. For instance, honey bees calculate the direction and distance from their hive to a good source of nectar from which they've returned. They then communicate this to other bees in the hive by acting out a 'waggle dance'. Not only is this accurate enough for other bees to be able to follow their directions, but the original bee continues the message for several hours, adjusting its calculation of the direction (which is given as a bearing taken from the sun) as time passes so that it remains accurate even as the position of the sun changes. Human IQ tests tend to have different sections testing a person's memory, reasoning, arithmetic, language, and concept-forming abilities. Looking at the abilities of other animals it immediately becomes clear that they all have differing abilities in each of these areas, and possess abilities in others that humans would not even imagine. Not only that, but the difference in the natural behaviour of animals is so great that it is often impossible to 'translate' a test designed for one animal (such as a human) into an equivalent that could be carried out by another (such as a dolphin). After many years of experiments, it seems that the human brain has adapted to be particularly specialised for language. Other apes and dolphins also appear to have this specialisation, and have been able to communicate with humans in startlingly coherent ways, including understanding word order in sentences. Chimpanzees - particularly the species known as bonobos - have the language capabilities of a 3-year-old human. Other, less social, animals appear to lack this specialisation but instead may have other abilities, such as prodigious memories