Intelligence is a subject that touches lots of other subjects, and where it does, they usually define the vocabulary slightly differently in each subject. In most cases, they use it in broadly the same way, but almost always, there are more questions than answers.
We all think we know what intelligence means. But when we go to measure it, we find that we don't really know what it means; each of us appears to have a slightly different idea, and all attempts to define it appear to lead to either circular definitions, or ones which don't seem to fully capture the 'spirit' of true intelligence.
From the development of intelligence tests by Dr Alfred Binet in 1904, there have been problems with the definition. In fact, Binet himself cautioned against regarding the numerical results of these tests (the intelligence quotient or I.Q.) as representing innate intelligence, and he was proved right when the tests of Evoked Potential were developed which showed that only about 70% of the I.Q. was down to this General Intelligence, with the rest being concerned with various Specific Intelligences.
This has led to there being a multitude of different Theories of intelligence, most of which disagree with each other, often to the extent of being diametrically opposed to each other in some facet of the theory.
If you start with the question "What is intelligence" and look at the different answers, you find broad agreement in the usage, with near total disagreement in the definitions, and this is before you start asking the difficult questions to do with Animal Intelligence, or looking at the interaction of Machines and Intelligence, let alone the problems dealing with the nature of Extra-terrestrial Intelligence.
Once you include machines, this raises the connection between Intelligence and Learning, which itself connects with Intelligence and learning disabilities. There are also some problems and advantages connected with Intelligence and Genius, which need to be considered by anyone who may be dealing with genius on a day to day basis. There are also problems with prejudice regarding intelligence (both high, and low) which are only just begining to be dealt with by the law makers.
On the whole, we have a very large subject, which we are only just begining to be able to investigate in a meaningfull way. Some time within the next 50 to 100 years, we will start to see detailed answers to some of the many interesting areas covered by this subject, and until then, we are still left with a large (and growing) number of questions that will have absolutely fascinating answers when we finally find them.
Part of the Intelligence Project