[throwaway468883]

The main issue is that intelligence isn't well-defined. Laymen can't agree on a definition. Specialists from different fields (say, psychology, neuroscience, computer science, developmental biologists and animal behavioral biologists) can't agree either. More egregiously, specialists within a single field can't agree either. For all the 1994 manifestos people like to throw at people in internet arguments, it doesn't mean everyone in the field (which was mostly psychologists and little else) agreed with it and it doesn't mean the people who did sign it could pin down what they said onto a single definition that made sense from both a scientifical and general understanding.