Identical twin studies suggest that some of intelligence is hereditary. (What theorists such as Hernstein call “g”) What this means is that if we look at performance on standardized exams if one identical twin raised apart does well on the exam, then there is a higher probability the other twin will do well. It is certainly conceivable that certain skills — pattern recognition, memory, and the ability to come up with alternate interpretations of data — are heritable. However given a particular package of heritable skills humans vary widely on how intelligent they can be.
Let us say that intelligence is the ability to solve problems. To see why it is not entirely heritable consider the case of someone who seizes on a bad solution to a problem and will not let it go. Once he has hit upon the solution (which may in fact have required intelligence) his solution will prevent him from solving further problems. Therefore despite his inherited ability to recognize patterns, remember patterns, and come up with alternative interpretations of data he will be poor at solving problems. You could say that he has deliberately reduced his intelligence.
If it is possible to reduce one’s intelligence deliberately it follows that it should be possible to deliberately increase one’s intelligence. It could be argued that inheritance places limits upon how high this can go (and in certain cases — e.g. Down Syndrome — this is undoubtedly the case) however given the existence of libraries and the internet it is possible to augment the patterns one comes up with on one’s own. Just as corrective lenses and telescopes can augment the eye, these technological aids can augment the mind.
Some might argue that what can be increased is “successful application of intelligence” while intelligence itself remains innate and unalterable. I would argue that “intelligence itself” should not be of interest to us. What we should care about is the ability to solve real problems. If that can be successfully trained then we can leave “innate intelligence” to the prigs.
How is it possible to increase intelligence then? I believe through two methods: caring and self-criticism.
Hubert Dreyfus’s model of skill acquisition has shown that caring about success is necessary for acquiring a skill. It is only when success makes us feel good and failure makes us feel bad that we internalize lessons about what works and what doesn’t work. The first requirement for teaching ourselves intelligence therefore is to care.
Some people cultivate intelligence by caring about being perceived as intelligent. This is a bad method. For one thing it turns them into obnoxious know-it-alls. But more importantly it is judging problem-solving at one remove, by checking to see if a solution is perceived as successful rather than actually being successful. A better method: come up with problems you actually care about and keeping trying to solve them. If they are unsolvable problems but ones which one can approach solving all the better. Philosophy provides a buffet of such problems — what good is life given we must die? How does matter think? What is the best way to live? Caring about finding solutions to these problems is a good step towards cultivating intelligence. As Mihaly Csikszentmihalyi has shown in his work on “Flow” the optimal problem is not so easy as to be boring and not so hard as to be frustrating.
A second path towards training intelligence is to challenge and criticize one’s solutions constantly. Again there is a social path towards criticsm — finding intelligent people to debate — and an individual one — debating different sides of oneself. Both are fine. What is crticical to criticism is that it avoids the trap of being caught in a local maximum, or being satisfied with a good enough solution rather than the best solution.
It might be that constant self-criticism is not the optimal path to happiness. I do believe it is the path to intelligence. And this satisfies a certain intuitive demand for justice. If intelligence is important we should wish it to be trainable and achievable through effort rather than the result of a genetic lottery. This also suggests that intelligence has more to do with the moral virtues than the advocates of heritable intelligence suggests. Humility and courage are both requirements for successful self-training.