>>9709658In short, because intelligence is malleable. Those who aren't getting any attention from girls spend all their time studying, thus increasing their reasoning ability and IQ.
http://www.cell.com/current-biology/abstract/S0960-9822%2811%2901267-XThe posterior hippocampi of average-IQ adult subjects who passed the difficult Knowledge exam for London taxicab drivers showed significant enlargement as opposed to before they began studying for it. (The posterior hippocampus is associated with memory and spatial navigation, both of which are strongly correlated with g.) Similar effects not observed in the control group or in those who failed. Pic related.
This was actually a repeat experiment with a larger sample size, i.e. the results are reproducible. And because all subjects are already grown adults, normal brain development does not confound the study's results.
So we have hard, physically-observable, causally-linked, reproducible evidence that the brain PHYSICALLY restructures itself in response to focused training. Since intelligence is a function of brain organization, it must therefore be possible to increase intelligence just as it is possible to decrease it.
