Well, my point was that you can't expect the same rate of advances from some IQ breeding programme that we get when breeding traits arising via loss-of-function mutations.

They seem to be replicating.

They don't seem to be replicating very well...

http://arstechnica.com/science/2014/09/researchers-search-for-genes-behind-intelligence-find-almost-nothing/

Sure, there's a huge genetic component, but almost none of it is "easily identified".

Generally you can expect that parameters such as e.g. initial receptor density at a specific kind of synapse would be influenced by multiple genes and have an optimum, where either higher or lower value is sub-optimal. So you can easily get one of the shapes from the bottom row in

http://en.wikipedia.org/wiki/Correlation_and_dependence#/media/File:Correlation_examples2.svg

i.e. little or no correlation between IQ and that parameter (and little or no correlation between IQ and any one of the many genes influencing said parameter).

edit: that is to say, for example if we have an allele which slightly increases number of receptors on a synapse between some neuron type A and some neuron type B, that can either increase or decrease the intelligence depending on whenever the activation of Bs by As would be too low or too high otherwise (as determined by all the other genes). So this allele affects intelligence, sure, but not in a simple easy to detect way.