It is negated. His assumption has several basic errors. The errors are that all the data for a personality must either come from the DNA or from perception.
First, form follows function and vice-versa. The vary process of building of the brian includes a curtian level of programming. The ROM and basic processors for an analagy. There in lies a curtain level of data transmition to the brain so some data is by the default nature of the structure provided to the brain. That default data and basic organisation is in effect "compressed", or perhaps pre-organised would be a better term , to perform curtain functions such as in the case of the parts of the brain that deal with vission and hearing.
There is a third place that the mind recieves data, itself. The mind creates it's own data by deriving data from the logical enferences of data already recieved and this is very likely the source for most if not all the 'missing' data that is required for personality. The brain does a tremendious amount of self organisation in the first years of life. Again, form follows function. Intellect, personallity, and all the other characteristic of a mind are very likely the senergetic effect of the DNA based starting point of the brain plus all the changes cause by both external data and internal derivations.
If Chomsky's assurtions were all there was to it then identical twin raised together or in identical inviroments would always make the same choices to the same stimuli. They do not so some other factor is at work.
That said there is also the likely hood that there is a "random number generator" built into the developement of the human mind/personality as a survial mechanism. In effect a mental anti-Darwanism system. It would NOT be in an animals best interest to always react to a given situation in the same way as this predicability would be an exploitable weakness. So for the greater good of the species some members will run and some will fight. The ones that act correctly survive and as humans can learn and comminicate that learning they will tell their offspring what worked and what did not. This was the original form of education (storytelling). This adds an additional level of adaptability to thinking creatures above and beyond DNA encoded instict. And a furture advantage to creatures that can communicate their experience by some other means than DNA to their offspring.
Well, there in lies the riddle. The brain can contain far more information than DNA can. DNA can supply the basic structure which can infuence HOW perceptions effect the brain. In effect the DNA and the 'code key' to deciphering the data obtained from the perceptions or perhaps it the the other way arround. It does not really matter to anyone except a few theoretical scientists which is the key and which is the code. In either case over time each will influence the other and the synergy of the two plus many other things blend to make a personality.
And there in lies another complexity. Some of the part of DNA are only use to create the original structure of the animal and then stop doing anything. Perhaps the encoding is conditionally based? A DNA fragment in a fetus may work differently because it knows what life stage it is in that the same DNA in a teenager, an adult, or a post menapausal person. In effect DNA may have many workable "decode keys" that produce useable information at the pro per point in an animals life cycle. Then if that is true who's to say the there is not a life-cycle point (decode key) where a large part of the DNA data is decoded in a slightly different way to provide some extra boot strap infomation to the brian. Perhaps in some of the part of the DNA that we don't understand there is a key sequence the says in effect 'read every seventh pair in rotating recirculating sequience to program this kids personality'. Biology tends to get more than one use out of most things. Why not DNA.
Simple facts and what can be devised from them,
human being exist they have personalities so those personalities have to be created/built/made whatever it happens so it must be posible that said just because we can not explain it RIGHT NOW does not mean that we will not be able to explain it someday.
As no one here is an expert reseraching this (at least no one has assert such expertese), then all we are doing here is trying futilely to explain to ourselves what we each think about the process to better understand our own views, to convince others of our own point of view, to convey to others our own view in hope of approval or validation, or for the enjoyment of the mental exercise. Which is of course determined by each of our respecive personallities regardless of how they came into being.
Charles L.