In this traffic lights metaphor, the will of the individual may be represented by the car driver. Obviously, the driver has his inherent own quality which influences the results of the vehicle’s activity.
Likewise, the driver will be responsible for the car’s maintenance, the one who can choose to train to a greater or lesser extent and who can decide on some of the conditions of the trajectory. However, to know the effect or influence on the quality and goodness of the car we will have to specify what we mean by goodness of a car and how we measure and compare it. In other words, we need to use quality indicators.
Now we are in a better situation to understand one of the important reasons of the polemic about genetic structure of intelligence and environmental influence.
If by intelligence we are referring to the time that it takes an automobile to go from one specific city to another, we have to recognize that this depends to a large extent on the type of highway, curves, the meteorological conditions, whether it is daytime or night time, the driver, etc.; all of these environmental conditions are more important than the car's power.
On the other hand, if by intelligence we are referring to the goodness of a automobile to perform any route, in any meteorological condition, with an average driver, etc., then, doubtlessly, the power of the car's motor will be one of the best indicators; a small group of indicators related to the fabric design -genetic structure- can make up a very significant index in respect to the searched for goodness.
Of course, other factors count, and flawed maintenance can make a car crash, but normally; this is prevented with minimum maintenance. A real example is a car that made the running-in in three cylinders, by the implicit will of the corresponding technicians. Real nice! There were never any particular problems with the motor afterwards.
Another interesting aspect of this metaphor is that many elements of an automobile are highly correlated from the technological point of view or modernity in spite of fulfilling functions that are independent of the vehicle's activity.
The subject of training can also be studied; a driver can learn the curves of a mountain highway and substantially improve the time needed for a specific route. However, this does not mean that the driver is better, or that the automobile is more powerful, or that if two years go by without travelling this route, or if the driver changes to another highway, he/she will maintain the advantages obtained from the training, etc.
On the contrary: “A good driver will always be a good driver.” Even though the curves are unknown for him.
On the other hand: a good automobile will always be a good automobile, even though it has a flat tire and does not move.
Finally, I want to point out that if we do not have the means to know the technical characteristics of a car when estimating them according to the time it takes for a specific route, we will make many errors -or the variance of the estimators will be great- due to the large amount of factors that influence the specific results of a particular route with a specific driver...
Take note that the mentioned factors cannot be easily isolated because each one of them has multiple factors that condition them. We cited that the same driver may be tired, happy, rushed…or the other way around.
Now, if what we really want is a measure of the goodness of the car in the performance of any function and be able to compare some with others in a simple somewhat precise fashion we would have to look for some type of indicator.
A good indicator of general goodness could be its price, but this depends on the market and includes aspects like famous people's cars or cars seen in movies, old cars, the effect of the brand and publicity, special accessories, taxes, etc. Also, this would not be useful to us for the case of intelligence, although there is a certain correlation between intelligence and economic power.
The motor's cylinder is a good and probably the most used indicator of a car's specific goodness. It is very good because it is independent of the external conditions, highly related to the price, to average velocity, to safety, to technology, etc.
If that corresponding to the consumption is added to the indicator we could have a compound more precise indicator than the previous. If it is of common use we could call it the "g" factor of the automobiles. Even if it were not the perfect indicator, it would be very comfortable; it would allow for simple comparisons and would be understood by everyone.
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