4.c) Cognitive science and intelligence test  

4.c.1) Hereditary versus predetermination  

It is important to stress that having a hereditary intelligence or any other hereditary character does not mean following a linear ratio or a predetermination of a particular value. The combination of genes offers a wide array of possibilities.

For this purpose, just remember that pink flowers may have red, pink, or white descendants in the typical examples of Mendel's laws.

The chart relating to the concordance in identical twins and just twin brothers can help us see the difference more clearly.

The comparison between these percentages of concordance not only allows us to perfectly differentiate between hereditary character and predetermination of a particular character but rather also to deduce information about the number of genes or chromosomes involved and the number of possible different expressions or characteristics.

For example, it seems that the blood group depends on just one gene while schizophrenia depends on various, possibly six or seven, although it is difficult to know with just this information. Also, for schizophrenia, the heritability of parents to children is very low even though it has a genetic concordance of 69%

The concordance of intelligence is not presented because it changes with the different studies. Although from the information available, I would say that it is mainly found on one chromosome.

4.c.2) Multiple functions and facets of intelligence  

Another problem as we have seen, is the definition of intelligence. Multiple functions and operatives modes configuring the cognitive processes affect the ability of measurement of intelligence test

However, it is not as serious as it seems; the fact that intelligence can be formed by various elemental faculties that are somewhat independent does not mean that they cannot be hereditary brain functions. Furthermore, if it turns out that one group of them has this characteristic; they will probably all have it.

On the other hand, the lack of a generally accepted definition of intelligence is very inconvenient given that I really think that there are many ways to deal with this concept. Even so, a way of avoiding this byzantine discussion is to reverse the concept so that it meets our needs:

-We will study the heritability of intelligence by understanding it as a group of faculties of intellectual reasoning measured by what is commonly called the intelligence test-

Afterwards, we may analyse if the results of the study can be generalized.

4.c.3) Continuous variable  

Intelligence is a continuous variable of Nature, which complicates the quantitative research of its heritability.

Normally, studies performed on continuous variables are based on the treatment of these variables as a sum of more elemental discreet variables. You have to take into account that, in general, the change of continuous variables is not easily compatible with the idea of change by random mutations.

Intelligence can be understood as a sum of relational functions such as above / below, larger / smaller, general / specific, etc. Although the appearance of a new relation could be understood due to random causes, the improvement or greater precision of an existing relation that could be produced in a similar fashion could turn out to be incomprehensible.

4.c.4) Cognitive ability test  

We find ourselves with two large problems when measuring these intellectual abilities. The first is derived from the fact that the display of these brain functions is very much influenced by the moment in which they are performed.

Tiredness, moods, and other various factors can significantly affect their expression from one day to the next or between the beginning and end of the same day.

The second is that each particular measurement uses a specific test and the results can vary according to: whether the individual has done a similar ability test in the past, the individual's personality or cultural affinity with the ability test. However, if it is well designed, this aspect should be fairly reduced.

In the quantitative data used from the longitudinal Young Adulthood study for the statistical analysis included in the IDI Study, the correlations between the different measurements of the same children of intellectual abilities are very low. The maximum is 33% in spite of the fact that the same people are being measured.

A simple conclusion would be to think that the brain functions of intelligence are not stable throughout life and that they are highly influenced by the environment. However, some experts believe that intellectual abilities are greatly stable throughout life, especially from 6 years of age on.

Popular language, as an expression of the collective unconscious, clearly expresses that intelligence is a fixed quality given that it uses the verb to be referring to permanent not transitory characteristics in expressions such as, "That person is very intelligent." Well, at least in Spanish this aspect is obvious.

4.d) Social and technical issues  

4.d.1) Shortage of statistical studies with adequate IQ data  

The studies of intelligence quotients in families with a large sample are relatively scarce, because the fieldwork that includes these type of variables tend to be more directed at studies of identical twins, twin brothers or adoption programs, and do not include the two progenitors.

Anyway, if there is another one! I would like have access to its row data.

They are also quite costly if you want to the results to have a guarantee of objectivity. A good sample design is needed and, there is the additional difficulty of obtaining volunteers for this type of statistical study, the performance of the intelligence test by specialized personnel, etc.

4.d.2) Access to quantitative data source  

Nevertheless, the most complicated thing for me was being able to find and access the original quantitative data source in order to perform my own statistical research and estimations.

In spite of the small magnitude of the analysed sample, the generation of variables by different groupings and criteria of the available values has allowed for the accessibility of a model that is very sensitive to the information. This characteristic, in my opinion, is one of the model's strong points; in spite of the vulnerability of the researched correlations, it is significant that some determination coefficients have been obtained that border close to the unit and that the thousands of checks curried out have a high level of consistency.

In defence of my small sample of quantitative data, I would like to say that I have been virtually travelling for more than one year to numerous worlds of professionals, national and international organizations dedicated to the study of intelligence, public organisms, universities, Internet news groups, international studies on twins, etc., asking for statistical data on intelligence quotients (IQ) of families. I even turned over the search to a psychometric company, but there were no results.

In the end, a search performed by the Google server's paid service found four different sites for me. I had entered three of them and not found the information. Fortunately the fourth bore its fruits, although with a certain amount of difficulty. At least I obtained a sample of quantitavie data, even though it was small.

I suppose that the personal character of the statistical data and its social and political implications hinders its access.

Likewise, I imagine that the authors of the majority of the thousands of statistical research articles published on this subject probably did not have access to the quantitative data source and limited themselves to commenting on the results published by other works and theoretical justifications of their personal point of views.

4.d.3) Moden computer technology  

The analysis of the correlations of variables and the models of regression by ordinary least squares have been easily made for quite some time.

Nonetheless, the computer capacity of calculation has spectacularly multiplied in recent years. The use of this great capacity of modern computer technology has been totally necessary in order to obtain the results achieved in the statistical research of the IDI Study.

For this purpose, it is worth pointing out that each time the quantitative data is brought up to date, the Excel math worksheet generates more than 10,000 random numbers, hundreds of variables, more than 100,000 coefficients of determination of linear regression for ordinary least squares of the different variants of the model, and presents me a 200 graphs with 16,000 values, that are, of course, in colour.

It used to take 3 to 7 seconds.