4.c) Cognitive science and intelligence test
4.c.1. Hereditary versus predetermination
It is imperative to stress that having an innate 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.
Let us 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 to see the difference.
The comparison between these percentages of concordance not only allows us to correctly differentiate between hereditary character and predetermination of a particular character but also to deduce information about the number of chromosomes or chromosomes involved and the number of possible different expressions or characteristics.
For example, it seems that the blood group depends on just one chromosome 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 on the table because it varies with the different studies. Although from the EDI Study, it appears to be 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 dangerous as it seems; the fact that intelligence is a group of 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 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 a typical intelligence test.
Afterward, we may analyze if the results of the EDI Study are standard results.
4.c.3. Continuous variable
Intelligence is a continuous variable of nature, which complicates the quantitative research of its heritability.
Typically, studies on continuous variables perform the treatment of these variables as a sum of more elemental discreet variables. We have to take into account that, in general, the change of continuous variables is not readily compatible with the idea of change by random mutations.
Intelligence can be like a sum of relational functions such as above/below, larger/smaller, general/specific. Although the appearance of a new function could be due to random causes, the improvement or greater precision of an existing function could turn out to be a little incomprehensible.
4.c.4. Cognitive ability test
There are two big problems when measuring these intellectual abilities. The first comes from the fact that the display of these brain functions depends on the time of the day.
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 one, 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 the design is adequate, this aspect should be minor.
In the quantitative data used from the longitudinal Young Adulthood study for the statistical analysis included in the EDI Study, the correlations between the different measurements of the same children of intellectual abilities are very low. The maximum is 33% even though they refer to the same people.
A simple conclusion would be to think that the brain functions of intelligence are not stable throughout life and that they highly fluctuate with the environment. However, some experts believe that intellectual abilities are incredibly 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 brilliant or knowledgeable. Well, at least in Spanish this aspect is obvious.