For a long time in some countries the idea has been maintained that certain races had a level of intelligence inferior to others, idea extracted from the application of certain intelligence tests that offered a comparable numerical data.
These results over time were invalidated because the intelligence tests themselves used in the statements of the questions a common vocabulary in certain races and not in others which explained the differences in the results obtained.
Thus, test built according to the peculiarities of each race have allowed to obtain levels of development equivalent between races, denying the myth that certain races were "superior" or "inferior" intellectually to others.
Despite the above there are still many aspects related to the race to discover, so in the cosmopolitan societies is habitual the mixture of them, which in some countries is called mulatto or Creole, which might be asked if these people are going to have Influenced their intelligence that is, those people who have a history of two races will be more or less intelligent?, then how does the race influence the intelligence?
The results show that taking as a point of comparison the white race, you get inferior results in the "almost White", followed by the "almost blacks", getting the "worst" score the black race.
These differences are not due to factors such as the parental economic level, the area where they live or the educational level, because they were controlled factors.
Among the limitations of the study is that it does not make a comparison by gender or by age, nor does it take into account fluid intelligence.
Despite the foregoing and contrary to what could be expected this study finds differences in terms of crystallized intelligence, taking into account that the educational level of the participants has been equated.
This investigation reopens an old "wound" by the specialists in psychometry with respect to the "justification" of the differences according to the race if they are or not due to the instrument used or to that actually different races present different Results.
In fact, the results scaled in function of a higher degree of white race or black race would go in that direction.
In spite of this, more research is needed before we can draw any conclusions about it, since it is not the first study that has indicated differences in this aspect that have then had to be withdrawn by methodological failures.