Educability-and-Group-Differences-1973-by-Arthur-Robert-Jensen

Intelligence of Racial Hybrids 229
interracial children born to white mothers could be due to the
genetic effect of the superior Negro father rather than to any
prenatal or postnatal environmental advantage afforded by having
a white mother.
NOTES
1. Skin pigmentation is usually measured by one of two methods. The
oldest method is by means of a ‘color top’, a disc having adjustable
sectors of different colors (e.g., black, white, red, yellow) which are
blended by spinning the disc; the sizes of the colored sectors are
adjusted so that when they are blended, they match the individual’s
skin color. The calibrated sizes of the colored sectors thus provide a
reasonably reliable, objective index of skin color. A more recent
method is based on the measurement of skin reflectance with a
photoreflectometer; reflectances are usually measured in three key
color ranges of the visible spectrum, using blue, green, and amber
tri-stimulus filters. The readings with each filter are usually made
on the underside of the upper arm, on the forehead, and on the back
of the neck, and the readings for the various sites are averaged. The
range of values found between African Negroes and English whites
follows a straight line; the genes for pigmentation appear to be
additive in effect. Technical details can be found in Harrison (1957)
and Harrison and Owen (1956, 1964).
2. The feasibility of this kind of study at the present time is not universally
unquestioned among geneticists. In a personal communication,
geneticist Peter L. Workman writes:
Since American Negroes do not comprise an equilibrium population,
morphological characters constituting an African appearance
segregate together with African genes. Holding constant external
appearance (skin color, lip breadth, etc.) might also partial out
most of the relevant information. Further, Heston’s method doesn’t
account for the non-equilibrium structure. Thus, although the
experimental idea is a good one, and MacLean and I will present
the appropriate methods in print shortly, I am very skeptical that
it could be done at this time. We need more African data [on
blood group frequencies].
3. Shockley (1970b) has also suggested dividing a large Negro group,
such as the total enrolment in an all-Negro school or college, into
two halves on the basis of some assessment of intellectual ability