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

328 Educability and Group Differences
several genetically independent (but phenotypically correlated)
objectively measured physical criteria for this classification, and
showed that the groups differed significantly on each one: skin
pigmentation, nasal width, lip thickness, hair texture, eye color,
jaw formation, interpupillary distance, and ability to taste phenylthiocarbamide.
The subjects thus classified into three groups
showed significantly different mean pursuit rotor scores in the
order: whites < mulattoes < blacks. The mean percentage of time
SUCCESSIVE BLOCKS OF 2 0/10 SEC. TRIALS
Figure 18.2 Mean percentage of time on target in successive blocks
of 20-second work and 10-second rest trials on the pursuit rotor,
for white and Negro children, practising with either the Right or
the Left hand. There are 38 subjects in each condition. (From
Noble, 1969.)
on target for the three groups were 4-6 percent, 2-6 percent and
2*1 percent, respectively (Noble, 1968, p. 231. It is not clear
from Noble’s account whether these percentages are for the first
trial block of six trials or for all trials.) Noble believed that strictly
environmental interpretations of these results in terms of socioeconomic
and cultural differences would find little evidential support.
‘On the contrary’, he writes, ‘there were numerous observations
to suggest that a large part of the interracial behavioral variance
is genetically determined’ (1969, p. 27). But Noble concludes: