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

Physical Environment and Mental Development 339
ossification (Naylor & Myrianthopoulos, 1967). Malnutrition
results in below-normal performance on infant tests of sensorimotor
development, yet Negro babies generally show advanced
performance on these tests as compared with the white norms.
Malnutrition impairs memory ability as well as other cognitive
functions, yet Negro children show little or no deficit in rote
memory. One of the most striking and consistent findings in the
research of Cravioto and others is that malnutrition markedly
increases the differences between siblings (and conversely reduces
sibling correlations) within the same family, both in physical and
mental characteristics. I have determined the mean absolute
difference between all sibling pairs enrolled in the elementary
grades of a California school system on a number of physical and
mental measurements, all put on the same scale, with a standard
Table 19.1 Mean absolute difference, \d\, and correlation, r, between
all siblings of school age in white and Negro families on eleven measures,
standardized within 6-month age groups, with a = 15 for every variable
in the combined populations
Variable
N
White
\d\ r N
Negro
\d\
r
Height 1154 12-69 0-44 731 12-84 0-43
Weight 1155 12-63 0-44 731 12-21 0-48
Memory I 573 14-52 0-27 369 14-25 0-29
Memory R 572 13-73 0-34 364 15-05 0-21
Memory D 568 14-46 0-27 358 14-23 0-29
Figure Copying 570 13-88 0-33 395 13-68 0-35
Verbal IQ 1133 13-29 0-39 582 12-83 0-43
Non-verbal IQ 1132 13-11 0-40 600 13-86 0-33
Total IQ 341 12-75 0-43 200 12-81 0-43
Vocabulary 244 12-75 0-43 417 12-73 0-44
Reading
Comprehension 251 12-93 0-42 408 13-89 0-33
All Variables 13-34 13-49