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

75 Motivational factors
A number of motivational factors have been investigated in
attempts to explain at least some of the Negro-white difference in
intelligence test performance in terms of differences in motivation.
The evidence to date does not support the differential motivation
hypothesis. This should not be too surprising, since experimental
studies of the effects of motivational factors on intelligence testing
have generally shown either very small or non-significant effects,
and when differences have been found they tend to show that
conditions most typical of those in which intelligence tests are
normally given yield the best scores. Burt and Williams (1962),
for example, found that children obtained slightly higher scores
when taking tests for school promotion rather than for experimental
purposes. Intelligence tests are quite insensitive to external
motivational manipulations. Tiber and Kennedy (1964) tested
middle- and lower-class white children and lower-class Negro
children with and without several different incentives, such as
praise after each test item, verbal reproof, and candy reward. These
various testing conditions had no significant effects on Stanford-
Binet IQs and showed no interaction with social class or race.
Tiber and Kennedy concluded that the IQ differences usually
found between such social class and racial groups cannot be
attributed to motivational differences. This conclusion is too
sweeping, of course, since other motivational factors not under the
experimenter’s control could affect test performance. But the fact
remains that scores on IQ tests have proved highly resistant to
experimental manipulations of incentives and motivational sets.