Utility of g
(1) Higher levels of g lead to higher levels of performance in all jobs and along all
dimensions of performance. The average correlation of mental tests with overall rated
job performance is around 0.5 (corrected for statistical artifacts).
(2) There is no ability threshold above which more g does not enhance performance. The
effects of g are linear: successive increments in g lead to successive increments in job
performance.
(3) (a) The value of higher levels of g does not fade with longer experience on the job.
Criterion validities remain high even among highly experienced workers, (b) That they
sometimes even appear to rise with experience may be due to the confounding effect
of the least experienced groups tending to be more variable in relative level of
experience, which obscures the advantages of higher g.
(4) g predicts job performance better in more complex jobs. Its (corrected) criterion
validities range from about 0.2 in the simplest jobs to 0.8 in the most complex.
(5) g predicts the core technical dimensions of performance better than it does the non-core
“citizenship” dimension of performance.
(6) Perhaps as a consequence, g predicts objectively measured performance (either job
knowledge or job sample performance) better than it does subjectively measured
performance (such as supervisor ratings).
Utility of g relative to other “can do” components of performance
(7) Specific mental abilities (such as spatial, mechanical or verbal ability) add very little,
beyond g, to the prediction of job performance, g generally accounts for at least
85-95% of a full mental test battery’s (cross-validated) ability to predict performance
in training or on the job.
(8) Specific mental abilities (such as clerical ability) sometimes add usefully to prediction,
net of g, but only in certain classes of jobs. They do not have general utility.
(9) General psychomotor ability is often useful, but primarily in less complex work. Their
predictive validities fall with complexity while those for g rise.
Utility of g relative to the “will do” component of job performance
(10) g predicts core performance much better than do “non-cognitive” (less g-loaded) traits,
such as vocational interests and different personality traits. The latter add virtually
nothing to the prediction of core performance, net of g.
(11) g predicts most dimensions of non-core performance (such as personal discipline and
soldier bearing) much less well than do “non-cognitive” traits of personality and
temperament. When a performance dimension reflects both core and non-core
performance (effort and leadership), g predicts to about the same modest degree as do
non-cognitive (less g-loaded) traits.
(12) Different non-cognitive traits appear to usefully supplement g in different jobs, just as
specific abilities sometimes add to the prediction of performance in certain classes of
jobs. Only one such non-cognitive trait appears to be as generalizable as g: the
personality trait of conscientiousness/integrity. Its effect sizes for core performance are
substantially smaller than g’s, however.
Utility of g relative to the job knowledge
(13) g affects job performance primarily indirectly through its effect on job-specific
knowledge.
(14) g’s direct effects on job performance increase when jobs are less routinized, training is
less complete, and workers retain more discretion.
(15) Job-specific knowledge generally predicts job performance as well as does g among
experienced workers. However, job knowledge is not generalizable (net of its g
component), even among experienced workers. The value of job knowledge is highly
job specific; g’s value is unrestricted.
Utility of g relative to the “have done” (experience) component of job performance
(16) Like job knowledge, the effect sizes of job-specific experience are sometimes high but
they are not generalizable.
(17) In fact, experience predicts performance less well as all workers become more
experienced. In contrast, higher levels of g remain an asset regardless of length of
experience.
(18) Experience predicts job performance less well as job complexity rises, which is
opposite the trend for g. Like general psychomotor ability, experience matters least
where g matters most to individuals and their organizations.