Table Of ContentFLUID ABILITY, CRYSTALLIZED ABILITY, AND PERFORMANCE ACROSS
MULTIPLE DOMAINS: A META-ANALYSIS
by
Bennett Eugene Postlethwaite
An Abstract
Of a thesis submitted in partial fulfillment
of the requirements for the Doctor of
Philosophy degree in Business Administration
in the Graduate College of
The University of Iowa
1
July 2011
Thesis Supervisor: Professor Frank L. Schmidt
1
Cognitive ability is one of the most frequently investigated individual differences
in management and psychology. Countless studies have demonstrated that tests
measuring cognitive ability or intelligence predict a number of important real-world
outcomes such as academic performance, vocational training performance, and job
performance. Although the relationship between intelligence and real-world performance
is well established, there is a lack of consensus among scholars with regard to how
intelligence should be conceptualized and measured. Of the more traditional theories of
intelligence, two perspectives are particularly dominant: the Cattell-Horn model of fluid
and crystallized intelligence and the theory of General Cognitive Ability (GCA or g).
Fluid ability (Gf) represents novel or abstract problem solving capability and is
believed to have a physiological basis. In contrast, crystallized ability (Gc) is associated
with learned or acculturated knowledge. Drawing on recent research in neuroscience, as
well as research on past performance, the nature of work, and expert performance, I argue
that compared to measures of fluid ability, crystallized ability measures should more
strongly predict real-world criteria in the classroom as well as the workplace.
This idea was meta-analytically examined using a large, diverse set of over 400
primary studies spanning the past 100 years. With regard to academic performance,
1
measures of fluid ability were found to positively predict learning (as measured by
grades). However, as hypothesized, crystallized ability measures were found to be
superior predictors of academic performance compared to their fluid ability counterparts.
This finding was true for both high school and college students.
Likewise, similar patterns of results were observed with regard to both training
performance and job performance. Again, crystallized ability measures were found to be
2
better predictors of performance than fluid measures. This finding was consistent at the
overall level of analysis as well as for medium complexity jobs. These findings have
important implications for both intelligence theory and selection practice.
Contemporary intelligence theory has placed great emphasis on the role of fluid
ability, and some researchers have argued that Gf and g are essentially the same
construct. However, the results of this study, which are based on criterion-related
validities rather than factor-analytic evidence, demonstrate that Gc measures are superior
predictors in comparison to Gf measures. This is contrary to what one would expect if Gf
and g were indeed the same construct. Rather, the findings of this study are more
consistent with General Cognitive Ability theory, which predicts that Gc indicators will
be the best predictors of future learning and performance.
Given that Gc measures demonstrate higher criterion-related validities than Gf
measures, Gc measures are likely to be preferred for selection purposes. Further, Gf
scores are known to decline with age while Gc scores remain relatively stable over the
lifespan. Thus, when used for selection purposes, Gf tests may underpredict the
performance of older workers. In contrast, research has shown that Gc measures are
predictively unbiased. Additional implications for theory and practice are discussed,
2
along with study limitations and opportunities for future research.
Abstract Approved: ____________________________________
Thesis Supervisor
____________________________________
Title and Department
____________________________________
Date
FLUID ABILITY, CRYSTALLIZED ABILITY, AND PERFORMANCE ACROSS
MULTIPLE DOMAINS: A META-ANALYSIS
by
Bennett Eugene Postlethwaite
A thesis submitted in partial fulfillment
of the requirements for the Doctor of
Philosophy degree in Business Administration
in the Graduate College of
The University of Iowa
1
July 2011
Thesis Supervisor: Professor Frank L. Schmidt
Copyright by
BENNETT EUGENE POSTLETHWAITE
2011
All Rights Reserved
2
Graduate College
The University of Iowa
Iowa City, Iowa
CERTIFICATE OF APPROVAL
_______________________
PH.D. THESIS
_______________
This is to certify that the Ph.D. thesis of
Bennett Eugene Postlethwaite
has been approved by the Examining Committee
for the thesis requirement for the Doctor of Philosophy
degree in Business Administration at the July 2011 graduation.
Thesis Committee: ___________________________________
Frank L. Schmidt, Thesis Supervisor
___________________________________
Kenneth G. Brown
___________________________________
Maria L. Kraimer
___________________________________
Michael K. Mount
___________________________________
Steven B. Robbins
For Sandra Jane White (1943 – 2011)
2
ii
ACKNOWLEDGEMENTS
I could not have completed a project of this magnitude on my own. A number of
individuals have provided valuable assistance throughout the dissertation process. I am
extremely grateful for their help and encouragement.
I want to thank my committee members for their feedback, questions, and time.
My study has been greatly improved as a result of their ideas. In particular, I want to
thank my advisor and committee chair, Frank Schmidt. Frank has won mentoring awards
at the University and national level. My experience during this dissertation has proven
that these awards are very well deserved. Frank identified the need to examine the
criterion-related validities of Gf and Gc in 2005, and the current study is an evolution of
his original idea.
Tamara Giluk’s involvement with this project predates my own. Throughout the
entire study, Tamara’s assistance has been invaluable. Tamara played a key role during
the literature search phase, and she spent many long days coding data. I look forward to
our continued collaboration in the future.
The staff of the Interlibrary Loan Department at the University of Iowa Libraries
was extremely helpful in accessing many difficult to obtain studies. In addition, I am
grateful to Michael Aamodt for sharing the most recent version of his Law Enforcement
Selection: Research Summaries. These detailed summaries were very useful in
3
identifying additional primary studies from the law enforcement domain. I am also
indebted to In-Sue Oh for his continual willingness to share his expertise on the technical
aspects of meta-analysis.
Finally, I want to thank my family for their love and support. They have
continually encouraged me to succeed in each endeavor that I have chosen to embark
upon. This dissertation was no exception.
iii
ABSTRACT
Cognitive ability is one of the most frequently investigated individual differences
in management and psychology. Countless studies have demonstrated that tests
measuring cognitive ability or intelligence predict a number of important real-world
outcomes such as academic performance, vocational training performance, and job
performance. Although the relationship between intelligence and real-world performance
is well established, there is a lack of consensus among scholars with regard to how
intelligence should be conceptualized and measured. Of the more traditional theories of
intelligence, two perspectives are particularly dominant: the Cattell-Horn model of fluid
and crystallized intelligence and the theory of General Cognitive Ability (GCA or g).
Fluid ability (Gf) represents novel or abstract problem solving capability and is
believed to have a physiological basis. In contrast, crystallized ability (Gc) is associated
with learned or acculturated knowledge. Drawing on recent research in neuroscience, as
well as research on past performance, the nature of work, and expert performance, I argue
that compared to measures of fluid ability, crystallized ability measures should more
strongly predict real-world criteria in the classroom as well as the workplace.
4
This idea was meta-analytically examined using a large, diverse set of over 400
primary studies spanning the past 100 years. With regard to academic performance,
measures of fluid ability were found to positively predict learning (as measured by
grades). However, as hypothesized, crystallized ability measures were found to be
superior predictors of academic performance compared to their fluid ability counterparts.
This finding was true for both high school and college students.
iv
Likewise, similar patterns of results were observed with regard to both training
performance and job performance. Again, crystallized ability measures were found to be
better predictors of performance than fluid measures. This finding was consistent at the
overall level of analysis as well as for medium complexity jobs. These findings have
important implications for both intelligence theory and selection practice.
Contemporary intelligence theory has placed great emphasis on the role of fluid
ability, and some researchers have argued that Gf and g are essentially the same
construct. However, the results of this study, which are based on criterion-related
validities rather than factor-analytic evidence, demonstrate that Gc measures are superior
predictors in comparison to Gf measures. This is contrary to what one would expect if Gf
and g were indeed the same construct. Rather, the findings of this study are more
consistent with General Cognitive Ability theory, which predicts that Gc indicators will
be the best predictors of future learning and performance.
Given that Gc measures demonstrate higher criterion-related validities than Gf
measures, Gc measures are likely to be preferred for selection purposes. Further, Gf
scores are known to decline with age while Gc scores remain relatively stable over the
lifespan. Thus, when used for selection purposes, Gf tests may underpredict the
5
performance of older workers. In contrast, research has shown that Gc measures are
predictively unbiased. Additional implications for theory and practice are discussed,
along with study limitations and opportunities for future research.
v
Description:Drawing on recent research in neuroscience, as well as research on past performance, the nature of work, and expert performance, I argue.
