Evolutionary Theory's Increasing Role in Personality and Social Psychology

Evolutionary Psychology
www.epjournal.net – 2007. 5(1): 84-91
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Original Article
Evolutionary Theory’s Increasing Role in Personality and Social Psychology
Gregory D. Webster, Department of Psychology, University of Colorado at Boulder. Webster is now at
Department of Psychology, University of Illinois at Urbana-Champaign, Champaign, IL 61820, USA. Email:
webster3@uiuc.edu.
Abstract: Has the emergence of evolutionary psychology had an increasing impact on
personality and social psychological research published over the past two decades? If so, is
its growing influence substantially different from that of other emerging psychological
areas? These questions were addressed in the present study by conducting a content
analysis of the Journal of Personality and Social Psychology (JPSP) from 1985 to 2004
using the PsycINFO online abstract database. Specifically, keyword searches for “evol*” or
“Darwin*” revealed that the percentage of JPSP articles drawing on evolutionary theory
was modest, but increased significantly between 1985 and 2004. To compare the growing
impact of evolutionary psychology with other psychological areas, similar keywords
searches were performed in JPSP for emotion and motivation, judgment and decision
making, neuroscience and psychophysiology, stereotyping and prejudice, and terror
management theory. The increase in evolutionary theory in JPSP over time was practically
equal to the mean increase over time for the other five areas. Thus, evolutionary
psychology has played an increasing role in shaping personality and social psychological
research over the past 20 years, and is growing at a rate consistent with other emerging
psychological areas.
Keywords: evolutionary psychology, personality, social psychology, publication trends,
history and systems of psychology, Journal of Personality and Social Psychology.
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Introduction
Although evolutionary psychology may be considered either a theoretical
perspective or a sub-discipline of psychology (Cornwell, Palmer, Guinther, and Davis,
2005), it is nevertheless an emerging area that is growing in influence. In their recent
article, Cornwell et al. showed that introductory psychology textbooks have given
increasing coverage to sociobiology, evolutionary psychology, or both, over the past 30
years (1975-2004). Although the tone of this increasing coverage became increasingly
positive (or at least less negative) over time, some inaccurate interpretations of

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Evolutionary Theory in Personality and Social Psychology

evolutionary psychology still persist. Cornwell et al. acknowledged that “much more work
is needed to evaluate fully how sociobiology or evolutionary psychology is being integrated
within the social sciences” (p. 371). To this end, the purpose of the present study was to
empirically evaluate the extent to which evolutionary theory has impacted articles
published in the flagship journal (the Journal of Personality and Social Psychology or
JPSP) of a specific sub-discipline of psychology (social-personality psychology) over the
past 20 years (1985-2004).
Method
PsycINFO keyword searches were performed using evolutionary psychology terms
(“evol*” or “Darwin*”) for articles published in JPSP from 1985 to 2004. For comparison
purposes, similar keyword searches were also performed for five other topics areas in
social-personality psychology: (a) emotion and motivation (“emot*” or “motiv*”), (b)
judgment and decision making (“judgment*” or “decision*”), (c) neuroscience and
psychophysiology (“neur*,” “physiologic*,” or “psychophysio*,” but not “neurotic*”), (d)
stereotyping and prejudice (“stereotyp*” or “prejudic*”), and (e) terror management theory
(“terror management” or “mortality salience”). Articles published in an October 2003
special section of JPSP on social neuroscience were not counted toward the neuroscience
and psychophysiology totals. These topic areas do not represent mutually exclusive
categories. For example, a JPSP article on the evolutionary psychology of terror
management theory would have counted toward both relevant topic areas.
The five additional topic areas represent a broad convenience sample of many
possible topic areas in social-personality psychology. Because evolutionary psychology can
be viewed as a psychological sub-discipline or a unique theoretical approach (Cornwell et
al., 2005), both psychological (stereotyping and prejudice) and interdisciplinary (emotion
and emotion, judgment and decision making) sub-disciplines were chosen, as well as both
methodological (neuroscience and psychophysiology) and theoretical (terror management
theory) perspectives that have recently influenced social-personality psychology.
The dependent variable was the proportion of the topic area articles out of the total
number of JPSP articles per year. Since these proportions exhibited some year-to-year
volatility, a three-year moving average was used to smooth short-term fluctuations in the
data. Because proportion data often violate the homogeneity-of-variance assumption of
regression (Judd and McClelland, 1989, pp. 525-526), an arcsine transformation was
applied to the three-year moving average proportions: sin–1(proportion1/2). Although all
analyses were performed using the arcsine transformation, the data presented in Figure 1
show the raw three-year moving average percentages. The independent variable was
publication year in JPSP. For each topic area, simple linear regressions were performed
predicting change in the transformed moving average proportions over time.
Results
See Table 1 and Figure 1 for results. Significant linear increases in JPSP articles
over time were detected for (a) evolutionary psychology, (b) emotion and motivation, (c)
stereotyping and prejudice, and (d) terror management theory. In contrast, significant linear
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decreases in JPSP articles over time were detected for (a) judgment and decision-making
and (b) neuroscience and psychophysiology.
The mean of the six topic areas’ change-over-time slopes (M = 0.0019) did not
differ significantly from zero (t = 0.96,
5
p = .38). Moreover, none of the topic areas’
individual slopes differed significantly from the mean slope of the other five areas.
Interestingly, the slope for evolutionary psychology was the same as the mean slope of the
other five topic areas (both Ms = 0.0019).
Although comparing the temporal slopes of these topic areas may be elucidating, it
should be done with caution. First, each of these topic areas began to emerge at a different
time. Thus, it may be difficult to compare an emerging topic area like evolutionary
psychology with more established ones like emotion and motivation or stereotyping and
prejudice. Second, only the linear effects of time were tested. It is certainly possible that
different topic areas may grow or decline at differing curvilinear rates over time in JPSP.
For example, some topic areas may have thresholds or tipping points after which they
rapidly gain (or lose) acceptance. Further, emerging scientific fields often undergo growth
spurts following identification (e.g., formal conferences) and institutionalization (e.g.
establishing a dedicated journal or program of study; Feist, 2006). While interesting, the
present data cannot speak to these possibilities.

Table 1. Linear regression results: Proportion (arcsine of three-year moving average) of
JPSP articles as a function of publication year (1985-2004) for six topic areas
Topic area
2
b
t16
R
Evolutionary psychology
0.0019
2.11*
.22
Emotion and motivation
0.0022
2.11*
.22
Judgment and decision making
–0.0026
–2.17*
.23
Neuroscience and psychophysiology
–0.0046
–4.75*
.58
Stereotyping and prejudice
0.0077
10.72*
.88
Terror management theory
0.0070
6.99*
.75

*p ? .05.
Discussion
Consistent with previous research that has shown evolutionary psychology’s
increasing role in introductory psychology textbooks (Cornwell et al., 2005), the present
research showed that evolutionary theory has been making substantial inroads into social-
personality psychology by publishing empirical articles in its flagship journal, JPSP.
Although the proportion of evolutionary psychology articles published in JPSP was
modest, it increased at a rate similar to other topic areas in social-personality psychology.
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Figure 1. Percentage (three-year moving average) of JPSP articles as a function of
publication year (1985-2004) for six topic areas (bs represent raw regression slopes)
Evolutionary Psychology
Emotion & Motivation
2
40
b = 0.035
b = 0.21
35
1
30
0
25
1985
1995
2005
1985
1995
2005
Publication Year
Publication Year
Judgments & Decisions
Neuroscience
20
5
b = -0.14
15
3
b = -0.19
10
1
1985
1995
2005
1985
1995
2005
Publication Year
Publication Year
Stereotyping & Prejudice
Terror Management
11
2
b = 0.39
b = 0.099
7
1
3
0
1985
1995
2005
1985
1995
2005
Publication Year
Publication Year
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Although the results were straightforward, they were not without their limitations.
First, there was some overlap in the areas examined, since the categories were not mutually
exclusive. For example, an article on evolutionary perspectives of emotion using
psychophysiological methods would have counted toward three of the six topic areas.
Second, popular topic areas in psychology, and perhaps social psychology in particular,
may wax and wane with historical changes in the socio-political zeitgeist or funding
changes in various research paradigms (Gergen, 1973). Thus, the linear trends observed
here may only represent 20-year snapshots of long-term cyclical trends. Third, since 1986,
JPSP’s page layout and the number of pages it publishes each year has been relatively
constant, which suggests that the percentage of journal space allocated to various topic
areas may resemble a zero-sum game. For example, evolutionary psychology may have
gained ground at the expense of one or more topic areas or theoretical approaches;
however, it is also possible that, because of its interdisciplinary nature, evolutionary
psychology has occasionally overlapped with other established areas (e.g., evolutionary
approaches to emotion and motivation), which would obfuscate the necessity of a zero-sum
scenario. Occasionally, specialized journals that cater to a specific topic area are
established that may attract manuscripts that would have originally considered JPSP as an
outlet. For example, the journal Neuropsychology, which began publishing in 1987, may
have contributed to the observed decline in social neuroscience articles published in JPSP.
Fourth, it is also possible that evolutionary psychology’s increasing influence in JPSP is
not due solely to growing acceptance, but rather to a combination of both growing
acceptance and increasing criticism; however, JPSP rarely publishes comments and
rejoinders that could artificially inflate a sub-discipline’s influence based solely on its
controversial nature.
How should these results be interpreted within the larger context of ongoing
publication trends in social-personality psychology, evolutionary psychology, and
psychology in general? First of all, the present findings should only be generalized to
articles published in JPSP, the flagship journal of social-personality psychology; however,
it is unlikely that the observed trends would differ markedly for similar high-impact social-
personality journals (e.g., Personality and Social Psychology Bulletin or PSPB). The extent
to which evolutionary psychology’s growing influence in social-personality psychology
may generalize to other psychological sub-disciplines (e.g., clinical, cognitive,
developmental, neuropsychology) is beyond the scope of the present study.
Other research on social-personality publication trends in leading journals such as
JPSP (Reis and Stiller, 1992; Webster, Bryan, Haerle, and O’Gara, 2005) and PSPB
(Sherman, Buddie, Dragan, End, and Finney, 1999) have shown that articles have become
longer, have included more authors and studies, and have employed more complex data
analytic techniques over time. Similar trends have been observed in evolutionary
psychology’s flagship journal, Evolution and Human Behavior, such that the numbers of
authors and studies have increased, as have the proportion of empirical (vs. theoretical or
review) articles (Webster, 2007). Psychology articles in general have seen (a) an explosion
in cited references (vs. other scientific disciplines, Adair and Vohra, 2003), (b) an increase
in cognitive psychology and a decrease in behavioral psychology (Robins, Gosling, and
Craik, 1999), and (c) an increase in article length that has leveled-off since the turn of the
century (Webster, in press). Thus, for better or worse, as evolutionary theory’s impact on
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social-personality psychology continues to grow, evolutionary psychologists can expect to
read, write, and review longer articles with more studies using more empirical methods and
increasingly sophisticated analyses.
On a related note, evolutionary and social-personality psychology have witnessed a
fruitful cross-fertilization over recent years. Perhaps most notably, evolutionary psychology
has received attention in both the leading personality (Buss, 1999) and social (Buss and
Kenrick, 1998) psychology handbooks. Similarly, the first comprehensive evolutionary
psychology handbook has included chapters on evolutionary personality psychology
(Figueredo et al., 2005) and evolutionary social psychology (Kenrick, Maner, and Li,
2005). Moreover, two pioneering edited volumes have been dedicated to the intersections
of evolutionary and social psychology (Schaller, Simpson, and Gangestad, 2006; Simpson
and Kenrick, 1997). Thus, evolutionary and social-personality psychology appear to have
engaged in beneficial interweaving of mutual theoretical influence.
What are the implications of these findings for the future of evolutionary
psychology in the context of social-personality psychology? First, the results suggest that
evolutionary theory has established a viable beachhead on the theoretical landscape of
social-personality psychology, and successfully planted its flag in the sub-discipline’s
flagship journal, JPSP. Second, evolutionary psychology’s growing influence in JPSP
articles appears to mirror the growth rates of other, similar topic areas, on average. Third,
as evolutionary psychological research becomes more empirical (Webster, 2007), it is more
likely to gain widespread acceptance in sub-disciplines such as social-personality
psychology, which has itself become more empirical by adopting more complex statistical
techniques (Reis and Stiller, 1992). Whereas social-personality psychology has witnessed
an increase in sophisticated research methods (Reis and Stiller, 1992), evolutionary
psychology is only just beginning to carve out its own niche of scientific methods
(Simpson and Campbell, 2005), which will require continued development and refinement
if evolutionary psychology is to flourish as an empirical science in the future.
Finally, although it is beyond the scope of the present findings, it is possible that the
evolution of scientific theory may itself mimic Darwinian selection pressures, as various
scientific theories merge or compete with one another over time. Moreover, the pursuit of
science may itself be a signaling display of intelligence and creativity for the mating
market, just as creating art and music appear to be (Miller, 1998). In addition, science and
math may represent “co-opted by-products of evolved adaptations” (Feist, 2006, p. 217),
such that they do not typically promote reproductive fitness directly, but may do so
indirectly, through their signaling intelligence to potential mates, or their contributions to
human society, or both. Although the present research cannot speak to these broader
implications (e.g., it is unlikely to impact the author’s fitness), it does provide an initial,
empirical snapshot of the emerging scientific symbiosis between evolutionary psychology
and social-personality psychology.
Acknowledgements: This research was presented as a poster at the 4th Evolutionary
Psychology Preconference at the Society for Personality and Social Psychology, Palm
Springs, California, January 2006. This material is based upon work supported by the
National Institute of Mental Health under Training Grant Award PHS 2 T32 MH014257
entitled “Quantitative Methods for Behavioral Research” (to M. Regenwetter, principal
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investigator). This research was completed while the author was a postdoctoral trainee in
the Quantitative Methods Program of the Department of Psychology, University of Illinois
at Urbana-Champaign. Any opinions, findings, and conclusions or recommendations
expressed in the publication are those of the author and do not necessarily reflect the views
of the National Institute of Mental Health.
Received 14 November 2006; revision received 10 January 2007; accepted 10 January
2007
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