fei75766_ch15_463-494.indd 475  02/24/20 10:48 AM
Chapter 15    Buss: Evolutionary Theory of Personality475
Fourth, one’s capacity andcommitment towork isthecorecharacteristic of
conscientiousness. Conscientious people arecareful anddetail-oriented aswellas
focused andreliable. Lessconscientious people arelessreliable anddependable and
tendtolackfocus. Conscientiousness signals toothers whom wecantrustwithtasks 
andresponsibilities andwhom wecandepend onintimes ofneed.
Finally, theevolved strategy ofopenness involves one’s propensity forinnovation 
andability tosolve problems. Itisclosely aligned withintellect andintelligence but
alsoawillingness totrynewthings andawillingness tohavenovel experiences rather 
thansticking withone’s routine. These people aretheexplorers ofagroup—they forge 
ahead where others arehesitant. Inancestral times thisquality might beexpressed 
inwillingness toexplore newterritories forfoodorvegetation, buttoday itmight be
expressed inartists andscientists whoareatthecutting edges ofideas andknowledge.
Buss(1991) argues thatofthefivepersonality dimensions, surgency/dominance, 
agreeableness, andconscientious arethemost important traits because theymost 
directly provide answers toahostofadaptive problems. Forexample:
• Who ishighorlowinthesocial hierarchy?
• Who possesses theresources thatIneed?
• With whom should Imate?
• Who might harm meorbetray mytrust?
• Who willmake agood member ofmygroup?
• Whom canItrustanddepend onwhen inneed?
Personality differences function tosolve adaptive problems byproviding answers to
these questions forboththeindividual and
forothers. Inthissense theyareindicators 
offitness, much likethepeacock’s plumage.
Origins of Individual Differences
Aswediscussed earlier, evolutionary the-
oryisinherently anature andnurture per-
spective when itcomes toorigins. Bussand
hiscolleague Heidi Greiling propose four
distinct sources ofindividual differences 
(D.Buss&Greiling, 1999). Inessence, 
these sources ofdifference come down 
tonature (biological-genetic) andnurture 
(environmental-social).
Environmental Sources
There arenumerous ways inwhich the
environment contributes toadaptive indi-
vidual differences. Adaptive differences 
increase reproductive success andone’s 
chance ofsurvival. Oneenvironmental 
source ofpersonality differences iswhat 
Busstermed early experiential calibration, 
People whogrow upwithout afather are
more likely tobesexually active early inlife.
Thisisanexample ofwhat Busscalls“early 
experiential calibration.” 
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