fei75766_ch15_463-494.indd 474  02/24/20 10:48 AM
Part V    Biological/Evolutionary Theories474
Itisnearly synonymous with“extraversion.” Inancestral times, these individuals 
were highinstatus andwere therefore attractive anddesirable mates. Putintothe
language ofevolution, surgency involves “hierarchy proclivities”; thatis,howpeo-
plenegotiate anddecide whoisdominant andwhoissubmissive. Thenegotiations 
happen, astheydoinmany animals, through competition andpower struggles. In
ancestral times, these competitions were more often thannotphysical andaggres -
sive,butcould alsobeverbal andthrough accumulation ofwealth andresources. 
Leaders arethose whotakecharge anddirect others, andwhether theytakecharge 
byforce orbypersuasion theyareacknowledged byothers tobeincharge andarein
adominant social position. Because power anddominance areattractive, these indi-
viduals alsotended tohavemore children. Surgency isalsomarked byatendency 
totakerisksandtoexperience positive emotion (i.e.,behappy) andinitiating and
maintaining friendships andrelationships. People highinsurgency arealsodriven 
andambitious.
Asecond dimension ofpersonality, agreeableness/hostility, ismarked byaper-
son’s willingness andcapacity tocooperate andhelpthegroup ontheonehand or
tobehostile andaggressive ontheother. Some people arewarm, cooperative, and
group-oriented, butothers aremore selfish andhostile toward others. Agreeable indi-
viduals arelikely towork tosmooth overgroup conflict andform alliances between 
people. Agreeable people foster group cohesion andtendtoconform togroup norms. 
They getalong andgoalong withothers. Inshort, agreeableness marks aperson’s 
willingness tocooperate.
Thethird adaptive personality system revolves around response todanger and
threat. Allanimals havealarm systems thatwarn them ofpotential danger andharm. 
Inhumans andother animals, thistakes theform ofanxiety asanemotional state
andemotional stability/neuroticism asadispositional trait.Vigilance orsensitivity to
harm andthreat isquite necessary andadaptive. Emotional stability involves one’s 
ability tohandle stress ornot.Some people arecalm under stress while others are
high-strung much ofthetime.
Fearandanxiety areadaptive emotions. Without them wewould certainly 
dieasindividuals andasaspecies. Aswediscussed intheMcCrae andCosta and
theEysenck chapters, neuroticism isthetendency toexperience negative emotion 
such asanxiety, guilt, andsadness. Thetendency tobesensitive tothreats, for
instance, maywellhave been adaptive indangerous environments likethose in
which ourancestors lived. Heightened anxiety would provide asignal ofdanger 
andthreat; itsabsence would quickly leadtoextinction ofthespecies. Consider a
hunter onthesavannah. Hehears thegrowl ofalarge animal andbecomes fearful. 
Hedrops back behind thebushes before theanimal becomes aware ofhispres-
ence. Ifhedidnotfeelanxious, hemight nothide, withdireconsequences forhis
safety. Bythesame token, theother extreme—hypersensitivity tothreats—would be
debilitating anddisruptive toeveryday functioning. Ifthesame manwhobecame 
fearful athearing thegrowl ofalarge animal alsobecame fearful withevery rus-
tlingofleaves orevery sound ofthewind, hewould have ahardtimefunctioning 
ineveryday life.Having some degree offearfulness isadaptive, andpeople with
thatquality were more likely tosurvive, reproduce, andpassonthatdisposition. 
Naturally selected traits arefavored iftheyincrease one’s chances ofsurvival and
reproductive success.Final PDF to printer