Index

For the benefit of digital users, indexed terms that span two pages (e.g., 52–53) may, on occasion, appear on only one of those pages.

Note: Tables and figures are indicated by t and f following the page number

abandonment340–41, 414, 465–66, 477, 618, 623, 626, 631–32

accommodation processes515–16

adaptation differences in partner loss685–87

adaptive calibration model498

adiposity49–50

adjustment relationship dissolution699–701, 712

adoptive vs. biological parents419–21

adulterous women336–37

adversity-exposed individuals496–97

affectionate communication166, 378

affection during courtship166

affective disengagement588

affective reactions to relationship dissolution562, 675–79, 683–85, 693–94

affective self-regulation to relationship dissolution. See self-regulation in relationship dissolution

age factors in consensual nonmonogamy467–69

agent-based simulation models106

agreeableness traits55

alcohol use362–63, 736–37

allometric (bodily scaling)163

alloparents198–99, 312

ALSCAP (Avon Longitudinal Study of Parents and Children)44–45

altruism81–82

ambition-industriousness24

androgen-linked facial features160–61

androgyny113

animal behavior and cognition. See nonhuman species

anisogamy826–27

anonymity and sex ratio112–13

antisocial tendencies toward infidelity615

anxiety and partner loss682

anxious jealousy335

approach behavior533

Argumentative Relationship Scale443–44

arranged marriages
in China289
in India285, 287–88, 551–52
mate guarding and339
in Muslim societies288–89
in Saudi Arabia289

artificial insemination304, 418, 421–22

artificial intelligence693

assurances in communication375

attachment anxiety/insecurity436–38, 440, 441f, 449t, 451f, 631–32

attachment/attachment theory
adaptation differences in partner loss686–87
affective reactions to relationship dissolution675–79, 677t, 693–94
divorce804–5
emotional attachment464, 561, 587, 612–14, 616–17, 799–800
infidelity and616–18
insecure attachment341, 384, 433, 436–38, 453–54, 538–39, 616–17
mate poaching626
in parenting428–29, 434–38, 440, 441f, 449t, 451f
possessive jealousy and315–18
relationship maintenance and538–40

attachment-avoidance behavior434–35, 436–37

attachment system activation434–40

attention in relationship maintenance540–41

attention-seeking behavior434

attractiveness. See physical attraction/attractiveness; See waist-to-hip ratio

attractivity139, 140, 141, 142–44

auditory courtship
affection through166
communication of content166
intelligence through167
in intersexual selection165–68, 173
sound properties and communication167–68
status through166

auditory modalities of perception270

Austen, Jane58–59

automobile type and attractiveness59

autosexual activity659

avoidance behavior366, 533, 617 See also attachment-avoidance behavior

awareness of others543–44

Babylonian Code of Hammurabi797–98

backup mate28–29, 320

Bangladeshi married women study544

Bateman gradient16–17

Beach, Frank139

behavioral mechanisms546–49

behavior/behavioral traits. See also jealousy; See also women’s sexual behavior
animal behavior and cognition See nonhuman species
approach behavior533
attachment-avoidance behavior434–35, 436–37
attention-seeking behavior434
avoidance behavior366, 533, 617
clandestine behavior406–7
competitive behavior135–36
courtship signals and13, 630
escape-avoidance behavior434–35
exploration behavior434
expressive behavior270
facilitative behavior361–62, 371–74
hyperactivating behavioral strategies434–35
lordosis behavior165
during menstrual cycle651–53
menstrual cycle and658–59
olfactory courtship and170
proximity-seeking behavior434
in relationship maintenance546–49
reward-seeking behavior536
risk-taking behavior25, 98, 146, 362–63, 470, 625
in sexual motivation131, 140, 658
sexual risk behavior494–95
strategies in romantic relationships507–8, 520–21
unwanted pursuit behavior704
women’s sexual behavior142–46, 148–49, 197–99

belief in relationship maintenance541–43

benefit-provisioning mate guarding400–1

betrayal-anger response and reactive jealousy342–43

Bierce, Ambrose42

“Big 5” personality dimensions574

bilateral dissolution701–2, 705–7, 719

biological determinism780–81

biological factors in relationship initiation270–71

biosociopsychological model of aging257

bird mating and testosterone129–30

birth-assigned sex/ gender488

body masculinity650

body mass index (BMI)49–50, 220

body odor170

boomerang effect813–14

booty-calls79–80, 83–84, 103

breakups324–25, 632–33, 698–99 See also divorce; See also relationship dissolution

breast cancer risk46–47

breast size/shape46–47

bridal fiction550–51

brooding after breakups704–5

business attire studies57–58

calling system in courtships274, 275–76

cardiovascular health49–50

caregiving system438–39

carotenoid coloration50

casual sex. See also short-term mating
after relationship dissolution712
CNM and467–68, 469–70
friends-with-benefits75, 79–80, 84, 102–3, 719–20
LGBTQ+ relationships228–29
mate poaching and628
in modern relationships75
in non-heterosexual relationship initiation process218–19, 234
one-night stands75, 333–34, 719–20
online dating107
personality traits and55
positive views of635–36
rivals and338
sex differences26, 96–97, 103, 234
sexual selection and17–18
sexual strategies theory87
uncommitted sex216, 218, 222, 228–29, 319, 362–63, 467–68, 657–58, 665–66

challenge hypothesis135–36

chastity preference23

cheating partners469–70

cheek-to-jaw-width ratio49

child abuse413–14, 418–19, 422

child custody750, 801

childhood adversity494–96

childless married couples313–14

childlessness290–91, 313–14, 430, 734, 751

child-parent relationship739–41, 741f

childrearing76–77, 304, 311, 326, 343, 453, 487–88, 534, 575–76, 732–33, 811

Chinese arranged marriages289

Chinese-Australian couples552–53

chronic isolation489, 490, 494–95

chronic strain perspective in divorce806

cisgender487–88, 491, 493

clandestine adultery758–59

clandestine behavior406–7

clothing as non-bodily traits56–58

coalitional aggression193–94

codependence in older relationships251

cognitive jealousy335

cognitive mechanisms
after divorce683–85
after partner loss562, 683–85
after spousal death683–85
experiences after partner loss683–85
holistic cognition541–42
mating cognition2
pattern recognition in animal studies763
in relationship maintenance540–43
strategies in romantic relationships507–8, 520–21

cohabitating couples787, 812–14

cohort effects in marriage802

collectivism531–33, 539, 542–46, 546f

commitment maximization strategy436–37

commitment-problem311–12

communication
affectionate communication166, 378
assurances in375
in auditory courtship166
comprehension and167
finances and569
hormonal mechanisms in361–62, 364–65, 367, 368, 370, 375–77, 380–81
infidelity and618–19
mediated communication and relationship dissolution720
openness in375
positivity in375
production trait167
of relationship status510–11
sharing tasks in375
in social networks375
sound properties and167–68

community divorce805

companionate love588

comparative fit index (CFI)446

comparative psychology2

compassion trait12, 80–82

compatibility trait12, 82–84

compensatory decision-making strategy106–7

competence trait12, 76–80

competing adaptation hypotheses174

competitive behavior135–36

complementarity model in relationship initiation283–84

comprehension trait167

conception window644

conceptual model of relationship functioning428f, 428–29

condition-dependent shifts in mating strategies25

conflict. See also sexual conflict in relationship maintenance
couple conflict437–38, 439–40
interparental conflict752–54
jealousy in relationship maintenance320–21
maladaptive couple conflict439, 443–44, 449–50
management of361–62, 365–71
post-separation parenting752–55
sexual conflict theory756
work-family conflict431–32

conscientiousness217–18, 404, 467, 566–67, 809

conscious awareness of mating psychology19

consensually desired mate choice20

consensual nonmonogamy (CNM)
alternative strategy to human mating476–77
as alternative to infidelity464–66, 472–73, 474–75
defined103, 827
future research directions88, 472–76
gender roles and218–19
individual differences in467–69
LGBTQ+ relationship dissolution783–85
mate guarding and407
relationship dissatisfaction/satisfaction578–79
relationship maintenance factors305, 464–72
social stigma of469–72

constructive-destructive reactions515

contest competition30–31, 36

context-specificity of sexual strategies19

continuity theory of normal aging257–58

Coolidge effect614–15

co-parental divorce805

CoRonavIruS Health Impact Survey (CRISIS)444

corticosteroids3

cortisol awakening response (CAR)376

cortisol in relationship maintenance149–51, 304, 364–65, 368–69, 372, 373–74, 376, 381, 385–86

cost-inflicting mate guarding402–3

cost-inflicting mateship27

counterinsemination strategies414–15

couple conflict437–38, 439–40

couple-initiated marriages551–52

Couple’s Relating to Each Other Questionnaires (CREOQ)259

courtship. See also gustatory courtship; See also intersexual courtship/selection; See also olfactory courtship; See also visual courtship
behavior during menstrual cycle651–53
dating in traditional courtships275–76
extra-pair courtship462
hiding flaws during630
intersexual courtship/selection175
introduction to13
traditional courtships273, 274–75, 277

covert aggression192–95

COVID-19 impact on parenting304–5, 440–46, 754

COVID-19 Pandemic Adjustment Study (CPAS)
adult attachment measures443–44
COVID-19 stressors444, 447–48, 448f, 450–51, 452
data analysis444–46, 445t
demographic characteristics444
discussion449–53
introduction to442–46
maladaptive relationship functioning443–44, 449–50
mediation paths448–49, 449t
parenting irritability444
participants and study design443
path analysis447
preliminary statistics446–49
psychological stress443–44
relationship quality443–44
results446–49
sample characteristics446

creativity traits60–61, 77–78

crisis perspective in divorce806

cross-generational change1–2

crossover theory431–32

cubic effects of deterrence593–94

cuckoldry413–14, 461–62, 473–74, 475

cultural practices
affordances relationship initiation286–87
dating culture274, 281
evoked culture531–32, 532f
gender-egalitarian cultures26
hook-up culture290–91
intercultural couples552–53
intimate partner violence535–36
monocultural couples552–53
older adult relationship initiation247–49
physical attractiveness269–70
relationship dissatisfaction/satisfaction569–70
in relationship initiation271–80
in relationship maintenance306, 528–29, 531–33
sociocultural models mate choice/preferences84–86
WEIRD cultures476

current health cues of partner quality48–50

cyclic perceivers (holistic thinkers)541–42

Damasio, A.765

dark triad traits615

Darwin, Charles15–17, 22, 30–31, 182, 183, 202, 764

dating culture274, 281

dating in traditional courtships275–76

deadbeat dads422

decision science1–2

decolonization practices549–53

defenses against intrasexual mating competition195–97

dehumanization of CMN people471

denial phase in mourning805–6

deoxygenated blood coloration50

Depression and Anxiety Scale (DASS)443–44

depression and partner loss682, 684, 685, 805–6

destructive couple conflict patterns437–38

deterrence magnitude592f, 592–93

developmental health
femininity and45–47
masculinity and47–48
physical cues of44
sexual dimorphism45–48
symmetry of facial cues44–45

Diagnostic and Statistical Manual of Mental Disorders (DSM-5)682–83

diathesis-stress model453–54

digital divorce772

dihydrotestosterone (DHT)128–29, 131, 133–34

direct aggression192

direct guarding tactics314

disappointment response and reactive jealousy342–43

Disney550–51

dissolution distress699–701

dissolution of marriage. See divorce

distal ecologies547–48

distal stressors785–87

distress from relationship dissolution699–701, 712

division of labor31, 563, 758, 783–85, 790–91

divorce. See also in-pair divestment; See also partner loss; See also post-divorce dating; See also post-separation parenting
adaptation differences in685–87
affective and cognitive experiences after683–85
attachment perspective675–79, 677t
attachment theory804–5
boomerang effect813–14
child custody750, 801
childless married couples313–14
community divorce805
consequences of811–15
co-parental divorce805
coping with687–89
defined798–99
digital divorce772
economic divorce805
economic risk factors808
educational attainment and808
emotional divorce767–68, 805
English-speaking democracies748–52
financial consequences of812–14
future research directions692–94
genetics and810
gray divorce810–11
grief after682–83, 689–92
health consequences809–10, 814
historical development of divorce laws799–801
impact of children750–51
impact on family739–41, 741f, 815–16
infidelity role in568
intergenerational transmission of807
interventions for adaptation problems689–92
legal divorce805
LGBTQ+ relationship dissolution788–90
lone parenthood815
marital satisfaction and567
marriage rank/cohabitation808–9
mental health and809–10, 814
no-fault divorce750, 766–68, 800
partner loss due to679–81
personality as risk factor809
physical health and809–10, 814
physical/mental consequences of681–83
post-dissolution relationship716
poverty after815
process theories805–6
protective factors in810
psychic divorce805
refined divorce rate802, 802t
relational mobility in rates of549
repartnering after813–14
rise of797–98
risks in807–11
social adjustment after815
social exchange theory804
theoretical perspective on804–6
time-related risk factors807
trends in801–4
unilateral divorce800
wide acceptance of290–91

divorce-stress-adaptation model688

divorce-stress-adjustment perspective806, 814

domestic violence. See also intimate partner violence
infidelity and462
paternal resemblance and415
possessive jealousy and303–4, 339–40
pregnancy- induced415
research on413–14
sexual jealousy and423

dominance in non-heterosexual relationship initiation process223

donor semen421–22

dual-career families376

dual process model of coping688–89

dual sexuality hypothesis662–63, 665–67

dyadic coping361–62, 371–74

dyadic methodology259

dyadic sexual desire56–57

dysregulation364–65, 368, 688

“early bird” chronotypes227–28

earning power and relationship dissatisfaction/satisfaction568

ecological parasite prevalence25

ecological validity138, 214, 573–74, 668–69

economic divorce805

economic inequalities85–86 See also socioeconomic status

education77–78, 272, 808

elderly intrasexual mating competition200–2

emerging adulthood theory731

emotional attachment464, 561, 587, 612–14, 616–17, 799–800

emotional divestment587–90, 597–98, 599–600, 603–4, 605

emotional divorce767–68, 805

emotional infidelity323, 579, 622, 709

emotional intensity theory (EIT)
defined591–94
effect of obstacles on intensity of romantic feelings594–98
energy conservation principle598–600
future research directions600–6
in-pair divestment and561, 586–87, 590–606
introduction to561, 586–87
overview of590–606

emotional intimacy277, 612–13, 614, 633, 635–36, 706–7

emotional jealousy216, 335, 572–73

emotional reactive jealousy343–44

emotional stability28, 55, 217–18, 269, 536–37, 550, 566–67

emotional support372

emotions. See also feelings; See also jealousy; See also love
access deficits573–74
control of2–3, 594
hatred753–54, 759–61
negative emotions246, 258, 496–97, 515–16, 517–18, 569, 701, 703–4, 709, 769
in nonhuman species763–64
positive emotions254, 258, 361–62, 371–72, 688, 699–701, 703–4, 710
in post-separation parenting768–71
regulation skills515–16
rejection-related759–60
socioemotional selectivity theory258, 511–12

endurance rivalry36

energy conservation principle598–600

English-speaking democracies748–52

environmental deprivation and unpredictability435–36

enzyme-linked immunosorbent assays (EIA)149

eroticism/erotic stimuli135, 145–46

escape-avoidance behavior434–35

estradiol
breast size/shape and46–47
during menstrual cycle645, 648, 649, 652
rat mating studies139–40
sexual activity and659
women’s sexual desire and144–45, 149

estradiol-to-progesterone ratio649, 650, 652

estrogen45–46, 140

estrus137, 139, 140

ethnocentrism292, 531–32

Euclidean algorithm for mating preferences106

Euro-American-centric epistemologies549–53

evoked culture531–32, 532f

evolutionary psychology and theory
cultural practices in relationship maintenance529–33
evoked culture531–32, 532f
intimate partner violence413–14
intimate relationships2
intrasexual mating competition183–89
LGBTQ+ relationship dissolution and779–82
mate-switching755
mismatches in mating61–62
models of mate choice86–88
monogamy and271
natural selection1–2, 15–16, 127–28, 144, 151, 159–60, 171–72, 324, 363, 676
on non-heterosexual relationship initiation213–15, 232
physical cues of partner quality61–62
post-divorce dating731–32
post-separation parenting748–49, 755–62
psychological traits in romantic/sexual partners86–88
relationship dissatisfaction/satisfaction570–73
in relationship dissolution708
in relationship initiation267–80
in relationship maintenance310, 321, 509–11, 529–33
sex differences189–90, 826–27
sexual antagonistic coevolution308–9
social intelligence360–61

evolutionary science1–2, 4, 11, 461–62, 644

Evolution of Human Female Sexuality (Thornhill & Gangestad)645, 669

evolved preferences for mating
agent-based simulation models106
anonymity and sex ratio112–13
compensatory decision-making strategy106–7
cortisol and partnership formation149–51
developments in103–7
Euclidean algorithm for106
evolved mate preferences95–103
future research on113–14
introduction to94–95
long-term mating97–100
mate preference priority model104–6
mismatched mate preferences110–13
in modern relationships102–3, 107–10
nonhuman species111–12
short-term mating100–2
summary of research151

Experiences in Close Relationships Scale-Relationship Structures (ECR-RS)443–44

exploration behavior434

expressive behavior270

extramarital affairs/sex59–60, 103, 322, 757 See also infidelity

extra-pair mating/partnerships. See also infidelity
affairs59–60, 103, 322, 757
courtship462
motivations for561–62
rates of333–34
relationship dissatisfaction/satisfaction and29, 316–17

extraversion217–18

extroversion55, 566–67, 614–15, 635–36, 685–86, 809

face-to-face contests194

facial cues2, 159–61

facial femininity22, 45–46, 161

facial masculinity47–48, 51, 160–61, 170, 172, 219–22, 645, 647, 648–49, 651, 654, 661–62

facial symmetry44–45, 49, 536–37, 647, 648

facilitative behavior361–62, 371–74

family. See also parenting; See also post-separation parenting
allocentrism of545–46
dual-career families376
impact of divorce739–41, 741f, 815–16
involvement in arranged marriages289
mixed family415
size and children576
specific variables of739–41, 741f
victimization and sexual identity formation494
violence and abuse after separation754–55, 761–62, 769–71
work-family conflict431–32

fast life history strategies496

father absence303–4

feelings. See also emotions
hateful feelings753–54, 760–61
human feeling studies764–66
hurt feelings749
intensity of romantic feelings589–90, 594–98
negative romantic feelings589, 600–1
reduction in intensity of romantic feelings589–90

felt security434

female-female mating competition190

female intrasexual mating competition345–46

female mating
attractivity139, 140, 141, 142–44
hormones/hormonal regulation and136–49
long-term mating preferences18, 24–25
nonhuman primate studies140–41, 146–47
proceptivity139, 140, 141, 144–45
receptivity139, 141, 145–46
relationship dissolution and709–10, 714
short-term mating preferences19, 28–30

femininity
developmental health and45–47
facial femininity22, 45–46, 161
non-heterosexual relationship initiation process219–23

fertility145, 398–99, 405

fight-or-flight response364

finances568, 812–14

fitness benefits in relationships529–31, 541, 759

flirting333–34, 348

food in gustatory courtship171–72

food provisioning59–60

forced copulation tactics33

forgiveness
hormonal mechanisms and361–62, 365–71
infidelity and322–25
older adult relationship maintenance and516

freedom of mate choice284–86, 290, 337–39

friends-with-benefits75, 79–80, 84, 102–3, 719–20

frustration attraction759–60

gaydar gaze228

gender differences
adoptive vs. biological parents419
in business attire studies57–58
commitment-problem311–12
compassion trait81–82
compatibility trait82–84
competence trait78
cortisol and partnership formation149–51
height traits in mate selection52–53
infidelity and619
intrasexual mating competition and183, 189–91, 345–46
in jealousy344, 350–51, 571–72
in long-term mating96–102
in marital satisfaction110, 376
in mate choice/preferences96
mate-switching632
muscularity traits53–55
in non-bodily traits58–61
older adult relationship initiation250–51
online dating preferences107–8
operational sex ratio186–87
parental investment theory184–85
post-divorce dating732–33, 742–43
in relationship maintenance304
sexual conflict and307–8
sexual frequency318–19
in short-term mating81, 96–102, 405–6
in social role theory85
speed dating108
traditional dating system276

gender-egalitarian cultures26

gender equality/inequality113, 247–48, 276–78

gender identity468–69, 473–74, 487–89

gender nonconformity4, 229, 495–96, 500, 501

genderqueer488

gender roles218–19, 570

gender segregation in arranged marriages288

gender/sexual diversity2, 4

generosity trait81

genetic traits43–44, 615, 810

geometric morphometric methods (GMM)49–50, 163

The Gerontologist256–57

gift-giving400–1, 403, 549

glucocorticoids194

golden mean rule575

good genes hypothesis27–28, 47–48, 50–55, 232, 613–14

gram-negative bacteria169

grandchild-grandparent relationship255

gratitude361–62

gray divorce810–11

grief and partner loss682–83, 689–92, 751–52

group sex475

gustatory courtship
food in171–72
in intersexual selection170–72, 174
mouth-to-mouth romantic kissing170–71, 174

Hadadah Ibis (amankankane) symbology274

Hadza hunter-gatherers134–35

harassment tactics33

harem polygyny31

hatred753–54, 759–61

health. See also developmental health
consequences after divorce809–10, 814
mental health concerns494–95, 809–10, 814
olfactory courtship and169
physical cues of partner quality48–50
physiological health concerns44, 809–10, 814
psychological health44, 737–38
psychosocial health74

Hefner, Hugh55–56

height traits52–53

Hendrix, Jimi55–56

hierarchy of needs489–90

high-maintenance partners315–16

high-quality mates43–44, 631, 701, 703, 738–39

holistic cognition541–42

holistic observation in animal studies763

hollow forgiveness323, 324

homogamy model in relationship initiation283, 284

homophobia228, 488–89, 578, 780, 785, 786

homosexuality. See LGBTQ+ relationships; See non-heterosexual relationship initiation; See same-sex competition

hook-up culture290–91

hormones/hormonal mechanisms. See also estradiol; See also testosterone
communication and361–62, 364–65, 367, 368, 370, 375–77, 380–81
conflict management361–62, 365–71
in contraceptives147
cortisol304, 364–65, 368–69, 372, 373–74, 376, 381, 385–86
dyadic coping361–62, 371–74
estrogen45–46, 140
facilitative behavior361–62, 371–74
female mating behavior and136–49
female reproductive and45–46
forgiveness361–62, 365–71
function of128
future research directions381–86
glucocorticoids194
hypothalamic-pituitary-adrenal (HPA) axis364–65, 368, 373–74, 376, 378–79
integrated model of relationship maintenance361–62
interactive relationship enhancement375–81
interactive threat mitigation365–74
introduction to127–28
in joint leisure activities361–62, 379–81
male mating behavior and128–36
ovulatory effects on mating101–2
oxytocin3, 304, 363, 368, 372, 373–74, 376–77, 379, 380, 383
progesterone645, 649, 652, 659, 664
in relationship maintenance360–61
in relationship science3, 12–13
sacrifice361–62, 365–71

housing type and attractiveness58–59

human feeling studies764–66

human leukocyte antigen (HLA)50–51

human mating strategies36–37

“Human Oestrus” (Thornhill & Gangestad)645

humor in relationships377–79

humor trait77–78, 167

hunter-gatherer societies530–31

hurt feelings749

hybrid relationships103, 113

hyperactivating behavioral strategies434–35

hyperreactive stress response systems496–97

hypogonadism manipulation133–34

hypothalamic-pituitary-adrenal (HPA) axis149–50, 364–65, 368, 373–74, 376, 378–79

idealistic love beliefs531, 534–35, 535f, 541–42

ideal vs. actual partner choice229–30

immune function44–45

immunocompetence handicap hypothesis (IHH)47–48

immunosuppressive effect of testosterone47–48

imprinting-like effect226–27

inclusive fitness509

income inequality47–48, 188–89

incremental lay theory542–43

independent model of self285–86

Indian arranged marriages285, 287–88, 551–52

Indian online dating279

indifferent responses to relationship dissolution705

indirect aggression192–95, 196–97, 325–26, 402

individualism542–44, 545–46, 546f

industrialization process256

I-ness251, 252

infidelity. See also extra-pair mating/partnerships
attachment orientation616–18
clandestine adultery758–59
conceptual overlap of mate poaching624–26
consensual nonmonogamy as alternative to464–66, 472–73, 474–75
consequences of620–23
defined827
domestic violence and462
emotional infidelity323, 579, 622, 709
factors affecting forgiveness322–25
future research directions634–35
impact on children623
impact on partners621–22
impact on unfaithful individuals621
informed consent and462–63
intimate partner violence and535–36
introduction to611–12
jealousy and343–44, 348
mate retention and314–15, 321–25
mate-switching and633
multipartner relationships and462–66
overview612–23
parental investment theory and613
personality traits and614–15
person-level predictors of613–18
post-separation parenting and752, 757–59
relationship dissatisfaction and29, 338
relationship-level predictors of618–19
role in divorce568
role in relationship dissolution534
sex differences613–14, 617–18, 621
sexual infidelity324, 614, 621–22
sexual permissiveness616, 622
situational predictors of619–20
summary of research635–36

information technology (IT)278

informed consent and infidelity462–63

in-pair divestment. See also divorce; See also partner loss; See also relationship dissolution
causes of590–600
deterrence magnitude592f, 592–93
emotional divestment587–90, 597–98, 599–600, 603–4, 605
emotional intensity theory561, 586–87, 590–606
future research directions600–6
introduction to586–87
reduction in intensity of romantic feelings589–90

insecure attachment341, 384, 433, 436–38, 453–54, 538–39, 616–17

insemination prevention strategies414

integrated model of relationship maintenance361–62

intelligence trait77–79, 167

intensity of romantic feelings589–90, 594–98

interactive relationship enhancement375–81

interactive threat mitigation365–74

intercultural couples552–53

interdependence theory464, 508–9, 511–20

intergenerational transmission of divorce807

International Classification of Diseases (ICD-11)682–83

International Sexuality Description Project624–25

internet dating. See online dating

interparental conflict752–53

interparental hatred760–61

interpersonal antagonism2–3

interpersonal deception2

interpersonal forgiveness323

interpersonal manipulation826–27

intersexual courtship/selection
auditory modality and165–68, 173
future research directions172
gustatory courtship170–72, 174
introduction to16–17, 158–59
modern courtship175
olfactory courtship169–70, 173–74
tactile courtship173
visual courtship and159–65, 172

intimacy
development in older adults518–19
emotional intimacy277, 612–13, 614, 633, 635–36, 706–7
evolution of2
self-disclosure and548–49
sexual intimacy372, 491–92, 611–12, 706–7, 711–12

intimate partner violence (IPV). See also domestic violence
adoptive vs. biological parents419–21
artificial insemination and421–22
cross-cultural investigations of535–36
deadbeat dads422
introduction to304, 413–14
partner aggression437–38
partner-directed abuse402–3
paternal assurance strategies414–15
paternal resemblance415–18
paternity probability418–22
physical aggression31, 191–92, 198, 325–26, 339, 402, 463
possessive jealousy and340
relationship dissatisfaction/satisfaction579
relationship ideals and550–51
sexual and gender diversity494–95
therapeutic implications423

intimate terrorism754–55, 770

intimidation tactics33

intrapsychic forgiveness323

intrasexual mating competition
biological market and186–89
covert aggression192–95
Darwin on182, 183, 202
direct aggression192
ecological factors186–89
evolutionary metatheories183–89
female-female mating competition190
females345–46
frequent victims and defenses against195–97
future directions for195–202
gender differences183, 189–91
identity features199–200
income inequality and188–89
indirect aggression192–95
introduction to13, 182–83
jealousy and185, 344–45
in lesser-studied groups199
lethal intrasexual competition462
LGBTQ+ relationships199–200
male-male mating competition190–91
mate guarding and402–3
mating systems and187–88
moral aim of470
older adults and200–2
overt aggression192
parental investment theory183–85
parents and200–2
poacher competition571
possessive jealousy and340
sex differences191–95
sex ratios and186–87
sexual conflict in relationship maintenance and311–12, 315
sexual strategies theory185
stalking as704
status competition197–99

intrasexual selection16, 214

intrusive contact704

investments in relationships519–20

in vitro fertilization (IVF)45–46

irritable parenting451–52

Islamic veiling57

isolation hypothesis815

jealousy. See also sexual jealousy
adaptive value of333–35
anxious jealousy335
attachment and315–18
betrayal-anger response and342–43
cognitive jealousy335
conflict and320–21
disappointment response and342–43
domestic violence and303–4, 339–40, 423
emotional jealousy216, 335, 572–73
emotional reactive jealousy343–44
experimental studies on348–50
freedom of mate choice337–39
gender differences in344, 350–51, 571–72
infidelity and343–44, 348
intimate partner violence and340
intrasexual mating competition and185, 340, 344–45
introduction to2
lack of in couples589
LGBTQ+ relationships and303–4, 349
mate retention tactics321
menstrual cycle and341–42
physical attractiveness and348, 349
possessive jealousy303–4, 335–42, 351–52
post-separation parenting761–62
preventive jealousy335
reactive jealousy303–4, 335, 342–44, 351–52
rival characteristics346–51
self-doubt response and342–43
sexual conflict in relationship maintenance320–21
sexual reactive jealousy343–44
subliminal priming studies350–51
types of335
waist-to-hip ratio (WHR) and349–51

joint leisure activities361–62, 379–81

Judaism and dating280–81

justification strategy708

Kahneman, D.765

Khotobah agreement in arranged marriages289

kindness trait80–81

kinesthetic modalities of perception270

kissing, mouth-to-mouth170–71, 174

labor market participation813–14

later-life partnerships. See older adult relationship initiation; See older adult relationship maintenance

LEAVES project691–92

legal divorce805

Lehrer, J.765–66

lethal intrasexual competition462

LGBTQ+ relationship dissolution
clarifications on780–81
concerns over780
consensual nonmonogamy783–85
division of labor and783–85
evolutionary psychology and779–82
features of783–87
future research directions790–92
language of781–82
minority stress785–87
occurrence of787–88
risk factors783–85
types of788–90

LGBTQ+ relationships. See also non-heterosexual relationship initiation
biological offspring of214
casual sex228–29
consensual nonmonogamy468–69
gaydar gaze228
homophobia and228, 488–89, 578, 780, 785, 786
intrasexual mating competition199–200
introduction to4, 13
jealousy and303–4, 349
mate retention tactics304
nonbinary235, 473–74, 488, 781, 791–92
older adult relationship initiation260–61
online dating preferences230
relationship dissolution561, 563
relationship satisfaction/dissatisfaction539–40, 578–79
same-sex competition2, 13, 16, 102, 198
self-regulation to relationship dissolution718–19
transphobia488–89

liberation hypothesis815

life expectancy increases246–47

life history theory2–3, 87–88, 435–37

Likert 7-point scale719

Lingāyat relationship initiation280

Linguistic Inquiry and Word Count (LIWC)173

liquid chromatography tandem mass spectrometry (LC-MS/ MS)149

LIVES project683, 684, 685–86

LIVIA project690–92

living apart together (LAT) relationships245–46, 248–49, 259–60, 563

long-distance relationships (LDRs)577–78

Longitudinal Study of Australian Children443–44

long-term mating/relationships
challenges18
deficits in preferences576–77
female-specific18, 24–25
finances and569
gender differences in96–102
key preferences97–100
male-specific18, 21
positive illusions in514–15
relationship dissolution and708
sexual conflict in relationship maintenance310–25, 326
theory of97–98

lordosis behavior165

loss phase in mourning805–6

love
as evolved emotion20–21
idealistic beliefs531, 534–35, 535f, 541–42
as instigator of filial disobedience337–38
low intensity of love591
luxury of love710
mate-switching hypothesis and29–30
pragmatic beliefs541–42, 588
romantic love286–87, 360–61
time spent with partner577–78

love hatred/loving hate759–60

love marriages286, 289–91

love match799–800

low intensity of love591

lumbar curvature of women164–65

luteinizing hormone (LH)142, 648–49, 651–52, 661

luxury of love710

Machiavellian women406–7

major histocompatibility complex (MHC)50–52

maladaptive couple conflict439, 443–44, 449–50

maladaptive parenting495–96

male facial shapes160–61

male-male mating competition190–91

male mating
hormones/hormonal regulation128–36
intrasexual mating competition345
long-term mating preferences18, 21
relationship dissolution and710–11, 714
short-term mating preferences18–19

manipulated risk595–96

marginalized relationships488–90, 491, 590–91

marital disaffection587, 590

marital satisfaction
cortisol levels and364–65, 385
in couple- initiated marriages551–52
divorce and567
gender differences in110, 376
measures of804
personality traits and566–67

marital websites279

marriage
arranged marriages285, 287–89, 551–52
avoidance of567–68
Bangladeshi married women study544
couple-initiated marriages551–52
love marriages286, 289–91
mate retention tactics314–15
rank/cohabitation in divorce808–9

masculinity
body masculinity650
developmental health and47–48
facial masculinity47–48, 51, 160–61, 170, 172, 219–22, 645, 647, 648–49, 651, 654, 661–62
non-heterosexual relationship initiation process219–23
vocal masculinity650–51

Maslow’s hierarchy of needs489–90

matchmaking websites279–80

mate choice/preferences. See also evolved preferences for mating; See also female mating; See also intersexual courtship/selection; See also male mating
backup mate28–29, 320
compassion trait80–82
compatibility trait82–84
competence trait76–80
condition-dependent shifts in25
evolutionary mismatches in61–62
evolutionary psychology models86–88
evolved mate preferences95–103
freedom of284–86, 290, 337–39
introduction to12
life history theory2–3, 87–88
parental investment theory88
preference overview19–20
psychological traits in76–84
reasons for84–88
sexual selection and36–37
sexual strategies theory in87
sociocultural models84–86

mate competition. See also intrasexual mating competition
attraction and derogation in32–33
contest competition30–31, 36
same-sex competition2, 13, 16, 102, 198
sexual selection through30–33
status and197–99

mate deprivation hypothesis34–35

mate equity and value631

mate guarding
benefit-provisioning mate guarding400–1
as conditional strategy404–6
contextual factors in405–6
cost-inflicting mate guarding402–3
future research directions407
individual differences in404–5
intimate partner violence and414
introduction to303–4, 397
investment and costs of mating398–99, 407
overview of33
possessive jealousy and335–42
resistance to406–7
tactics in399–403

mate poaching
attachment orientation626
conceptual overlap with infidelity624–26
consequences of628–29
defined624
enticement strategy628
future research directions634–35
introduction to611–12
overview of33, 624–29
personality traits in625
sex differences624–25
situational predictors of626
strategies for627–28
summary of research629, 635–36

mate preference priority model104–6

mate preferences268–69, 536–38, 647–51

mate retention tactics304, 314–15, 321–25, 326

maternal morbidity and mortality398

mate-switching
break-up and remating632–33
consequences of633
evolutionary perspective755
future research directions634–35
hypothesis28–30
infidelity and633
introduction to611–12
mate equity and value631
new and desirable partner631
overview of629–34
process of632–33
reasons for630–31
relationship load630
summary of research634, 635–36
types of people631–32

mating bias33–34, 35–36

mating cognition2

mating psychology310–11, 562, 644, 659, 660f, 667–68

mating-specific adaptations18

Mechanical Turk652

mediated communication and relationship dissolution720

men’s fertility98

menstrual cycle
alternative views on664–65
behavioral measures661–62
body masculinity and650
courtship behavior during651–53
cyclic variation in mating psychology659, 660f
dual sexuality hypothesis662–63, 665–67
facial masculinity648–49, 661–62
female mating behavior and136–37
findings on151
future research directions667–68
historical overview645
hormones and141–46
introduction to643–44
jealousy and341–42
mate preferences and647–51
in mating psychology and644, 659, 660f, 667–68
methodological considerations147–48, 659–62
motivational priorities hypothesis665
ovulation/ovulation shifts142–46
ovulatory shift hypothesis646, 662–64
sexual behavior and658–59
sexual desire during653–57, 663f
sociosexuality and657–58
spandrel hypothesis664, 668
theoretical foundations646
vocal masculinity650–51

mental health concerns494–95, 809–10, 814

microaffirmations498–99

mind-body split763–64

minimum obligatory parental investment17–18, 96, 536–37

minimum sexual attraction76

minority stress488–89, 785–87

Minuchin, Salvador763

mismatched mate preferences110–13

mixed family415

mixed-gender threesomes (MGTs)475

mixed-martial-arts fighters163

mixed-sex relationships781–82

modern relationships
casual sex in75
evolved preferences in102–3, 107–10
intersexual courtship/selection in175
monogamy in75
online dating107–8
overview of75
practices in relationship initiation256, 272, 276–78
psychological traits in romantic/sexual partners75
sexual conflict in relationship maintenance325–26
speed dating108–10, 150

monocultural couples552–53

monogamy
defined461–62
evolutionary principles271
as gold standard470
mate guarding and337
in modern relationships75
rarity among primates529, 530–31
serial monogamy318, 758–59
social monogamy75, 611–12
sociosexuality in467–68

morphological cues11–12

morphometric analyses3

Morrison, Toni528

mortality rates188–89, 398

motivational intensity theory (MIT)591–92

motivational mechanisms533–40

motivational priorities hypothesis665

motivation transformation513

mourning partner loss682

mouth-to-mouth romantic kissing170–71, 174

multipartner relationships. See consensual nonmonogamy

musculature /muscularity traits53–55, 162–63

Muslim dating280

mutual disengagement701–2

mutual violent control754

namesaked children420–21

National Social Life Health & Aging Project (2005-2006)258

naturalism135, 384, 780–81

natural selection1–2, 15–16, 127–28, 144, 151, 159–60, 171–72, 324, 363, 676

neck musculature in men162

negative emotions246, 258, 496–97, 515–16, 517–18, 569, 699–700, 701, 703–4, 709, 769

negative inducements314

negative romantic feelings589, 600–1

Nesse, Randall764

NESTOR longitudinal survey data258

networks in communication375

neural network modeling1–2

neuroendocrinology2, 3

neuroticism55, 566–67

“night owl” chronotypes227–28

no-fault divorce750, 766–68, 800

non-allometric (non-bodily scaling)163

nonbinary235, 473–74, 488, 781, 791–92

non-bodily traits43–44, 55–61

non-heterosexual relationship initiation
casual sex and218–19
evolutionary perspective on213–15, 232
future directions230–35
ideal vs. actual partner choice229–30
introduction to212–13
parent-similarity preferences226–27
partner identitification227–29
self-similarity preferences223–26
sex differences219–22
sexism and223
sex roles and223

nonhuman species
emotions in763–64
evolved preferences for mating111–12
female intrasexual mating competition345–46
introduction to1–2
mate guarding336, 337
primate mating studies131–33, 140–41, 146–47, 529, 530–31
primates and testosterone131–33
rat mating studies130–31, 138–40
sexual conflict in relationship maintenance307–9

nonmonogamous relationships. See casual sex; See consensual nonmonogamy; See short-term mating

nonprimary relationship464

normative functioning434–35, 438

nubility46

Obergefell v. Hodges Supreme Court ruling786

older adult intrasexual mating competition200–2

older adult relationship initiation
age of initiation and life course stage247
attitudes and impact on offspring254–56
being together and apart251–53
cultural context of247–49
forms of245–46
future directions258–61
introduction to13, 243–45
LGBTQ+ relationships260–61
living apart together (LAT) relationships245–46, 248–49, 259–60, 563
motivation/lack of motivation in250–51
old age and246–47
sexuality and253–54, 259
successful aging256–58
summary of research261
Type A, living together252
Type B, living apart253
Type C, living together253
Type D, living apart253

older adult relationship maintenance
accommodation processes515–16
forgiveness and516
interdependence enhancement518–20
interdependence theory508–9, 511–18
introduction to507–8
investments in relationships519–20
positive illusions514–15
relationship maintenance processes507–11, 520–21
self-disclosure518–19
self-expansion519
staving off alternatives516–18
transformation of motivation513
willingness to sacrifice513–14

older adult repartnering245, 247–49, 250–51, 252–53, 254, 255, 258–59

oldest-old demographic246–47

old-old demographic246–47

olfactory courtship
health and169
in intersexual selection169–70, 173–74
as psychological and behavioral cues170

olfactory modalities of perception270

one-night stands75, 333–34, 719–20

online dating
impact of11–12
LGBTQ+ preferences230
mate preferences107–8
propinquity in281
relationship initiation278–79

openness in communication375

openness traits55

open relationships464, 475

operational sex ratio (OSR)25, 186–87

oral sex219, 401

orgasm-oxytocin link376–77, 380

out-of-wedlock childbearing290–91

overt aggression192

ovulation/ovulation shifts
attractivity and139, 140, 141, 142–44, 655
female mating and101–2, 136–49
mate value and28
proceptivity and139, 140, 141, 144–45
rat mating studies138–40
receptivity and139, 141, 145–46

ovulatory shift hypothesis646, 662–64

oxygenated blood coloration50, 159

oxytocin3, 304, 363, 368, 372, 373–74, 376–77, 379, 380, 383

oxytocin receptor (OXTR) gene383–84

pair-bonding3, 82–83, 150–51, 313, 436, 530–31

parasite prevalence25

parasite stress theory168–69

parental intrasexual mating competition200–2

parental investment theory (PIT)
gender differences184–85
infidelity and613
intrasexual mating competition183–85
introduction to13, 16–18
in mate choice/preferences88
mate preferences and536–37
minimum obligatory parental investment17–18, 96, 536–37
post-divorce dating733, 735t
relationship satisfaction and567
sexual asymmetry in59–60
sexual conflict in relationship maintenance307–8, 312–14

parent-child relationship739–41, 741f

parenting. See also family; See also post-separation parenting
after divorce815
alloparents198–99, 312
attachment in428–29, 434–38, 440, 441f, 449f, 451f
attachment system activation434–40
childrearing76–77, 304, 311, 326, 343, 453, 487–88, 534, 575–76, 732–33, 811
as chronic stressor429–33
conceptual model of relationship functioning428f, 428–29
couple conflict437–38, 439–40
COVID-19 impact on304–5, 440–46, 754
deadbeat dads422
father absence303–4
future directions453
influence in relationship maintenance545–46
irritable parenting451–52
LGBTQ+ relationship dissolution and790
life history theory435–37
maladaptive parenting495–96
partner support and438–39
relationship functioning in couples437–40
relationship maintenance and304–5, 545–46
sleep deprivation/quality433
socio-economic hardship432–33
transition across parenthood430–31
transition to parenthood427–28, 430
work-family conflict431–32

parent-similarity preferences226–27

partner access deficits573–74

partner aggression437–38 See also intimate partner violence

partner-directed abuse402–3 See also intimate partner violence (IPV)

partnering dating in relationship initiation276–78

partner loss. See also divorce; See also spousal death
adaptation differences in685–87
affective and cognitive experiences after562, 683–85
affective reactions to562, 683–85
coping with687–89
depression and682, 684, 685, 805–6
due to divorce or spousal death562, 679–81
future research directions692–94
grief after682–83, 689–92
interventions for adaptation problems689–92
physical/mental consequences of681–83

partner quality. See physical cues of partner quality

partner support436–37, 438–39

passion545–46, 588

passive-active reactions515–16

paternal assurance strategies414–15

paternal resemblance415–18

paternity uncertainty22–23, 318–19, 418–22

pathogen prevalence47–48

pathological hatred753–54

patriarchal power systems87

pattern recognition in animal studies763

peer victimization494

Perceived Relationships Quality Component (PRQC) Questionnaire443–44

perceptual mechanisms540–43

perimeter-to-area ratio49

period effects in marriage802

personal ads in social media278

personality/personality traits
“Big 5” personality dimensions574
casual sex and55
cues to partner quality55
marital satisfaction and566–67
in mate poaching625
measurement of2–3
non-heterosexual relationship initiation process215–18
physical cues of partner quality55
in relationship satisfaction566–67
as risk factor for divorce809

personality science2–3

personal mate value25

personal self in relationship initiation285–86

personal space violations704

phylogenetic inertia86–87

physical aggression31, 191–92, 198, 325–26, 339, 402, 463