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Final

Sex Psych Final Exam.docx

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Department
Psychology
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Psychology 2075
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Lorne Campbell

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Sex Psych Final Exam Lecture 7 – Casual Encounters  4 items needed for a safe spring break: o Sunscreen o First aid o Condoms o Plan B  Norms: o Group holiday with friends; perpetual party atmosphere; high alcohol consumption; sexually suggestive contests and displays; perception that casual sex is common  Norms appear far more permissive on spring break vacation than at home  Sexual partnerships during spring break initiate rapidly (often within hours of meeting) and are temporary (not lasting beyond spring break)  Theory of Interpersonal Behavior (Triandis) o Attitudes, norms, and situational expectations influence behavioural intentions o Intentions, in turn, influence behaviour o Situational conditions and prior experience can also influence behavior o Your attitude of norms and intentions influence the likelihood you will behave in this way  Maticka-Tyndale, Herold, & Mewhinney (1998) Study o 66 men and 85 women, largely between the ages of 21-23  Surveyed before and after spring break: wanted to determine if intentions going in correlated with actual actions o Over 80% of students traveling with friends o Almost every student had prior sexual experience o Majority of men intended to have casual sex o Minority of women intended to have casual sex  Actual behaviors from study o 72% of men and 77% of women DID NOT have sexual relations during spring break  A clear majority did not have sexual relations during spring break  False consensus?  norm is wrong, they most likely WILL NOT having casual sexual relations with people they just met o 15% of men and 13% of women [2% different – not sig dif] had sexual relations with someone met on spring break  Even though majority of men said they would have sex on spring break and the minority of women said they would, it ended up being the same for actual behaviour; most did not engage in casual sex, even though desires differed going in  Why have casual sex on spring break? o Men  Intentions  Spring break experience (engaging in activities conducive to casual sex i.e. drinking, drugs) o Women  Intentions  Spring break experience  Peer influence (role modeling and pacts) - depends on what friends are like i.e. if I do, you do  Binge drinking during spring break is a regular occurrence  Sönmez et el. (2006) o Tourism is even more likely to constitute the context in which risk behaviours occur when its consumers happen to be young adults, accompanied only by friends or other peers o The tripartite relationship among youth, tourism, and risk taking has the potential to constitute a serious public-health hazard  Bringing in sickness and disease from all over the world, could go home with disease they picked up on spring break, go home and spread when get home  Disinihibiting Effect o High-risk behaviors are linked to situational disinhibition in settings encouraging sexual and emotional transience o Social norms, expectations, and behavioral intentions for casual sex and excessive drinking  Questions asked prior to spring break:  Questions asked after spring break: o Social pressures!  51% reported drinking alcohol because everyone around them was drinking  16% reported using drugs for the same reason  19% indicated they drank alcohol or used drugs in order to “fit in” o Other outcomes  Decisions to wear condoms were negatively influenced by being drunk (23%) or under the influence of other drugs (8%) - this is a worry; for these individuals, many of them will go home with and STI  68% reported regretting having sex after drinking and 10% following drug use  aka I wish I didn’t do that  Same number of men and women are saying they had sex with random people  Studies are finding that men and women are engaging in the same rate of sex on spring break even though more men go in wanting it  Alcohol and Casual Sex o Alcohol interferes with the ability to reason o Alcohol consumption is positively related to engaging in high-risk sexual behaviours; for example:  Sex outside a long-term relationship  Having sex on a first date  Decreasing intentions to use condoms  Conner and Flesch (2001) o Students recruited in a University affiliated bar in the UK, between 7:30-11:00pm o Each individual was asked to read one of four scenarios and answer some questions  A total of 8 experimental conditions  Condom availability: yes or no  Alcohol consumed in scenario: yes or no  Alcohol consumed by participant: yes or no  Would you have sex with this person? o A lot of interesting results emerged, including:  If a condom was available, people were more likely to say they would have sex  If the participant had been drinking, they reported being more likely to have sex o Past behaviour predicted intentions to have casual sex  MacDonald, Zanna and Fong (1996) o Alcohol myopia hypothesis  Alcohol intoxication decreases cognitive capacity  When intoxicated, people may attend to only the most salient aspects of a situation (e.g., reward, not the risk)  So, alcohol itself NOT a disinhibitor; instead, it leads people to behave in a manner consistent with the salient cues available in a given setting - narrow focus on what they can gain, not thinking about the risk therefore not looking at the negatives and consequences  Experimental Studies o Two conditions (men only): sober, alcohol  In the sober condition: participants completed the primary dependent variable (video)  In the alcohol condition: participants first consumed enough alcohol to make them legally intoxicated and then they completed the primary dependent variable (video) o Men watched a video created by the researchers depicting a realistic, engaging scenario in which a young couple have to decide whether to have sex without a condom  Both people were attractive and interested in having sex  It was established that the female character was on the pill  No condom available; they talk about how to get one, but to no avail; they mention they are both “clean”; he asks her what she wants to do, and she says “I don’t know, what do you want to do?” o The experimenters asked the men: so, what would you do?  “If I were in this situation, I would engage in sexual intercourse with the woman in the video”  1 = strongly disagree; 9 = strongly agree o Intoxicated men: 6.78 o Sober men: 3.63  They conducted the same study, leading people in the sober condition to believe that they were drinking alcohol o Same pattern of effects  They also conducted a field study, showing the video to people in a campus pub (the same one on the video) at the beginning of the night (sober) or later in the evening (intoxicated); collected data from both men and women o Same pattern of effects  Alcohol and perception – “beer goggles” o Alcohol consumption increases ratings of attractiveness to faces of the opposite sex o Alcohol consumption also has detrimental effects on visual perception  For example, an increase in myopic refraction and a decrease in oculomotor control, contrast sensitivity, and visual acuity o Souto et al. (2008): alcohol consumption may reduce the ability to discern asymmetries in people’s faces, making them appear more attractive  Maybe people find people more attractive after consuming alcohol because they are less able to pick up on asymmetries  Study o Sober and intoxicated participants were shown a series of simple geometric images o They responded on whether they perceived the image to be symmetrical or asymmetrical, they were designed to be perceived to be asymmetrical but not easy to do so o Intoxicated subjects were significantly less likely to detect asymmetry than were sober subjects  Personality o The strongest personality predictor of short-term mating is impulsive sensation-seeking (fpeople who have higher degree of risk taking get a higher rush, engage in more risky behaviour)  E.g., men’s patronage of prostitutes o Impulsive sensation-seeking is closely associated with the Big Five dimensions of low agreeableness and low conscientiousness o Also, extraverts are more likely than introverts to endorse favourable attitudes about having multiple sex partners and to engage in sexual intercourse with more partners than introverts do  Schmitt and Shackelford (2008) o Cross cultural study with over 13,000 participants o 3 traits (high extroversion, low agreeableness, and low conscientiousness) strongly predicted interest in short-term mating  That is:  Desiring short-term sexual opportunities  Reporting a more unrestricted sociosexual orientation  Having engaged in short-term mate poaching attempts  Having succumbed to short-term poaching attempts of others  Lacking relationship exclusivity  Casual Sex o Hooking up (one night stand)  A sexual encounter which may or may not include sexual intercourse usually occurring on only one occasion between 2 people who are strangers or brief acquaintances o Booty call  A meeting with someone you now for the express purpose of having impromptu sex o “Fuck Buddy” (FB)  A regular sexual relationship that turns into friendship o Friends with benefits (FWB)  The addition of sex to an existing friendship without a romantic commitment  Regan and Dreyer (1999) – Motives o Similarities  Sexual desire  Sexual experimentation  Physical pleasure  Alcohol use o Differences  Men: Status enhancement; normative peer group behaviour  Women: Increase probability of long term commitment  Grello et al. (2006) o First sexual encounters are frequently casual sexual encounters o Casual sex occurred more often between friends than strangers on a college campus o Men having casual sex reported the fewest symptoms of depression o Women having casual sex reported the most depressive symptoms  Paul and Hayes (2002) o A qualitative analysis of hook-ups on campus (187 participants) o Student’s estimates of other college students that have “hooked-up” was 85% o Actual hook-up rates in their sample was 70%  overestimating norm by 15%, perceived norms for certain behaviours may lead to more pressure to do so o On average, participants reported 10.28 hook-ups during their college career (no differences between men and women)  Typical Hookups • Feelings experienced after a typical hook-up, you can feel happy and sad at same time over certain aspects of things – Feeling regretful or disappointed (especially for females): 35% – Good or happy: 27% – Satisfied (especially for males): 20% – Confused or unsure: 11% – Proud (especially for males): 9% – Excited/nervous: 7% – Uncomfortable: 5% – Desirable or wanted: 2%  Regret over bad hookups o Women: shame and self blame for engaging in sexual behaviors in the context of a hook- up; not knowing their partner o Men: disappointment over a bad choice of a hook-up partner (unattractive or has a reputation for being promiscuous)  Campus hook-up culture o Prevalent on college campuses (even though students tend to overestimate the prevalence) o Men and women share similar motives for hook-ups, but differ in important ways o The primary feeling experienced after a hook-up is regret (for both men and women, but stronger for women) Lecture 8 – Love and Sex  Over 2000 years ago… Plato’s “Symposium” o Socrates and friends eulogize love  The earth came into existence following a period of chaos, and then love was next to come into being. Love was believed to be the central and defining feature of all human behavior  “See, how she leans her cheek upon her hand! O that I were a glove upon that hand, that I might touch that cheek!” - William Shakespeare, Romeo and Juliet, 2.2  People still write letters to Juliet asking for love advice in Verona  Romantic novels most popular genre in 2009 (13.2% of ALL book sales that year, or $1.36 billion)  WHAT IS LOVE? o Watson (1924)  An innate emotion elicited by cutaneous stimulation of the erogenous zones o Freud (1992/1951)  The desire for sexual union is at the core of emotion  When that desire is blocked, one compensates for the resultant frustration by idealizing the other person and falling in love with him/her o Fromm (1956)  Love is a device used to reduce one’s sense of isolation and loneliness o Rubin (1970)  Love is an attitude held toward another, which predisposes one to think, fell, and act in certain ways toward that person o Swenson (1972)  Love is behaviour such as giving gifts, sharing activities, and disclosing intimate information o Centers (1975)  Love is a response evoked in people when their interaction with another is rewarding o Skolnick (1978)  Love is a constructed experience built with feelings, ideas, and cultural symbols  Moulin Rouge: “the greatest thing you’ll ever learn is just to love and be loved in return”  Tina Turner: “Oh what’s love got to do, got to do with it. What's love but a second hand emotion? What's love got to do, got to do with it. Who needs a heart, When a heart can be broken”  Gonzaga et al. (2001). Love as a commitment device o Human survival depends on formation of cooperative alliances, long-term mateships, successful reproduction, and the raising of vulnerable offspring until their age of reproduction o Emotions help individuals form and maintain reproductive relations (love as an emotion, feeling about being drawn to someone) o Commitment problem—staying with one person in the face of alternatives (lots of potential alternatives to current relationship and in order to stay committed, love may have evolved so that we stay focused on that person) o Love promotes commitment in two ways  1) outward expression of love in word, deed, and gesture communicates commitment to intimate partners, thereby enhancing processes that protect and strengthen the bond  2) experience of love motivates approach toward an intimate partner (and away from others)  When your in love with someone you do things on daily basis to show that you love them, even though you don’t mean to ie they have a meeting that day, you wake them up, doing things for them, showing them your committed - then they can feel confident that they have a committed partner  Gonzaga et al. (2006) o A sample of women asked to relive experiences of love with their partners o Videotaped from the upper torso to the top of the head  Expressive behaviour while recounting love experiences were coded o Self-reports of love correlated with expressive behaviour (e.g., Duchenne smiles (kind and not fake), affiliative head nods) o Also, expressive behaviour correlated with oxytocin release  Oxytocin o A mammalian hormone that acts primarily as a neurotransmitter in the brain o When released, oxytocin evokes feelings of contentment, reductions in anxiety, and feelings of calmness and security around a mate o Linked to commitment and long-term pair bonding o Have developed nasal vapor that has oxytocin that crosses into blood stream quickly  Pair bonding o In every known culture, formal marriage arrangement between men and women exist o Jankowiak and Fischer (1992)  Romantic love is found worldwide  Over 90% of people In the world will marry at least once during their lives (Buss, 1985)  Marriage is prevalent, cultural influences who marries who (parents choosing, gay o Marital attachment is a universal feature of human existence, and most people in the world marry only one person at a time (Fisher, 1992)  Different faces of love o Helen Fisher – model of mating, reproduction and parenting o Mating behaviors guided by 3 distinct emotion systems: lust, attraction, and attachment o Behaviors related to each set of emotions are believed to be governed by a unique set of neural activities  Suggests there are different systems that are designed to make us feel like we are attracted to something else, see systems on following slides  LUST SYSTEM o Motivate individuals to locate sexual opportunities o Mainly associated with estrogens and androgens in the brain  ATTRACTION SYSTEM o Directs individual’s attention toward specific mates o Makes people crave emotional union with this person o Associated with high levels of dopamine and norepinephrine and low levels of serotonin in the brain  ATTACHMENT SYSTEM o Focused on the maintanece of close proximity o Linked with feelings of comfort and security, and feelings of emotional dependency o Associated with oxytocin (mostly for women) and vasopressin (mostly for men)  Pair Bonds and Health o Broken social ties, or poor relationships, correlate with increased vulnerability to disease o Heart attack victims are more likely to have a recurring attack when they live alone o The happiest University students are those that feel satisfied with their love life o Those who enjoy close relationships cope better with various stresses, including bereavement, rape, job loss, and illness o Happily married individuals are less likely to experience depression than unhappily or unmarried individuals o Married men and women report more happiness than people who have never married, who have separated, or have divorced o Humans may therefore be designed to respond positively when a long-term mate is secured and relationships endure  Idea that we tend to do better when we have strong social bond and relationships, can come in many forms but especially marriage or relationships from psychical diseases and psychological problems  Just being married, regardless of quality of marriage, you can predict they will be healthier and live longer for the most part  How long is long?? Fisher (1998) o Fisher (1998) suggests that although long-term relationships have obvious reproductive and health benefits, the desire to stay in one relationship wanes as a function of the amount of time it takes an infant to become less dependent on parental investment (approximately 4 years  about the breaking point, if you get past that you will probably stay together, if not probably will end)  Why 4 years?? o Enough time to meet, fall in love, and produce offspring o Interest in each other wanes after children are born o Also wanes after NO CHILDREN are born o Fisher—planned obsolescence (replace, move on) of the pair bond  Strong evolutionary forces to come together, but also strong urges to stray after time, some people are better at resisting these urges  Problem of Commitment: Alternatives o If we have a lot of alternatives available, we feel less committed to our partner even if we are happy in our relationships o Having more options in online dating made it less likely for people to find mates, always thinking there is something better b/c there are so many options  ie charlie’s angels studies- rated girls worse after watching charlies angels o Men felt less love after looking at hot women. Men are able to shift feelings of love due to social comparison o Women’s love for partner wasn’t changed after looking at hot men. However after looking at slides of men with power or status, women rated less love for partner o When men or women are exposed to either good looking and /or powerful people, they see there is better than what they already have  Simpson, Gangestad & Lerma, 1990 o In this study brought men and women into lab, asked to flip through various ads and told they would be asked to make judgments on quality ect, afterwards, they are asked to go through and rate attractiveness of people in ads. o Seperated participants in two groups: dating and not dating, men and women o People who were single (men and women) rated these people much more attractive than those who were in relationships o People in relationships that were committed were using these photos as threat and thought that they were not attractive o Single people could also just be on the look out for someone so they may seem them as more attractive than they truly are o People in relationship are able to derogate the attractiveness of others to show their commitment for others  Lydon et al. (1999) o Manipulated interest o Those in committed relationships rated alternative partner as less appealing o See picture of person and some info, researchers would say by the way this person likes you and is looking forward to meeting you. They manipulate how interested the other person (hypothetical person) is in you  people were committed to their own partner  Miller (1997) o More committed people spent less time viewing slides o Were less likely to break up 2 months later o Procedure: Used slide projector, sat you down. Your already in a committed relationship, asked to go through slides of attractive individuals, each picture is self timed and when you want to you can click through. o Individuals that were more committed to relationships clicked through quickly. o Those who looked at pictures faster, were more likely to stay in relationship and engage in behaviors that say your committed (inattention to alternatives) o People who went through them slowly were more likely to break up within 2 months o Research shows you are more likely to not pay attention to alternatives the more committed you are to relationships  Maner, Gailliot, and Miller (2009) o Face pops up, circle pops up, you have to say where the circle is, the faster you do it means the faster you move your attention away from face and say where circle is; longer it takes you the more fixated you were on the face o Mating (lust, kissing) or neutral state (talk, floor) was induced by participants viewing masked priming words o Mating prime reminded them that they were in a relationship o At an automatic level under concious awareness, people in relationships are able to quickly more their attention from alternatives o Although no significant difference between single and committed participants was observed in a control condition, committed participants were significantly less attentive than single participants to attractive opposite sex targets in the mating prime condition o When primed with mating, committed participants were less attentive than single participants to images of attractive opposite sex targets  lower-order perceptual processes that may aid in maintaining relationship commitment when people are faced with desirable relationship alternatives  Misremembering Reality o Wanted to see if people who saw the attractive face re created an attrative face using a pixelated face o People that were single, when saw attractive face was rated most attrative, if they saw the ugly face would make it really ugly o people in relationships made the attractive and re created them as not as attractive and made the uglier ones a little bit more attracted as originally  derogating (belittling) alternatives  Automatic Accomodation – Hafner and Ijzerman (2011) o Looked at automatic facial reactions to faces of one’s partner and stranger expression different emotions  When we do and do not mimic others’ facial expressions o You and parter comes into lab, took pictures (ie looking sad, upset ect) now they present pics to you of parters and other you don’t know and got to see how you responeded to the faces o Say you see your partners angry face average response is to automatically smile. You are not responding like they are - not responding to escalate. If it is a strangers face, they are more likely to mimic anger o Partner sad, you are more likely to mimic sadness (feel sad for them) o Suggests people in relationships responds in ways to accomodated and help move the conversation in a more beneficial direction  Ovulating women pose a threat to committed men – Miller and Maner (2010) o Female confederate; tracked her menstrual cycle o Interacted with male participants  Trained her how to interact with male participants, males thought she was a participant too, women was rated as acting the same behavioral wise all throughout cycle o Men rated her attractiveness o Difference between single and committed men:  Single men were more attracted around her ovulation, men in commited relationships rated her less attactive seemed like a threat  Rated her the same when not around ovulation  The Triangular Theory of Love: Sternberg (1986) o Love has 3 fundamental components:  INTIMACY  Emotional component  Feelings of closeness or bonded  PASSION  Motivational component  Physical attraction and drive for sexual expression  COMMITMENT  Cognitive component  Short-term—do I love this person? Long-term—desire to remain in the relationship o Relationship satisfaction is greatest when partner’s “triangles” match  8 types of Love: o Nonlove: absence of all three o Liking: high intimacy o Infatuation: high passion o Empty: high commitment o Romantic: high intimacy and passion o Companionate: high intimacy and commitment o Fatuous: high passion and commitment o Consummate: high levels of all three  Love and Language o Fehr (1988)—the prototype of love and commitment  Sternberg—commitment is a part of love  Fehr—commitment and love are related, but independent o What are the core elements of love and commitment, and what are more peripheral features of love and commitment? o Asked students to list features of love and commitment to see what features most people believe are core elements of these categories  Number of unique features generated: Unique Features of Love Unique Features of Commitment Unique Features of Love and Commitment Happiness Perseverance Caring Want to be with other Living up to your word Responsibility Friendship Faithfulness Trust Feel free to talk about anything Obligation Devotion Warm feelings A promise Sharing Accept other the way s/he is Being there for the other in good times Sacrifice Understanding and bad Honesty Euphoria Mutual agreement Helping Sexual passion Give your best effort Loyalty Closeness Attention focused on other Put other first Empathy Reliable Supportiveness Heart rate increases Work toward common goals Giving Feel good about the self Feel trapped Forgiveness Giving and taking Have a lot in common Hard work Miss other when apart * Largely cluster around the * Largely cluster around the theme of experience of positive affect making a decision and following through with it  Love and “In Love” o Meyers and Berscheid (1997)  Social categories exist that people naturally use to communicate with each other  We can experience love for a number of targets  Parents, spouse, dog, children, siblings, money, cars, success o But being in love with a target implies a different type of relationship  One that includes sexual attraction and desire  Make a list of people/ things/pet, ect you love, then you separate the ones you feel sexual attraction towards, and then write down names of people that you are in love with  Size of circle reps # of names in that category. Biggest list was love for a number of targets, next were people they were sexually attracted to and smallest was people was in love with them o If the are in the “in Love” (romantic union) category there is a 92.9% that they are also in the “Love “ too (really like them, care, friend)  if you put someone in the “in love category” you are highly likely to also have them in the sexual attractions and love category  Status of Research on Love o Berscheid: “How many meanings does the word ‘love’ have? Legion.” o Fletcher et al.: “Deciding which specific measure to use when assessing relationship quality can be a nightmare for researchers given the huge miscellany of existing scales and the multitude of terms that have been used to describe what different scales measure.”  Through research literature over time, people have given many meanings of love, making it very difficult to get the real meaning of love if you boil it all down you tend to get these two categories:  PASSIONATE LOVE o A state of intense longing for union with another, a feeling that is aroused particularly in the early stages of a romantic relationship o Thinking of loved one activates brain regions that are responsible for producing the exhilarating physiological effects (e.g., heightened energy, restlessness, loss of appetite, inability to sleep) associated with cocaine use  Put people (have already said they are passionately in love with partner) in MRI and look at patterns of blood flow in brain: people either look at pic of friend or lover. When people in love look at pictures of lover  increased blood flow and dopamine (etc.) is seen which has the side effects of being in love (loss of appetite, etc.) o Passionate love spikes early and then starts to dwindle  COMPANIONATE LOVE o Combines feelings of intimacy, commitment and deep attachment toward others o Feeling close and intimate with someone is based at least in part on how close and intimate you perceive that person feels toward you  Intimacy process model o Romantic relationships often contain a mix of both passionate and companionate love, but the absence of companionate love in particular can spell trouble for the stability of a relationship  Seems to be the glue that holds the relationship together overtime • Baumeister and Bratslavsky (1999): links between passion and intimacy o Passion is the first derivative of intimacy o When intimacy shows relatively large and rapid increases, levels of passion will be high; likewise, when intimacy levels remain unchanged over time, passion will be low  Everyday routine unfolds, love and compassion will probably remain constant, but say one day say there is something novel - causes a spike in intimacy sex o Rubin & Campbell (2011)  Daily changes in intimacy linked with passion  Daily means for intimacy and passion across diary period o We are motived to seek new knowledge and experiences (we are curious and motivated to grow) -- relationship partners help us do this o Rate of “growth” slows over time (slowdown in intimacy) the “I’” becomes “we” after being together for a certain amount of time – things start to slow, the routine sets in, you know each other fairly well now, relational boredom o Consistent with Baumeister  when things slow down intimacy cant grow, if there is something you can do to get the relationship out of the rut, focus on new activities to off set boredom  ie researcher Velcro arms and legs with partners in fun challenge. Whole time they are doing it, physical contact, laughing and working together. More fun then doing it alone. Partners that engage in novel activities together have more love = intimacy 5.6 5.5 5.3 5.2 5.1 passiony 4.9 4.8 4.7 4.612 34 5 67 89 10 11 12 13 14 15 16 17 18 19 20 21 Lecture 9 – Sperm Competition  Insemination vs. Fertilization o In sexually reproducing species, insemination does not equal fertilization o In many sexually reproducing species (humans), one sex has an intermittent sex organ (E.g. males have a penis) o Males donate gametes, females receive gametes o Sperm is not delivered directly to an egg  To what degree do male and female psychologies do to deal with sperm competition?  Sperm competition = o The competition within a single female between the sperm from two or more males for the fertilization of the ova (Parker, 1970)  The study of sperm competition focuses on two processes: o How males compete to fertilize a female’s egg once the initiation of copulation has occurred o How females non randomly bias paternity between two or more male’s sperm  Sperm competition if Nonhuman species o The number of sperm transferred to the female may be the most important factor for success in sperm competition o Hypothesis: males should deliver more sperm when the risk of sperm competition is higher [more sperm = more likely for success]  Across species, investment in sperm production should be linked with risk of sperm competition  Within species, males should allocate their sperm in a prudent fashion (inseminate more when risk of sperm competition is higher)  Empirical support o Nematodes  Sperm size correlates with sperm competitiveness  Species with greater risk of sperm competition produce larger, but more costly, sperm o Yellow dung flies  Exposing dung flies to greater levels of sperm competition produced increases in testis size after only 10 generations (Hosken & Ward, 2001) o Prudent sperm allocation: Within a given species, will a male produce lower amounts of sperm when the competition is low and produce higher amounts of sperm when competition is high?  Experiment: male rats spent 5 days with a female rat prior to estrus (but separated by a mesh cage), and then they were allowed to mate. Or, a female rat spent 5 days with a male rat prior to her estrus but then was allowed to mate with a different, unknown male rat (for her estrus)  Less sperm was inseminated with the female rat the males had spent time with  Relative testicular size in animals increases when the sperm competition is high o Gorilla: .018% of body weight [low competition] o Chimpanzees: .268% of body weight [high competition] o Humans: .062% of body weight [somewhere in the middle]  Female infidelity and sperm competition o If women have sex with more than one man during the life-span of the sperm (~ 5 days), then conditions exist for sperm competition o Simmons et al. (2004)  In a large sample of men and women, 28% of men and 22% of women reported engaging in extrapair copulations (EPCs)  A literature review suggests that rates of extrapair paternity are in the region of 2%  Males at some risk for cuckoldry (husband of an adulteress) o One of the best predictors of extramarital sex and infidelity is premarital sexual permissiveness (Thompson, 1983)  Sociosexual orientation  More sexually unrestricted persons report having more sex partners and are more likely to engage in one-night stands  They also report being more inclined to pursue extra-pair involvement  Double mating o Baker and Bellis (1995)  Reported that 17.5% of British women in their sample “double-mated” at some point during the first 50 copulations of their life-time o Laumann et al. (1994)  83% of respondents who reported having 5 or more sexual partners in the past year also reported that at least two of these relationships were concurrent o Baker and Bellis (1990)  Women more likely to double-mate when probability of conception is highest  They suggested that women may therefore actively promote sperm competition  Sexual Fantasies o On average, men fantasize about having sex with more than one woman concurrently more so than women (Ellis and Symons, 1990) o However, a non-trivial percentage of female respondents also fantasize about having sex with 2 or more men concurrently  Hunt (1974)—18%  Wilson (1987)—15%  Person et al. (1989)—27%  Pelletier and Herold (1988)— 29% o Symons (1979)  Sexual fantasy provides a window through which to view evolved human psychology  If so, results suggest that human female sexual psychology may include design features dedicated to the pursuit of polyandrous sex (which promotes sperm competition)  Prudent Sperm allocation in Men? o Mean number of sperm per ejaculate in humans: 175 million (Smith, 1984) o Frequent ejaculation results in decreased sperm counts (Tyler et al., 1982) o Interestingly, masturbatory ejaculates contain fewer sperm than do copulatory ejaculates (Zavos & Goodpasture, 1989) o Baker and Bellis (1993) suggested these lost sperm are older and less competitive o The number of sperm contained in a man’s ejaculate varies considerably o Baker and Bellis (1989)  10 couples provided ejaculate specimens  Collected via masturbation, or during intercourse with a condom  Asked participants how long they had spent together since last copulation prior to the specimen being provided  Longer time together since last copulation = less sperm ejaculated, but ONLY for sexual encounters with the partner (not masturbation) o Baker and Bellis research used a between, not within, subjects design o Baker and Bellis (1993)  Conducted follow-up research with 24 couples  A total of 84 copulatory ejaculates were provided by the couples  More time together since last copulation = less sperm per ejaculate within participant o Shackelford et al. (2002)  Argued that total time spent apart since last copulation is a more logical indicator of sperm competition than time spent together  Proportion of time spent apart from his partner since last copulation:  Rates partner as more attractive  Feels that other men find his partner more attractive  Reports greater interest in copulating with his partner  Feels that his partner wants to copulate with him  Shackelford et al. (2005) o Focused on “mate guarding” activities and in-pair copulations (IPCs) o Suggested that mate guarding and IPCs may have evolved as anti-cuckoldry tactics o Two studies: one asked men about their behavior, the other asked women about their partner’s behavior o Mate g
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