Flashcards in Lecture 3 (Mate Choice 2) - Slides Deck (20)
Two Types of Sexual Selection Adaptations
And Examples in males/females
- Males: Shoulder - Hip Ratio, Masculine face, Low-pitched voice
- Signals of testosterone
- Female: Waist to hip ratio, feminine face, high-pitched voice
- Signals of estrogen
- Traits develop on a continuum such that some individuals have more elaborate or well developed traits
- Because these traits are metabolically costly, it signals that you had access to resources (different for each sex) if you are able to develop them
- Androgens influence how we develop AFTER puberty manifest masculinity/femininity in the face and voice
- Masculine faces = testosterone, feminine = estrogen
- Estrogen might be interfering with testosterone instead of not as much testosterone
- Causes phenotypic differences
- Using Psychomorph, a face shaping software we can calculate the differences in
- Averaging many faces together can give us an average of a general male or female face
- Comparing the structure of the face, we can subtract the average male/female face from the current face and make them more m/f
- We always want to make sure all test categories are either all manipulated or not manipulated
(Average pitch for each, morphic?)
- Vocal fold vibration, large folds = lower frequency
- Pubertal testosterone causes vocal fold growth. Both males and females experience a drop.
- Males drop is twice that of females
Manipulating voice pitch
- Vowel sounds to eliminate content dependent effects of the language and because pitch is not present in everything we say.
- We don't manipulate frequency on numerical difference (30hz either way) because frequencies are not perceptually equal. We manipulate by equivalent rectangular bandwidths (0.5 typically)
Ornaments (4 Criteria)
1 ) Heritable
- Is m/f heritable? ~1/2 is due to heritability, inherited by your same sex parent
2) Communicate Mate Value
Males: Testosterone predicts dominance and health.
- Low T predict ED, cardiovascular disease, diabetes and lower immune system response.
- 2 reasons why immune system is important: (direct) higher T have higher immune systems so partner won't get sick, (children) no benefits to offspring
Females: Predicts Fertility and Health
- VP Correlated with RP (Perceived as younger - Psychological Adaptation)
- Desire for children correlated with facial masculinity in females (and are also rated as more attractive and have more estrogen)
3) Increase Reproductive Success (3 ways to examine it)
a. Mate Preferences: signals fitness benefits (fertility/health)
Men: Voice: Doesn't matter how high or low VP is manipulated, once it's raised it's more attractive. Higher VP = more attractive, f, younger, less dominant. Face: prefer facial f, prefer different ethnicities differently. Also bodies (see other card)
Females: Voice: Prefer lower VP and perceived as more m, attractive and dominant. Body: Shoulder-2-Hip (Broad shoulders can be considered an ornament and a weapon) Face: Prefer m/f depending on cycle, f men are perceived, higher VP in women prefer more m. as more friendly and may invest more.
- Relative mate value of the individual influences preference in VP
- Women prefer lower VP for ST most when fertile/non and raised least for LT when fertile
- Creates a trade-off. Fitness Benefits to High T: Health/dominance (why?), Fitness Risks: mating effort, reduced paternal care, and infidelity risk.
- Feinberg et al. (2006): women who have higher levesl of E vary less in Voice prefernces across cycle.
- Fertile women prefer facial m for ST and less in LT than non-fertile
- Females prefer m more if they have a partner
4) Difficult to Fake
- We can fake beards, and cosmetics
- We deliberately and unconsciously change our voice pitch
- Fracarro (2012) - Individuals threw their voice and rated for attractiveness.
- Females: Preferred normal to lowered (because they prefer higher anyways),
- Males: Raising voice made normal voice seem more attractive.
Cornwell & Perrett (2008)
- Heritability criteria for ornaments example
- Photos of students & parents rated on m/f
- Maternal femininity predicted daughter femininity
- Paternal masculinity predicted son masculinity
Thornhill & Gangestad (2006)
- Measured male facial masculinity and female face f
- Correlated to respiratory illness and duration (more m/f = less and quicker)
- Negatively correlated with antibiotic use in males, why?
High T = fast immune response
- Men: Waist-to-Hip (0.7 is most attractive) ratio, estrogen directs fat to thighs/hips/butt. Signals fertility status and pregnancy
- Cross cultural variation: Hunter/Gatherer: Prefer higher ratio because they go through cycles of famine/feast. Linked to the ability to preserve foods. Women with higher WHR are carrying their resources.
- Social learning explanation: Culture depict this as sexy. Weight has decreased but not WHR
- Karremans et al (2010) - see other flash card
- T directs fat to waste
Karremans et al. 2010
- Body preferences of blind/sighted/blinded-folded men
- Gave visual and tactile inspections
- Touch and rate adjustable dress figure (WHR at 0.7 vs 0.84)
- All thought 0.7 was more attractive
Women's Face Preferences
Feminized Male Faces: Warm, Honest, Cooperative, Higher quality parent
Masculinized: Cold, Dishonest, Uncooperative, Lower quality parent
Perceptions of Infidelity
- O'Connor et al., 2011) Raise/Lower VP of males/females, 2 AFC paradigm, asked males and females about infidelity
- Men's voices are rated as more attractive but are more likely
- O'Connor 2014: Perceived as more infidelity across all ST and LT, but are more attractive in an ST than an LT.
Perception of Investment (O'Connor, Fraccaro & Feinberg, 2012)
- Relationship investment related perceptions: who is more likely time & effort, financially generous and save vs. spend money and who was more attractive for ST vs. LT
- Masculinized less likely to invest time/effort and financially generous but still more attractive for ST/LT
- Women who prefer more masculine men may perceive more m as more generous or attractive
- Women who though m voices were more generous also thought they were more attractive for LT
Women's Mating Strategies
- Dual Mating Strategy
1) Obtain the highest quality LT mate who will invest in offspring
2) Obtain highest quality genes possible for offspring
- Trade-off between the two exists: mate value, fertility status, resources. If you have resources then m may be more preferred.
- No pattern in preferences for videos of m/f face/voice videos
- Attractiveness correlated to preferences for masculinity, but not individually to faces or voices specifically
Summary of Women's Mate Preferences
- M preferences stronger when women can/want to conceive (Indirect, genetic benefits)
- Women who are higher in mate value have stronger preferences of m
- May be better able to obstain/retain more m men as mates
- Other women may pursue m men as extra-pair partners
3 ways to Increase Reproductive Success
1) Mate Preferences - having these traits
2) # of sex partners.
Have more partners:
- Men with lower VP'
- M/W with attractive voices
- Men with high S2H ratio, women with low W2H ratio
- More likely to be an extra pair partner and acting as a extra-pair partner
3) # of offspring
- Apicella, Feinberg, Marlow (2007): Hunter-Gatherers - Men with lower VP have more offspring, but did not predict the amount of offspring that died for various reasons (May not confer infant health, sexually sellected, not naturally)
- Atkinson 2012 Natural fertility population, women higher VP had more children and grandchildren and directly predicted RS
Why do multiple ornaments evolve? (2 reasons)
1) Backup Traits/Redundant Signals: Correlated traits and preferences
- Different ornaments communicate the information about the same quality, but communication is imperfect so multiple expressions may be necessary to generate overall quality assessments
- Reduces error in mate choice
- M/W with f/m faces have higher/lower VP
- Scent: Females who liked pig pheremones liked facial m more
2) Multiple messages: Different things are being signalled in different ways that are related (e.x. Health and height)
- Different ornments different underlying qualities, but communicate overall quality
- Masc. and fluctuating asymmetry