PSYA3 - Relationships

Parental Investment Theory

Quotes...

“Eighty percent of married men cheat in America. The rest cheat in Europe”

“If you never want to see a man again, say, ‘I love you, I want to marry you. I want to have children…’ – they leave skid marks.”

“A successful man is one who makes more money than his wife can spend. A successful woman is one who can find such a man.”

"As long as a woman can look ten years younger than her own daughter, she is perfectly satisfied." Oscar Wilde

What do these have in common?

Trivers (1972)

• Trivers defined parental investment (PI) as, “any investment by the parent in an individual offspring that increases the offspring’s chance of surviving (and hence reproductive success) at the cost of the parent’s ability to invest in other offspring.”

• PI includes the provision of resources (such as food, energy and time used in obtaining food and maintaining the home and territory), time spent teaching offspring, and risks taken to protect young.

Sex differences in parental investment

•The female egg cell is much more costly to produce than a male sperm cell.

•Females must nourish for the offspring for 9 months, which means she can only have a limited number of offspring.

Limited offspring for females

•Breastfeeding can last for up to 4 years in some societies (Shostak, 1981).

•In the UK and other Western cultures the average is between 3 and 12 months.

•By contrast, a male can have a virtually unlimited number of offspring (provided he can find females to mate with him!)

Sex differences in parental investment

• Best way to maximise males reproductive success is to mate with as many partners as possible

• Or, men need to concern themselves of the fidelity of their mates so they can be sure she’s mothering only their children

• Best way to maximise females reproductive success is to get the best protection/resources for her children

Sexual Jealousy

Buss 1992: Asked participants to imagine their partners having sex/being in love with someone else and measured stress responses.

• Men more stressed at the idea of them being sexually unfaithful – he therefore risks investing in offspring that were not his own

• Women more stressed at the idea of them loving someone else –and therefore risked the diversion of resources away from her and her family

Optimum number of offspring?

• Trivers argued that there’s an optimum number of offspring for each parent. A low-investing male could afford many offspring and may favour a ‘quantity rather than quality’ approach.

• Females, on the other hand, would prefer quality rather than quantity. Consequently, females generally need to be much more choosy about whom they mate with.

World records!

The world record for the number of children is 888, fathered by Ismail the Bloodthirsty (1672-1727), an Emperor of Morocco; a Russian woman gave birth to 69 children!

Stats- lone parent families

1.9 million single parent families:

1, 690, 000 are lone mothers

210, 000 lone fathers

What does this tell us?!

Differences in parental investment

• Brain size (big head babies!)

• Minimum costs of having a baby (40 weeks vs. a few minutes)

• Cuckoldry

• Sexual and emotional

jealousy

• Geher- ANS response to imagined stressful parenting situations (costs)

Maternal Investment

There are two consequences of the high cost of maternal investments:

• Short term: men look for fertility; women look for ‘mate insurance’ (back up man)

• Long term: men look for parenting skills and faithfulness; women look for resources, commitment and protection.

Differences in sexual behaviour

TASK 1: On your sheet make notes on the differences research has shown about men’s and women’s sexual behaviour:

• Casual sex

• No. Of partners

• Sexual jealousy

Task- 40 mins

TASK 2: Write a response to Michael Gove’s statement that ‘lads mags’ encourage a shallow approach to women that causes feckless fathers and family breakdown.

(Use ideas from the evolutionary approach to support your argument.)

AO2/AO3: Evaluation of PI theory

• Inconclusive empirical support: according to Daly and Wilson (1988) children under the age of 2 are at least 60 times more likely to be killed by a step-parent – almost always a stepfather – than by a natural parent.

• This is exactly what evolutionary theory would predict, since step-parents and stepchildren are genetically unrelated, whereas a child inherits half its genes from each biological parent.

• However, most stepfathers don’t kill or abuse, and a minority of biological fathers do: these findings are difficult to square with any explanation based on shared/non-shared genes.

• Has societal and family structure changed significantly since Trivers published this theory in 1972?

AO2/AO3: Evaluation of PI theory

• How do evolutionary psychologists explain maternal neonaticide?

• More tricky still for evolutionary theory to explain is the case of the woman who kills her newborn baby (neonaticide). According to Pinker (1997), when such an act takes place in conditions of poverty, it could be regarded as an adaptationist response. The psychological module that normally induces protectiveness in mothers in their newbornsis switched off by the challenge of an impoverished environment. This means that both killing and protecting are explained by evolutionary selection. As Hilary Rose (2000) says, this explain everything and, therefore, nothing.

Consolidation task

• Give this essay an AO1 mark and an AO2 mark.

• Think about why you chose the scores you did.

Parent – Offspring Conflict (POC)

The offspring are not completely passive in the process

Trivers (1974)

• Children desire greater investment than their parents have been selected to provide.

• Parents try to allocate resources to their offspring in order to ensure that the maximum number of offspring survive.

• However, conflict occurs when each child wants more resources than the parent is prepared to give.

Resource allocation

• A parent shares 50% of her genes with each child and is inclined to spread resources equally among all children in the family.

• However individual offspring will want more than their ‘fair share’ at the expense of other offspring.

• As a result sibling rivalries may develop as children compete for attention and resources of parents

Competition between siblings

•The child will want to delay weaning as long as possible, often in contrast to mother’s wishes

•Parents encourage their children to value their siblings more than they naturally would

•Parents punish conflict between siblings and reward co-operation, against the child’s natural instincts.

Conflict exists before and after birth

• During pregnancy – the potentially fatal condition pre- eclampsia.

• At some point when a new child is born the parent has to transfer investment from the older child to more vulnerable young.

• Sibling rivalry also exists in the animal kingdom. For example the black eagle and hyenas

• In humans sibling rivalry is usually more intense when the children are closer in age and of the same gender

Discuss

• What is your position in the family?

• If you are the oldest what are your first memories of a sibling being born?

• How do your parents view your personalities, how would they describe the differences between you?

• How often do you fight or argue?

• Do you believe birth order influences your personality?

• Do parents have favourites?

• How much do you know about middle child syndrome?

Some famous siblings

• Noel and Liam Gallagher

• Kylie and Danni Minogue

• David and Ed Miliband

What do the Psychologists say?

Search David and Ed Miliband brothers in arms

or brothers at war? – Telegraph

www.telegraph.co.uk/news/politics/labour/7734013/David-and-Ed-Miliband-brothers-in-arms-or-brothers-at-war.html

Evaluation of POC theory

Substantial empirical support

Cross-cultural research indicates that parental investment is lower in families:• with at least one step-parent;

• when fathers question their paternity;

• when infants are ill, weak or deformed;

• during periods of famine;

• when families are poor or lack social support;

• when mothers are very young;

• when families have too many children;

• when birthing space is too short (Daly and Wilson, 1984)

• Stepfathers are more likely to kill their stepchildren, the same is true for child abuse, as indicated by samples of children dying before the age of 15 and samples of children suffering head and other injuries (Daly and Wilson, 1994)

• Even when financial resources and marital status are held constant, younger mothers are more likely to kill their infants than are older mothers (Daly and Wilson, 1988), and older mothers are less likely to abuse or harm their infants (Daly and Wilson, 1985)

Evaluation of POC theory

Why is P-O Conflict Relevant?

• Where does parent- offspring conflict fit into an exam question?

"Discuss the relationship between sexual selection and human reproductive behaviour"

- Define concepts sexual selection / intra/inter sexual selection

- Leads to certain behaviours: discuss a mate choice - men go for younger women, women more choosy and a couple of examples of supporting research - comment on this research

- Link into parental investment, you should then be able to evaluate the theory in terms of reductionism, determinism, ethical issues , culture, gender etc.

Task

• Plan question 4, page 51: “Discuss evolutionary explanations for sex differences in parental investment and parent-offspring conflict.” (9+16 marks)

• You will be writing this essay in timed conditions next lesson (40 minutes)

Homework

• Read pages 52-53 in preparation for next lesson’s topic

40 years of marriage..

• A married couple in their early 60s are celebrating their 40th wedding anniversary in a quiet, romantic little restaurant.Suddenly, a tiny yet beautiful fairy appeared on their table.She said, 'For being such an exemplary married couple and for being loving to each other for all this time, I will grant you each a wish.'

The wife answered, 'Oh, I want to travel around the world with my darling husband’ The fairy waved her magic wand and - poof! - two tickets for the Queen Mary II appeared in her hands.

The husband thought for a moment: 'Well, this is all very romantic, but an opportunity like this will never come again. I'm sorry my love, but my wish is to have a wife 30 years younger than me’.The wife, and the fairy, were deeply disappointed, but a wish is a wish.

So the fairy waved her magic wand and poof!...The husband became 92 years old.

The moral of this story:Men who are ungrateful should remember fairies are female!