DEVELOPMENT, GENES & THE BRAIN

Development describes how a creature changes over time. It include changes brought about by the environment (nurture) but we will be looking in more detail at changes brought about through maturation (nurture).

Maturation includes all the changes that occur for biological reasons. These can be broken into several stages of development:
  • Pre-natal maturation: changes that occur in the womb
  • Post-natal maturation: changes that occur in infancy and childhood
  • Adolescence: changes that occur in the teenage years and into adulthood
  • Adulthood: changes that continue over the rest of your life
We now understand that maturation is shape by genes.

A gene is a set of biological information contained on a strand of DNA. At conception, each human acquires 50% of their genes from each parent. Genes are inherited.

The complete description of all your genes is your genotype. What you actually turn into and how your behave when all your genes interact with each other and with your environment is your phenotype. Even people with the same genotype (such as identical twins) may have different phenotypes.

THE ROLE OF GENES IN DEVELOPMENT
WHAT YOU PARENTS GAVE YOU

Genes are strands of DNA and DNA comes twisted into "double chains" called chromosomes.  Humans have 23 pairs of chromosomes in each cell in their body.

Two chromosomes are particularly important for determining sex: the X and the Y chromosome. If you inherit two X chromosomes (XX), you are genetically female; if you inherit a Y chromosome from your father (XY), you are genetically male.

Genes like these which always lead to certain characteristics are dominant genes. A dominant gene only needs to be on one of a pair of chromosomes to take effect.

Genes which do not always lead to certain characteristics are recessive genes. Recessive genes have to be on both of a pair of chromosomes to take effect.
Eye colour illustrates dominant and recessive genes. The gene for brown eyes is dominant. If the brown-eyed gene is on each of the chromosome pair that determines eye-colour, you will be brown-eyed. To be blue-eyed, you need to have the blue-eyed gene on both of the chromosome pairs, not just one.

PRE-NATAL DEVELOPMENT

In the womb, human life begins as a zygote (fertilised egg). Maturation transforms the zygote into an embryo and then a foetus.

The genes that have been inherited shape the way the zygote matures. Over the first few weeks, the zygote divides and multiplies its cells in a process called mitosis. Zygotes are fragile and fewer than half survive the first two weeks (Hall, 2004). After 5 days the zygote has 100 cells, but after 9 months the foetus will have billions of cells.

As the cells multiply, they become more specialised. At around 2 weeks, the placenta forms and the zygote attaches itself to the lining of the uterus: it is now an embryo.

The embryo matures until about 8 weeks, developing a neural tube that will turn into the spine. At the end of this stage, eyes, ears and nose have appeared.

At 9 weeks, the embryo is about the size of a kidney bean but it resembles a human being and is termed a foetus. Between 9-12 weeks, arms and legs start to move (but this can't be felt) and the sex organs begin to differentiate. By the time the foetus has reached the sixth month of development (24 weeks) it weighs 1½ pounds and can respond to sounds.
You don't need to know all these details of pre-natal development but it's good to learn ONE example of the sort of changes brought on by genetic instructions.
Pre-natal development is mostly maturation due to genes. However, there are some environmental influences too. A teratogen is any substance that can have a bad effect on the developing foetus. Teratogens normally affect the foetus because the mother has taken them into her body and they pass through to the foetus through the placenta. Teratogens include alcohol, nicotine and drugs but also pollution and chemicals in food. Even stress can cause chemicals to be released in the mother's body that affect the development of the foetus.
Drinking excessive alcohol while pregnant can cause foetal alcohol spectrum (FAS). It is unknown how much alcohol is needed to cause damage, and so many doctors recommend completely avoiding alcohol  during pregnancy. Children with FAS may have a small head size and abnormal facial features. They also tend to have poor impulse control, learning difficulties and lower IQ scores. These problems  carry on into adulthood (Streissguth et al., 2004).
You may have noticed "poor impulse control" and made a connection to Eysenck's psychoticism (P) trait. You did? Good!

POST-NATAL DEVELOPMENT

After they are born, infants develop motor skills (movement). Gross motor skills involve groups of muscles to do things like stand up, walk and jump. Most children can do these things by the end of their second year. As they mature (4-5 years), they develop more complicated gross motor skills, like riding bikes or catching balls.

Fine motor skills are more precise, use fewer muscles but often involve hand-eye coordination. This includes eating with spoons and forks, drawing, using buttons and tying laces.
Again, you don't need to know most of this, but it's helpful to be able to give one example of children's maturation at a certain age.
Brain development happens very quickly. The brain grows faster than any other organ in a child's body. Neurons forms and synapses develop between them. At birth, a child's brain is only 30% of its adult weight; by age 2 it is 70% of its adult weight.

This is accompanied by emotional development. Children develop emotional self-regulation: the ability to understand and control their own emotions.  It involves restraining some emotional responses or delaying them so that they can be shown in a more appropriate way later. The classic example is holding your temper.
Eysenck's neuroticism (N) trait reflects how difficult someone finds emotional self-regulation; very difficult for high-N individuals
There is also a development of empathy, the ability to recognise and understand other people's emotions. Children who possess empathy are less likely to be antisocial.
Eysenck's psychoticism (P) trait reflects how difficult someone finds empathy; very difficult for high-P individuals

ADOLESCENT DEVELOPMENT

Adolescence begins at puberty and ends with adulthood and usually covers the 10-18 age range.

Hormones drive physical changes in adolescence, but the release of hormones is dictated by genes.  In addition, environmental factors like diet and exercise also influence the release of hormones (for example, puberty begins earlier if you are overweight). The release of hormones in adolescence is controlled by the pituitary gland.

Testosterone is the male growth hormone; oestrogen is the female growth hormone. During adolescence, growth hormones increase height, muscle mass and lead to the growth of secondary sexual characteristics (breasts, body hair).  There is a redistribution of body fat and an increase in the size of lung and heart, leading to more strength and stamina.
The brain develops in this period and there are big changes in the frontal lobes, which continue to mature right up until the end of adolescence (Casey et al. 2005). Immature functioning of the frontal lobes might be responsible for risk-taking behaviour in adolescence. There are also changes in levels of serotonin and dopamine, especially in the limbic system, which increases emotionality.
Don't teach "Expelliarmus!" to someone whose frontal lobes are still maturing!
Eysenck's extroversion (E) and psychoticism (P) traits reflect a tendency towards risk-taking for high-P, high-E individuals; neuroticism (high-N) is linked to emotionality.
The adolescent brain works much faster than a child's brain, with processing speed peaking around age 15. There are improvements in attention, memory (especially working memory) and metacognition (which includes skills like planning ahead and interpreting things in different ways).

This new style of thinking is hard to get used to and adolescents may experience unusual thinking problems. The imaginary audience is a tendency for adolescents to imagine everyone is listing to them; the personal fable is a tendency to imagine that there will be no harmful consequences.

However, environmental changes are also going on. Adolescents distance themselves from their parents and develop new social relationships with peers. Cultural pressures begin to affect adolescents. These are pressures to conform to norms of behaviour regarding sex, belief, appearance and recreation. Adolescents can find it stressful to handle these new peer groups and cultural pressures. This makes it hard to tell whether development during adolescence is due to maturation or environmental factors.
One example of biological/behavioural change during adolescence is all you will need.

ADULT DEVELOPMENT

Adults experience primary aging, which is normal maturation, but also biological changes due to lack of physical exercise and poor diet, which is secondary aging.

In early adulthood (ages 20–40), our physical abilities are at their peak, including strength, perception and heart functioning.  Aging speeds up during middle adulthood (ages 40–65) with decline in vision, hearing, and immune-system functioning, as well as the end of reproductive capability for women (menopause). Hormonal changes take place during menopause, which may result in emotional swings, problems with attention and memory and changes in sexual interest.

During late adulthood (age 66+), reaction time slows further, muscle strength and mobility decrease, hearing and vision decline, and the immune system weakens.Many of the changes in the bodies and minds of older adults are due to a reduction in the size of the brain and loss of brain plasticity. Memory declines in old age. In general, an older person's procedural memory tends to remain stable, while working memory declines. In some cases, these changes mask the symptoms of dementia, including diseases like Alzheimer's.
As with the previous sections, you only need to know one example of biological/behavioural changes in adulthood.

Your Key Question for the Cognitive Approach asks how psychology can help older people suffering from dementia.

HUMAN DEVELOPMENT & EVOLUTION
HOW WE EVOLVED TO GROW UP LIKE THIS

Evolutionary Theory claims that humans have descended from ape-like ancestors over millions of years. Many of the genes were possess we have inherited because they had fitness to help our human and pre-human ancestors survive in the past.
You can see this at work in recessive genes like the genes for eye colour. These originally appeared as random mutations. In fact, the gene for blue eyes is called OCA2 and it first appeared in one human living over 6,000 years ago (Eiberg et al., 2008). The gene is neither positive nor negative for survival in itself, but when both the mother and the father carry the gene, there is a chance the child will receive OCA2 on both chromosomes and grow up to be blue-eyed.
Other genes have a more obvious survival value. In human beings, having a large brain has survival value. This is why we have inherited genes that programme our bodies to grow such large brains in our early years. This comes at a cost.
Many wild animals can stand up and walk within hours of being born. Human babies must usually be a year old before they can even begin to do this. This shows out is is a survival trait for animals to develop gross motor skills quickly. Human babies are working on their large brains and rely on their parents to protect them from dangers and bring them food. To help with this, we have evolved to become attached to our children and they become attached to us.
You can see the same evolutionary pressures at work during adolescence. With many animals, like cats, the young begin moving away from the mother and exploring their environment at a very young age. You can see young kittens practising hunting and fighting. It's cute! But human children stay under their parents' care until adolescence. Adolescence is when they start practising adult skills and behaviours. This is also because of the great amount of time it takes to grow a complete human brain.

APPLYING HUMAN DEVELOPMENT TO REAL LIFE
AO2

Addiction​
As part of the Biological Approach, you study the effects of drugs on the brain. Developmental psychology explains some of the features of addiction.
The Biological Approach is good at explaining why drugs are addictive - they affect the reward pathways in the brain. It's not so good at explaining two other things:
  1. why people start taking drugs in the first place, and
  2. why some people quit drug-taking but other people don't
This is where developmental psychology comes in.

Drugs are teratogens - if the mother is taking drugs, they may pass through the placenta and damage the foetus in the womb. Foetal Alcohol Syndrome (FAS) is an example of this.
Youngentob et al. (2007) also show that children born with FAS are also more likely to grow up to be alcohol users; they acquire a predisposition towards alcohol addiction.

Heroin is even more addictive than alcohol and babies of heroin-users can be born addicted. This is known as Neonatal Abstinence Syndrome (NAS) and the baby goes through the same withdrawal symptoms as an adult addict: high-pitched crying, sweating, vomiting, etc.
Troubling report on addicted babies in the USA, including addiction to painkillers
Babies and young children are shielded from cultural pressures to experiment with drugs. These pressures affect adolescents much more strongly. In addition, the changes in hormones and brain structure during adolescence promote risk-taking behaviour, which includes drug abuse. The "personal fable" is a thinking error likely to lead adolescents into drug abuse through the belief that they will not suffer any bad consequences from it.
Aggression

Babies experience a lot of frustration when they are tired, hungry, uncomfortable, etc. However, aggression peaks for toddlers during the "terrible twos". Two-year-old children have enough gross motor skills to move about and they are using language. They are also beginning to show self-awareness. This leads to frustration, because they want to do things they lack the fine motor skills for or the language skills to ask for. These leads to tantrums.

An interesting study by Rogoff & Mosier (2003) compared US families with Mayan Indian families in Guatemala. Among the Mayans, the "terrible twos" are unknown. Rogoff & Mosier gave children an interesting object to play with (an embroidery hoop). US mothers would make the toddler share the toy with an older brother or sister; the Mayan mothers would insist that the toddler kept the toy, telling older brothers or sisters to wait for their turn 97% of the time.

Mayan mothers expect an older sibling to defer to the toddler for the sake of good relations and the toddler grew up without tantrums. The Mayan parenting-style may seem as if you are "spoiling" the toddler. However, the Rogoff & Mosier found that 61% of the interactions of Mayan children were cooperative, whereas 68% of the American children's reactions were competitive.

This suggests that some childhood aggression is more cultural than biological. If the parenting-style involves forcing toddlers to obey, it produces more defiance; if it involves demanding that older children but the toddler first, it helps children grow up without tantrums.

Aggression also peaks in adolescence. This is another age when young people have social ambitions (to make friends, meet the opposite sex, gain status and independence) but may lack the skills or resources to do this, leading to frustration. Moreover, hormonal changes and under-developed frontal lobes may contribute to aggressive behaviour (such as "fights" with parents and social aggression with peers).

Again, this aggression may be as much cultural as it is biological. Europe and (especially) America are characterised by an "individualist" culture which promotes the idea of everyone getting what they are entitled to. If this is true, then a more "cooperative" parenting-style - like the Mayan mothers - might produce less frustration for adolescents.
Goulston's "cooperative" parenting style may help adolescents handle aggression better. But will parents see this as "spoiling" a disrespectful child instead?

EVALUATING BIOLOGICAL DEVELOPMENT
AO3

Credibility

The idea that human development is due to biological maturation has a lot of evidence to support it.

Crucial to this view are developmental milestones. These are behaviours that happen at a certain point in development for all humans, everywhere. For example, human babies start walking and then talking during their second year. Adolescents go through predictable changes, although the exact time scale involved varies from person to person. Similarly, the decline in memory in old age is predictable, although the exact time scale varies.

If any of these developmental milestone do not occur, this is a warning that the child is suffering from a developmental disorder (such as autism, which may cause a delay in a child learning language or playing with others).

One of the biggest boosts to this view came from research into the human genome, which was finally decoded in 2003. This gives us much more understanding into how possessing or lacking a particular gene shapes the way a child develops. It's been known for a long time that genes determine things like eye colour and hair colour, but we're also coming to understand how genes influence more complex behaviour, giving us predispositions to behave in certain ways.
Objections

​The main objection to this view of development is that it does not give enough importance to the environment. In other words, there is too much nature and not enough nurture.

For example, some genes do not influence physical characteristics unless certain environmental 'triggers' occur. The triggers (such as stress) may be needed to "switch on" genes for depression or schizophrenia later in life.

Since the 1990s, there has been a growing field called epigenetics, which looks at how genes themselves may be changed by environmental stressors like starvation, drug use or childhood abuse.

For example, Meaney et al. (2004) identified epigenetic changes in rats. Rat pups who were groomed by their mothers in the first week of life went through a genetic change that made them better able to recover from stress than the “low-nurture” rats who did not receive mother-love.
Michael Meaney's study helps explain Eysenck's neuroticism (N) trait. The "high nurture" rats were more able to control their stress-response, making them more stable (low-N). This suggests environment might be responsible for more than the 25% that Eysenck credits it with.
Differences
The Exam Board expects you to compare the biological explanation of development with the Freudian explanation of development. Freud's ideas are explained on another page. For now, I'll compare and contrast the biological explanation with the situationalist explanation that  development is learned.
The biological explanation of personality supports the nativist (nature) view of human development, but the Learning Approach takes the situationalist (nurture) view that development is due to the environment.

There are many studies supporting the idea that development is learned. Bandura's "Bobo Doll" studies show that children imitate  role models. Classical and Operant Conditioning both offer explanations for development.
  • Classical Conditioning shows that behaviour is an unconditioned response to some stimuli but may become a conditioned response to a neutral stimuli. This ties in with brain plasticity; because of conditioning, your brain alters in the way it responds to things.
  • Operant Conditioning shows that personality may come about through reinforcement, either positive reinforcement (getting something you like) or negative reinforcement (the end of something you don't like).

Strict Behaviourists like B.F. Skinner would argue that ALL behaviour is learned and that human beings are born as tabula rasa (a bank slate), with development happening later. Developmental milestones like walking and talking are all learned.

This view fails to explain why developmental milestones occur at the same age for all children and there are problems explaining how really complex behaviour (like language) can be learned so quickly through trial-and-error.

Biological determinists would argue that ALL behaviour is maturation and that human beings are born with a genetic destiny they cannot help but obey.

This view fails to take into account new discoveries about genes "switching" on and off and epigenetics, where genes change due to environmental stressors. It also ignores cross-cultural differences in development, such as the Mayan toddlers who didn't go through the "terrible twos" in the study by Rogoff & Mosier (2003).

Most psychologists take a middle way between these extremes. Genetics gives us predispositions to behave a certain way, but we can resist these impulses if we try.
Applications

The biological view that development is maturation has led psychologists to investigate biological treatments for developmental problems. This has led to the growth in prescribed drugs for conditions like Attention Deficit Hyperactivity Disorder (ADHD).

ADHD is a learning difficulty that affects 3-7% of school-age children and can lead to behaviour problems in the classroom as well as an inability to concentrate. A drug used to treat ADHD is Ritalin. Ritalin is not fully understood (although it is prescribed to over 600,000 children in the UK) but it seems to work by increasing the brain's uptake of serotonin. Serotonin is an inhibitory neurotransmitter so it calms down (inhibits) over-excited brain functions.
In terms of Eysenck's personality theory, the symptoms of ADHD sound like neuroticism (N); increasing serotonin would make children less neurotic.
If the nativist viewpoint is correct, then development is maturation, which is innate and difficult to change. However, epigenetics recognises that genes can change. Stress and a lack of love and security in early years seem to bring about epigenetic changes that make a child grow up less able to cope with anxiety and stress. You can see this in the Meaney et al. (2014) study on anxious rats.

This would suggest that parenting and fostering for children are more important than ever. If a child receives love and emotional security and an early age, it may grow up to be less stressed and healthier.
You normally think of the nativist perspective and the Biological Approach as opposed to ideas like parenting styles, recommending drugs or surgery instead. This just goes to show the crossover going on in neurocognitivism these days.

EXEMPLAR ESSAY
How to write a 8-mark answer

Evaluate the biological explanation of how children develop. (8 marks)
  • An 8-mark “evaluate” question awards 4 marks for describing individual differences from the biological perspective (AO1) and 4 marks for evaluation (AO2). You need a conclusion to get a mark in the top band (7-8 marks).

Description
Child development begins in the pre-natal stage. At around 8 weeks the embryo has developed a neural tune (spine) along with hands and feet.
In the post-natal stage, the newborn develops motor skills and the brain grows rapidly, going from 30% of adult weight at birth to 70% by age 2.
During adolescence, there are hormonal changes and the frontal lobes continue to develop until around age 18.
In adulthood, abilities peak in the 20s and start to decline in the 40s. Working memory declines in old age along with sight, hearing and immunities.

Evaluation
The idea that biological maturation determines development is credible because of our mapping of the human genome and the existence of developmental milestones that are the same in all cultures.
However, there are arguments that environment and nurture influence development just as much as genes. For example, Rogoff & Mosier found that Mayan two-year olds don't throw tantrums because they are parented differently.
The difference with the learning approach to development is that it claims behaviour is learned through conditioning or by imitating role models, rather than coming from inside us when we mature.
The biological approach has benefited society by developing drugs like Ritalin, which help with developmental problems like ADHD by correcting the balance of serotonin in the brain.

Conclusion
Biology explains a lot of development but not all; modern epigenetics shows that are genes are altered by our environment, such as how much love we are shown as children..
  • Notice that for a 8-mark answer you don’t have to include everything about development. I haven’t mentioned the other parts of the brain, testosterone or the evolutionary view of adolescence. But it is a balanced answer - one third description, one half evaluation.