Edexcel A Level Biological Psychology

Monozygotic twins

Identical, share 100% of their genes as they come from one fertilised egg.

What should be considered about MZ twins?

- Do not share the same environment

- There are some physical differences, such as fingerprints

- Can become less identical over time

- Some characteristics, such as IQ and personality might become more alike as twins age

Epigenetic modification

Different environmental influences affect which genes are switched on and off. Younger MZ twins have few epigenetic differences.

Dizygotic twins

Not identical, come from two separate eggs fertilised at the same time. Share 50% of genes.

Why are twin studies useful?

If a characteristic comes from genes, MZ twins should be more likely to share it. Psychologists can compare behaviour between a group of identical twins and fraternal twins to see which group shared the most similarity.

Concorance rate

The extent to which the same behaviour is the same between twins. An agreement rate when both twins have got a characteristic.

Strengths of using twin studies

- Twin studies are the main way of finding out if genes have any influence on behaviour.

- Both twins share their environment, so there should not be many environmental differences between the twins.

Weaknesses of using twin studies

- MZ twins will be treated more like twins than DZ twins, so environments are not the same.

- Epigenetic modification, there are differences between twins. Difficult to say if a characteristic is caused by genes conclusively

Gottesman and Shields (1966) procedure

- 16 year period (longitudinal) using 5 twin studies

- To see if there was a relationship between genetic make up and development of schizophrenia by looking at concordance rate

- 57 twin pairs (24 MZ and 33 DZ)

- Hospital notes and semi-structured interviews

Gottesman and Shields (1966) results

- MZ twins - 42%

- DZ twin - 17%

Gottesman and Shields (1966) conclusion

Genes do play a role in the development of schizophrenia, but can't conclusively say it is solely due to genes.

Why are adoption studies useful?

It is the only direct way to isolate the influence of genes and the environment.

In what circumstances in adoption studies suggest the roles of genes?

Similarities between child and their biological parents

In what circumstances in adoption studies suggest the roles of environment?

Similarities between child and their adoptive parents

Kety et al (1994)

- Research in Finland

- Sample of 155

- 9 adopted children, 8 had biological mothers with schizophrenia or a form of psychoses

Strengths of adoption studies

- Developmental trends (patterns) can be studied because studies are longitudinal. Same children can be studied at different times during development.

- Control for environment, separates genes from environment.

Weakness of adoption studies

- Adopted children are often placed into families very similar to their biological families

- They are matched, so the environments might not be as different as thought

What are the 3 main brain scanning techniques?

PET scans, CAT scans and fMRI scans

How do PET scans work?

- inject patient with FDG (radioactive)

- task is given to stimulate the brain

- glucose is used up, radioactive atoms break down, gamma rays produced

- high activity (red)

- low activity (blue)

What are PET scans useful for?

Investigating areas of the brain that are not functioning normally, indicate damage or tumours.

Strengths of PET scans

- Reasonably non-invasive, less dangerous than surgery

- Valid measure

- Reliable because it can be repeated and same results found again

Weaknesses of PET scans

- Invasive

- Ethical implications, need informed consent and a good reason to carry it out

- Can cause panic if claustrophobic

- Difficult to isolate different brain functioning precisely, as they will be using other parts of the brain as well.

Hard to claim exactly what part of the brain is performing which function

How do fMRI scans work?

- uses blood flow of brain to indicate level of activity

- head placed in large electromagnet

Strengths of fMRI scans

- No danger from radiation

- Detection of blood flow is very precise so slight changes can be detected

- Medical use, looking at brain structure and functioning

Weaknesses of fMRI scans

- Cannot look at receptors of neurotransmitters unlike PET scans

- Too much head movement can distort imaging

- The brain is never at rest, so it is not easy to gather a baseline measure

- Risks, such as those with pacemakers and those who are claustrophobic.

How do CAT scans work?

- Multiple X-ray beams passed around the head at different angles

- Detailed 3D image

What are CAT scans useful for?

Detecting areas of brain damage after an accident or position of tumours

Strengths of CAT scans

- Less harmful than PET scans

- Can detect changes in physical structures, so good for detecting tumours or haemorrhages

- Not painful, non-invasive

Weaknesses of CAT scans

- MRI gives a clearer picture

- Involves X-raying which can cause damage, notably cancers.

Research using PET scans

Raine (1997)- investigate whether people charged with murder and pleading NGRI have brain differences that might link to their aggression.

Research using fMRI scans

Dimoka (2010)- if brain function and structure linked to trust and distrust. Found that credibility and discredibility linked to cognitive brain areas in the prefrontal cortex. Benevolence and malevolence linked to emotion area (limbic system)

Research using CAT scans

Betts (2009)- case of Herbert Weinstein, 64 year old man who strangled his wife. Defence was that a cyst had caused pressure on his prefrontal cortex, affecting understanding. CAT scan evidence of differences in his brain relating to schizophrenia.

Correlations

A way of looking at relationships between two variables, not causes. If two variables are correlated, you can predict one from the other.

In a correlation, the SAME person produces the two scores. True or false?

True

What type of data is used in correlations?

Numerical data

What are the three important features of correlation design?

1. There is no IV or DV, only two variables of equal importance

2. Hypothesis will be about a relationship between two variables (not a difference)

3. Hypothesis could be directional as it could predict a positive or negative correlation.

Name an example of co-variables in biological psychology

Measuring the number of genes a person shares (closeness of family relationship) and a behavioural charactersitic such as the amount of aggression they show.

What type of graph do you use to show correlations?

Scatter diagrams

Types of correlations

- Positive correlation

- Negative correlation

- Uncorrelated

Which inferential statistic test do you use for correlations?

Spearman Rank Correlation Coefficient

How do you carry out a Spearman's rho?

1. Rank starting from the lowest score (rank 1)

2. If there are two or more scores the same, allocate those scores the same rank by finding the middle rank

How can you analyse correlations?

1. Spearman's rho

2. Draw a scatter graph then look at the line of best fit

How do you interpret the results of the Spearman's test?

- If both scores rise, there is a positive correlation. A result of +1 means a perfect positive correlation

- A result of 0 means no correlation

- If one score rises and the other falls there is a negative correlation.

Positive correlation

Both co-variables increase

Negative correlation

When one variable increases and the other variable decreases.

What are the two main parts in the nervous system?

Central nervous system and Peripheral nervous system

What does the CNS consist of?

Brain and spinal cord

What is the role of the CNS?

Central processing and control point for all human behaviour. Processes all information from the senses and is responsible for controlling behaviour.

What is the role of the spinal cord in the CNS?

Connects the brain to the rest of the body, and allows messages to be passed from body to brain and from brain to other parts of the body.

Neurones

Nerves in the CNS that communicate with other cells at the same time

Neurotransmitter

A chemical involved in passing information from one neurone to another in synaptic transmission

Structure of a neurone

What are the parts of the neurone?

1. Cell body

2. Nucleus

3. Myelin sheath

4. Nodes of Ranvier

5. Axon terminal

6. Terminal buttons

7. Dendrites

8. Axon

9. Schwann's cells

How is a message carried by the neurone?

- Ions such as sodium, potassium, chlorine and calcium arise in certain quantities

- When voltage outside and inside differ, the action potential is sent

- AP travels into the axons

- Releases the neurotransmitter

Synaptic transmission

How a message is carried by a neurone by action potential

How is a synaptic transmission generated?

1. Electrical impulse down the axon triggers release of neurotransmitters from axon terminals.

2. Released into synaptic gap to be picked up by the receptors on dendrites or to be taken up again for re-use

Pre-synaptic neurone

Neurone sending the message

Post-synaptic neurone

Receiving neurone

Neurotransmitters in synaptic transmission

- When AP reaches axon terminal, calcium channels open, flooding terminal button with calcium ions

- Vesicles release neurotransmitter

- Vesicles fuse with the membrane

Receptors in synaptic transmission

- Designed to bind to a specific neurotransmitter

- When detecting the neurotransmitter, it will be absorbed by the post-synaptic neurone

- Any not absorbed will be destroyed or reabsorbed by pre-synaptic neurone

Function of neurotransmitters

Chemical messengers that act between neurones in the brain. Allows the brain to process thoughts and memories.

4 common neurotransmitters

- Acetylcholine

- Noradrenaline

- Dopamine

- Serotonin

Acetylcholine

Stimulates muscle contractions, key function in motor control and movement. Memory, attention and alertness. Expressions of anger and sexuality.

Noradrenaline

Mood control, sleeping, dreaming and learning.

Dopamine

Posture and control of movement. Reinforcement in learning, and dependency such as addictions. Hormonal regulation, such as menstrual cycle.

Serotonin

Mood control, particularly limbic system. Feeling pain, sleep, regulating body temperature and hunger.

The brain is in two halves, called...

Hemispheres, which is lateralisaion.

Corpus callosum

Section that joins the two hemispheres

Cortex

Outer layer of the brain

Pre-frontal cortex

- Has connections with parts of the brain relating to neurotransmitters, such as dopamine and serotonin

- Regulating emotions, so aggression comes from LACK of regulation or control over behaviour

Orbitofrontal cortex

Accepting delayed gratification and deferring rewards

Ventromedial cortex

Experience of emotions.

Lateral prefrontal cortex

Making choices in behaviour by letting us see options.

What are the differences between the left and right hemisphere pre frontal cortex?

Left hemisphere involved in positive emotions and right hemisphere with negative emotions.

Prefrontal cortex role in aggression

Damage to prefrontal cortex:

- Focus on the present

- Not be able to plan long term

- Wanting immediate rewards

- Unable to control aggressive reactions

- Raine et al (1998) emotional impulsive aggression had low prefrontal cortex functioning

Amygdala

- Limbic system

- Self-preservation, flight/fight response

- Centre for emotions and motivation

- Combines all sensory modality to give an instinctive feeling or reaction

- Identifying threat

Animal studies involving amygdala

If amygdala is stimulated using electrical current, the animal shows aggression. If amygdala is removed, animal becomes passive and unresponsive and doesn't respond to fear.

Hypothalamus

- Limbic system

- Maintain homeostasis - regulating hunger, thirst and response to anger, agression

- Regulating hormones used to signal between organs and tissue

- Hormones regulating sexual function, testosterone production

Recreational drug

Drugs taken for pleasure

Examples of recreational drugs

Cocaine, heroin, cannabis and ecstasy

Psychoactive drug

Drugs that have an effect on the CNS

Specific mode of action

Act in a specific way in the synapse

Reward pathway in the brain

Pleasure centre, where pleasure seems to be so desired that the animal will continue to behave in such a manner that the pleasure received. The desire for pleasure over-rides other drives

Effects of nicotine in the synapse

- Release more neurotransmitter in response to an impulse

- Increases number of impulses

- More dopamine in the reward system

What is the long term effect of nicotine in the synapse?

- Binding over time affects receptors, decreases dopamine receptors

- Change in the shape of the cell

- Without nicotine, more dopamine is required to stimulate the post-synaptic neurone to a 'normal' level

Desensitisation

When more of a substance is required to achieve the same response, leading to addiction.

Effects of cocaine in the synapse

- Blocks reuptake

- More neurotransmitter (dopamine) in the synapse

- Over-stimulation at the post-synaptic receptors

What are the long-term effects of cocaine in the synapse?

- Dopamine receptors become damaged

- Become fewer

- Desensitisation

- Addiction

Effects of cannabis in the synapse

- Binds to cannabinoid (CB1) receptors

- Blocks their activity

- Can affect GABAergic neurones and stop them from inhibiting dopamine production in the reward system

- Excess dopamine, gives 'high'

How can cannabis affect memory function?

- Binds to cannabinoid receptors, blocking them

- Less activity in neurones in the hippocampus

- Making memories can be affected

What is a hormone?

A chemical produced by the body that sends messaged to organs of the body via the bloodstream.

How is testosterone production controlled?

Hypothalamus and pituitary gland control how much testosterone the testes produce and secrete. Hypothalamus sends a signal to pituitary gland to release gonadotrophic substances.

How does testosterone lead to aggression?

Anti-natal exposure to testosterone has an effect on the developing brain, leading to increased spatial ability and (possibly) competitive aggression

Beeman (1947)

Castrated male mice had reduced aggression. Later, injected the mice with testosterone which re-established aggression.

Dabbs (1987)

- Measured levels of testosterone in the saliva of 89 male prisoners involved in violent/ non-violent crime

- Level of testosterone was higher in those who had been involved in violent crimes

- Higher levels of testosterone were also rated by peers as being tough (correlational)

Serotonin explanation for aggression

- Low levels of serotonin being indicated by low levels of metabolites

- People who engage in aggressive behaviour and have poor levels of control have low levels of metabolites

Mann (1990)

People given a drug that lowers levels of serotonin were more aggressive (measured by questionnaire)

Evolution

How inherited characteristics in organisms evolve from generation to generation.

Survival of the fittest

Those who are more adapted to the environment survive, and they pass on those genes to their offspring to aid survival

Natural selection

The way some characteristics may aid survival over other characterisitcs