Unit 2 Psychology

Central nervous system (CNS)

The CNS consists of the brain and spinal cord. It processes information and coordinates behaviour. The brain interprets sensory information and controls responses while the spinal cord carries messages between the brain and the rest of the body.

Peripheral nervous system (PNS)

The PNS connects the CNS to the rest of the body. It carries sensory information towards the CNS and motor information away from it. The autonomic nervous system controls involuntary functions such as heart rate and digestion.

Structure of a neuron

Neurons are specialised cells which transmit information.

Dendrites receive messages from other neurons. The cell body contains the nucleus.

The axon carries electrical impulses away from the cell body.

The myelin sheath insulates the axon and increases the speed of transmission. Axon terminals release neurotransmitters.

Resting potential and action potential

A resting neuron has a resting membrane potential of approximately -70 millivolts. When stimulation reaches the threshold of approximately -55 millivolts an action potential is triggered. This is an electrical impulse which travels along the axon towards the terminal buttons.

Synaptic transmission

When an electrical impulse reaches the terminal buttons it causes vesicles to release neurotransmitters into the synaptic gap.

Neurotransmitters travel across the gap and bind to specific receptors on the postsynaptic neuron.

This can trigger a new electrical impulse if the threshold is reached.

Termination of synaptic transmission

Neurotransmitters are removed from the synaptic gap when they are broken down by enzymes or reabsorbed by the presynaptic neuron through reuptake.

Reuptake allows neurotransmitters to be reused.

Once neurotransmitters are cleared synaptic transmission ends.

Neurotransmitters and their functions

Noradrenaline is associated with mood and learning.

Dopamine is involved in movement and reinforcement.

Serotonin regulates mood and sleep.

Excitatory and inhibitory neurotransmitters

Excitatory neurotransmitters increase the likelihood of a neuron firing an action potential. Glutamate is an example. Inhibitory neurotransmitters reduce the likelihood of an action potential. GABA is an example and acts as the brain's natural braking system.

Structure of the brain

The cerebral cortex is divided into four lobes.

The frontal lobe is involved in decision-making and behaviour.

The temporal lobe is involved in hearing and memory.

The parietal lobe processes sensory information.

The occipital lobe processes visual information.

The limbic system

A group of structures beneath the temporal lobes involved in emotion and memory.

Amygdala - regulates emotions and aggression

Hippocampus - forms and retrieves memories

Thalamus which relays sensory information

Hypothalamus which regulates hormones and body rhythms

The prefrontal cortex and aggression

The prefrontal cortex is located behind the forehead and helps regulate behaviour and social interaction.

It is involved in decision-making and suppressing aggressive impulses.

Damage can cause irritability and poor impulse control.

The orbitofrontal cortex helps predict the consequences of behaviour.

The amygdala and aggression

Processes emotions and responds to potential threats.

It receives information from the senses and can activate the hypothalamus when a threat is perceived.

If it misinterprets a situation as threatening it may trigger an aggressive response.

Connections with the prefrontal cortex help regulate these responses.

The hypothalamus and hippocampus in aggression

The hypothalamus regulates hormones and the autonomic nervous system.

It can activate the fight-or-flight response and is linked to testosterone regulation.

The hippocampus forms memories which can influence future emotional responses.

It connects with the amygdala and prefrontal cortex.

Hormones and aggression

Testosterone is associated with aggression and competitive behaviour.

The hypothalamus is involved in regulating testosterone.

Cortisol is a stress hormone involved in fear and stress responses.

Hormonal activity may influence aggressive behaviour but does not determine how an individual will act.

Genes and aggression

Genes influence biological characteristics which may contribute to behaviour.

The MAOA gene produces an enzyme which breaks down neurotransmitters such as serotonin and dopamine.

The low-activity MAOA-L variant has been associated with increased aggression particularly following provocation or adverse experiences.

Twin studies and genetic relatedness

Monozygotic twins share approximately 100% of their genes while dizygotic twins share approximately 50%. Researchers compare similarities in aggressive behaviour between the two types of twins. Greater similarity between MZ twins may suggest a genetic influence although shared environments can also affect behaviour.

Types of body rhythms

Circadian rhythms last approximately 24 hours such as the sleep-wake cycle.

Ultradian rhythms occur within a 24-hour period such as the stages of sleep.

Infradian rhythms last longer than 24 hours such as the menstrual cycle.

Circannual rhythms occur over approximately one year.

Internal pacemakers and external zeitgebers

Internal pacemakers are biological mechanisms which regulate body rhythms.

External zeitgebers are environmental cues which help synchronise these rhythms.

Light is the main external zeitgeber for the sleep-wake cycle. Other cues include exercise and mealtimes.

The suprachiasmatic nucleus (SCN)

The SCN is an internal pacemaker located in the hypothalamus. It regulates the circadian sleep-wake cycle by responding to information about light received from the eyes. It communicates with the pineal gland and helps control melatonin production.

Melatonin and the sleep-wake cycle

Melatonin is a hormone produced by the pineal gland.

Darkness increases melatonin production which promotes sleepiness.

Light reduces melatonin production and encourages wakefulness. Changes in light exposure can therefore affect the timing of the sleep-wake cycle.

Disruption of circadian rhythms

The sleep-wake cycle can be disrupted by shift work and travelling across time zones. Artificial light from electronic devices can also interfere with melatonin production. Disruption may cause tiredness and reduced concentration. Exposure to natural daylight and carefully timed artificial light can help regulate the body clock.

Infradian rhythms and the menstrual cycle

The menstrual cycle is an infradian rhythm lasting approximately 28 days. It involves recurring hormonal changes which prepare the body for pregnancy. If an egg is not fertilised the uterine lining is shed during menstruation and the cycle begins again.

Hormonal regulation of the menstrual cycle

The hypothalamus releases gonadotropin-releasing hormone which stimulates the pituitary gland. The pituitary releases FSH which stimulates egg development and oestrogen production. LH triggers ovulation. Progesterone is released after ovulation to prepare the uterine lining for implantation.

Hormones and mood during the menstrual cycle

Changes in oestrogen and progesterone can influence mood and behaviour. Premenstrual syndrome can involve irritability and mood swings before menstruation. Some individuals experience more severe symptoms including depression. Hormonal changes can also affect attention and memory.

Seasonal affective disorder (SAD)

A mood disorder involving episodes of depression during autumn and winter. Symptoms can include low mood and tiredness as well as oversleeping and reduced motivation. It is associated with reduced exposure to daylight which can disrupt the circadian rhythm.

Causes and treatment of SAD

Reduced daylight can increase melatonin production and contribute to tiredness.

Low light can also reduce serotonin activity which is associated with mood regulation.

Light therapy involves exposure to bright artificial light to help regulate the biological clock and improve symptoms.

Hoefelmann et al. (2006)

Investigated sleep quality and lifestyle factors among 989 Brazilian students attending night classes.

Questionnaires were completed initially and repeated nine months later.

Initially 45.7% reported poor sleep quality and 76.7% slept under eight hours.

Some lifestyle factors were associated with sleep in the initial analysis but these relationships were not confirmed in the prospective analysis.

Evaluation of Hoefelmann et al. (2006)

The study used self-report questionnaires which may reduce validity because participants could inaccurately report their sleep and lifestyle.

More than half of the original participants were lost at follow-up.

Only night-class students were sampled which limits generalisability. However the research has real-world value because it highlights sleep problems among students.

Correlational research

Correlational research investigates the relationship between two measured variables without manipulating them.

The variables are called co-variables.

Researchers use correlations to identify patterns and relationships but cannot establish that one variable causes another.

Types of correlation

A positive correlation occurs when both co-variables increase together.

A negative correlation occurs when one co-variable increases while the other decreases.

Zero correlation means there is no clear relationship between the variables.

Scatter diagrams and correlation coefficients

Scatter diagrams display the relationship between two co-variables using plotted points. An upward pattern indicates positive correlation while a downward pattern indicates negative correlation.

Correlation coefficients range from -1 to +1. Values closer to either extreme indicate a stronger relationship.

Evaluating correlational research

Correlations cannot establish cause and effect because researchers do not manipulate variables.

The direction of the relationship may be unclear and a third variable may influence both co-variables. However correlations are useful when manipulating variables would be unethical or impractical.

Spearman's rank correlation test

An inferential statistical test used to investigate whether there is a significant correlation between two co-variables.

Interpreting Spearman's rank

The calculated value is compared with a critical value from a statistical table. If the calculated value equals or exceeds the critical value the result is significant and the null hypothesis is rejected. A significance level of p ≤ 0.05 means there is a 5% or lower probability that the result occurred by chance.

Brain-scanning techniques

CAT scans use X-rays to produce images of brain structure. PET scans use radioactive tracers to measure metabolic activity in the brain. fMRI scans measure changes in blood oxygen levels to identify active brain areas. These techniques allow researchers to investigate links between brain activity and behaviour.

Evaluation of brain-scanning techniques

CAT scans provide structural information but involve exposure to radiation.

PET scans provide information about metabolic activity but require radioactive tracers.

fMRI provides detailed functional images without radioactive tracers but can be expensive and requires participants to remain still.

Raine et al. (1997)

Investigated brain activity in 41 murderers pleading not guilty by reason of insanity and 41 matched controls. Participants completed a continuous performance task while a radioactive glucose tracer was used. PET scans measured metabolic activity in different brain areas. Murderers showed reduced activity in the prefrontal cortex and differences in other brain regions.

Raine et al. (1997) findings and evaluation

The murderers showed lower activity in the prefrontal cortex and parietal areas as well as higher activity in the occipital lobe.

They also showed asymmetrical amygdala activity with lower activity on the left and higher activity on the right.

The findings support a relationship between brain functioning and aggression but the correlational design cannot establish causation.

Brendgen et al. (2005)

Investigated genetic and environmental influences on physical and social aggression using twins from the Quebec Newborn Twin Study.

Complete data were collected from 234 twin pairs.

The researchers used teacher ratings and peer ratings to measure aggression when the children were six years old.

Brendgen et al. (2005) findings and evaluation

Physical aggression ratings were more strongly correlated in MZ twins than in DZ twins suggesting a genetic influence.

Social aggression ratings were roughly equally correlated in both types of twins suggesting a stronger environmental influence.

The use of teacher and peer ratings strengthened measurement but the sample was limited to six-year-old children.

McDermott et al. (2008)

Investigated whether the MAOA gene predicted behavioural aggression following provocation.

The sample consisted of 78 male students with different levels of MAOA activity.

Participants took part in a game involving an opponent who could steal their earnings.

Retaliation was measured by the amount of hot sauce allocated to the opponent.

McDermott et al. (2008) findings and evaluation

Following high provocation 44% of participants with MAOA-L allocated the maximum amount of hot sauce compared with 19% of participants with MAOA-H.

This suggests that low MAOA activity may be associated with increased aggression following provocation.

The study supports a gene-environment interaction but its all-male student sample limits generalisability.

Psychoanalysis

Developed by Freud and based on the idea that unconscious thoughts and conflicts influence behaviour.

It aims to uncover unconscious material and help individuals develop insight into their feelings and behaviour. It is generally non-directive and allows clients to explore their thoughts.

Psychoanalytic techniques

Free association involves clients saying whatever comes into their mind without filtering their thoughts. Dream analysis involves interpreting the content of dreams to identify unconscious conflicts. Both techniques aim to reveal thoughts and feelings which may not be consciously recognised.

Transference and countertransference

Transference occurs when a client transfers feelings about an important person from their past onto the therapist.

Countertransference occurs when the therapist transfers their own feelings onto the client. Recognising these processes can help reveal unconscious relationship patterns.

Object relations theory

The object relations school focuses on the importance of early relationships with caregivers.

These relationships shape internal representations of other people and influence later relationships.

Early experiences help form an internal working model which affects how individuals understand and respond to others.

Evaluation of psychoanalysis

Psychoanalytic interpretations can be subjective because different therapists may interpret the same behaviour differently.

Treatment can also be expensive and take many years.

Eysenck's 1962 review suggested that recovery rates were not necessarily higher with psychoanalysis than without treatment.

Observational research and sampling

Observational research involves watching and recording behaviour without manipulating an independent variable. Event sampling records every occurrence of a particular behaviour. Time sampling records behaviour at set intervals. Tallying records how frequently a behaviour occurs.

Types and evaluation of observations

Structured observations use predetermined behavioural categories while naturalistic observations take place in real-life settings.

Overt observations involve informed participants while covert observations do not.

Structured methods can improve reliability but naturalistic methods may have greater ecological validity.

Qualitative data and thematic analysis

Qualitative data consists of descriptive information such as words and observations.

Thematic analysis identifies repeated patterns and themes within this data.