Biological appraoch

Believes that behaviour can be explained in terms of inherited characteristics (genes) as well as other physiological factors (e.g. hormonwa, chemicals in brain).

All behaviours can be explained at the level of functioning of our biological system.

Strands:

1. Physiological approach- all behaviour is due to functioning of internal body parts e.g. brain, nervous systems, hormones and chemicals.

2. Nativist approach- behaviour’s inherited (passed down through genes from one generation to the next).

3. Medical model- treatment of psychological disorders based on same principles used to treat physical diseases (argument-psychological problems ultimately have physical cause and can be treated using medical methods).

What are the three assumptions?

1. Evolutionary influences.

2. Localisation of brain function.

3. Neurotransmitters.

• Evolve means to change over time. Evolution explains how human mind/behaviour have changed over millions of years so they’re adapted to demands of our individual environments.

Notion of adaptiveness based on: Theory of natural selection- Darwin.

• Idea that any genetically determined behaviour that enhances an individual's chance of survival and reproduction will be naturally selected  i.e. genes passed onto next generation.

• Takes place at level of genes i.e. altruistic behaviour (parents risk lives to save offspring) enhances survival of that individual's gene pool.

Key concept: Environment of evolutionary adaptiveness (EEA).

• Environment which species is adapted and the selective pressures that existed at that time.

• Evolutionary psychologists don’t assume that all forms of behaviour are adaptive-only ones that will ensure survival in environment.

• For humans, most recent period of evolutionary change was 2 million years ago when humans moved from forest life to developing savannahs in Africa.

• Can explain why humans have large brains relative to their body size-theory proposes that brain evolved in response to complex social organisation of our species (those humans with particular abilities more likely to survive e.g. those better at forming alliances/relationships more likely to survive in complex social world therefore genes for such behaviours are the ones that are passed on).

• Principle: certain areas of brain have different functions.

• Cerebral cortex covers brain and area of brain responsible for higher order cognitive functions.

Four lobes:

• Cerebral cortex divided into 4 regions:

• frontal (creative,thinking,personalities.)

• parietal (sense e.g. temperature,touch,pain).

• temporal (memory processing and processing auditory info).

• occipital (visual and receiving info directly from eyes).

Localisation of language:

• Specific areas of brain linked to language.

• 19th century, French neurosurgeon Paul Broca studied 8 patients with language problems. Examined brains after death and found had damage to specific areas of left hemispheres.

• Area now called Broca's area: associated with speech production

• ^located in posterior portion of frontal lobe.

• Carl Wernicke (German neurologist) discovered another area of brain involved in understanding language.

• Area now named Wernicke's area: Posterior portion of left temporal lobe (patients could speak but unable to understand language)

• Neurons: electrically excitable cells that form basis of nervous system.

• Nervous system flexibility: enhanced by having branches at end of neuron (dendrites) so each neuron connects with many others.

• One neuron communicates with another neuron at a synapse (message relayed by chemical messengers-neurotransmitters). Neurotransmitters released from presynaptic vesicles in one neuron (stimulate or inhibit receptors in other neuron). Synaptic cleft/gap is about 2 nm (nanometres) wide.

Neurotransmitters and mental health:

• Significant role e.g. serotonin plays role in mood, sleep, appetite. Too little serotonin found in people suffering from depression. Some antidepressant medications work by increasing availability of serotonin at postsynaptic receptor sites.

• High levels of neurotransmitter dopamine been associated with symptoms of schizophrenia. This supported by fact drugs that block dopamine activity reduce schizophrenic symptoms.

Evolutionary theory

• Proposes relationships form with individuals who posses certain traits.

• Traits that enhance successful reproduction are naturally selected.

• However, males and females experience different selective pressures.

• Males- do well to mate frequently and select women who’re more fertile and healthy (smooth skin, glossy hair, red lips,thin waist=physical attractiveness).

• Females-seek signs of fertility and healthiness but more concerned on who can provide resources need for offspring to survive (food, shelter).

• Evolutionary processes can be seen in parental investment theory (Trivers, 1972) which offers explanation about why certain relationships are formed.

• E.g. between young women and older men.

• Accordings to PIT as female mammals invest more in their offspring (carry baby) they must be choosier in finding partner so seek out male that can provide most resources.

Neurotransmitters

• Chemicals in brain powerful effect on emotions, influences perceptions of others e.g. those who we may enter into relationships with.

• E.g. Dopamine-pleasure seekings/reward-driven behaviour, so setting goal of finding partner and being driven to achieve this, will give us a ‘hit’ of dopamine. (explains why humans driven to form relationships-give us ‘natural high’).

• Oxytocin-hormone linked to human bonding/increasing trust and loyalty and high levels of oxytocin have been linked to romantic attachment; lack of physical contact with partners reduces level of oxytocin, leading to feelings of longing to bond with one's partner again.

• Offer another explanation to forming relationships, specifically romantic ones as we have a natural chemical drive to bond with others.

Example: Explaining formation of sibling relationships

• In addition to natural selection there’s kin selection.

• Traits that enhance the survival of those who have similar genes are also selected to promise survival of our groups genes.

• We have natural incentive to look after our siblings and to invest time and energy etc unto ensuring they’re protected and healthy.

First assumption: psychological disorders like depression, anxiety and schizophrenia have a physiological cause.

• Therapy: medical model (based on view that mental illnesses are like physical illnesses-have physical cause characterised by clusters of symptoms (syndromes) so can be treated physical way.MM recommends patient should be treated for their mental illness through direct manipulation of their physical body processes e.g. drug therapy.

Second assumption: changes in brain's neurotransmitter systems will affect our mood, feelings, perceptions and behaviour.

• Therefore, advocates of biological approach would suggest psychotherapeutic drugs can be used to alter action of neurotransmitters and treat mental disorders.Generally, drug therapy operates by increasing/blocking action of neurotransmitters in brain, turns influence of our emotions, thoughts and actions.

Third assumption: localisation of brain function; drugs target specific regions of brain which are involved in psychological disorder. e.g. the limbic system regulates emotions. and disturbances in this part of brain may affect mood.

What are the three main types of psychoactive drugs?

1. Antipsychotics.

2. Antidepressants.

3. Antianxiety.

Antipsychotic drugs

• Treats psychotic mental disorders like schizophrenia.

• Patient with this has last touch with reality and has little insight into their conditions.

• Conventional antipsychotics used primarily to combat positive symptoms of schizophrenia (e.g. delusions and hallucinations).

• These drugs block action of neurotransmitters dopamine in brain by binding to (not stimulating) dopamine receptors.

• Atypical antipsychotic drugs (Clozaril) acts by only temporarily occupying dopamine receptors and rapidly dissociating to allow normal dopamine transmission.

• Explains why AAD have lower levels of side effects (tardive dyskinesia-involuntary movements of mouth and tongue) compared with conventional antipsychotics.

Antidepressant drugs

• Depression is thought to be due to insufficient amounts of neurotransmitters like serotonin being produced in the nerve endings (synapse).

• In normal brains, neurotransmitters are constantly being released from nerve endings, stimulating neighbouring neurons.To terminate their action, neurotransmitters are reabsorbed into nerve endings and are broken down by enzyme.

• Antidepressants work by reducing rate of reabsorption/blocking enzyme that breaks down the neurotransmitters.

• Both of these mechanisms increase amount of neurotransmitters available to excite neighbouring cells. Most commonly prescribed antidepressant drugs are selective serotonin reuptake inhibitors (SSRIs) like Prozac.

• Work by blocking transporter mechanism that absorbs serotonin into presynaptic cell after it has fired. As a result, more of the serotonin is left in the synapse, prolonging its activity and making transmission of next impulse easier.

Antianxiety drugs

• Group of drugs most commonly used to treat anxiety and stress are benzodiazepines (BZs).

• They’re sold under various trade names like Librium and Valium.

• Bzs slow down activity of central nervous system by enhancing activity of GABA (biochemical substance/neurotransmitter) that's the body's natural form of anxiety relief.

• Beta-blockers (BBs) used to reduce anxiety.

• BBs reduce activity of adrenaline and noradrenaline, which are part of the response to stress.

• BBs bind to receptors on cells of heart/other body parts that are usually stimulated during sympathetic arousal.

Blocking receptors=harder to stimulate cells in this part of body so heart beats slower and with less force, and blocked vessels don't contract easily. Results in fall of blood pressure so less stress on heart. Person feels calmer and less anxious.

Drugs versus placebo

• Randomised control trial is used to compare effectiveness of drug versus a placebo (substance that has no pharmacological value but controls for belief that ill you’re taking will affect you).

• Soomro et al (2008) reviewed 17 studies of the use of SSRIs with OCD (has a component of depression) patients and found them to be more effective than placebos in reducing symptoms of OCD up to three months after treatment i.e. short term.

• Study highlighting superiority of drugs compared with placebos is Kahn et al (1986) followed 250 patients over 8 weeks and found BZs to be significantly superior to placebos.

• However, one of issues regarding evaluation of treatment is that most studies are only of 3 or 4 months duration so little long term data exists (Koran et al 2007)

Side effects

• SSRIs: nausea,headaches and insomnia. (Soomro et al 2008) These may not seem that terrible but often are enough to make a person prefer not to take the drug.

• Tricyclic antidepressants: hallucinations and irregular heartbeat (more side effects than SSRI so more likely to be used in cases where SSRIs aren’t effective.

Symptoms not cause

• Common criticism is that while drugs may be effective in treating symptoms of psychological disorders, this therapy does not address the underlying cause(s).

• e.g. if a person is suffering depression in adulthood because of serious childhood trauma, than antidepressants may provide an effective short-term solution for individual, but in long term disorder wont be dealt with leading to ‘revolving door syndrome’ where patient is back and forth to their doctor as disorder never cured.

Comparison with other treatments

• Relative to other treatments (e.g. psychotherapy), drug therapy is cheap from the patient- in UK prescribed on NHS.

• Practitioner has to invest less time in patient because only meet every couple of months after initial consultation to discuss whether drugs having positive effect/making progress.

• Therefore, this type of therapy is efficient and easy to administer compared to other forms of therapy.

Use of placebos

• Studying effectiveness of drugs- fundamental research ethic is that no patient should be given treatment known to be inferior. 

• If effective treatments exist, should be used as control conditions when new treatments are tested. Substituting placebo for an effective treatment doesn’t satisfy duty as exposes individuals to treatment known to be inferior.

Patient information

• Valid consent/lack of it.Patients find it difficult to remember all facts relating to side effects/not in frame of mind to digest info so true valid consent is an illusion.

• Medical professionals may withhold some info about drugs e.g. not fully explain pharmacological benefits of drugs are slim.

• Some medical professionals may exaggerate the benefits of taking medication and may fail to inform patient of other therapeutic options due to ‘quick fix’ nature of drug therapy.

Methodology

• Quasi-experiment. Matched pairs design. IV: NGRI and DV: Brain difference.

Participants:

• Murderers (experimental group). 41 murderers (39 men 2 women).

• Mean age: 34.3 years.

• All charged with murder/manslaughter and all pleaded NOT guilty by reason of insanity (NGRI)/incompetence to stand trial.

• Referred to University of California for examination to obtain proof of their diminished capacity.

• Reasons for referral were that they had some form of mental impairment as shown in the table:

Mental Disorder                                                            Number

Schizophrenia                                                                6

History of head injury/organic brain damage                      23

History of psychoactive drug abuse                                   3

Affective disorder                                                            2

Epilepsy                                                                         2

History of hyperactivity and learning disability                     3

Personality disorder                                                         2

The participants were instructed to be medication free, which was checked with a urine scan, for two weeks prior to brain scanning.

Control group:

• Formed by matching each murderer with a normal individual of the same sex and age.

• The six schizophrenics were matched with six schizophrenia from a mental hospital.

• The other controls had no history of psychiatric illness, nor was there a history of psychiatric illness in any close relatives, and no significant physical illness.

• None were taking medication.

• Opportunity sampling. PET scan used to study active brain.

• All participants given an injection of a ‘tracer’ (fluorodeoxyglucose/FDG). This tracer is taken up by active areas of the brain and thus was possible to compare brains of NGRI and control groups.

• All participants asked to do a continuous performance task (CPT). This task specifically aimed to activate the target areas of the brain so the investigators could see how the different areas functioned.

1. Participants were given a chance to practise the CPT before receiving the FDG injection.

2. 30 seconds before the FDG injection participants started the CPT so that the initial task novelty wouldn't be FDG labelled.

3. 32 minutes after FDG injection a PET scan was done of each participant. 10 horizontal slices (pictures) of their brain were recorded using the cortical peel and box techniques. The article provides precise details of scanning techniques so that the study could be replicated.

Brain differences: The study found reduced activity in the brain of BGRI participants in areas previously linked to violence: prefrontal cortex, left angular gyrus, corpus callosum, in the left hemisphere only there was reduced activity in the amygdala, thalamus and hippocampus.

The study found increased activity in the brain of BGRI participants in areas not previously linked to violence: cerebellum, in the right hemisphere there was increased activity in the amygdala, thalamus and hippocampus.

The study found no difference between NGRI group and controls in areas not previously linked to violence:caudate, putamen, globus pallidus, midbrain.

In summary, murderers had:

• Reduced activity (i.e. reduced glucose metabolism) in some areas, notably the areas previously linked to violence.

• Abnormal asymmetriesreduced activity on left side of brain, greater activity on the right. This applies to some of the areas identified in the hypothesis as being linked to violence (the amygdala, thalamus and hippocampus).

• No differences in many brain structures, notably structures associated with mental illness but not violence.

Performance on CPT: Both groups performed similarly on the continuous performance task. Therefore any observes brain differences were not related to task performance.

Other differences not controlled for: Some differences between the NGRI group and control group were noted-

• Handedness: 6 murderers left handed but in fact has less amygdala and higher medial prefrontal activity than right-handed murders.

• Ethnicity: 14 murders were non-white but a comparison between them and white murderers showed no significant difference in brain activity.

• Head injury: 23 murderers had a history of head injury, but they did not differ from murders with no history of brain injury.

• Past research (animal and human studies) has identified links between areas of the brain and aggression as shown in the table below. These findings are supported by this study.

• Taken together these findings provide preliminary evidence that murderers pleading NGRI have different brain functioning to normal individuals.

• However, neural processes underlying violence are complex and cannot be reduced to a single brain mechanism. Violent behaviour can probably best be explained by the disruption of a network of interactions brain mechanisms rather than any single structure.

• Such disruption would not cause violent behavior but would predispose an individual of violent behaviour.

Confounding variables: The study was carefully designed involving a large sample and matched controls. However, Raine et al. acknowledged that head injury and IQ have not been ruled out as contributory factors.

Warning:

Raine et al. emphasise that it is important to recognise what these results do not demonstrate.

1. Results don’t show violent behaviour is determined by biology alone; clearly social, psychological, cultural and situational factors play important roles in predisposition to violence.

2. Results don’t show murders pleading NGRI aren’t responsible for their actions nor that PET can be used as a means of diagnosing violent individuals.

3. Results don’t show brain dysfunction causes violence. It may be brain dysfunction is an effect of violence.

4. Results don’t show violence can be explained by results; results relate only to criminal behaviour.

Nevertheless the findings do suggest a link between brain dysfunction and a predisposition towards violence in this specific group (BGRI murderers) which should be further investigated.

 Brain structure :Limbic system (prefrontal cortex,amygdala, hippocampus and thalamus).

Associated behaviours found in past research: Emotion. Learning, memory and attention; abnormalities in their functioning may result in reduced sensitivity to conditioning.

Might explaing: Abnormal emotional responses.Failure of violent offenders to learn from experience.

Brain structure: Prefrontal cortex

Associated behaviours found in past research: Deficit linked to impulsivity, loss of control, immaturity, and inability to modify behaviour. All of these are associated with increased aggressive behaviour.

Might explain: Aggressive behaviour.

Brain structure: Amygdala

Associated behaviours found in past research: Aggressive behaviour in animals and humans. The destruction of the amygdala in animals results in lack of fear.

Might explain: Fearlessness associated with violent activity.

Brain structure: Hippocampus

Associated behaviours found in past research:Modulates aggression in cats and together with the prefrontal cortex may be responsible for inhibiting aggressive behaviour.

Might explain: Lack of inhibition of aggression.

Brain structure: Angular gyrus

Associated behaviours found in past research:Damage to the left’ deficits in verbal and arithmetic abilities.

Might explain: Low verbal IQs and poor school performance of violent offenders, which might predispose them to a life of crime.

Brain structure: Corpus callosum

Associated behaviours found in past research: Dysfunction related to a predisposition to violence and poor transfer of information between hemispheres.

Might explain: Reduced processing of linguistic information that has been  found in violent groups.

Brain structure: Right hemisphere

Associated behaviours found in past research: Dominance of right hemisphere: less regulation by left hemisphere inhibitory processes, negative emotions, inappropriate emotional expression.

Might explain: Lack of control over expressing violence.

Quasi- experiment:

• Experiment because there is an IV (NGRI/not) and a DV (activity of brain regions).

• However, IV in this study (criminal status of participant) was an existing condition of the individual, not manipulated by the experimenter.

• So this means it’s a quasi experiment and causal conclusions aren’t justified.

• As Raine et al. point out in their conclusions, the findings don’t show that violent behaviour is determined by biology alone.

• Raine et al. suggests that psychological cultural and situational factors play important roles in predisposition to violence.

• Thus the limitation of the method is that no causal conclusions can be drawn.

• Danger is that readers misinterpret findings and assume criminal behaviour is predestined and inescapable.

Research technique:

• Data collected using PET scans.

• This permits researchers to study brain in a way not possible until recently.

• In past, researchers relied on post-mortem examinations where brain physiology couldn't be linked to behaviour.

• PET scans permit researchers to study detailed regions of brain.

• PET scans enable brain action to be examined, which in this study meant Raine et al. could see how brains of different individuals differed in way they processed info.

The sample:

• Murderers not typical of all violent individuals. This is something Raine et al. acknowledged.

• Findings don’t show that all violent offenders have such brain dysfunctions; study can only draw conclusions about this kind of violent offender- namely an individual with some recognised form of mental impairment.

• So, crime is one of murder and many violent crimes don’t involve murder. Means that conclusions are restricted to a very particular group of people.

• Raine research in the association between criminal behaviour and brain disfunction. E.g. a study by Yang and Raine (2009) was a meta-analysis of 43 imagining studies that considered antisocial and violent behavior. Conclusion:significantly reduced prefrontal activity in antisocial and/or violent individuals.  Findings supported by genetic studies that indicate ‘criminal genes’. One candidate for this is MAOA gene (monoamine oxidase A) causes abnormally high levels of the neurotransmitter dopamine.

• Recent study by Tiihonen et al (2015) analysed genes of 895 Finnish prisoners, found association between this gene and increased likelihood of committing violent crime.

• However, genes are only predisposing factors. Neuroscientist, James Fallon, analysed his own genes and found that he had genetic and brain characteristics of a violent criminal- but he wasn’t one. He suggested that his positive experiences during childhood meant that his potentially criminal tendencies weren’t triggered. This is diathesis-stress explanation- genetic predisposition manifested if certain stressors trigger it, such as a difficult childhood. e.g. Charles Whitman.

Valid consent:

• Participants in this study were murderers who pleaded guilty by reason of insanity. Suggests they may not have been mentally competent to provide valid consent.

• Participants may not have fully understood what they would be required to do. E.g. may have found performance task difficult and this would have potential to lower self esteem, an example of psychological harm.

• Not have realised what would be involved in a PET scan and may have found a distressing experience.

• They may not have fully understood their right to withdraw at any time, especially as they were prisoners. They may have felt they couldn’t simply say they no longer wished to take part.

Socially sensitive research:

• Another important ethical issue is the broader social implications.

• ‘Socially sensitive research’ refers to any research that has consequences for the larger group of which the participants are members.

• E.g. research on drug addiction/homosexuality.

• If research indicates murderers are born rather than made this may have consequences that would be disadvantageous for people with similar brain abnormalities- might be imprisoned without any trial/reference to their social cirunstabces.

• Thus research findings have implications for the prisoners.

• Means that important decisions have to be made about the way such research is conducted and reported.

Scientific approach

• Neurotransmitters and localisation of the brain function i.e. biological systems shows that biological explanations have clear variables that can be measured, tracked and examined. This enables psychologists to conduct scientific research studying these variables. E.g. Research on drug therapy has investigated links between psychoactive drugs and the production of certain neurotransmitters (i.e. dopamine) and linked this to behaviour.

• Psychosurgery involves functionally removing parts of the brain. Such procedures are based on earlier research that has linked areas of the brain to certain behaviours like aggression.

• Raine et al. made use of PET scans to compare 14 areas of the brain in murderers (pleading NGRI) compared with non-murderers.These examples of research are scientific insofar as they fulfil aims of scientific research- to conduct objective, well controlled studies and demonstrate causal relationships.

• Strength is that it leads itself to scientific research that can be used to support biological explanations.

Deterministic approach

• If we know what ‘predetermines’ our behaviour, we are more likely to be able to treat people with abnormal behaviour.

• Psychologists seeks for example, to understand functioning of neurotransmitters on normal and abnormal behaviour.

• e.g. the neurotransmitter dopamine has been linked with mental disorder schizophrenia. Evidence comes from number of sources.

• e.g the drug amphetamine is known to increase levels of dopamine and large doses of the drug can cause symptoms associated with schizophrenia e.g. hallucinations.

• Second line of evidence comes from drugs that are used to treat schizophrenia (antipsychotics) which reduce symptoms and known to reduce dopamine levels suggesting high levels of dopamine are causing these symptoms.

• Similar research conducted with psychosurgery. e.g brain scans have shown that certain areas of the brain are more active than others in patients with OCD.

• (Determinst)

• The cingulotomy (form of psychosurgery) is therefore designed functionally to sever these areas in order to reduce symptoms of OCD.

• Research suggests OCD is caused by activity in these areas of the brain-determinist explanation.

• Strength of causal understandings is that they enable us to control our world.

• If we understand prolonged stress causes physical illness, then we can reduce negative effects by treating stress in short term. If mental illness caused by biological factors then we can treat it using biological methods.

so strength is that it is determinist and provides explanations about causes of behaviour and that we can use such understanding to improve people's lives.

Successful applications

• Lead to many successful applications. e.g. research into relationship between abnormal levels of neurotransmitters and criminal behaviour has implications for offering pharmacological treatments to criminals, leading to lower recidivism rates and safer societies. 

• e.g. Cherek et al. (2002) showed that males with conduct disorder and criminal behaviour had reduced levels of aggression and impulsivity after a 21 day course of an SSRI antidepressant compared to a control group taking placebos.

• Lead to forms of treatment for mental disorder like drug therapy and psychosurgery.e.g. effectiveness if capsulotomy in treatment of OCD. Cosgrove and Rauch (2001) reported recovery rates of 67% which is reasonably high.

• Drug therapy produces rather mixed results because drugs affect people differently. However, partially popular form of treatment because easy and enables many people with mental disorders to live relatively normal lives outside mental hospitals.e.g. bipolar disorder (manic depression) has been successfully treated with drugs- Viguera et al. (2000) report than more than 60% of bipolar patients improve when taking the drug lithium.

Reductionist approach

• Reduce complex behaviours to a set of simple explanations e.g. reducing experience of stress to the action of hormone adrenaline.

• Reductionism is a part of understanding how systems work, but problem is  we may lose real understanding of the thing we are investigating.

• e.g. suggests that an illness like schizophrenia is basically a complex physical-chemical system that has gone wrong.

• Psychiatrist R.D. Laing (1965) claimed that such an approach ignores experience of distress that goes along with any mental illness so incomplete explanation.

• So, simplified explanation may prevent us reaching a true understanding of target behaviour.

Nature rather than nurture

• Mental illness has multiple causes but approach focuses on just biology (nature) and ignoring life experiences (nurture) and psychological factors like how people think and feel.

• e.g.biological approach to explain schizophrenia is concerned with abnormal levels of certain neurotransmitters rather than how patients feel about their illness.

• Biological approach to treatment therefore is concerned with adjusting abnormal biological systems rather than with talking to patients about how they feel.

Individual differences

• Is nomothetic approach, looking to make generalisations about people and find similarities. Tends to ignore differences between individuals e.g. when stressed some people produce higher levels of adrenaline than others which affects long term effects of stress. Biological research often focuses on just a few individuals and assumes everyone's biological systems behave in the same way.

• Research on biological systems tends to sue male rather than female participants (animals and humans) because female hormone cycles may interfere with biological research. Such research bias could produce erroneous picture of behaviour one with male bias. e.g. Taylor et al. (2000) suggests men react to stress with a ‘fight or flight’ response but women show a ‘tend and befriend’ response.

• Gender difference seen in many species with females responding to stressful conditions by protecting and nurturing their young (‘tend’ response) and by seeking social contact and support from other females (the ‘befriend’ response).

• Difference been attributed to fact that women produce hormone oxytocin when stressed, sometimes called the ‘love hormone’.