Outline and evaluate cultural influences of gender development (8+16)

Cross-cultural similarities appear within gender roles for example through division of labour. Food preparation and childcare is seen to be predominantly carried out by women while men would hunt and provide resources. In some some societies these 'female' roles will be shared, however have not be found to be predominantly carried out by males. 

Murdoch and Provest found strong indications of consistent cross-cultural masculine and feminine activities. For example, smelting of ores, metal work and lumbering were 100% or nearly 100% predominantly masculine activities whereas laundering, cooking and fetching water were only carried out by 10% of males. This provides evidence towards an evolutionary approach as similar activities were seen across cultures suggesting an evolutionary basis. This study used a 'Standard Cross cultural sample' therefore the sample raises issues of reliability due to the relevance of each of the categories within a society. For example someone may be unmarried in one society due to lack of partners and in another due to choice. Such factors are ignored with this study making it reductionist therefore we cannot determine the extent to which findings can be generalised. 

Williams and Best found a high degree of cross cultural agreement between masculine and feminine adjectives. Men were seen as dominant and aggressive and women as nurturing and submissive. This suggests that are universal stereotypes about male and female characteristics. Methodological strengths of the study include it was longitudinal, conducted over 30 years therefore provides the ability to determine a pattern overtime. This provides greater reliability in findings creating support linking towards an evolutionary explanation of gender role as similar gendered ideas were displayed. Methodological problems occur as participants may have shown demand characteristics and expected to attribute certain words to male or female and therefore doe not truly represent what the students thought themselves. Resulting in the study being potentially less reliable and less generalisable. However, a large sample was used of over 2800 students form 30 different countries. Therefore it could be argued that findings may have sufficient validity and reliability which could be used to justify the conclusions drawn. Overall supporting an evolutionary cause of gender roles rather than a cultural one. 

A positive of cross-cultural research suggests it satisfies the demand to be both emic and etic. It is etic as it is able to understand cultures with that cultures own terms and is etic as researchers can leave their own cultural biases and view cultures objectively. However, as many studies were originally based in the US it could be argued they attempt to replicate findings in other countries involving an imposed etic. This assumes that all measures of gender stereotypes are the same across cultures, which is unlikely to be the case. Results gained therefore may lack internal validity and not be a measure of true gender role stereotypes in each culture. 

Both Murdoch and Provost, and, Williams and Best studies suggest gendered characteristics and stereotypes are consistent across cultures and such studies take an evolutionary approach. This is retrospective and attempts to make generalised assumptions with little experimental evidence raising issues of reliability and validity. There is also an issue with such research in measuring exact gender role perceptions as they can change quickly. Therefore conclusions drawn at one period of time will not likely be valid in the future. Also feminists have criticised the evolutionary explanation as an attempt to give gender roles a biological basis to keep females in the traditional subordinate role and draw attention away from the male dominance and patriarchy. If this view continues to be accepted with will be reinforced in each generations further moving away from gender equality. 

However, real world applications from research such as globalisation must be considered. This may cause less cultural differences with masculine and feminine differences being reduced through legislation and equal opportunities, suggesting social influence may be stronger than biological or evolutionary ones. Therefore refuting a biological basis for cultural variations in gender development. 

Outline and evalute social influences of gender development (8+16)

Parents play a major role in social influence in the gender development of their child e.g. naming their child. For example shared gender names such as Alex may lead to less gender typed socialisation. Traditionally minded parents are likely to treat boys and girls differently due to gender. When the child shows gender appropriate behaviour they will likely be rewarded through praise and attention, therefore reinforcing behaviour. The child will also observe parents as being different in appearance and behaviour further influencing gender role development. 

Later on peers also have an influence. Those of the same gender will likely have been raised in a similar way and will show behaviour consistent with the child's gender perceptions. Peers will often provide reinforcement for gender appropriate behaviour and punishment for gender inappropriate behaviour e.g. not including them in games.

Media provides another source of models through television, books, films and toys. Males are likely to be portrayed as independent with interests in e.g. sports, and women portrayed as submissive, in a homemakers roles. Individuals can learn from such behaviours through vicarious reinforcement, as they observe outcomes of different behaviours. This can result in similar behaviour if the possible reward outweighs the possible cost.

Langlois and Downs found father were more disapproving, than mother, of their sons' gender inappropriate behaviour e.g. playing with dolls. A similar pattern was found in peer reinforcement with boys reacting more negatively to gender inappropriate behaviour than girls, possibly due to social influences portraying male behaviour as more desirable. Also supporting that positive reinforcement may influence gendered behaviour. However, issues occur as research used methods of self-report requiring parents to report on their child's behaviour and gender development. Results may have suffered social desirability, with parents trying to portray their children in the best light, therefore results lack internal validity and reliability. Therefore may not represent the actual social influence parents have on gender roles. 

Williams et al observed the introduction of TV into Canadian communities. Communities with the widest range of TV channel access has the strongest sex-typed stereotypes, while having less TV channels resulted in weaker stereotypes. This supports social influences for gender development as through vicarious learning and media exposure this influenced the children's gender views. However, methodological issues occur as questionnaires were used to measure stereotypes. Some questions may have used terms the children did not understand causing them to guess. Therefore do not represent the children's actual views. Also due to the lack of control of extraneous variables in research caused the results to have a lack of internal validity. 

Both Langlois and Downs and William's studies highlight the importance of role models as in both studies it is seen social influences influence development. Whether they come from parents, peers of the media. Models should be positive and show a range of behaviour to help move away from sexist stereotypes. It is difficult to determine the extent of social influence as there is the issue of separating social, cultural and cognitive influences on development. However, research can lead to positive real world applications as if social influence plays a role, the media could be used to display men and women in roles normally associated to the opposite sex, this can help lead to greater equality among the sexes. 

Social influence has be criticised for ignoring the role of biological factors in gender such as influence of prenatal hormone influences e.g. in rough and tumble play. Also this approach is deterministic to suggest children have no choice but to respond to the social influences they receive. Social learning theory provides an alternative to the strict determinism of operant conditioning but could still be seen as not allowing enough room for free will. Therefore due to this a biosocial approach may be more accepted as this takes into consideration social and biological factors in gender development. 

Outline and evaluate gender schema theory (8+16)

Gender schema theory (GST), based on the work Piaget, involves organisation of related concepts regarding gender. GST suggests as we develop, our gender behaviour and awareness develops, as our gender schemas get stronger. According to Trautner gender schemas start to develop at 2 to 3 years old. 

In group and out group schemas can be formed and influenced gender schemas. In group schemas are attitudes and behaviours expected of the childs own gender whereas out group schemas are attitudes expected of the opposite gender. Positive viewing of the in group motivates children to learn more about their own gender and can explain why children disregard information that is not consistent with their own in group schemas. This theory also predicts that gender schemas effect what behaviours are remembered. 

Interaction with the environment through playing with toys and socialising with peers helps develop schemas, which can lead to stereotypes about what toys, clothing and behaviours are suitable for their gender. Adults and peers can also reinforce gender schemas through reward and punishments, for gender appropriate or inappropriate behaviour. 

Martin and Little found children younger than 4 showed no signs of gender stability or constancy. Yet showed strong stereotypes in regards to gender roles. Therefore this provides support for gender schema and refutes Kohlberg's theory, as he suggested constancy must be achieved for gender role behaviour to develop, which is not the case. GST proposes that schemas start to form from around 2 years old, which is a more realistic prediction than Kohlberg's cognitive theory, allowing for individual difference of gender development and does not state everyone experiences the same development at the same age. Also providing overall support towards a more psychological explanation of gender development. It suggests schemas, no matter when they are they are developed, provide the starting point of further gender development placing emphasis onto the nurture side of the nature/nurture debate. 

Eisenberg et al found that 3-4 year olds justified their choice of gender specific toy without referring to gender stereotypes, suggesting a possible evolutionary or biological basis rather than a cognitive one. This provides evidence towards nature rather than nurture. Methodological issues occur with this study as the research sets the agenda with the study, this is often that case within gender schema research, meaning such studies lack external validty and may not reflect behaviour in a real life setting. Also issues within observational studies occur as the children would have known they were being observed therefore may have shown demand characteristics and chosen the toys that they believed they were expected to choose. Therefore the study lacks internal validity as the children did not choose the toys because of their gender schema alone. The study highlights that biological influences may drive gendered behaviour to some extent but also socialisation provides an influence. 

Ethical issues must also be considered in regards to child research. Harm and benefits of research must be carefully considered. Gender research is often based at a developmental level using children is therefore unavoidable. Informed consent must be gained from the child's parents. From research positive real world applications occur as if gender schema and roles can be influences socially, this suggests children can be taught to have non-sexist schemas. This would help towards achieving further gender equality.

Both Martin and Little, and Eisenberg's studies provide evidence towards both a psychological and biological basis from gender role development suggesting the complex interaction of nature and nurture that likely occurs in development. However, issues of such studies also include that are deterministic in suggesting that we have no choice in our behaviour and only act according to schemas.  The role of free will is ignored. Findings are inconclusive and only provide evidence of schemas existing but cannot explain why these gender based attitudes would motivate behaviour. Therefore gender schema will unlikely be able to offer a complete explanation. 

Outline and evaluate Kohlberg's theory of gender development (8+16)

Kohlberg’s theory is based on the cognitive development approach of explaining gender development. This is based on Piaget’s theory. This details that the child is the active learner, and focuses on development, rather than addressing learning of information or specific behaviours. It also proposes development occurs in stage which is thought to be universal.

Stage 1 is gender labelling occurring between ages 1.5 to 3 years old. In this stage children can recognise they are male or female based on appearance. Helping them to form female and meal categories, but knowledge is incomplete. 

Stage 2 is gender stability which normally occurs between 3 to 5 years old. Children realise gender is consistent over time with boys growing into men and girls into women. They may not realise gender is consistent across all situations. 

Stage 3 is gender constancy and is generally thought to develop between 6 to 7 years old, although some argue this develops as late as adolescence, suggested that Kohlberg mistook a phase of gender assertion for full constancy, with children realising gender is permanent. Gender constancy is an understanding that gender is constant across all situations, even if there is a change in appearance, gender remains the same. 

Thompson found two year olds could recognise their own gender correctly 76% of the time. But, children aged 3 were correct 90% of the time supporting Kohlberg's theory of gender labelling as they had an increased ability to recognise own gender when older. Slaby et al's study provides further supporting evidence involving asking children questions to assess their understanding of gender i.e. will you be a mummy or a daddy when you grow up? Results found that children were not able to recognise gender was consistent over time until they reached the age of 3-4, in line with Kohlberg's theory, therefore providing support for it. However, research lacked mundane realism therefore lacks external validity. The children would have been aware they were being assessed therefore may have displayed demand characteristics giving answers they thought the research wanted. Therefore findings may not be representative of the children's true gender development. 

Munroe et al found the theory generalised across culture therefore providing evidence for the universality of the stages. In cross-cultural studies children from different cultures followed the 3 stages, suggesting there may be an evolutionary link in gender development. A criticism of Kohlberg's theory is it suggests gender typical behaviour only occurs once constancy had been achieved but gender schema theory suggests this happens as soon as schemas start to form which, according to Trautner, is around the age of 2-3 years old.

Thompson, Slaby and Munroe's research findings provide supporting evidence of Kohlberg's theory. These stages of development were consistent with findings and supports the idea of the stages being universal. However, from such research the theory may be suggested to be incomplete as not all research found these results. Slaby and Frey found gender consistent appeared younger than Kohlberg's theory predicted, as young as 5 years old. Even in early infancy boys and girls begin to show preferences for their gender related toys which creates doubt on Kohlberg's theory of universal stages of development.

Research into gender development often uses children therefore ethical issues must be considered in regards to child research. Harm and benefits must be carefully considered in deciding whether the research is justifiable. Gender research is often based at a developmental level therefore using children is unavoidable and informed consent from parents must be gained. 

Kohlberg's cognitive approach cannot explain differences in prenatal hormones and how this may affect development. Therefore the biological approach may help to provide a more complete view, taking into account changes before and after birth. Therefore the theory is reductionist as it determines stages and divides complex mental processes into simplified time-allocated phases. Individual differences are not accounted for therefore this does not provide a complete understanding of gender development. 

Outline and evaluate research into gender dysphoria (8+16)

The DMS-5 classifies gender dysphoria as people whose gender at birth is contrary to the one they identify with. This diagnosis is a revising of the DSM-IV which previously classified the disorder as Gender Identity Disorder.

A biological explanation is that dysphoria has an origin in prenatal hormonal abnormalities. This is argued to lead to lower than typical activity levels in boys and high activity levels in girls. A biosocial element is added to the explanation as, it is suggested that less than usually active boys and more than usually active girls will not fit in with peers and their gender group leading to dysphoria.

Another biological approach suggests a mismatch between hormones and genetic sex on individuals. Androgen Insensitivity syndrome (AIS) and congenital adrenal hyperplasia (CAH) may result in intersex individuals due to prenatal surges in hormones causing external genitalia not to match the genetic sex. Resulting in them being mislabelled as the wrong gender. This may then display as gender dysphoria in individual during later life as their biological identity conflicts with their socially assigned gender.

Brain-sex theory proposes transsexual brains may not match their genetic gender. The BSTc in heterosexual men is twice as big as in heterosexual women, containing double the neurons. Zhou et al found male to female transsexuals had the same number of neurons in the BSTc as females. Also the number of neurons in the BSTc of female to male transsexuals was similar to the male range, suggesting a correlational link. Therefore suggesting a biological cause for gender dysphoria. However, correlational results do not indicate cause and effect. It cannot be concluded whether the BSTc caused the dysphoria or was a symptom of it. 

Chung et al noted differences in the BSTc between males and females only developed in adulthood. However, feelings of dysphoria often appeared in early childhood, discrediting brain-sex theory as the BSTc may not be a cause but is a symptom of gender dysphoria. Therefore weakening the argument for a purely biological explanation for gender dysphoria suggesting biological links may be symptoms and not causes.

A psychological explanation could also suggest how dysphoria may develop. It is suggested parents that give their children more attention when behaving in non-gender typical ways, which encourages such behaviour to continue through the processes of operant conditioning. However, such psychosocial approaches have little supporting them as with research it is difficult to isolate a cause. Therefore research lacks reliability and validity. Therefore conclusive supporting evidence cannot be drawn regarding its influence on the development of gender dysphoria. Biological explanations suffer similar issues as the is no clear biological determinant causing the dysphoria. Therefore a biosocial approach may be more appropriate in drawing a more conclusive conclusion to the cause of gender dysphoria.

Theories into gender dysphoria are reductionist and oversimplify a complex disorder being explained through biological or psychological factors. Such explanations cannot explain why individuals with similar traits may not experience the disorder. Therefore a biosocial approach in principle may have an advantage of a purely biological or psychological explanation as it appears that dysphoria is caused by an interaction between the two. However, the extent to which these two factors work together is difficult to determine therefore such an approach has been criticised. 

Socially sensitive issues are raised in research due to possible social implications. If the cause is biological it may help society to be more accepting as it is seen as due to genes and not by choice. If evidence suggests a psychological cause, such individuals may face further discrimination as they are seen to 'choose' this behaviour and deviating from what is socially acceptable. Psychological explanations may also result in those with dysphoria being treated as 'sick' which raises severe ethical issues as gender identity cannot be forced upon individuals. However, through research we can gain wider knowledge of what 'gender' really means.  

Oultine and evaluate the biosocial aproach to gender development (8+16)

The biosocial approach considers an interaction between biological and social factors. For example Money et al proposed that after a biological male or female is born, and labelled as such, gender identity is shaped through social influence. If labelled male they are treated by society in a masculine way, if female treated in a feminising way. Overall, it is suggested that environmental and social factors can override biological sex at birth.

It is proposed that if intersex individuals were mislabelled at birth that child would take on the labelled gender as long as this occurred before the age of 3. For example if a biological female was labelled and treated as a boy, they would label themselves as a boy regardless of biological sex. Therefore the label an individual is given at birth is the most important element, as the theory suggests they will assume that gender identity. 

Wood et al proposed that the biological differences between males and females cause psychological differences to develop as they are brought up in that respective gender role. This leads to gender role assignment e.g. men are stronger therefore viewed as the hunter and women give birth therefore suited to child care. Therefore supporting the biosocial approach as the respective gender roles are supported by biological differences throughout life. 

Money et al's theory has been criticised with evidence from the case study of David Reimer, who after having his penis removed in a botched circumcision, was unsuccessfully raise as a girl. David became deeply depressed and when told the truth reverted back to his biological male gender. This study suggests biological factors override psychological ones. However, this is a single case study and we cannot generalise findings and assume everyone would behave the same. Other confounding variables, such as his identical twin brother, may have shaped his gender development. Therefore the extent to which biological and social factors influence gender development is not entirely clear.

Imperato-McGinley's study of the Batista family reported four biologically male children, born with AIS, being raised as female due to their external genitalia appearing female. During puberty when testosterone release increased, this caused their male genitalia to appear. All the children accepted this change without difficulty, weakening the biosocial approach as findings suggest biological factors override social ones. It is also argued this change was readily accepted as the 'girls' never truly identified with the female role and were expecting to become male, as AIS had been seen in relatives. Providing further support for a biological approach.

Both Money and Imperato-McGinley's studies highlight that the biosocial approach is unable to explain each individuals' gender development. With these studies often it was overriding factors that had appeared to be the main influence. However, the biosocial approach highlights that nature and nurture likely interact, biological sex causes physical differences, which then lead to psychological difference based on they way they are treated in their gender role. But, this is not supported by all . Those of radical social constructivism reject the biosocial approach believing biology in itself is a social construct.

Research has led to real world application of helping towards gender equality. The evolutionary approach is seen as a force against this suggesting sex differences are innate and cannot be changed through altering social context. Whereas if a social approach is taken this suggest that social roles can be changed leading to changes in psychological differences between men and women and greater equality.

The biosocial approach may provide an 'answer' to the nature nurture debate as both are considered in this explanation. However, research may prove one factor overrides another for example social factors are due to our biology and how others perceive us, therefore may take on an overriding role. Also within the studies of David Reimer and the Batista family biology clearly played a strong role with gender identity, therefore weakens a biosocial approach and suggests biology ultimately plays an overriding role. 

Outline and evaluate evolutionary explanations of gender development (8+16)

Evolutionary explanations explain gender roles as forming due to different selective pressures of males and females that provide an adaptive advantage to aid survival and reproduction. This explanation see males as hunters and females as domestic gathers. 

Short-term mating strategies suggest males will compete for the most fertile mates therefore develop their physical strength and aggression in order to do this. They look for youth and physical attractiveness among females as a sign of fertility. Women normally look for long term mates due to their high parental investment. When using short-term mating strategies males have low parental investment as they can impregnate several women is a short period of time with little effort. Women have high parental investment as they have to carry the child for 9 months and raise it, therefore they choose mates with large resources and low risk of abandonment. 

The 'meat sharing' strategy is used to explain why long-term mating strategies developed, and also the male hunter role and the female nurturer/gatherer role. Females have to spend time gestating and nurturing the child therefore cannot hunt. Therefore stay at home and look after a man's children and home. In return he finds food and shares it over an extended period of time.

Buss found women tended to make mate choices based on status and availability of resources and men based choice on youthfulness and good looks. From this it could be concluded that gender differences and preferences are rooted in evolutionary mate selection. Buss suggested these preferences are due to parental investment which differs for each gender. This study used a large sample, 37 cultures were surveyed, followed by an analysis of over 10,000 questionnaire responses. This helped to increase the reliability of findings. However, within methods of self-report demand characterises may have influenced answers. Answers may have be based on their personal life, and the respondents may have also interpreted the questions in their own cultural terms. Therefore the study may lack internal validity in measuring purely evolutionary gender views due to the many extraneous variables that would have likely influenced questionnaire responses. Therefore this study cannot conclusively provide evidence for gender roles being purely evolutionary.

Clark and Hatfield found males were more likely to respond positive to offers that involved sex, supporting the theory males are more likely to use short-term mating strategies supporting an evolutionary explanation for gendered behaviour. However, this study was conducted using a small sample of university students therefore results can only generalise to this age group, providing low external validity. Therefore cannot be used as conclusive support towards an evolutionary explanation of gender development.

Both Buss and Clark and Hatfields' studies found characteristics of male and female gendered behaviour. These characteristics could be argued to provide support towards evolutionary explanations. However, issues occur such as research relies solely on comparative studies providing correctional data. Therefore raises the question of why we should support an evolutionary approach when assumptions cannot be experimentally tested. Such an approach is reductionist as it ignore the role of environmental, cognitive and psychological influences which other research has found to have an influence on us acquiring gender roles.

This approach may also be argues to be deterministic ignoring the role of free will. However, evolutionary psychologists tend to argue free will is adaptive e.g. people have a strong will to mate but choose who to mate with. This has adaptive advantage as we can choose to mate with those with the best possible genes. Further determinism could be argued as the role of social and cultural factors is ignored. Personality may dictate a large part of who we form relationships with, this is not considered, and suggests gender roles are inevitable. Therefore research into this area is socially sensitive as some may view research as further reinforcing evolutionary male sexual aggression and female subservience role. 

Outline and evaluate the role of genes and hormones in gender devleopment (8+16)

Each cell of the body contains 23 chromosomes that carry genes containing genetic instructions on an individuals physical and behavioural traits. The sex chromosome pair is responsible for determining the sex of the child. For example the female pair is XX and males is XY.

During early prenatal development there is no viable genitalia. At 3 months, if the foetus is to develop as male the testes produce testosterone causing male genitalia to develop. However, if male embryos are exposed to too little testosterone, or females exposed to high levels of testosterone this can result in the child being born intersex. Therefore genes and biological factors explain how individuals view their own gender.

Hormones influence brain development and genitalia which may influence gendered behaviour. Male and female hormones influence both genders in different ways. Male hormones 'masculinalise' the brain, female hormones led to better social skills and empathy. If female and prenatally exposed to high levels of male hormones this can explain why some girls develop 'tomboyish' behaviour. Hormones continue to have a role throughout life e.g. increases during puberty. 

Young et al conducted an animal study injecting female monkeys with male hormones, producing female monkeys with male characteristics. Including engaging in more rough and tumble play and were more aggressive. It is suggested this is similar as to how human male hormones affect male brain development making them masculine. Within animal research we are able to gain some understanding of how genes and hormones may affect gendered behaviour, as testing this in humans would be unethical. But, we cannot assume for certain that genes and hormones affect humans in the same way. Ethical issues also arise as some may argue exposing animals to such tests with hormones exposure is cruel and morally wrong. However, such research strengthens a biological cause for development of gendered behaviour.

David Reimer provided support for a biological cause as he was unable to adjust to his newly assigned female gender. Money assumed environmental factors could override biological ones, this proved to be untrue. This case study demonstrates how strong biological factors can override environmental factors in gender development. Additionally, Reimer ended his life through suicide, which is far from typical, which may suggest that the trauma of being raised in his non-biological gender may have caused long-lasting psychological damage. However, this is a single case study therefore findings cannot be generalised and we cannot assume biological factors will always override psychological ones.

Congenital adrenal hyperplasia (CAH) occurs when XX females are exposed to prenatally high levels of male hormones which can result in varying formations of male genitalia causing some to be raised male and some female. Research suggests that gender assigned at birth is accepted by some but not others. Therefore it is reductionist to assume that hormones or genes alone can explain gender development as this is not the case.

Understanding gender development has real world application, seen in the Olympics. Originally genetic sex was the determining factor whether an athlete completed as male or female. But, through further understanding of gender a ruling was put in place meaning genetics was no longer a decisive factor. Individuals, such as genetic males, were only excluded from female event if obviously physically male, leading to greater equality. 

Young' research and the case study of David Reimer linked gender to be largely determined by biological causes such as genes and hormones, suggesting gender identification is largely caused by these factors. However, from CAH studies we see whether the assigned gender is accepted or not varies between individuals making it difficult to determine the main influencing factor. A purely genetic and hormonal approach ignores the role of free will and is deterministic as individuals have the choice of their gender which they may change later on. Therefore highlight that a complex interaction of both nature and nurture would best describe gender development and that a purely biological explanation is too simplistic. 

Outline and evaluate sleep walking as a sleep disorder (8+16)

Sleep walking is a parasomnia in which an individual engages in activities normally characterised by the awake brain. This is most common in childhood, affecting 20% of children and less than 3% of adults. It most commonly occurs during NREM and slow wave sleep (SWS). It is believed to be a disorder related to arousal with EEG recording during sleep walking showing a mixture of delta waves, typical of SWS, but also beta waves, characteristic of the awake brain. Theories propose it occurs when a person in SWS is woken but arousal in the brain is incomplete therefore causing the disorder.

Another explanation suggests sleep walking is a developmental disorder. It is suggesting that the system that normally reduces motor activity in SWS is not sufficiently developed in some children and it also may be underdeveloped in some adults causing the disorder. 

Sleep walking can be explained using the diathesis-stress model which proposes that a genetic vulnerability may be the underlying cause. But, sufficient environmental triggers are needed to trigger the disorder. Other medical disorders such as fever, asthma, seizures, sleep apnoea and psychiatric disorders have been linked to sleep walking suggesting it may be the cause of a symptom of another underlying problem.

Broughton et al found it is ten times more likely for sleep walking to occur if a first degree relative has a history of sleep walking, compared to the general population, supported in twin studies and close family members both showing sleep walking, providing evidence of a genetic link for the disorder. However, sleep walking will not always despite a genetic vulnerability. Therefore environmental factors likely influence sleep walking e.g. stress, alcohol and sleep deprivation have been linked to sleep walking. This provides support for the diathesis-stress model and highlights how nature and nurture may interact causing an individual with a genetic vulnerability yo show the disorder.

Lecendreux et al reported a 50% concordance rate in MZ twins showing sleep walking compared to 10-15% in DZ twins suggesting a genetic link. This also highlights the importance of environmental influences as MZ twins did not have 100% concordance, suggesting the environment plays a mitigating role. MZ twins likely experience similar environmental influences due to them looking similar. This may have an influence on psychological development causing them to develop similar disorders due to being treated similarly by those around them. However, twin studies may lack external validity as twins will experience different environmental factors than the rest of the population therefore results may not be generalisable to the population therefore results may not be generalisable and findings may not explain how others develop sleep walking. 

Understanding sleep walking has real world application. In some cases it has been used as legal defence for murder. Therefore it is important to establish the level of control an individual has while sleep walking. In one case Jules Low attacked and killed his elderly father, citing sleep walking as a defence. He was ultimately acquitted after tests showed he had a tendency to sleep walk. But, it is unclear whether this was the case during the attack. Some may voluntarily expose themselves to risk factors while others may not. Therefore improving our understanding of sleep walking is essential to establish whether individuals can be held responsible for behaviour.

Both Broughton and Lecendreux research focused on the assumption that sleep walking has a biological cause and both can be argued to have found evidence for such an assumption. However, through such research it is suggested environment plays a role too. Explaining sleep walking through purely biological means is reductionis and fails to explain the complex nature of sleep walking that occurs through the interaction of genes and the environment. Also such explanations do not consider the role of free will,therefore argued to be deterministic. However, if certain environmental stressors increase sleep walking occurrence, by controlling environmental factors we can reduce incidents of sleep walking, even with genetic vulnerabilities helping us to gain further understanding of sleep walking as a disorder. 

Outline and evaluate narcolepsy as a sleep disorder (8+16)

Narcolepsy means 'seized by sleepiness', symptoms include; bouts of extreme sleepiness during the day, cataplexy, a loss of muscle tone causing the individual to collapse. These are often brought on by extremes of emotion e.g. excitement or rage. Sleep paralyse may occur which is an inability to move just before falling asleep or waking up. Hypnagogic hallucination may occur when awake making it hard to distinguish between reality and hallucinations. Normally beginning in adolescents or early childhood and may continue throughout life.

One explanation is it is a malfunction in the system that regulates REM sleep. This may explain symptoms such as cataplexy and REM type hallucinations. Cataplexy may be explained through neurons in the medulla, that are normally active during REM sleep, become active while the individual is awake and sends signals to the spinal cord to suppress skeletal muscle movement during waking hours. Another explanation links to lower levels of hypocretin, and narcolepsy, as this is a hormone which promotes wakefulness. Mutations on genes that control hypocretin release have been linked to narcolepsy. 

Nishino et al found those with narcolepsy had lower levels of hypocretin within their cerebrospinal fluid. However, correlational data cannot conclude whether low levels of hypocretin caused narcolepsy or whether it was only a symptom. Low levels of hypocretin have been suggested to have a genetic link however narcolepsy does not always run in families weakening a purely biological explanation to the disorder. Lower hypocretin levels maybe due to environmental factors such as brain injury, infection or a result of an auto-immune attack. To assume that hypocretin is solely responsible for narcolepsy is reductionist as we do not fully understand the complex process, and we may be over simplifying it to out own understanding.

Honda et al suggested another explanation of a link to a mutation in the immune system, linking to Nishino's suggestion of an auto immune attack being a possible cause. Studying narcoleptic patients they found an increased type of HLA. This link was observed in all Japanese patients studies with a similar association of 85% in Caucasians supporting the link. However, in African-Americans this was only present in 65-67% of narcoleptics. Therefore it is likely cultural and biological factors work together to predispose someone to narcolepsy. As this HLA variant was not found in all narcoleptics across cultures it suggests a lack of external validity and limits what generalisations can be made. A criticism for the HLA link is that higher amounts of HLA are present in both narcoleptics and the general population who do not suffer the disorder. Therefore suggesting HLA is the only cause is reductionist as it may be only indirectly involved. 

A psychological explanation may be used in a small number of cases where narcolepsy has been found to run in families. Some form of the disorder may show and cause others to feel sleepy around them e.g. through yawning. Although, when considering the sever nature of symptoms, e.g. cataplexy, a psychological explanation in unlikely to be the cause, and most evidence points towards a biological cause.

Both Nishino and Honda's studies link narcolepsy to a biological cause, but ignores the role of environmental factors, making it reductionist, as these may trigger the disorder. Through such research it is suggested that nature and nurture work together in order to predispose someone to a narcoleptic attack. For example someone with a vulnerability to narcolepsy may need the right environmental trigger e.g. strong emotions for symptoms to show highlighting how the two work together. Therefore both biological and environmental factors will need to be considered in order to help those manage symptoms of the disorder. However, such studies often ignore the role of free will, making it deterministic. If emotional arousal causes its onset then, as we have some level of control over our emotions, we can control it to some extent. Therefore research has positive real world applications as mood controlling therapies such as CBT and self-talk may allow us to better control out emotions therefore we can have a better control of narcolepsy onset. 

Outline and evaulate explanations for insomnia (8+16)

Insomnia is the 'inability to sleep', including struggling to fall asleep (initial insomnia), difficultly remaining asleep (middle insomnia) or waking up too early (terminal insomnia). Risk factors that influence insomnia can include age or gender with women being more likely to suffer. Older age groups may suffer health problems, which in turn affects sleep quality. 

There are two types of insomnia; primary which is a disorder on its own and secondary which is a symptom of another underlying problem. Primary insomnia is sleeplessness not attributed to any medical, psychiatric or environmental cause, lasting over a month, according to the DSM. Primary insomnia consists of two sub types; pyschophysiological insomnia, a form of anxiety induce insomnia, referred to as learnt or behavioural insomnia. As the individual worries about falling asleep, and becomes tense making it harder to sleep. Idiopathic insomnia has no visible cause. It is a lifelong syndrome, apparent from birth, and is theorised to be caused by an under active sleep system or over active awakening system. 

Horne suggested that there is only secondary insomnia and with 'primary insomnia' the cause is yet to be identified. Secondary insomnia is a symptom of another underlying cause e.g. depression or heart disease. It could also be due to due caffeine or alcohol intake or medication. Therefore treating the underlying cause should help treat the insomnia e.g. those suffering from depression may sleep better after taking anti-depressants. 

Spielman et al proposed a distinction of component of insomnia. Predisposing factors may include a genetic vulnerability or physiological factors such as hyperarousal. In order for insomnia to be triggered the Diathesis-stress model proposes environmental factors are needed to expose the predisposed vulnerability, therefore triggering insomnia. Perpetuating factors such as stress and tension contribute to maintaining insomnia and may explain how chronic insomnia develops. This suggests that insomnia is a complex disorder and therefore it may be appropriate to consider these different component in deciding on appropriate treatment. 

Morin et al examined the relationship between stress, coping skills and pre-sleep arousal between good sleepers and insomniacs. Both groups reported similar stressful events but insomniacs rated minor daily hassles with greater intensity compared to good sleepers suggesting personality may be a risk factor. Those with internalising problems will have higher levels of emotional arousal which can contribute to the onset of insomnia. However, with the correctional data we cannot establish cause and effect, it may be those who suffer insomnia also suffered more stress life events, and not reported all of them, than the control group. Therefore results may lack internal validity, and such confounding variables affect the generalisation of results therefore we cannot determine the extent to which personality and the ability to cope with stress links to insomnia. However, positive real world applications come from research such as developing therapies such as CBT in order to reduce symptoms. If stress can be managed it may reduce tendencies for insomnia.

Roth et al found insomnia often proceeded rather than followed cases of mood disorders suggesting it may be beneficial to treat the insomnia regardless of it being primary or secondary. This study used a large sample of 15,000 Europeans which is beneficial as it increases the reliability of findings allowing for wider generalisations. This gives us a greater understanding of the disorder and that in some cases the insomnia may cause other disorders. 

Such research by Spielman, Morin and Roth highlights the complex nature of the disorder and suggests insomnia can have different attributable causes therefore it is deterministic to assume that all cases can be identified or attributed to a cause. Chronic insomnia is highly complex and for it to be broken down and explained in any simple way is reductionist. Reliability and validity of measures of insomnia have been criticised as they are based on reports of patients and interviews. Interviewers may interpret the information differently than what the patient intended, highlighting the subjective nature of diagnosing insomnia itself. 

Outline the nature of sleep (8)

Sleep is a state of consciousness where responsiveness to external environment is diminished. It occurs daily as a circadian rhythm with the average adult sleeping for 8 hours out of 24. Within sleep itself, an ultradian rhythm exists with 5 distinguishable stages. EEG machines have helped us to identify these stages objectively. 

Lifespan changes occur within sleep. Infants sleep up to 16 hours a day with 15% spent in REM. After 1 year REM decreases and total sleep time is about 13 hours a day, with an entire sleep cycle taking 45-60 minutes to complete. In childhood 30% of sleep is spent in REM with about 12 hours a day spent sleeping. In adulthood to complete on sleep cycle takes about 90 minutes and consists of both slow wave sleep (SWS) or NREM and rapid eye movement (REM) sleep. Throughout the night the length of time in REM increases with each cycle and NREM decreases. 

The sleep stages consist of stages 1 and 2 which are periods of light sleep and people are easily woken. Alpha waves, characteristic of the awake brain begin to disappear. Slower theta waves, sleep spindles and k-complexes high in amplitude are recorded. Heart rates slows, metabolic rate and temperature drop and brain waves begin to slow down.

Stages 3 and 4 are states of deeper sleep and it is harder to wake someone in these stages. Delta waves become evident in brain activity. These stages are also known as slow wave sleep (SWS). During SWS growth hormones are released to repair proteins and cell synthesis occurs. Metabolic rate, heart rate and temperature are at their lowest points. 

Stage 5 is also known as REM or rapid eye movement sleep. In this stage the body is paralysed but the eyes are moving. This state is often linked to dreaming and brain waves resemble that of someone who is awake. 

Outline and evaluate lifespan changes in sleep (8+16)

Sleep changes occur throughout life with infants sleeping the longest, up to 16 hours a day. 15% of this is spent in REM sleep. However, sleep is not continuous and they tend to wake up every hour due to their sleep cycles being shorter than adults and their need to feed regularly. Sleep stages are similar to adult SWS and REM but are immature versions known as quiet and active sleep. After 1 year REM decreases and brain activity begins to resemble that of an adult with total sleep time being around 13 hours a day with the entire sleep cycle taking 45-60 minutes. In childhood 30% of sleep in REM with about 12 hours per day spent sleeping. 

There are several explanations as to why babies have this longer sleep period. One explanation is based on an evolutionary approach. This suggests babies sleep longer to allow parents to carry out daily duties therefore this sleep pattern is adaptive. However, as with any evolutionary explanation that are purely speculative and cannot be proven conclusively as they are post hoc. 

The biological approach provides a different explanation explaining that babies sleeping patterns are due to their immaturity. Longer sleep patterns may be due to the vast amount of learning that is taking place. REM has been linked to production of neurotransmitters and consolidation of memory. As babies are born immature, they are expected to sleep more therefore this approach suggests sleep is important for mental health and development. Evidence for this comes from non-human animal studies such as dolphins. They are born mature and are able to swim and have almost no REM sleep. This supports that a biological approach can explain lifespan changes in sleep and why babies spend a vast amount of time sleeping. However, results from non-human animal studies lack external validity due to differences of anatomy  between them and humans. The study can only suggest why such sleep behaviours occur, it cannot provide conclusive evidence to explain babies sleep patterns. However, such studies can help towards drawing conclusions. Without any studies this approach would be purely speculative. 

Stickgold et al suggest may link to human development as we age. Evidence suggests REM may be linked to consolidation of procedural memory whereas SWS may be important for semantic and episodic. This may explain why REM is high in babies as they rapidly develop and also whit it decreases with age. This supports the assumption of lifespan changes occurring within sleep. Therefore provides validity to the theory of lifespan changes occurring. However, them memory consolidation process is difficult to measure. Therefore we are making the assumption that REM is linked to this based on correctional data which may decrease its reliability. However, it can be concluded changes in REM and SWS occur as we age with evidence of this coming from EEG recordings. 

Another significant lifespan change in sleep occurs during old age. Adults typically sleep for 8 hours going through the sleep/wake cycle stages, with 25% of sleep spent in REM sleep and in old age sleep time remains roughly the same. Although REM sleep decreases to 20% of total sleep time and SWS is as low as 5% or non-existent in some, meaning less growth hormone is released for bodily repair. Age may bring a phase advance in circadian rhythm, feeling sleepier earlier and waking up earlier.

The reduction of sleep in old age may be due to health problems which affect sleep, not purely due to lifespan changes. Sleep disorders such as sleep apnoea interrupts sleep and may be used to explain why SWS is lower as sleep is more easily disturbed resulting in less growth hormone being produced, from less time spent asleep. Therefore research has ed to practical application of treatments being created e.g. melatonin supplements to aid sleep. Highlighting how research can be used in the real world to produce treatments to aid in better sleep. 

Outline and evaluate evolutionary explanations as a function of sleep (8+16)

The four main evolutionary theories all explain sleep as an adaptive response to aid survival.

Energy conservation theory suggests warm blooded mammals must conserve energy in order to maintain a constant body temperature. This is problematic for smaller mammals as they have higher metabolic rates therefore use more energy. Evolutionary theorists argue sleep enforces periods of inactivity to conserve energy, as metabolism is lower when asleep.

Food requirements have been suggested to determine sleep. All animals need to eat to survive therefore sleep may have evolved around this. Herbivores such as cows eat food low in nutrients therefore spend a vast amount of time grazing, and little time sleeping. Carnivores such as lions eat food high in nutrients therefore can afford to spend less time eating. they also have no predation risk therefore can spend more time sleeping. 

Meddis proposed the 'waste of time hypothesis' suggesting sleep serves the purpose of helping animals to avoid predators when they are most vulnerable, as sleeping ensures they remain still when they have nothing better to do. 

Predator avoidance links to this and Siegel et al argued it would be riskier for the animal to stay awake due to predator risk and risk on injury. He suggested sleep could enable both energy conservation and predator avoidance, as long as the animal sleeps in hidden safe places. 

Cappellini et al found a negative correlation between metabolic rate and sleep in smaller mammals, having a higher metabolic rate but sleeping less supporting that food requirements may influence sleep. Smaller mammal, with a high metabolic rate, will have to eat more frequently in order to sustain their high metabolic rate, creating a restrain on sleep, as they must spend more time foraging. Suggesting a trade off between sleep and foraging. Within the study a standardised procedure was used therefore provides more reliable results with higher internal validity. However, this study only focuses on land mammals therefore may not be generalisable to all species, therefore lacks external validity. It also does not explain how evolutionary pressures affect sleep patterns for all species. 

Horne et al proposed a combined approach to try and explain areas which a purely evolutionary theory failed to explain such as why we have a strong drive for sleep when deprived. This approach proposed some elements of sleep are for restoration and some are for occupying unproductive hours e.g. conserving energy, for small animals. This suggests that evolutionary approaches do have validity however individually they cannot fully explain function of sleep. Horne also proposed a distinction between core and optional sleep. Core sleep is equivalent to SWS and optional is equivalent to REM. Optional sleep is argued to be dispensable and used to occupy unproductive hours and used to conserve energy supporting the energy conservation theory. However, restoration theorists would argue REM plays an important role in brain functioning and is not simply used to waste time.

Both Capellini and Horne's research can provide support towards some explanations with the evolutionary approach of sleep. However, research cannot provide conclusive evidence towards one sole evolutionary theory highlighting the subject is inconclusive and debatable. However, they suggest how sleep has evolved to aid survival for example the Indus dolphin sleeps for short periods of time, of a few seconds, in order to avoid debris. Such pressures could be argues to play an overriding factor in sleep behaviour  as they determine the animal's survival chances, providing support for an evolutionary function of sleep. 

Many studies are based on animals therefore findings cannot be generalised to humans as our environmental pressures are different e.g. we have no predator risk and food is generally available. Therefore according to the evolutionary approach we should not need to sleep, but we sleep for 8 hours a day. This highlights a possible biological and restorative need rather than being controlled by evolutionary pressures. Humans generally dictate their sleep patterns, yet evolutionary explanations ignore this therefore are deterministic, ignoring our own conscious decisions in sleep patterns.

Outline and evaluate restoration theory as a function of sleep (8+16)

Sleep is devided into slow wave sleep (SWS) and REM. Oswald proposed SWSaided in body repair and REM aided brain recovery. During SWS, growth hormone is released aigining in development during childhood and during adulthood it enables protei synthesis and cell growth aiding in bodily recovery. It has also been suggested that lack of SWS can result in redcued functionis of the immune system.

REM sleep is highest in babies and higher in premature babies. This may be due to humans being born immatues and requiring rapid brain growth and development. Animals born mature have little REM sleep suggesting a link between REM and neural development, another restorative function.

Siegel et al proposed REM sleep allowed for a break in neurotransmitter activity therefore allowing the neurons to regain sensitivity. Neurons are vital for bodily functioning. Anti-depressantcs have been seen to increase levels of neurtransmitter and abolist REM as a side effect, assumed to be due to receptors not needig to be regenerated. This highlights a possible link between neurtransmitter restoration and REM sleep.

Dement et al woke cats each time they entered REM sleep and found all the cats died highlighting lack of sleep can have serious consequences. However, other confouding variables such as stress of the environment may have contributed to the cats death therefore the study lacks internal validity as it was not purely a measure of sleep deprivation. Ethical issues are a concern as this could be have seen as a form of animal torture and it is questionable whether it can be justified as in the name of science. Results from cats cannot be generalised to humans therefore the study may not be justifiable and lacks external validity. However, it is clear that sever sleep deprivation has negative effects, even if indirectly linked to stress. 

Horne proposed a distinction between core and optional sleep. Core sleep is equivalent to SWS and optional is equivalent to REM. Optional sleep is argued to be dispensible and used to occupy unproductive hours and used to conserve energy. However, restoration theorists would argue REM plays an important role in brain functionins and is not simply used to waste time. Evidence of the importance of sleep is seen in human case studies of deprivation.

Peter Tripp, stayed awake for 201 hours and suffered severe negative effects such as abusive, unpleasant behaviour and suffered hallucination and paranoia. Contrasting this, Randy Garner beat Tripp's record but suffered non eof the negative effects Tripp had shown. Restoration theories are reductionist as individual differences are not considered. From researchwe see individuals cope with deprivation differently and therefore will likely have different levels of restorative function from sleep. However, single case studies have low external validity making it difficult to draw firm conclusions regarding the restorative function of sleep. However, both experienced REM rebound helping conclude sleep likely provides a restorative function.

Restoration theories are limited as they cannot explain all sleep patterns. For example the EEG recordings of dolphins have found no evidence of REM sleep. Yet resoration theory suggests REM sleep is needed for brain restoration. Sleep differences cannot be explained and to suggest sleep only holds resorative function may be resductionist and over simplified. Some may argue an evolutionary approach would lead to better understanding of sleep as different environmental pressures would have shaped sleep patterns. However, during sleep animals become essentially paralysed leaving them vulnerable, suggesting sleep must have an important restorative function as they repeated put themsleves at risk during sleep. 

Research findings from Dement and the two cases studies highlight that sleep deprivation has sever consequences. These uch consequences can vary between individuals, but most research can help us draw the conclusion that sleep aids in some restorative function, although we cannot determine the extent of restoration that sleep has. Positive application of research could aid towards better sleep hygiene helping to reduce the negetaive effects of sleep deprivation and/or help to prevent it.

Outline and evaluate the consequences of disruption of biological rhythms (8+16)

Consequences of disruption of biological rhythms are seen in jet lag and shift work. Normally exogenous zeitgebers allow our bodies to adjust gradually. But, rapid changes can cause them to become desynchronised. Symptoms of desynchronisation include decreased alertness and performance, fatigue and nausea. 

Shift work may involve working during the night when our internal body clocks are normally set to induce sleep, causing a breakdown between exogenous zeitgebers and endogenous pacemakers. In low light conditions melatonin is released to induce sleep. Therefore if awake during darkness hours this can cause decreased alertness. This also contributes to lower quality daytime sleep as melatonin levels are low. This can lead to sleep deprivation and a permanent state of dysychronisation. This can also increase stress levels which long term can have detrimental effects on health. 

Jet lag is a physiological effect of a disrupted circadian rhythm which occurs through travelling through time zones quickly meaning our internal body clock does not match external zeitgebers. Biological clocks cannot cope with large shifts with the SCN taking several cycles to resynchronise. It is suggested to aid resynchronisation, and is most beneficial to, follow exogenous zeitgebers e.g. meals and sleep times and following the biological clock can cause synchronisation to take longer. 

Recht et al studies US baseball teams who travelled coast to coast to play games. Results found teams travelling east to west, experiencing a phase delay, won 44% of games opposed to west to east teams, experiencing a phase advance, won only 37%. This difference may be explained through a disrupted rhythm therefore may provide support that disruption can lead to decreased performance. However, results were drawn based on correlation evidence therefore other confounding variables such as east coast teams being better at baseball and referee bias may have affected results. Therefore the study lacks internal validity. Also the difference in results between east and west coast teams was only 7% which may not be a high enough statistical difference to drawn conclusive results as to the affects that a disrupted biological rhythm has on performance. 

As shift work and jet lag are unavoidable most research has focuses on how to reduce its harmful effects.

Boivin et al found artificial bright lights was effective in resetting biological rhythms. Four groups were exposed to varying light levels with the group exposed to the brightest light being the most responsive to having circadian rhythms rest. This suggests even artificial light can aid in helping reset disrupted rhythms. This has positive real world application as, if bright lights can be used in the workplace to aid in readjusting biological rhythms . This could help increase alertness during the night which may help to reduce the risk of work place disasters such as the Chernobyl disaster occurring. 

However, this was a laboratory experiment therefore may lack external validity and findings may not be indicative of real life. Also participants were volunteers therefore may have been motivated to find a solution to their possible sleep problems therefore showed demand characteristics subconsciously. Therefore findings may apply to a real workforce and they may be less motivated and less likely to notice their rhythms change. Further issues arise within this study as it only focuses on the role light plays influencing biological rhythms despite temperature and social cues being found to have a strong influence. Therefore this study is reductionist and only focuses on a simplified understanding of exogenous zeitgebers.

Recht and Boivin's studies suggest that disruption occurs within everyone therefore needs to be treatable. However, such studies may be euro-centric as there is evidence of people coping in daylight year round e.g. Inuits. Therefore studies may be targeted at one specific culture and not generalisable to all. Therefore from research it is evident disrupted rhythms can cause problems, but the same factors do not cause disruption for all. Therefore the best method of treatment will also likely be subjective to the individual.  

Outline and evaluate research into the role of endogenous pacemakes and exogenous zeitgerbers (8+16)

Endogenous pacemakers are biological clocks within organisms. In mammals the main pacemaker is the suprachiasmatic nucleus (SCN), located in the hypothalamus. The SCN receives information on light via the optic nerve, occurring even when our eyes are closed as light penetrates through our eyelids. This helps to keep circadian rhythms synchronised with the outside world. When the SCN receives information about light is sends a signal to the pineal gland which regulates the production of melatonin. In low light it increases production, as melatonin is the hormone which induces sleep through inhibiting brain mechanisms which provoke wakefulness. 

Exogenous zeitgebers are external cues that help to regulate biological rhythms, known as entrainment. The opposite of this is free running where the biological clock operates without external cues. Light is the dominate zeitgeber in humans. The light sensitive protein CRY responds to light, shifting biological rhythms and has been found to reset the SCN and other bodily oscillators. Social cues such as meal times play a role as the liver and the heart are seen to be reset as the cells respond to eating. This suggests environmental factors play a role in biological cycles. Temperature is also important for the onset of hibernation in some animals. In the absence of light, temperature may become the dominant zeitgeber that resets biological rhythms. 

Morgan et al bred 'mutant' hamsters with a circadian rhythm of 20 hours instead of 24. The mutant SCN was transplanted into normal hamsters,which then displayed the 20 hours rhythm. This highlights the importance of the SCN and the possible dominant role it plays in controlling our biological rhythms. However, this study does not explain how exogenous zeitgebers may have interacted with the SCN to maintain a 22 hour rhythm. It is reductionist to assume only the SCN plays a role as we know exogenous zeitgebers interact with endogenous pacemakers to keep rhythms synchronised. Ethical issues also arise as the animals were left permanently damaged. Research may be justified if it has an important application to human behaviour research. However, generalisation problems occur between non-human animals studies to humans, therefore limits the conclusions which can be drawn. 

Campbell et  al altered participants circadian rhythms through shining lights on the backs of participants' knees demonstrating the existence of other endogenous pacemakers. Their circadian rhythms shifted demonstrating other oscillators must exist to help keep the biological clocks synchronised. This supports the assumption that light acts as an exogenous zeitgeber through its interaction with the protein CRY to reset the biological clock. Highlighting that a relationship exists between exogenous zeitgebers and endogenous pacemakers. This also suggests humans do not solely need light to penetrate the eyes. Blood may also be a messenger carrying light signals from the sun to the brain. However, such explanations may be reductionist to assume light is the main exogenous zeitgeber as other external influences such as temperature and social cues work with endogenous pacemakers to maintain rhythms. 

Both Morgan's and Campbell's studies demonstrate the importance of interaction of endogenous pacemakers and exogenous zeitgebers. They also highlight that most mammals have similar endogenous pacemakers to influence rhythms. Both studies took a biological approach ignoring the role of free will we have in overriding internal clocks, therefore is deterministic. We are not governed completely by biological programming and we can override them if we wish. 

Also from such research we can identify that nurture has a strong influence. As, our environments interact with internal biological clocks suggesting both appear to be equally important. Our endogenous pacemakers can keep a rough measure biological rhythms but the environment and stimuli appear to be important in keeping it completely synchronised. However, we cannot determine the exact amount of influence endogenous pacemakers and exogenous zeitgebers have on our rhythms, we can only conclude they interact. 

Outline and evaluate research into infradian and ultradian rhythms (8+16)

Infradian rhythms are biological rhythms lasting more than 24 hours e.g. the menstrual cycle which is regulated by the secretion of oestrogen and progesterone over a month. It was originally thought to be controlled by the hypothalamus acting as an endogenous pacemaker. But, evidence shows external zeitgebers play a role. Another example is PMS which occurs a few days before menstruation and is characterised by loss of appetite, stress and poor concentration. 

Russel et al used sweat of donor women causing other female participants menstrual cycles to become synchronised with that of the donor suggesting exogenous zeigebers influence a women's infradian rhythms and that endogenous pacemakers and exogenous zeitgebers interact to control infradian rhythms. However, a small sample was used and results may have occurred due to random occurrence raising issues of validity of findings. But, other research has found similar findings suggesting it is reliable and valid. The women used in the study has similar length menstrual cycles which may have acted as a confounding variable in whether their infradian rhythms synchronised or not, evidence of women with different length cycles synchronising would be needed to increase the external validity of findings. This study is reductionist and only focuses on the role of hormones and other factors such as the environment are ignored. Such factors may have acted as confounding variables influencing the menstrual cycle and thus the women's infradian rhythms. 

Issues occur into research especially regarding PMS, as this has cited as a mental disorder and used as legal defence e.g. Ms English drove her car into her partner after an argument, killing him, using PMS as legal defence resulting in her being put on probation. Such anecdotes are deterministic and suggest women have no control over their behaviour when influenced by such infradian rhythms. This could result in responsibility being taken away from women who behave aggressively, and violent women being acquitted for violent acts. 

Ultradian rhythms are biological cycles that last less than 24 hours. An example of this is the stages of sleep. Stages one and two are light sleep, heart rate reduces and muscles relax. Stage two also has noticeable sleep spindles and K-complexes. In stage 3 sleep spindles decline being replaced by delta waves. Stages 3 and 4 are slow wave sleep (SWS). Stage 4 is deep sleep, delta waves increase and metabolic rate is low. It takes about an hour to pass through stages 1-4 and after 90 minutes after falling asleep REM is entered. As the night progresses more time is spent in REM. This is fairly universal but there are developmental differences.

Dement and Klietman found participants when woken during REM sleep dreaming was reported 90% of the time and was recalled in detail. Only 7% reported dreaming in NREM. EEG recordings were used in order to wake participants up during different stages of sleep providing results with higher reliability and validity as researcher could determine which stage of sleep participants were in. From findings it could be assumed that REM sleep is dreaming sleep. However, this assumption is reductionist assuming all individuals will experience that same ultradian rhythms. Dreaming was not always reported in REM, additionally dreaming was reported in NREM although not as frequently. Results were inconclusive meaning the REM dream link is still unclear and that further research is needed in order to gain a better understanding of why dreams occur within this ultradian rhythm.

Russell, and Dement and Kleitman's research provides us with evidence of internal infradian and ultradian rhythms which help control cycles within the body. Such research is mostly conducted in a laboratory setting which lacks external validity as results may not generalise to real life settings. However, research has a piratical application to help us gain a better understanding of how our biological rhythms work. This may aid in providing better treatment for those who cannot synchronise rhythms or have difficultly controlling behaviour because of them. 

Outline and evaluate research into circadian rhythms (8+16 marks)

Biological rhythms are cycles with the body which are controlled by endogenous pacemakers and exogenous zeitgerbers e.g. light and social cues. Circadian rhythms are biological cycles that last 24 hours e.g. the sleep/wake cycle. The main biological clock in mammals is the suprachiasmatic neucleus (SCN) which aids in keeping biological rhythms synchronised with the outside world through regular events such as meal times. 

The sleep wake cycle is governed by external cues e.g. light and social cues but there is also an endogenous clock which is free running, working without external cue. It sets a rhythm at about 24-25 hours. The external cues help the endogenous clock to remain synchronised with the outside world. Studies have shown circadian rhythms persist despite isolation from natural light, but are not accurate highlighting the importance of exogenous zeitgerbers. 

Core body temperature is another circadian rhythms. It is it lowest around 4:30am at 36 degrees c and highest at 6pm at 38 degrees c with a slight dip occurring at midday, even without eating. 

Hormone production also follows a circadian rhythm with cortisol levels being lowest around midnight and highest around 6am. Cortisol plays a role in making us alert therefore explains why awoken in the middle of the night we struggle to function. Melatonin and growth hormone also follow a circadian rhythm both peaking at around midnight. 

Aschoff and Wever found participants to have circadian rhythms between 24 and 25 hours, when placed in an underground, with some as long as 29 hours. Rhythms persisted in the absence of external cues supporting the assumption of circadian rhythms being internal. Limitations of this study include low external validity as it was conducted in a laboratory setting therefore findings cannot be generalised to real life. However, it could be argued in a real life setting absence of external cues would never be an issue. But, such studies can be used to help gain further understanding of how our circadian rhythms work. However, participants may have shown demand characteristics as they were aware they were being monitored affecting the reliability and validity of results. 

Michel Siffre spend 6 months in a cave without external cues and found his circadian rhythms varied from a 25-30 hours. This highlights the presence of an internal circadian clock but also highlights the importance of exogenous zeitgebers to regulate rhythms as his circadian rhythms were not maintained at 24 hours. However, results from a single case study may not provide accurate generalisations on how others would respond to a lack of external cues. Confounding variables such as temperature, air pressure and being connected to monitoring equipment may have affected sleep quality and length, therefore reliability and validity of results may be questioned. Also results suffer gender bias and it cannot be assumed women's circadian rhythms would have similar responses due to hormonal differences.

Research findings have positive real world application particularly in the area of chronotherapeutics, which recent research in Germany has found, to influence the effectiveness of drugs therapies. For example aspirin is effective in reducing the chance of a heart attack if taken in the evening as most attacks occur in the early hours of the morning. Therefore research into circadian rhythms may help to increase effectiveness of treatments for disorders and illnesses. 

Both Aschoff and Wevers's and Siffre's studies suffer the issue of the use of abnormal environments. This may have affected length and quality of sleep, acting as a confound variable therefore affecting the validity of findings. Additionally, participants in both studies were able to us bright artificial lights which other research has found to cause rhythms to shift, further affecting the studies internal validity. Such research can be used to highlight the existence of free running circadian clocks. However, they are not accurate therefore suggesting the importance of interaction with external zeitgebers to maintain circadian rhythms.