Psychology

Human beings are the bipedal primates that belong to the species Homo sapiens in the Hominidae, in the great ape family.  We have a highly developed brain that is capable of abstract reasoning, language, introspection, and in problem solving.  Just like many other higher primates, we are generally social in nature however, the only distinction we possess in nature is that we are able to use the systems of communication for self-expression, the exchange of ideas, and organization.

Another aspect that makes us more different to other higher primate animals is the fact that we are able to understand and influence our environment, seeking to explain and manipulate the natural phenomena through science, philosophy, mythology and religion.  Human beings differ from the other animals in the sense that we posses the sense of perception.  A human body is organized to offer support not only to for the sense of perception but also in having a rational soul as its substantial soul (Chazan, 1998).  Here, the human being is responsible for actualization of the matter composing a human being and in the unity of the activity of human beings.  We are able to make judgmental decisions that affect us and those around us for good relations.

Morally, in order to understand the nature of human beings, we should be able to appreciate that humans are naturally weak, hasty, ignorant, and unjust. They are also said to be unappreciative, anxious, obstructive, fearful, mean, stingy, and misery.  Human beings love to argue and despairs when in poverty and in sickness.  These characteristics are always present in one but they always increase or decrease, surface or fade according to the upbringing and the amendment of the spirit.
These are by no means exclusive to every individual that possesses them (Wright, 1994).  First, we find out that some of the challenges that we face in our day-to-day life are determined by the placements of the planets, each of these represents different aspects of their mental and physical nature.  Therefore, at the time of birth different techniques may be used to estimate the issues that will eventually unfold throughout their lives.

Human beings are pack animals that have a characteristic of grouping together for the purpose of safety and well-being and the ability to attract each other, which is a principal towards our survival.  The manner in which we respond to these behavioral patterns and the expectations we seek from how others will respond to our actions are programmed into our behavioral or emotional loop during the earliest experiences (Chazan, 1998).  This point of view is determined in that the process starts in the womb just before birth, the unborn infant is basically aware of the mothers emotional and psychological responses to it at the most primal time (Chazan, 1998.

The character of a mature human being is being adopted mostly from their caregivers for food, warmth and many other things for survival, these are basically the parents.  Therefore, because of this, should the caregivers be less than good enough, the infants will resume that any harm is within themselves, that their disturbing behavior is as a result of their parents behavior, and this is likely to extend throughout their lives (Wright, 1994).  To save this kind of a circumstance, we often try to modify our behavior by interrupting the natural contact to change the behavior.

The human person is obviously connected with how much the world makes sense to us and how much we feel about others that we make contact with and in the understanding about their making.  The human species go by their personal worlds structures, systems, and the values that we believe to they are acceptable.  People differ in the way they handle certain issues at hand.  Some people believe that they are reasonable in taking violent actions in order to meet their goals.  This is though not acceptable by many.  Therefore, in this case contact and expression are the key components that can restore this to bring it to a balance.  It is through this that they can explore, express and achieve balance.  It is important to understand that the human character is influenced by the changes that take place intra-organismically within a person.  These changes enable a person to identify the limits of their capabilities both physically, emotionally and spiritually (Chazan, 1998).  An example is that people can estimate whether a certain behavior is acceptable to those they are close to or not, or they can determine if a certain mathematical problem is within their capacity to solve.  These intra-organismic processes allow human beings to observe and practice the existing and new ideas and their behaviors.

Some risky behaviors may be because of the unexpressed self-struggling to emerge on certain issues.  To help the people at this stage, they should be given genuine means of expression this may reduce the internal pressure that leads to this behavior.  On the other perspective, listening, performing, creating, and sharing are the aspects that can help them become aware of how their world makes sense to them and how others view the sense that they make.

The biopsychological behavior of human beings is a combination of the biological and the social factors that are used to explain the human behavior.  The scientists assess that human behavior can be explained by the genetics and heredity factors among them.  In case of genetics, the component that is responsible for this is the DNA, a special component of the cells.  The DNA structure is characterized by a number of subsections which dictate various functions of the human body and behavior. First is intelligence, which is partly determined by the genes.  This is strongly verified within the IQ intelligence of twins.

The biological approach also explains certain strange behaviors that are received through heredity and genetics.  A study that was conducted upon two brothers that were diagnosed with schizophrenia found out that a large percentage of these individuals had actually the same components that were similar in nature.  This showed that they had inherited these traits from their parents (Wright, 1994).  However, this does not mean that they should behave in the same way.

Persons or human beings may possess the same biological composition but have different character traits.  Another factor that determines the human behavior is that it is related to certain uncontrollable conditions that are common in all individuals.  For example, when a person is subjected to extreme hunger, the brain conditions them to look for something edible e.g. fruits or any thing edible.  Another example on the same note is that one of sleep (Chazan, 1998).  Sleep is controlled by a part of the brain called medulla oblongata.  It is the role of the brain to trigger sleep unconditionally. However, people sleep differently that is, some sleep more than others.  In this case, the medulla may be undergoing some malfunction or when it is working excessively, an individual will tend to sleep a lot more than the other.

We can understand the human behavior through cognitive development.  Through this approach, human beings are able to get meaning about the phenomena and the surrounding environment by drawing and establishing relationships between the mind and the objects or events occurring within the surrounding environment. As the mind develops and gets accustomed with certain ideas, they begin to react towards them in a way that brings about different reactions to them (Wright, 1994).  This leads to a person having a different attitude towards a certain item from another.  The psychological analysis of the human mind enhances us to understand the reason about certain emotions.  Through this, we can be able to understand why and how people react emotionally towards a certain issue while some others may not be affected in any way.  This largely is dependent on the role that the mind has on that particular issue or individual.  An example is that people may react to the temperature differences in different ways.

Biopsychological Social aspect is another aspect that tells us more about the human behavior.  Here, we consider the influences that the family and culture have on the human behavior.  It should be noted that in social analysis, there is a difference between ideal behavior, actual behavior and believed behavior.  For instance, a family may differ in the manner in which it tackles its events and issues from another while certain behaviors may be deemed unacceptable in some varied cultures.
Human personal traits are adapted to the environmental pressures, particularly the social ones.  This encourages a wide range of varied traits between the individuals.  People are able to respond to environmental warnings that are associated with impending punishments.  Through this aspect, people are able to develop a character of fear that is mostly common in the human species (Wright, 1994).

Human beings possess a certain aspect of self-motivation.  This is arrived as individuals cannot rely on other individuals for motivation.  This plays a key role where the individual gathers the courage and strength to achieve certain goals.  Therefore, this is essential in the development of new undertakings or making a positive change towards life.  Human character is modified by the needs that are demanded by the individual. Almost in every day today living human survival is defined by a series of key fundamental needs. These needs occur in an order of importance. They are highly hierarchical and it is after satisfying the very basic wants at one level that one graduates to satisfy needs on another category (Chazan, 1998).  These needs can be categorized as follows there is the need for survival, these survival levels consists of the basic need to sustain life the need for safety WHICH  involves protection from possible threat such as disease, violence among others the need of social belonging, this involves the need to be liked and wanted by family members, friends, coworkers, and others that they associate with there is the need for esteem, this involves the need to feel important from within and from other people that are surrounding us finally, there is the need for self-actualization, this means knowing our limits and trying to perform, within those limits, to our full potential. All these are the major aspects that are important in the modification of the human character.

We are the only animals that can think, this is because we can remember the past as discrete events then connect these with the present conditions.  Then on this basis, we can consciously decide what to do and project possible present actions into the future consequences of those actions (Chazan, 1998).  This is the reason as to why human beings respond differently to issues pertaining what they have at hand.  This is most fundamental aspect which differentiates the humans from the animals that usually react to stimuli.

The ability to think also means that we have two ways of viewing things, which is instinctively and intellectually.  The instinctive way of viewing things is instant and uncontrollable.  On the other hand, the intellectual view is always learned and alterable, it is based on the culture and the society in which the person lives.  We are able to use it to alleviate the effects of the instinctive view.  Another key aspect of human nature is the ability to pair themselves into social groups.  When staying alive it is not just the responsibility of the individual, but other members of the species that help the individual to survive, and vice versa.  This implies that human beings are dependent of each other (Chazan, 1998).  The purpose of a social group is often dictated by how well it serves to promote the survival of the other members.

In the case of people with the same background, the individuals make are usually real changes to the feelings and behavior as a result of interactions with others that are perceived to be similar and desirable.  According to the psychological principles, people regulate their beliefs with respect to others to whom they usually feel similar to attain an expected balance. The individuals also are said to be influenced by the majority, that is when an individuals social group that is large enough holds a particular attitude, this is likely to affect an individual in one way or another in his efforts to adjust to the environment (Wright, 1994). Additionally, an individual can change his mind according to an opinion that is due to an influence of another person believed to be an expert on the matters that are being handled.  This modifies a human behavior in one way or another.

Humans have the most complex society than any other animal in the planet Earth.  This is because we extend our self-preservation beyond the personal physical survival.  We live in the extremely independent and complex societies where people band together in groups for basically mutual aid and protection.  Such groups include families, friendships, associations, tribes, clans, and states or nations.  These individuals benefit by supporting each other and the group, because the group reciprocates by supporting the individual.  This is the reason for the protection offered unconditionally to the member of a certain group or location.  Humans in the process have developed societies that go beyond the needs of the present (Chazan, 1998).  For example, in the case of food and water, if the future is uncertain about their existence, to safeguard the future needs there is to be a way to transport the present resources into the future in a way that is not perishable.  Efforts are made by the members of a group to help in the survival of the group in the future in a way that is acknowledged later (Chazan, 1998).  This brings an aspect of safeguarding interests for the benefit of the group.

Humans differ in the way they posses their self control, this is understood as being a subset of emotional intelligence.  Here, a person may be intelligent yet he is still unmotivated to decide certain tasks.  This is natural and common to all individuals in a way that an individual has to be boosted to be able to handle the motivation.  A reward either tangible or intangible that is offered after a person has done an action will most definitely boost the morel of the individual.

In the everyday life, there are occurrences that are both within an individuals control and those that are beyond the control of them.  Therefore, people have to make choices and decisions about the situations that occur in our everyday lives.  The reasons why people make such decisions are diverse.  Some are complex whereas some are simple.  These decisions may have an impact or no impact on the individual life (Wright, 1994).  Many of the simple decisions people make do not require much thought and some can even be reached without awareness of the mind.  This is the major reason as to why people tend to take other issues more seriously than others, though they all require the involvement of the mind.

Another aspect about human behavior is that human beings are driven by reasons and emotions.  Humans are resourceful and evaluative as they strive to capitalize on their own interests.  Therefore, an individual interest can converge or diverge from the interests of an organization or group. In addition to that, it has been recognized that humans are driven by emotions that can be accorded with rational behavior e.g. when fear evokes caution in the face of danger.  Emotions can also be odd with rational behavior e.g. when pain avoidance leads to an unwillingness to tackle difficult decisions.  This therefore means that all in some circumstances the behavior of human beings is affected by the circumstances they are in (Wright, 1994).

In the case of the human sexual behavior, many kinds of activities that are engaged by human beings are generally governed by the social rules that are culturally specific and vary widely.  These rules are known as the morality and norms of the sexual behavior.  These norms and morals relate to issues including deception, legality, fidelity, and consent.  Some of these are known as sex crimes in some locations while in other locations they are not.  This brings about the difference in the way people perceive issues relating to sex.

The law of natural selection also plays an important role in the human behavior.  By applying this law to the general ecological and social environment on the primate man, certain specific predictions on the behavioral tendencies are derived.  It is suggested that discrimination may be derived from the primitive territorial behavior but that nationalism may have little connection with the territory (Wright, 1994). Therefore, individual from different territorial groupings may view others as inferior due to nationalism and self identity.  On other hand, the attitudes of the adolescents are also derived from the biological and the social factors.  Consequently, the adult attitudes for the teenagers sometimes appear to have a genetic bias (Wright, 1994).  All these cases are as a result of the difference in the status of both individuals.

There has been the behavior of humans to control and depend on one another.  An example is about the parents and their children.  Here, babies learn to cry for them to control their parents, this evokes the responses that are based on the fundamental habits in their parents (Chazan, 1998).  For the children the mastery of the adulthood environment is their strongest incentives to learn to speak, and later to read and write.  On the other hand, parents dominate their children through the obsession of the habits to them of either affectionate independence or fear while the husbands on the other hand tend to control their wives. Because of fear of loosing economic support, wives comply and they resort to sympathy (Wright, 1994).  This shows how people in the family relate with one another.
There is the issue of the influence of conformity, power and authority within the humans.

Conformity is expressed when an individual shows a particular opinion or behavior with an aim of fitting in a given situation and in order to meet the expectations of another, though he does not necessarily have in possession of that opinion or does not believe that the opinion is appropriate.  On the other hand, power is that ability to force a particular way through the control of the outcomes.  And finally, authority is that power that is believed to be rather legitimate by those that are subject to it.  Therefore, human beings have the tendency of fighting for the power, conformity and authority in the society where they live.  This gives them an exclusive behavior that they dominate above other higher primates.

Until the latter part of the 20th century, there had been no evidence for the heritability of IQ and it was just an assumption of the practitioners (Nature vs Nurture, 2005). However, this is not anymore he case today as the heritability of IQ has already been tested through several studies especially on twins and adoptees. Although some of the results point to the factor of nurture in the area of intelligence, there is an overwhelming weight of evidence in favor of the role of nature in shaping cognitive abilities. The only thing that varies from one study to another is how much of the results can be due to heritability.

Various studies on the biological inheritance of intelligence have been conducted by doctors, scientists, and geneticists, and have been published in several academic journals both online and offline. These studies all say one thing that somehow nature is partly, or even mostly, responsible for determining intelligence.

The main aim of this essay is to provide evidence for the aforementioned statements on the role of nature in shaping intelligence. Specifically, this essay will present the latest studies on the heritability of intelligence as well as evidence from twin studies. Moreover, this essay seeks to explain that even some studies whose findings do not exactly link nature and intelligence may also point out to such claims.

Evidence from Twin Studies
Twin studies provide the most qualified proof for the role of nature in determining intelligence. The reason is that, ideally, twins have an identical genetic make-up so that a phenomenon in one of the twins that is exhibited by the other twin is already a strong proof for the assumption that such a phenomenon is inherited. Various current twin studies will be presented and criticized in the following paragraphs to fulfill the aims of the essay.

Jacobs, Os, Derom,  Thiery (2007) found out that the fact that the twins share the same placenta and have a common blood circulation possess high heritability estimates at 82 for the verbal IQ, 72 for vocabulary IQ, 73 for the performance IQ, and 83 for the total IQ. These findings led to the conclusion that general cognitive ability (represented by the symbol g) is one of the most inherited dimensions of human behavior (Jacobs et al., 2007). The results of this confirmed previous studies like those of Wainwright et al. (2005) which found that genetic g accounted for 32 to 72 of the phenotypic variances, and explained 56 of variation in Verbal IQ and 42 for Performance IQ in the academic skills scores. The results suggest that general academic ability is more likely a result of genetic influences rather than common environmental influences. Another earlier study conducted by Singer et al. (2004) found out that general intelligence had a high heritability estimate of 74. In the same year, Price et al. (2004) found that this general intelligence is most pronounced by middle childhood and that the same genetic factors are responsible for individual differences when it comes to verbal and nonverbal abilities. Still, a study in Russia in the same year explored the genetic and environmental influences in cognitive abilities (Zyrianova, 2004) and found that cognitive characteristics are for the most part under genetic influences with estimates of heritability at 53.

These five aforementioned studies suggest a genetic basis for intelligence, specifically the general cognitive ability g. These studies directly investigated the various cognitive and even noncognitive abilities of twins and, through the data acquired from intelligence tests, came up with the conclusion that intelligence has a strong genetic basis.

Other studies, however, did not consider all the cognitive abilities but instead focused on a particular ability such as vocabulary (Van den Berg et al., 2004) and mathematical ability (Ando, 2004) and found the same genetic basis for intelligence. Van Den Berg et al. (2004) found that heritability varied from 50 to as high as 63 for vocabulary test scores from 997 adult twins or siblings of twins. The study also found out that genetic factors are responsible for the stability in vocabulary knowledge over time, where heritability reached 76. Furthermore, the study did not detect any noticeable influence from shared environmental factors, and although the males generally outperformed the females, results were similar for both sexes. Another study in Japan in the same year focused not on vocabulary but on mathematical achievement and was able to specifically underline the particular role that genetic influence has on mathematical ability (Ando, 2004). The study found that mathematical performance is largely an interplay of both additive genetic and shared environmental factors. Through univariate genetic analysis, the study was able to exactly link the two components of mathematical performance  verbal cognitive and spatial cognitive ability  with the additive genetic factor to explain the former and the common environmental factor to explain the latter. Although the study on mathematical performance found an almost equal influence of both nature and nurture in the development of mathematical abilities, it established the idea that intelligence with numbers is never possible without a substantial amount of genetic factor. The shared environmental factor in the development of mathematical skills is an obvious influence of education and other visible external factors. However, the existence of the additive genetic factor, whose influence is obviously not visible, was ascertained by this study.

Other twin studies focused on specific aspects of intelligence such as memory (Volk et al., 2006 Singer et al., 2005), speed in perceptual discrimination and IQ (Luciano et al., 2004), and academic achievement (Chertkova, 2004). Nevertheless, the same thing was found that intelligence is mostly inherited. A study conducted by Volk et al. (2006) found that free recall of unrelated and categorized words, as well as cued recall of categorized words, was found to be moderately heritable at 55 and vocabulary score was highly heritable at 77. Singer, MacGregor, Cherkas,  Spector (2005) found that memory ability has a heritability estimate of 45 which is relatively higher than the shared family environmental influences whose heritability was estimated only between 32 and 33. This study may not have established a strong genetic basis for memory. Nonetheless, it was able to somehow prove that the genes count more than the environment when it comes to shaping memory. Another study involving Australian and Dutch twins tried determining the heritability of the cognitive abilities of perceptual discrimination speed and IQ (Luciano et al., 2004). This particular study showed that genetic effects influenced IQ more than familial environmental effects. A Russian study conducted by Chertkova (2004) focused on the genetic influences in terms of academic achievement and found that achievement in humanitarian subjects or the social sciences were relatively more influenced genetically than achievement in the natural sciences. Based on the results of the study, the heritability of the Russian language was registered at 77 while that of Physics only at 26. Nevertheless the study was able to confirm that at least some of the genetic contribution to school achievement may only reflect the genetic contribution to general cognitive functioning (Chertkova, 2004). It can be seen from these four aforementioned studies as well as in the previously discussed study on mathematical performance that although there is admittedly an environmental factor in shaping cognitive abilities, still the role of the genes in determining intelligence cannot be emphasized more heavily.

There were also a number of twin studies that focused on problems and disorders but yielded results in favor of our thesis that intelligence is biologically inherited. Oliver  Plomin (2007), in their longitudinal study on language, cognition and behavior problems, used multivariate genetic analyses which allowed them to conclude that genes are generalists and environments are specialists (Oliver  Plomin, 2007). This simply means that similarity in performance across age and within and between abilities and disabilities in learning is largely due to genetic factors. On the other hand, differences as to performance are largely brought about by environmental factors. In another study, Reynolds, Fiske, Fratiglioni, Pedersen,  Gatz (2006) explored the heritability of cognitive dysfunction and found out that 35 of the likelihood of ones having cognitive dysfunction is due to heritable influences and the remaining 65 is due to nonfamilial environmental influences. The two aforementioned studies showed that although the environment was a necessary factor, still the genetic remains to be of extreme significance. In the study by Oliver and Plomin, nature and nurture seem to possess an equal influence on learning. On the other hand, Reynolds et al. (2006) emphasizes the relatively more significant influence of the environment compared to genetic factors. Nevertheless, these findings do not at all change the fact that a part of intelligence is biologically inherited.

Other twin studies focused on aspects of behavior that determined intelligence such as extraversion. Pincombe, Luciano, Martin,  Wright (2007) found in their study on the heritability of extraversion and its relationship with IQ that all extraversion facets were significantly influenced by genes. The heritability of activity was estimated at 25 while that of warmth was 54. The study also found out that there is a strong correlation between excitement-seeking and IQ and this is solely due to genetic influences. The study attributes such genetic effects to the influence of brain dopamine, a neurotransmitter that is known to have significance on both personality and cognition. The results of this particular study show that since certain aspects of the personality such as extraversion have a strong genetic basis, and that personality and intelligence are usually parallel, it therefore follows that intelligence too is heavily influenced by the genes.

Lastly, there were also twin studies that focused on suspected physical determinants of intelligence such as birthweight (Newcombe et al., 2007 Derom et al., 2004). Newcombe, Milne, Caspi, Poulton,  Moffitt (2007) conducted a study based on the hypothesis that birthweight predicts IQ and found that an increase of 1000 g in birthweight was associated with a 3 point increase in the IQ. In an earlier study, Derom, Thiery, Van Gestel, Jacobs, Vlietinck,  Fryns (2004) found that this phenomenon of correlation between birthweight and IQ is more pronounced in opposite-sexed twin pairs, especially with a female co-twin who is heavier than her twin brother. The findings of these two studies show that intelligence may indeed be genetically determined at birth and may even be physically indicated by certain physical attributes such as birthweight. The problem with these findings however is that birthweight may be due to several factors such as the volume of body fat or the weight of the bones, thus there is a need for a more in-depth study on what are the specific components or aspects of birthweight that more likely determine or predict intelligence.
Evidence from Family Studies

Family studies also provide some evidence for the genetic basis of intelligence. In a study undertaken by Thomas Bouchard of the University of Minnesota, the correlation between IQs is highest among identical twins and lowest among unrelated people. Identical twins reared together accounted for a percentage correlation 86 in their IQs. Identical twins reared apart accounted for 76 fraternal twins, 55 biological siblings reared together, 47 and unrelated people, 0 (Nature vs Nurture, 2005).

Family studies involving correlation of child-parent verbal ability scores also help establish the claim that intelligence is biologically inherited. The findings of these studies show that the verbal ability scores of children and their birth parents have a relatively higher correlation compared to those between adopted children and their birth parents, and even much higher than those between adopted children and their adoptive parents (Nature vs Nurture, 2005).

Conclusion
The heritability of intelligence has been one of the most highly-debated topics since the advent of neurology and psychoanalysis. However, it was not only until the latter half of the 20th century that twin studies and family studies have actually been conducted to investigate on the matter and to ascertain if the claim is true as well as to determine which part of intelligence was nature and which part was nurture. Twin studies proved the existence of a genetic basis for intelligence through direct experiments with all of the cognitive abilities or a specific ability at a time. Certain cognitive abilities which were equally or unequally influenced by both the genes and the environment still somehow proved the indispensability of the genes as a complement to the environment in the development of intelligence and cognitive abilities. Similarly, twin studies on behavior disorders, extraversion, and physical aspects such as birthweight also pointed out to the same conclusions. Lastly, family studies on IQ correlation among twins and verbal ability scores between children and their parents also proved that intelligence is all in the genes.

Functionalism being the philosophy of the mind has had a great impact on the study of the science of psychology influencing it both in the direction of applied science as well as in the behaviorism direction. With functionalism, it is possible to study the subjective mind and at the same time explore behavior objectively.

Functionalisms influence on applied and behavioral trends
Functionalism as described by William James looked not only into the structure but also to the reason why people behaved in a certain way. It therefore seeks to explain the human mind in a systematic way with greater accuracy. The functionalist view of consciousness is that it exists for a given purpose. Since psychology involves studying the mind and human behavior, the functionalism trend fitted well in understanding how an organisms consciousness helps it to adapt to the environment. A good example of applied psychology as explained under functionalism is that bodily responses lead to emotional responses (Oglethorpe University, 2010).

Although behaviorism does not recognize psychology as a mind science but as a science of behavior, the functionalism trend tends to relate these two phenomenons. Functionalism does not wholly abolish behaviorism but actually bridges behaviorism with applied psychology. A functionalist will relate a certain behavior with an organisms consciousness and in the process advance behaviorism. In the above example of the body response to various encounters, the element of external environment (a characteristic of behaviorism) is still recognized as it stimulates the mind (a characteristic of functionalism) (Oglethorpe University, 2010).

In conclusion, there is no doubt that functionalism is a bridge between the study of the mind in a subjective manner and study of behavior in an objective approach. As such, functionalism advanced applied psychology and behaviorism in psychology.

Media has become a powerful tool for disseminating information on what is socially desirable or not.  Countless hours are spent on advertisements and television programs that tell viewers how to lose weight or use cosmetic products to enhance beauty.  Reality shows featuring surgeries for aesthetic purposes are gaining in popularity.  It is not a surprise that research studies have found a strong correlation between media influence and body esteem.

In the last decade, there has been a growing interest among the academics on the topic of body image.  Mass media and diverse socio-cultural pressures are seen to cause an increased awareness of being thin as ideal and to contribute to the misperception of body weight (Ansari, Clausen, Mabhala  Stock, 2010, p. 584).  Gender and age have been associated with how one perceives ones body and ones appreciation of it.  Among socio-cultural factors, what stands out is the influence of media.  Among women, the thin ideal has been most the prominent idea espoused by fashion models and superstars.  Among men, the term leaner structure has been used to identify their ideals.

The significant effect of media on body-esteem falls in the realm of social comparison. According to Bessenoff (2006), women who are exposed to the ideal body shape (i.e. thin ideal) make serious comparisons about their own body.  This results in dissatisfaction and negative feelings towards their body and weight.  Bergrstrom, Clayton and Malheim (2009) further identifies that the single significant factor affecting the comparison is the extent of discrepancy between the ideal and ones own body image.  This is further supported in Heinberg, Stormer and Thompsons (2006) findings that comparisons of their bodies to that of others often lead to unhappiness among women.  Negative mood also increased among women who compared themselves to thin models.  These body dissatisfaction and stressors according to Soukup, Beiler,  Terrell (1990) may influence body concerns.

It appears that the adolescent population, is becoming acutely attuned to their weight and body (Ata, Ludden  Lally, 2006, 1024).  One of the negative effects of such phenomenon is the increasing number of eating disorders among adolescents.  The pressure to lose weight was highly correlated with low body-esteem and body image.  As expressed by Bassenoff (2006), the thin ideal advertisements influenced mood, self-esteem, concerns about weight and depression. In a study by Ata et al. (2006), it has been found that females are at a higher risk of eating disorders than males.  There is significance therefore, in adding to the body of existing literature that explores how media influences the creation of body image and the development of body-esteem.

As television viewers ourselves, we have varied experiences of being affected by media, and certainly in terms of our own body image.  Conversations about body weight are common among university students, especially among females who are constantly worrying whether they have reached the thin ideal.  From these, we have decided to design the current research study.  The purpose of this study is to investigate the effects of viewing thinner versus full-body celebrities on body-esteem and stress in college-aged women.  It is hypothesized that exposure to images of celebrities with different body types will affect body-esteem scores, which will increase stress levels.  Furthermore, the researchers also hypothesize that participants who are exposed to larger media images will have more positive body-esteem scores, and therefore lower stress levels, than those who are exposed to pictures of thinner women.

Methodology
Sample. A total of eighty (80) female respondents were considered as subjects for this experiment. They were university students who were at least eighteen (18) years old.  The participants were expected to participate for approximately thirty (30) minutes.  In exchange, they received one PIPER credit for every half hour.  Information regarding cancellation were given so that participants who signed up but were unable to attend informed the experimenters ahead of time.

Two groups of approximately 40 participants were tested for the proposed hypotheses. Participants were randomly assigned to either the thin group or the fat group.  Participants in the thin group viewed pictures of thin celebrities while those in the fat group viewed pictures of fat or big structured celebrities.

Instrument  Participants were asked to complete a series of questionnaires with regard to the appeal of women in the images shown.  A total of eight (8) pictures of celebrities were used in the experiment.  Four (4) of the celebrities have thin frames or body structure while the rest of the four (4) have large frames or relatively bigger body structures.

The first part of the questionnaire contained a demographic sheet which gathered information about the participants age, course, college year level, and ethnic background.   The second part of the questionnaire measured body-esteem.  It used a survey derived from the Body Attitudes Questionnaire that measures the respondents degree of and reasons for satisfaction or dissatisfaction with 49 various parts or processes of the body and with the total body. The questionnaire was cut down from 49 to 12 body parts. The participants rated celebrities and themselves on a total of 12 different parts using a Likert type scale ranging from 1 to 5. An example of a body part to rate is nose. A respondent rates the nose of the celebrity in the picture and her nose on a scale of 1 (strong negative feelings) to 5 (strong positive feelings).
 
A shortened, 10 item version of the General Well-Being Schedule (Andrews  Robinson, 1991) was used to measure stress.  The questions chosen from the Schedule are directly or indirectly related to stress.  The participants responded to the questions on a 5, 6, or 10 point Likert type scale.

Procedure  An administrators instruction sheet was attached to guide the researcher who administered the experiment.  This was made to ensure that a standard operating procedure was followed.

Participants were provided with two copies of the informed consent form to review and sign. One copy was collected by the researchers, while the second copy was given to the participant.

The participants proceeded to viewing the pictures of the celebrities, depending on which group they belonged. After taking a few minutes to examine the pictures, participants were presented with a scale to rate the celebrities bodies.  Once the rating scale was accomplished, the participants rated themselves using a slightly modified version of scale used to rate the celebrities bodies. Once both Body Esteem surveys were completed, a stress measure was administered, the General Well-Being Test.

Lastly, the researchers collected the finished surveys and gave the participants two copies of the debriefing form to review and sign. One copy was collected by the researchers, while the second copy was given to the participant.

Data Analysis. Data was submitted for statistical data analysis.  For Likert type scale of survey, chi-square or the Cochran Q was used for statistical analysis.  The data will be tested based on the hypothesis stated by the researchers.

The term local clinical scientist is used by psychologist to refer to the study of people through experimentation and observation for the purpose of promoting change. As clinical psychology grew, psychiatrist and neurologist continued to focus on treating serious mental distress. Between 1900 and 1930, clinical psychology mainly dwelt with assessment and it only advanced into the field of treatment when the World War two begun (Cash  Pruzinsky, 2002). After the soldiers returned form the war, psychologist begun to notice psychological trauma symptoms which was called shell shock or posttraumatic stress disorder and could be treated effectively during the initial stages (Cash  Pruzinsky, 2002). Female psychologist formed an association which aimed at assisting the society to cope with war related stress, and advising young mothers on child rearing.

As the field grew, a program was set up that focused on training doctoral level clinical psychologist who started to help veterans in need of care. A scientist-practitioner model was drafted by a panel of professionals who operated in the counseling field with an aim of uplifting the standards of counseling training and practices (Cash  Pruzinsky, 2002). Counseling psychologists were required to incorporate both practice and science and become knowledgeable in research as well as have a broad understanding of a persons condition.

Despite the fact that clinical scientist and psychiatrist have a common aim of relieving mental distress, their form of training and methodologies are different. Medical psychologists are clinical scientist trained to prescribe and undertake physical examinations as well as interpreting laboratory tests. Clinical scientists usually work with families, individuals, couples, children, and communities.

Human beings are the bipedal primates that belong to the species Homo sapiens in the Hominidae, in the great ape family.  We have a highly developed brain that is capable of abstract reasoning, language, introspection, and in problem solving.  Just like many other higher primates, we are generally social in nature however, the only distinction we possess in nature is that we are able to use the systems of communication for self-expression, the exchange of ideas, and organization.
 
Another aspect that makes us more different to other higher primate animals is the fact that we are able to understand and influence our environment, seeking to explain and manipulate the natural phenomena through science, philosophy, mythology and religion.  Human beings differ from the other animals in the sense that we posses the sense of perception.  A human body is organized to offer support not only to for the sense of perception but also in having a rational soul as its substantial soul (Chazan, 1998).  Here, the human being is responsible for actualization of the matter composing a human being and in the unity of the activity of human beings.  We are able to make judgmental decisions that affect us and those around us for good relations.

Morally, in order to understand the nature of human beings, we should be able to appreciate that humans are naturally weak, hasty, ignorant, and unjust. They are also said to be unappreciative, anxious, obstructive, fearful, mean, stingy, and misery.  Human beings love to argue and despairs when in poverty and in sickness.  These characteristics are always present in one but they always increase or decrease, surface or fade according to the upbringing and the amendment of the spirit.
These are by no means exclusive to every individual that possesses them (Wright, 1994).  First, we find out that some of the challenges that we face in our day-to-day life are determined by the placements of the planets, each of these represents different aspects of their mental and physical nature.  Therefore, at the time of birth different techniques may be used to estimate the issues that will eventually unfold throughout their lives.

Human beings are pack animals that have a characteristic of grouping together for the purpose of safety and well-being and the ability to attract each other, which is a principal towards our survival.  The manner in which we respond to these behavioral patterns and the expectations we seek from how others will respond to our actions are programmed into our behavioral or emotional loop during the earliest experiences (Chazan, 1998).  This point of view is determined in that the process starts in the womb just before birth, the unborn infant is basically aware of the mothers emotional and psychological responses to it at the most primal time (Chazan, 1998.

The character of a mature human being is being adopted mostly from their caregivers for food, warmth and many other things for survival, these are basically the parents.  Therefore, because of this, should the caregivers be less than good enough, the infants will resume that any harm is within themselves, that their disturbing behavior is as a result of their parents behavior, and this is likely to extend throughout their lives (Wright, 1994).  To save this kind of a circumstance, we often try to modify our behavior by interrupting the natural contact to change the behavior.

The human person is obviously connected with how much the world makes sense to us and how much we feel about others that we make contact with and in the understanding about their making.  The human species go by their personal worlds structures, systems, and the values that we believe to they are acceptable.  People differ in the way they handle certain issues at hand.  Some people believe that they are reasonable in taking violent actions in order to meet their goals.  This is though not acceptable by many.  Therefore, in this case contact and expression are the key components that can restore this to bring it to a balance.  It is through this that they can explore, express and achieve balance.  It is important to understand that the human character is influenced by the changes that take place intra-organismically within a person.  These changes enable a person to identify the limits of their capabilities both physically, emotionally and spiritually (Chazan, 1998).  An example is that people can estimate whether a certain behavior is acceptable to those they are close to or not, or they can determine if a certain mathematical problem is within their capacity to solve.  These intra-organismic processes allow human beings to observe and practice the existing and new ideas and their behaviors.

Some risky behaviors may be because of the unexpressed self-struggling to emerge on certain issues.  To help the people at this stage, they should be given genuine means of expression this may reduce the internal pressure that leads to this behavior.  On the other perspective, listening, performing, creating, and sharing are the aspects that can help them become aware of how their world makes sense to them and how others view the sense that they make.

The biopsychological behavior of human beings is a combination of the biological and the social factors that are used to explain the human behavior.  The scientists assess that human behavior can be explained by the genetics and heredity factors among them.  In case of genetics, the component that is responsible for this is the DNA, a special component of the cells.  The DNA structure is characterized by a number of subsections which dictate various functions of the human body and behavior. First is intelligence, which is partly determined by the genes.  This is strongly verified within the IQ intelligence of twins.

The biological approach also explains certain strange behaviors that are received through heredity and genetics.  A study that was conducted upon two brothers that were diagnosed with schizophrenia found out that a large percentage of these individuals had actually the same components that were similar in nature.  This showed that they had inherited these traits from their parents (Wright, 1994).  However, this does not mean that they should behave in the same way.

Persons or human beings may possess the same biological composition but have different character traits.  Another factor that determines the human behavior is that it is related to certain uncontrollable conditions that are common in all individuals.  For example, when a person is subjected to extreme hunger, the brain conditions them to look for something edible e.g. fruits or any thing edible.  Another example on the same note is that one of sleep (Chazan, 1998).  Sleep is controlled by a part of the brain called medulla oblongata.  It is the role of the brain to trigger sleep unconditionally. However, people sleep differently that is, some sleep more than others.  In this case, the medulla may be undergoing some malfunction or when it is working excessively, an individual will tend to sleep a lot more than the other.

We can understand the human behavior through cognitive development.  Through this approach, human beings are able to get meaning about the phenomena and the surrounding environment by drawing and establishing relationships between the mind and the objects or events occurring within the surrounding environment. As the mind develops and gets accustomed with certain ideas, they begin to react towards them in a way that brings about different reactions to them (Wright, 1994).  This leads to a person having a different attitude towards a certain item from another.  The psychological analysis of the human mind enhances us to understand the reason about certain emotions.  Through this, we can be able to understand why and how people react emotionally towards a certain issue while some others may not be affected in any way.  This largely is dependent on the role that the mind has on that particular issue or individual.  An example is that people may react to the temperature differences in different ways.

Biopsychological Social aspect is another aspect that tells us more about the human behavior.  Here, we consider the influences that the family and culture have on the human behavior.  It should be noted that in social analysis, there is a difference between ideal behavior, actual behavior and believed behavior.  For instance, a family may differ in the manner in which it tackles its events and issues from another while certain behaviors may be deemed unacceptable in some varied cultures.
Human personal traits are adapted to the environmental pressures, particularly the social ones.  This encourages a wide range of varied traits between the individuals.  People are able to respond to environmental warnings that are associated with impending punishments.  Through this aspect, people are able to develop a character of fear that is mostly common in the human species (Wright, 1994).

Human beings possess a certain aspect of self-motivation.  This is arrived as individuals cannot rely on other individuals for motivation.  This plays a key role where the individual gathers the courage and strength to achieve certain goals.  Therefore, this is essential in the development of new undertakings or making a positive change towards life.  Human character is modified by the needs that are demanded by the individual. Almost in every day today living human survival is defined by a series of key fundamental needs. These needs occur in an order of importance. They are highly hierarchical and it is after satisfying the very basic wants at one level that one graduates to satisfy needs on another category (Chazan, 1998).  These needs can be categorized as follows there is the need for survival, these survival levels consists of the basic need to sustain life the need for safety WHICH  involves protection from possible threat such as disease, violence among others the need of social belonging, this involves the need to be liked and wanted by family members, friends, coworkers, and others that they associate with there is the need for esteem, this involves the need to feel important from within and from other people that are surrounding us finally, there is the need for self-actualization, this means knowing our limits and trying to perform, within those limits, to our full potential. All these are the major aspects that are important in the modification of the human character.

We are the only animals that can think, this is because we can remember the past as discrete events then connect these with the present conditions.  Then on this basis, we can consciously decide what to do and project possible present actions into the future consequences of those actions (Chazan, 1998).  This is the reason as to why human beings respond differently to issues pertaining what they have at hand.  This is most fundamental aspect which differentiates the humans from the animals that usually react to stimuli.

The ability to think also means that we have two ways of viewing things, which is instinctively and intellectually.  The instinctive way of viewing things is instant and uncontrollable.  On the other hand, the intellectual view is always learned and alterable, it is based on the culture and the society in which the person lives.  We are able to use it to alleviate the effects of the instinctive view.  Another key aspect of human nature is the ability to pair themselves into social groups.  When staying alive it is not just the responsibility of the individual, but other members of the species that help the individual to survive, and vice versa.  This implies that human beings are dependent of each other (Chazan, 1998).  The purpose of a social group is often dictated by how well it serves to promote the survival of the other members.

n the case of people with the same background, the individuals make are usually real changes to the feelings and behavior as a result of interactions with others that are perceived to be similar and desirable.  According to the psychological principles, people regulate their beliefs with respect to others to whom they usually feel similar to attain an expected balance. The individuals also are said to be influenced by the majority, that is when an individuals social group that is large enough holds a particular attitude, this is likely to affect an individual in one way or another in his efforts to adjust to the environment (Wright, 1994). Additionally, an individual can change his mind according to an opinion that is due to an influence of another person believed to be an expert on the matters that are being handled.  This modifies a human behavior in one way or another.

Humans have the most complex society than any other animal in the planet Earth.  This is because we extend our self-preservation beyond the personal physical survival.  We live in the extremely independent and complex societies where people band together in groups for basically mutual aid and protection.  Such groups include families, friendships, associations, tribes, clans, and states or nations.  These individuals benefit by supporting each other and the group, because the group reciprocates by supporting the individual.  This is the reason for the protection offered unconditionally to the member of a certain group or location.  Humans in the process have developed societies that go beyond the needs of the present (Chazan, 1998).  For example, in the case of food and water, if the future is uncertain about their existence, to safeguard the future needs there is to be a way to transport the present resources into the future in a way that is not perishable.  Efforts are made by the members of a group to help in the survival of the group in the future in a way that is acknowledged later (Chazan, 1998).  This brings an aspect of safeguarding interests for the benefit of the group.

Humans differ in the way they posses their self control, this is understood as being a subset of emotional intelligence.  Here, a person may be intelligent yet he is still unmotivated to decide certain tasks.  This is natural and common to all individuals in a way that an individual has to be boosted to be able to handle the motivation.  A reward either tangible or intangible that is offered after a person has done an action will most definitely boost the morel of the individual.
In the everyday life, there are occurrences that are both within an individuals control and those that are beyond the control of them.  Therefore, people have to make choices and decisions about the situations that occur in our everyday lives.  The reasons why people make such decisions are diverse.  Some are complex whereas some are simple.  These decisions may have an impact or no impact on the individual life (Wright, 1994).  Many of the simple decisions people make do not require much thought and some can even be reached without awareness of the mind.  This is the major reason as to why people tend to take other issues more seriously than others, though they all require the involvement of the mind.

Another aspect about human behavior is that human beings are driven by reasons and emotions.  Humans are resourceful and evaluative as they strive to capitalize on their own interests.  Therefore, an individual interest can converge or diverge from the interests of an organization or group. In addition to that, it has been recognized that humans are driven by emotions that can be accorded with rational behavior e.g. when fear evokes caution in the face of danger.  Emotions can also be odd with rational behavior e.g. when pain avoidance leads to an unwillingness to tackle difficult decisions.  This therefore means that all in some circumstances the behavior of human beings is affected by the circumstances they are in (Wright, 1994).
 
In the case of the human sexual behavior, many kinds of activities that are engaged by human beings are generally governed by the social rules that are culturally specific and vary widely.  These rules are known as the morality and norms of the sexual behavior.  These norms and morals relate to issues including deception, legality, fidelity, and consent.  Some of these are known as sex crimes in some locations while in other locations they are not.  This brings about the difference in the way people perceive issues relating to sex.

The law of natural selection also plays an important role in the human behavior.  By applying this law to the general ecological and social environment on the primate man, certain specific predictions on the behavioral tendencies are derived.  It is suggested that discrimination may be derived from the primitive territorial behavior but that nationalism may have little connection with the territory (Wright, 1994). Therefore, individual from different territorial groupings may view others as inferior due to nationalism and self identity.  On other hand, the attitudes of the adolescents are also derived from the biological and the social factors.  Consequently, the adult attitudes for the teenagers sometimes appear to have a genetic bias (Wright, 1994).  All these cases are as a result of the difference in the status of both individuals.

There has been the behavior of humans to control and depend on one another.  An example is about the parents and their children.  Here, babies learn to cry for them to control their parents, this evokes the responses that are based on the fundamental habits in their parents (Chazan, 1998).  For the children the mastery of the adulthood environment is their strongest incentives to learn to speak, and later to read and write.  On the other hand, parents dominate their children through the obsession of the habits to them of either affectionate independence or fear while the husbands on the other hand tend to control their wives. Because of fear of loosing economic support, wives comply and they resort to sympathy (Wright, 1994).  This shows how people in the family relate with one another.
There is the issue of the influence of conformity, power and authority within the humans.

Conformity is expressed when an individual shows a particular opinion or behavior with an aim of fitting in a given situation and in order to meet the expectations of another, though he does not necessarily have in possession of that opinion or does not believe that the opinion is appropriate.  On the other hand, power is that ability to force a particular way through the control of the outcomes.  And finally, authority is that power that is believed to be rather legitimate by those that are subject to it.  Therefore, human beings have the tendency of fighting for the power, conformity and authority in the society where they live.  This gives them an exclusive behavior that they dominate above other higher primates.

Until the latter part of the 20th century, there had been no evidence for the heritability of IQ and it was just an assumption of the practitioners (Nature vs Nurture, 2005). However, this is not anymore he case today as the heritability of IQ has already been tested through several studies especially on twins and adoptees. Although some of the results point to the factor of nurture in the area of intelligence, there is an overwhelming weight of evidence in favor of the role of nature in shaping cognitive abilities. The only thing that varies from one study to another is how much of the results can be due to heritability.

Various studies on the biological inheritance of intelligence have been conducted by doctors, scientists, and geneticists, and have been published in several academic journals both online and offline. These studies all say one thing that somehow nature is partly, or even mostly, responsible for determining intelligence.

The main aim of this essay is to provide evidence for the aforementioned statements on the role of nature in shaping intelligence. Specifically, this essay will present the latest studies on the heritability of intelligence as well as evidence from twin studies. Moreover, this essay seeks to explain that even some studies whose findings do not exactly link nature and intelligence may also point out to such claims.

Evidence from Twin Studies
Twin studies provide the most qualified proof for the role of nature in determining intelligence. The reason is that, ideally, twins have an identical genetic make-up so that a phenomenon in one of the twins that is exhibited by the other twin is already a strong proof for the assumption that such a phenomenon is inherited. Various current twin studies will be presented and criticized in the following paragraphs to fulfill the aims of the essay.

Jacobs, Os, Derom,  Thiery (2007) found out that the fact that the twins share the same placenta and have a common blood circulation possess high heritability estimates at 82 for the verbal IQ, 72 for vocabulary IQ, 73 for the performance IQ, and 83 for the total IQ. These findings led to the conclusion that general cognitive ability (represented by the symbol g) is one of the most inherited dimensions of human behavior (Jacobs et al., 2007). The results of this confirmed previous studies like those of Wainwright et al. (2005) which found that genetic g accounted for 32 to 72 of the phenotypic variances, and explained 56 of variation in Verbal IQ and 42 for Performance IQ in the academic skills scores. The results suggest that general academic ability is more likely a result of genetic influences rather than common environmental influences. Another earlier study conducted by Singer et al. (2004) found out that general intelligence had a high heritability estimate of 74. In the same year, Price et al. (2004) found that this general intelligence is most pronounced by middle childhood and that the same genetic factors are responsible for individual differences when it comes to verbal and nonverbal abilities. Still, a study in Russia in the same year explored the genetic and environmental influences in cognitive abilities (Zyrianova, 2004) and found that cognitive characteristics are for the most part under genetic influences with estimates of heritability at 53.

These five aforementioned studies suggest a genetic basis for intelligence, specifically the general cognitive ability g. These studies directly investigated the various cognitive and even noncognitive abilities of twins and, through the data acquired from intelligence tests, came up with the conclusion that intelligence has a strong genetic basis.

Other studies, however, did not consider all the cognitive abilities but instead focused on a particular ability such as vocabulary (Van den Berg et al., 2004) and mathematical ability (Ando, 2004) and found the same genetic basis for intelligence. Van Den Berg et al. (2004) found that heritability varied from 50 to as high as 63 for vocabulary test scores from 997 adult twins or siblings of twins. The study also found out that genetic factors are responsible for the stability in vocabulary knowledge over time, where heritability reached 76. Furthermore, the study did not detect any noticeable influence from shared environmental factors, and although the males generally outperformed the females, results were similar for both sexes. Another study in Japan in the same year focused not on vocabulary but on mathematical achievement and was able to specifically underline the particular role that genetic influence has on mathematical ability (Ando, 2004). The study found that mathematical performance is largely an interplay of both additive genetic and shared environmental factors. Through univariate genetic analysis, the study was able to exactly link the two components of mathematical performance  verbal cognitive and spatial cognitive ability  with the additive genetic factor to explain the former and the common environmental factor to explain the latter. Although the study on mathematical performance found an almost equal influence of both nature and nurture in the development of mathematical abilities, it established the idea that intelligence with numbers is never possible without a substantial amount of genetic factor. The shared environmental factor in the development of mathematical skills is an obvious influence of education and other visible external factors. However, the existence of the additive genetic factor, whose influence is obviously not visible, was ascertained by this study.

Other twin studies focused on specific aspects of intelligence such as memory (Volk et al., 2006 Singer et al., 2005), speed in perceptual discrimination and IQ (Luciano et al., 2004), and academic achievement (Chertkova, 2004). Nevertheless, the same thing was found that intelligence is mostly inherited. A study conducted by Volk et al. (2006) found that free recall of unrelated and categorized words, as well as cued recall of categorized words, was found to be moderately heritable at 55 and vocabulary score was highly heritable at 77. Singer, MacGregor, Cherkas,  Spector (2005) found that memory ability has a heritability estimate of 45 which is relatively higher than the shared family environmental influences whose heritability was estimated only between 32 and 33. This study may not have established a strong genetic basis for memory. Nonetheless, it was able to somehow prove that the genes count more than the environment when it comes to shaping memory. Another study involving Australian and Dutch twins tried determining the heritability of the cognitive abilities of perceptual discrimination speed and IQ (Luciano et al., 2004). This particular study showed that genetic effects influenced IQ more than familial environmental effects. A Russian study conducted by Chertkova (2004) focused on the genetic influences in terms of academic achievement and found that achievement in humanitarian subjects or the social sciences were relatively more influenced genetically than achievement in the natural sciences. Based on the results of the study, the heritability of the Russian language was registered at 77 while that of Physics only at 26. Nevertheless the study was able to confirm that at least some of the genetic contribution to school achievement may only reflect the genetic contribution to general cognitive functioning (Chertkova, 2004). It can be seen from these four aforementioned studies as well as in the previously discussed study on mathematical performance that although there is admittedly an environmental factor in shaping cognitive abilities, still the role of the genes in determining intelligence cannot be emphasized more heavily.

There were also a number of twin studies that focused on problems and disorders but yielded results in favor of our thesis that intelligence is biologically inherited. Oliver  Plomin (2007), in their longitudinal study on language, cognition and behavior problems, used multivariate genetic analyses which allowed them to conclude that genes are generalists and environments are specialists (Oliver  Plomin, 2007). This simply means that similarity in performance across age and within and between abilities and disabilities in learning is largely due to genetic factors. On the other hand, differences as to performance are largely brought about by environmental factors. In another study, Reynolds, Fiske, Fratiglioni, Pedersen,  Gatz (2006) explored the heritability of cognitive dysfunction and found out that 35 of the likelihood of ones having cognitive dysfunction is due to heritable influences and the remaining 65 is due to nonfamilial environmental influences. The two aforementioned studies showed that although the environment was a necessary factor, still the genetic remains to be of extreme significance. In the study by Oliver and Plomin, nature and nurture seem to possess an equal influence on learning. On the other hand, Reynolds et al. (2006) emphasizes the relatively more significant influence of the environment compared to genetic factors. Nevertheless, these findings do not at all change the fact that a part of intelligence is biologically inherited.

Other twin studies focused on aspects of behavior that determined intelligence such as extraversion. Pincombe, Luciano, Martin,  Wright (2007) found in their study on the heritability of extraversion and its relationship with IQ that all extraversion facets were significantly influenced by genes. The heritability of activity was estimated at 25 while that of warmth was 54. The study also found out that there is a strong correlation between excitement-seeking and IQ and this is solely due to genetic influences. The study attributes such genetic effects to the influence of brain dopamine, a neurotransmitter that is known to have significance on both personality and cognition. The results of this particular study show that since certain aspects of the personality such as extraversion have a strong genetic basis, and that personality and intelligence are usually parallel, it therefore follows that intelligence too is heavily influenced by the genes.

Lastly, there were also twin studies that focused on suspected physical determinants of intelligence such as birthweight (Newcombe et al., 2007 Derom et al., 2004). Newcombe, Milne, Caspi, Poulton,  Moffitt (2007) conducted a study based on the hypothesis that birthweight predicts IQ and found that an increase of 1000 g in birthweight was associated with a 3 point increase in the IQ. In an earlier study, Derom, Thiery, Van Gestel, Jacobs, Vlietinck,  Fryns (2004) found that this phenomenon of correlation between birthweight and IQ is more pronounced in opposite-sexed twin pairs, especially with a female co-twin who is heavier than her twin brother. The findings of these two studies show that intelligence may indeed be genetically determined at birth and may even be physically indicated by certain physical attributes such as birthweight. The problem with these findings however is that birthweight may be due to several factors such as the volume of body fat or the weight of the bones, thus there is a need for a more in-depth study on what are the specific components or aspects of birthweight that more likely determine or predict intelligence.
Evidence from Family Studies

Family studies also provide some evidence for the genetic basis of intelligence. In a study undertaken by Thomas Bouchard of the University of Minnesota, the correlation between IQs is highest among identical twins and lowest among unrelated people. Identical twins reared together accounted for a percentage correlation 86 in their IQs. Identical twins reared apart accounted for 76 fraternal twins, 55 biological siblings reared together, 47 and unrelated people, 0 (Nature vs Nurture, 2005).

Family studies involving correlation of child-parent verbal ability scores also help establish the claim that intelligence is biologically inherited. The findings of these studies show that the verbal ability scores of children and their birth parents have a relatively higher correlation compared to those between adopted children and their birth parents, and even much higher than those between adopted children and their adoptive parents (Nature vs Nurture, 2005).

Conclusion
The heritability of intelligence has been one of the most highly-debated topics since the advent of neurology and psychoanalysis. However, it was not only until the latter half of the 20th century that twin studies and family studies have actually been conducted to investigate on the matter and to ascertain if the claim is true as well as to determine which part of intelligence was nature and which part was nurture. Twin studies proved the existence of a genetic basis for intelligence through direct experiments with all of the cognitive abilities or a specific ability at a time. Certain cognitive abilities which were equally or unequally influenced by both the genes and the environment still somehow proved the indispensability of the genes as a complement to the environment in the development of intelligence and cognitive abilities. Similarly, twin studies on behavior disorders, extraversion, and physical aspects such as birthweight also pointed out to the same conclusions. Lastly, family studies on IQ correlation among twins and verbal ability scores between children and their parents also proved that intelligence is all in the genes.