Although the majority of the general population decides not to offend and commit criminal acts, a significant proportion decides otherwise. Crimes are different, people are atypical, situational conditions and motives are diverse. Psychology's existence is based upon individual differences.

What will work for one person will not work for another. Impartiality and the scientific method are both integral components to psychology's mode of practise. The aim of psychological theories to understanding crime and delinquency is to speculate at what makes human beings act the way they do, absolutes play no function in psychology. Bernstein (ed), 2003,p; 31-32).

Legally we deal with the "crime" and not with the individual, yet psychologically we can be concerned with the individual to understand the nature and extent of criminality. The crime can then be seen to be the end result of the behaviour and interpretation and recognition of the "symptoms" could therefore reveal the causation. Psychology may not offer solutions, but can offer an insight into the criminal mind to produce broad general categories that can prove indispensable to implementing crime prevention strategies and policies.This essay will focus upon the major four psychological theories, the bio-psychological, the psychoanalytic, the cognitive and learning theories to the understanding of the aetiology of crime, comparing certain aspects to the sociological theories to assess the value and to evaluate the usefulness of the principles relevant to contemporary society Two fundamental points will now be explored. What is crime? And what is the relationship between psychology and crime? Crime is an act that is capable of being followed by criminal proceedings. The legal system represents society's consensus of what is acceptable behaviour.

However over time society's values and morals can alter and criminal law can reflect these changes, for example, abortion, suicide and homosexual behaviour have now been decriminalised. Whilst through advances in technology new laws emerge such as computer fraud and video piracy. A change in society's morals have now seen truancy included in legislation reflecting society's tolerance towards certain types of behaviour. The cause of crime within psychology is examined clearly within the positivist tradition. The relationship between psychology and crime is to isolate variables, which produce criminal behaviour.

The methodology used is "scientific" in orientation as methods to control, measure and determine relationships between variables are systematic and can be replicated. (Bernstein (ed) 2003, p; 29). The position psychology has in being able to examine the internal mechanics of individual's thoughts processes and actions enable predictions in human behaviour based upon empirical evidence. This aspect highlights the close relationship between biology and psychology. The implications of the psychobiological theories of criminality will now be discussed and evaluated.Biochemistry, genetics and neurophysiology are justifiable arguments with some observed experimental evidence to support the theory.

The genetic theory of crime holds the view that crime is a direct product of heredity factors, a criminal is "born" rather than "made". This positivist theory derives from Lombrosso who was a 19th century physician and criminal anthropologist, (Williams 2001, p;141), but for the relevance of this essay the more recent biological theories of genetic heredity and neuropsychological testing will now be explored.The genetic study of chromosome abnormality will be detailed with consideration to the role that they play on a person's criminality. Lastly decisions will be affirmed that ascertain whether or not the respective biological theory has application in contemporary society. A study that indicates that biological theories of crime are both accurate and relevant in contemporary society has been performed by Osborn and West (1979). The family study revealed that having a convicted biological father would markedly increase the risk of conviction in a son.

Farrington et al (1986) provided similar information on family backgrounds of offenders showing comparable behaviour patterns of criminals and their relatives. (Harrower 2001, p; 20-21). Gabrielli (1984:891) study revealed that having a convicted biological father would increase the risk of conviction in a son even if he were adopted at birth to a non-criminal middle class family. With assertions such as these backed up with sound methodology (Mednick 1988:5) it appears that certain biological factors are inherited down the family that cause criminality.

Because the correlation is strong and owing to the fact that genetic research has experienced significant advances it appears that this biological theory will have great application in future years. However the genetic theory alone does not explain how some children with criminal parents do not go on to lead criminal lifestyles. If genetics were solely responsible the results would be 100% conclusive. Another criticism is that genetics does not explain how many delinquent youths stop their activities when they reach their early twenties and settle down to family life highlighting individual choices and rational thought patterns.Social scientists would suggest that the socialisation and environment factors could be an influential factor when assessing whether criminality runs in families. Cultural differences and the social class position of the family need to be explored for a more comprehensive conclusion as Differential Association theory states that criminal behaviour is a learned process.

Individuals whose environment provides the opportunity to associate with criminals will therefore learn those skills. The interactions and values are then internalised. (Williams 2001, p;280).However feminist writers have a valid criticism when they state these studies and theories in general according to Gelsthorpe and Morris, (1990), have been developed from male subjects and validated upon male subjects.

Whilst there is nothing wrong with this, the problem is that these studies and theories have been extended generally to include all criminals, defendants and prisoners. Research that examines the role in which the central nervous system affects criminality is considered within the field of neuropsychological functioning. (Parsons 1977 p;47).The studies describe the way in which the brain relates to the behaviour of an individual. Buikhuisen (1987) research involved itself in studying not only the biological make-up of the subject but also the social background and the environmental factors which also contribute to criminality. The research argues that repeated convicted offenders have been shown to have deviant neuropsychological functioning It is the combination of biological and social determinants that Mednick (1988:248) argues undoubtedly increases predictive efficacy.

Although there has been much debate over the validity of this biological theory the point to note is that this study has carved itself a niche in which it attempts to explain criminality. This theory shows that biological theories are continuing to emerge and hold at least some relevance in contemporary society. Furthermore with regard to studies such as Mednicks it may well be that a new era of biosocial theories will be seen to be intrinsic in explaining crime in the 20th century, thereby refuting the notion that biological theories are a legacy of the 19th century.Another area of genetics that is also relevant is chromosomal abnormality.

It was discovered that there existed males who had two Y-chromosomes and one X chromosome and it was proposed that this leads to aggression in males that makes them more prone to violence (Jacobs et al: 1991). From this, the belief was that these men were more likely to be imprisoned for criminal behaviour. However these studies have encountered several surprises. Mednick (1998) research shows no strong correlation that indicates that XYY males were more criminal than normal males.

Owen (1972) indicated that the XYY male has an increased chance of being imprisoned not because of the aggressiveness but because of low intelligence. Furthermore this theory was trialed in a courtroom and was proved to be inadmissible evidence. (Mednick 1988:248). Under both a legal and a social science viewpoint we can assume that this theory isn't viable in contemporary society. In the areas of neuropsychological testing, it appears that owing to the weak correlations in research in determining crime this biological theory is minimal.The theory that showed the most promise in determining crime was the heredity study that demonstrated how some criminal genetics are inherited.

From this we can assume that genetic heredity has application in contemporary society. However considerations must be extended to neuropsychological testing of how this biological theory is now moving into a biosocial theory that incorporates environmental and social factors into research patterns. Criminology has now focused towards a comprehensive sociology of deviance over the years.Social controls rather than crime causation have become matters for concern. (Walton P, Young J 1998 p;221).

Criminal behaviour has been examined and determined so far by innate genetic and physiological incapacities, in other words, "a criminal is born bad". Eysencks trait personality theory attempts to incorporate biological, social and individual factors. Eysenck refers to the autonomic nervous system that controls breathing, sweating and body movement that can affect the ability to learn and to be conditioned to environmental stimulus.Eysenck also refers to how socialisation develops the conscience that is then internalised in different ways to develop basically three different personality types which are extroversion, neuroticism and psychoticism. Eysenck claims extroverts are socially impulsive and seek excitement and stimulation, stating extroverts have a genetic imperative that forces them to behave in certain ways and which makes them more difficult to condition.

Eysenck then proposes a connection between extroverts and criminal behaviour. (Hollin C 1989, p;53-55).Eysencks research was carried out upon criminals inside prison through the use of personality questionnaires. It can be argued the validity and reliability is not consistent in this approach. This theory is minimal in some ways, as it does not account for individuals multiple traits, for example, would a person respond in the same way to the same situation twice? Also the personality results could actually be a consequence of the experience of the individual been inside prison. This type of theorising neglects the "grey area" of criminality as not everybody who commits crimes ends up inside prison.

This trait theory can provide an indication of how a person may act, but it does not offer a detailed prediction. This theory views personality as the motivating force of behaviour as opposed to conditioning. Trait personality theory describes more than it explains which is viewed as a tautological approach to explaining criminal behaviour. (Muncie et al 1996 p;85-87). This theory has the potential to provide predictive personality details to be studied scientifically but it has yet to fulfil this potential, as far more research needs to be done and the lack of empirical verification remains a serious weakness.The trait theory was developed and enhanced from the behaviourist tradition as discovered by Ivan Pavlov (1904), a Russian physiologist and later carried on with the work of Skinner (1930) and Bandurra (1983) whose research led the theory to claim all behaviour is a learned process.

(Bernstein et al 2003, p;187;196). As Eysenck believed individuals were different to condition to the environment affecting the learning capabilities. From psychologists from Freud onwards the social aspect is recognised in relation to the experiences of the individual that then can in turn affect the biological makeup of the person.Frequently reference is made to problems within the socialisation process, something, somewhere, somehow has "gone wrong" in this process so as not to produce a well-rounded well-adapted individual, but on the contrary a maladjusted personality that is predisposed not to recognise various rules and regulations that exist within society.

(Williams 2001,p;193-208). Freud identified childhood experiences as being the key to the understanding of deviant behaviour. John Bowlby for example has argued that the failure of the mother to satisfy her child's "basic human needs" for emotional security that can then result in a psychopathic personality.There are methodological problems with these theories and maybe research such as Merton's anomie theory or the Chicago schools notion of social disorganisation can offer a different perspective when searching for the causes of crime. (Muncie 1996 p;65). Cohen's notion of the delinquent subculture share the same strands of thought, whilst understanding the relevance of subculture the Labelling perspective identifies how criminal behaviour becomes to be understood as deviant and analyses the impact of the labelling process.

(Walklate 1998, p;24).Nonetheless these learning and psychoanalytical theories have relevance in contemporary society as psychologists use behavioural therapy in a number of ways for a number of reasons. Psychologists began to look to the work of computer scientists in trying to understand the more complex behaviour that they felt learning theory or conditioning oversimplified. The mental processes referred to as cognition processes apply directly to the study of thinking, concept formation and problem solving skills. Cognitive behavioural therapy is a term that has largely replaced behavioural modification.

It combines various forms of conditioning with cognitive interventions to directly modify thinking patterns that are assumed to cause pathology. The procedures have elements of Pavlovian language and operant learning principles as very often the therapy instructs subjects to reinforce appropriate thinking and punish pathological thinking. (Williams 2001, p;279-280). The cognitive behavioural theory has application in contemporary society influencing many crime reduction programmes initiated by the Labour Government of today.Enhance Thinking Skills is a programme that seeks to change offenders thinking and behaviour through a structured series of exercises designed to teach problem solving skills and has been accredited for use in prisons and the community. One to One Offending Behaviour follows the same lead but includes training in social skills.

Aggression Replacement Training works with offenders to break the cycle of violence exploring the individual's interaction with the environment by analysing the way thoughts and feelings lead to acts of violence.These are relatively new and interesting influential programmes targeted as the root causes of crime and adapted into various alternative sentences that reflect the legal and societal views of crime causation. This theory shows the most promise in determining crime in contemporary society, however considerations should be given to the personality theories as to whether the lack of empirical verification means either that there is no relationship between genes and behaviour, or simply that genetic science is not sophisticated enough yet to isolate this relationship is a question that remains unanswered.It should not be viewed or believed that the origin of crime is due to unfavourable social conditions in which the criminal lives, as there are crimes that cannot be explained by social conditions alone, however Marxist criminologists suggest the characteristics of capitalism and consumerism can be given a place in the aetiology of crime. The economic system and its consequences according to Willem Bonger can weaken social feelings. (Muncie et al 1996, p;40-42).

The economic climate can be seen to have direct relevance to unemployment that can lead to many crimes especially fraudulent bankruptcy and theft.Katz's modern research Seductions of Crime pays reference to factors of the individual or social structural causation. (Muncie et al 1996, p;145-159). The psychology of the criminal are problems that the practises of law encounter when revealing the circumstances and causes that induced the criminal to commit the crime giving reference to a whole array of psychological evaluations as mitigating circumstances.

Criminal profilers who assist the police in their detective work use the relevance of geographical place, economic and psychological and social conditions that assist them in their search for the motives and the offenders.The answer remains as to how far one theory is capable of winning all the arguments. Certain theories explain certain behaviour better than others, but given the widespread nature of crime, then no one theory is indeed possible. Crime as Durkheim has argued is a social fact (Muncie 1996 p;47-50), that will require in future years the uses of scientific and qualitative ethnography among many other research methods to isolate variables that produce criminal behaviour.

So far these theories can be viewed retrospectively working back from the offender to see how the psychological seeds of the criminal behaviour begins when instead their should be aims to establish a predictable link to be able to make forecasts in advance. If psychology considered and involved the wider social structures and environmental influences, psychological enquiry may well contribute substantially to understanding crime in the future. (Moir 1995,p;24&61).