Biological influences are seen to be the first causes of delinquency (but by no means the worst). All behaviour including delinquency is affected in some parts by biological factors. Certain brain functioning can have an effect on aggression including lowered serotonin levels as this increases the likelihood of aggressive behaviour which is often associated with delinquent behaviour. Other biological process come into play in delinquency too and Raine (1993), found that delinquents tend to have a lower heart rate and lower skin response, how this affects delinquency is unknown but it does provide insight into the biological origins of delinquent behaviour.
Poor cognitive development as well as lower IQ levels have also been found to be associated with delinquency, Moffit (1993) notes that even mild neuropsychological deficits present at birth can snowball into serious behavioural problems by affecting an infants temperament, these deficits can affect children’s control of behaviours such as language, aggression, oppositional behaviours and attention and hyperactivity (discussed further in psychological factors).
Often these biological predictors of behaviour may not be the main factors in developing delinquent behaviours, but when likened with social factors the likelihood of delinquency is increased. Other biological influences that may affect delinquent behaviour include but are not limited to low birth weight, parental drug abuse while pregnant, complications at birth, lack of maternal bonding, hormones (testosterone) and head injuries.
“Pregnancy and birth complications are risks for Central Nervous System damage resulting in neurological and neuropsychological deficits that can lead to persistent and violent offending, these complications are not always directly related to violence, but are related primarily when combined with social risks such as maternal rejection, low socio- economic standards (SES) or family instability (Farrington & Coid, 2003). If a child is born with a neuropsychological deficit, into a low SES household, he/she may not get the necessary care, the mother in turn may reject the child or not bond with the child as the child is not responsive to the mother. These factors increase the likelihood of the child developing delinquent tendencies and is often referred to as the stress-diathesis model, where a person is predisposed biologically to certain mental problems and they are set off by environmental stressors.
The first and most important socialization we do is within our family. It is within families that we learn behaviours, outcomes of behaviours and consequences of certain behaviours. Family factors are therefore seen as one of the most important predictors in delinquent behaviours and various factors within the family unit all contribute to, or prevent the development of delinquent behaviours. Loeber (1990), notes that factors in the family are among the best predictors in later delinquency in offspring.
Inadequate parenting practices are again powerful predictors of delinquency. According to Farrington’s Cambridge study in Delinquent Development (1984), the boys who experienced extremes of poor parenting, harsh discipline and low family income were overrepresented among the most persistent offenders.Poor parental supervision allows for a child to do as he pleases as he has no boundaries and parents are not involved enough to teach a child right from wrong, also delinquent behaviour may be a way of extracting attention from parents.
The practicing of harsh or erratic discipline again presents a problem with boundaries, when parents only punish their children depending on their mood the child is in a constant state of flux and cannot discern right from wrong as one day he may exhibit a behaviour and get away with it and the next day be punished for it. This will ultimately lead a child to push the boundaries to test what he/she may get away with. Farrington found that antisocial parents tend to select antisocial partners and these antisocial parents often exhibit increased levels of conflict, offer poor parental supervision and harsh and erratic punishment.
These high levels of conflict amongst the family are also associated with the gradual development of aggression as a child learns how to socialize and deal with situations from their parents. If their parents often use aggressive tactics when interacting with each other and their children, the child learns to deal with any number of feelings aggressively. This is consistent with the social learning theory of Albert Bandura, and is a combination of both direct and vicarious modeling. A child learns from their parents how to deal with situations often using aggressive tactics displayed by both parents. Moffit (1993) argued that when a child’s vulnerability is compounded with such negative family conditions, life-course persistent offending is most likely (cited in Sampson & Laub, 2005).