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David Nussbaum

Psychology of Criminal Behaviour: A Canadian Perspective Chapter 2: Theories of Crime: Biological and Evolutionary Explanations CHAPTER 2: Theories of Crime: Biological and Evolutionary Explanations LEARNING OBJECTIVES 1. Describe the range of biological explanations of crime, which include genetics, neurochemistry, hormones, psychophysiology, and more. 2. Explain the basic principles of evolutionary psychology and demonstrate how these principles are used to understand crime in general as well as more specific forms of crime and specific types of criminal offenders. 3. Demonstrate that biological and evolutionary theories of crime are as much about the environment as they are about biology and evolution. 4. Demonstrate that biological and evolutionary explanations are not incompatible with traditional theories of crime (e.g., social learning theory, presented in Chapter 3), but rather are complementary. CHAPTER SUMMARY There are multiple pathways to crime. The focus in this chapter has been on evolutionary and biological explanations. Multiple pathways exist within each perspective, including biological factors such as genetics, neurochemistry, hormones, and psychophysiology. Evolutionary perspectives are complex, and evolution is comprised of a series of micro evolutionary theories (e.g., life history theory, frequency dependent selection). Biological and evolutionary explanations of crime underscore the importance of the environment. Environmental insults (e.g., a mother who drinks during pregnancy) change the “biological” makeup of an individual such that he or she is now predisposed to a future criminal lifestyle. Evolutionary mechanisms were shaped by the environment, albeit a distant one. Evolution itself has determined our minds such that they adapt and change to current environmental cues. The theory of evolution has more in common with “environmental” theories such as social learning (discussed in Chapter 3) than one might think. The only difference is that evolution focuses on the learning environment of the entire species whereas social learning theories focus on the learning environment of an individual. It is a myth that evolutionary accounts of crime contradict traditional theories. Evolutionary perspectives simply focus on providing ultimate explanations, and traditional criminological theories focus on more proximate explanations. The perspectives tend to complement rather than contradict. When theories do diverge it indicates that one perspective is incorrect. This chapter has shown that “the evidence for genetic influences on criminality is no longer scientifically questionable” (Ellis 2008: 249). It has also demonstrated that the path to crime is complex and that a number of biological subsystems interact with one another to increase risk of future criminality, with the environment greatly influencing whether certain biological predispositions will manifest. Copyright © 2011 Pearson Canada Inc. 14 Psychology of Criminal Behaviour: A Canadian Perspective Biological and Evolutionary Explanations Evolution is uncontested in scientific circles. However, evolutionary psychology, in particularly evolutionary forensic psychology, is in its infancy. More research from different perspectives is required. The link between evolutionary and biological explanations of crime is a natural one. In the evolution section, we focused on psychological mechanisms that have evolved in response to ancestral selection pressures. This does not negate the existence of evolved biological mechanisms such as those reviewed in the first part of the chapter. LECTURE OUTLINE 1. What Makes a Strong Theory?  Numerous textbooks and experts have defined the meaning of theory.  the definition here represents an amalgamation of perspectives: a theory is an explanation of a particular phenomenon  a strong theory: 1. is parsimonious; 2. clearly identifies the causal mechanisms and corresponding mediators and moderators underlying the phenomenon of interest; 3. is testable and hence falsifiable via hypotheses and predictions; 4. is based on empirical data and is modified in response to new data; 5. possesses interdisciplinary compatibility; and 6. respects gender, ethnicity, and culture. 7. “Does this perspective provide a good theory of crime?” e.g., are certain explanations stronger (causal evidence is presented versus correlational evidence?) 2. Background: Historical Context:  phrenology is theoretical perspective stating there is a relationship between the shape and size of a person’s head and his/her personality, mental ability, and behaviours.  Spurzheim students, applied the principles of phrenology to explain why 30 women had killed their children.  Spurzheim concluded that the women suffered from an underdeveloped part of the brain responsible for loving children.  Spurzheim failed to include a comparison group—women who had not killed their children  phrenology eventually died out but an Italian physician, one step further and began comparing criminals (men, and women and prostitutes), to “normal” segments of the population  Lombroso argued that criminals possess distinctive physical features (sloping foreheads and twisted lips not observed in his “normal” subjects.)  referred to these features as atavisms  suggested that criminals were evolutionary throwbacks who had more in common with Neanderthals than modern-day man Copyright © 2011 Pearson Canada Inc. 15 Psychology of Criminal Behaviour: A Canadian Perspective Biological and Evolutionary Explanations  Lombroso remains the “father of criminology.”  Darwin published On the Origins of Species in 1859, almost 17 years before Lombroso published the first volume of The Criminal Man.  Darwin posited that humans had evolved from ancestral species via the mechanisms of natural selection.  Galton founded eugenics—the theory that was ultimately responsible for the forced sterilization (or worse) of thousands of “unfit” individuals in the United States during the early part of the twentieth century and for the atrocities under Hitler’s regime (forced abortion, sterilization, and, ultimately, death camps.  a number of social scientists have dismissed or scorned biological and/or evolutionary approaches.  The study of biology and evolution has advanced considerably since Darwin and Lombroso 3. Researching Biological Explanations of Crime:  Behavioural genetics researchers use twin methodology: are identical twins are more likely to commit crime than non-identical twins?  Molecular biologists compare the genetic makeup of a group of “criminals” to one of “non-criminals” to look for distinct genetic differences between the two.  Neurochemical approaches examine how genes actually express themselves in terms of the brain’s neurotransmitter systems.  other researchers rely on brain-imaging techniques such as computer tomography (CT) to assess brain functions and impairment in antisocial individuals.  Defining crime is a complex task.  some researchers examine the link between biology and crime: compare “normal” individuals to individuals who officially diagnosed with antisocial personality disorder (ASPD), conduct disorder (CD), or psychopathy,  others use measures of aggression or composite indices of antisocial behaviour obtained via self-report or from parents or teachers.  Researchers often define crime using current legal definitions, examine biological factors to correlate or predict official criminal offending (use the form of arrests or convictions).  Targets of study focus on males or females.  may study children, adolescents, adults, or specific groups of offenders 4. Genetics and Crime—Twins, Adoption, and Molecular Genetics: Twin studies  need to disentangle genetic and environmental influences. Is criminal behaviour a result of genes or socialized attitudes and life skills  behavioural genetics relies heavily on the study of twins and adoptions which can help separate genetic from environmental influences Copyright © 2011 Pearson Canada Inc. 16 Psychology of Criminal Behaviour: A Canadian Perspective Biological and Evolutionary Explanations  Every human being shares about 99 percent of his or her DNA sequence with the rest of the human species.  The percentage of DNA that humans collectively share is fixed and accounts for our basic similarities  Behavioural genetics focuses on the remaining 1 percent of the variance  Monozygotic (MZ) or identical twins are genetically identical. They share 100 percent of their genes  dizygotic (DZ) or fraternal twins are no more alike than non-twin siblings, sharing on average only 50 percent of that 1 percent  frequency of criminal behaviour is converted into a concordance rate that represented the percentage of both twins classified as “criminal.”  Concordance rates would be calculated separately for MZ and DZ twins and then compared.  A concordance rate of 30 percent for the DZ twins would mean that if one of the DZ twins was “‘criminal,” then there was 30 percent chance that the other DZ twin was also criminal  Evidence for a genetic contribution to crime is inferred if concordance rates are higher among MZ than DZ twins.  Concordance rates are typically converted into a heritability coefficient—a descriptive statistic that represents the proportion of phenotypic variance in a given behaviour (e.g., criminal) that can be attributed to genetic variation among individuals  more complex statistical approaches such as biometric ▯modeling have been used to estimate heritability coefficients  statistical ▯modeling—permits the estimation of two types of environmental factors: 1. shared environmental factors (i.e., aspects of the environment shared by all family members, such as living in poverty); and 2. non-shared environmental factors (i.e., aspects of the environment not shared by all family members, such as exposure to different peer groups or differential treatment by parents  genetic studies are about genes and are about environment.  this type of twin study may overestimate or underestimate the genetic contribution for several reasons 1. parents are more likely to provide similar environments for MZ twins than their DZ counterparts 2. inheritability estimates for MZ twins may be confounded by prenatal factors that by definition aren’t necessarily genetic e.g., MZ twins usually share one placenta and DZ twins usually have two separate placentas  earlier twin studies were also criticized for using small sample sizes and for being subject to political influence Copyright © 2011 Pearson Canada Inc. 17 Psychology of Criminal Behaviour: A Canadian Perspective Biological and Evolutionary Explanations Adoption Studies  Adoption research has taken one of two forms: 1. parent–offspring: concordance rates (or correlations) between adoptive parents and adoptees’“ antisocial behaviour” are compared to concordance rates (or correlations) between biological parents and adoptees. If the concordance rates/correlations are higher for the biological parents and the adopted offspring than the adoptive parents and the adopted offspring, genetic contributions to antisocial behaviour are inferred 2. sibling–offspring: concordance rates between adoptive siblings are compared with concordance rates between biological siblings. One strong adoption study of 14 427 nonfamilial adoptions in Demark between 1924 and 1947found: if both the biological and adoptive parents had no criminal record, then only 13.5 percent of adopted sons had criminal records; if the adopted parent had a criminal record and the biological parent did not, this percentage increased marginally to 14.7 percent. In contrast, 20 percent of adopted sons had a criminal record if the biological but not the adopted parent also had a criminal record, but the highest level of criminality (24.5 percent) was observed if both sets of parents—biological and adoptive—had criminal records.  the study demonstrate that genes play a role in explaining crime and that environmental effects are important.  Adoption studies limitations: 1. generalizability; and 2. environments of adopted offspring tend to be more advantageous relative to the general population,  meta-analytic review of studies (aggregating the results of 10 independent adoption samples and 42 independent twin samples): the variance in antisocial behaviour could be partitioned as follows: heritability,.41; shared environment,.16; and non-shared environment,.43.  Moderators examined included: 1) zygosity determination (self-report vs. blood typing, or both); 2) assessment method (e.g., parental ratings of antisocial behaviour vs. teacher- and self ratings vs. official criminal records); 3) operational definition of antisocial behaviour (e.g., psychiatric diagnoses of conduct disorder and antisocial personality disorder vs. legal definitions, official criminal convictions vs. overt aggressive behaviour— e.g., gets into fights, uses a weapon frequently); 4) sex of the participants; and 5) age of the participants.  highlights of the results of the moderator analysis: the observation that twin studies garnered higher heritability estimates than adoption studies and that genetic effects were slightly higher for females than males; that the genetic proportion of variance increased with age (genes exerting more influence during adulthood than childhood).  both genetics and the environment both contribute to variance in antisocial behaviour. Copyright © 2011 Pearson Canada Inc. 18 Psychology of Criminal Behaviour: A Canadian Perspective Biological and Evolutionary Explanations  research increasingly shows that the gene–crime link is most likely not direct but rather a function of the mediational effects of inherited characteristics that predispose an individual to antisocial  genetics might reduce or magnifying the effects of environmental risk factors  behavioural geneticists: are there interactive effects between genes and the environment?  The evidence demonstrates that childhood maltreatment (e.g., physical abuse, emotional abuse, sexual abuse, neglect) contributes to the development of antisocial and criminal behaviour  less clear is why 50 percent of maltreated children do not engage in delinquency, aggressive behaviour, or criminality  one study used a genetic risk continuum based on their co-twin’s conduct disorder status and the pair’s zygosity: the experience of maltreatment (as reported by parents) increased the probability of receiving a conduct disorder diagnosis by 1.6 percent among children deemed “lowest genetic risk”—i.e., MZ co-twin did not have CD diagnosis; the probability of receiving a conduct disorder diagnosis increased to 23.5 percent among children deemed “highest genetic risk”—i.e., MZ co-twin had CD diagnosis. Molecular Genetics Research  Twin and adoption studies illustrate that there is a clear link between genetics and antisocial behaviour (actual functional gene(s) involved has not been identified).  The main function of a gene is to produce proteins comprised of amino acids—the basic building blocks of life.  Proteins are responsible for the phenotypic expression of our genotype.  Faulty genes either reduce too much or too little of a particular protein. Human genes are  Caspi and colleagues (2002), using an epidemiological study, demonstrated an interaction between a specific gene [monoamine oxidase A (MAOA), a sex-linked gene] and a well-known risk factor—childhood maltreatment.  The MAOA gene is responsible for encoding the MAOA enzyme, which in turn is responsible for metabolizing key brain neurotransmitters such as norepinephrine (NE), serotonin (5-Ht), and dopamine (DA), all of which have been implicated in aggression and various forms of antisocial behaviour.  The two existing versions of the MAOA gene—low activity and high activity—are the result of apolymorphism.  Researchers found evidence for a strong gene by environment interaction across all four measures of antisocial behaviour—conduct disorder, violent convictions, violent disposition, and antisocial personality disorder symptoms.  While maltreatment by itself had deleterious effects, its effects were exacerbated by the presence of a low-activity MAOA gene. Copyright © 2011 Pearson Canada Inc. 19 Psychology of Criminal Behaviour: A Canadian Perspective Biological and Evolutionary Explanations  Thus there is increasing evidence that the low-activity version of the MAOA gene, sometimes dubbed the “warrior gene,” plays a significant role in the expression of antisocial behaviour, particularly aggression and violence  more importantly, the low-activity MAOA gene only expresses itself in the presence of certain environmental cues, such as childhood abuse or provocation. 5. Neurochemistry and Crime—Hormones and Neurotransmitters:  Genes are largely responsible for the expression of hormones and neurotransmitters.  the endocrine system regulates hormone production and distribution,  the nervous system regulates the production and function of neurotransmitters. Hormones and Crime  The endocrine system governs more than 50 hormones  hormones are released into our bodily fluids (typically via the bloodstream) by nine primary glands that comprise the endocrine system (e.g., hypothalamus, thyroid, and gonads—testes and ovaries).  only specific target cells will actually respond to a given chemical message  regulate metabolism, growth, and development, and impact behaviour.  imbalances may be minor, resulting in mood swings or severe, resulting in serious illness or death  testosterone is implicated in criminal behaviour, violence and aggression,  Testosterone is a steroidal hormone of the family of androgens.  responsible for developing and maintaining male primary and secondary sexual characteristics  The relations between aggression and testosterone is well established in the animal world  earlier meta-analyses reached the same conclusion—the relations between testosterone and aggression in humans is positive yet weak.  two factors moderated the effect: age and time of day testosterone readings  Gender, offender status, and method of testosterone or aggression measurement did not influence the magnitude of the findings.  these studies were correlational – few if any have shown that testosterone levels are either causally related to or predictive of future aggression  plausible that aggression actually causes testosterone levels to increase or that some additional third mediating variable(s) is accounting for the effect  physical and chemical castration studies have shown that sexual re- offending is reduced in offenders who have undergone chemical and/or physical castration versus those who have not or who did not comply with anti-androgen medication Copyright © 2011 Pearson Canada Inc. 20 Psychology of Criminal Behaviour: A Canadian Perspective Biological and Evolutionary Explanations  premenstrual syndrome (PMS), has been studied in the context of crime and aggression and has been used (albeit rarely) successfully as a legal defence in Britain and the United States and as a mitigating factor in Canada Neurotransmitters  neurotransmitters are chemical messengers that operate in the brain and are the messengers of the nervous system.  Neurons or nerve cells transmit instructional signals from one part of the body to another and neurotransmitters play a critical role in this communication process.  there are two types of neurons—pre-synaptic (the sender) and postsynaptic (the receiver).  The postsynaptic cell receives the message using its dendrites.  Narrow gaps or synapses exist between the pre-synaptic and postsynaptic cells.  Some of these synapses are electrical and some are chemical (electric impulses are converted to chemical signals by the neurotransmitters)  Neurotransmitters are stored in synaptic vesicles.  Three neurotransmitters in particular have been studied in relation to crime: serotonin, dopamine, and norepinephrine. Serotonin:  The neurotransmitter serotonin, or hydroxytryptamine (5-HT), plays an important role in behavioural inhibition and mood regulation  produced from an essential amino acid, tryptophan.  Tryptophan is not produced naturally within the body but must be obtained from diet (protein-based foods such as turkey and chocolate).  there is a link between a malfunctioning serotonin system and impulsivity, irritability, and aggression – found in studies that operationalized malfunctioning serotonin systems as low levels of serotonin, low levels of its precursors such as tryptophan, low levels of its metabolites and faulty serotonin receptor sites on the postsynaptic neuron  one meta-analytic review of 16 studies illustrated that serotonin levels were substantially lower among antisocial individuals than non-antisocial individuals – the effect was even more pronounced for individuals under the age of 30 versus individuals over 30  The effect did not change as a function of gender, target of violence, history of suicide, or alcoholism.  epidemiological research design was used to test the serotonin aggression hypothesis between blood serotonin (high levels of blood serotonin mean low brain serotonin levels).  results confirmed a moderate (positive) correlation between blood serotonin levels and violent criminal behavior for men but not women and results did not vary as a function of whether or not criminal behaviour was measured officially or via self-report. Copyright © 2011 Pearson Canada Inc. 21 Psychology of Criminal Behaviour: A Canadian Perspective Biological and Evolutionary Explanations  thus research clearly suggests that there is a correlation between a malfunctioning serotonin system and aggression.  other research illustrates that low levels of serotonin increase impulsivity (a known correlate of aggression) and suggests that serotonin may exert its influence indirectly on aggression through the mediator of impulsivity or perhaps negative mood.  Dopamine  The release of dopamine causes feelings of pleasure that accompany factors such as sex, love, and food.  The dopamine pleasure centre can be triggered artificially with illicit drugs, alcohol, and nicotine, (known to increase aggression).  research examining the dopamine/aggression link is relatively sparse in comparison to the serotonin literature base and is somewhat mixed, with some linking both high and low levels of dopamine with aggression  this may be explained by one hypothesis that posits that individuals with low levels of dopamine require greater levels of stimulation to experience pleasure and are more likely to develop addictions to illicit drugs such as cocaine that quickly increase dopamine levels and create an immediate “high” but also have the side effect of increasing aggressive tendencies.  dopamine also regulates other neurotransmitters, including serotonin and norepinephrine – dopamine exerts its influence indirectly via these neurotransmitters  More research is needed to fully understand the role that dopamine plays in antisocial behavior and aggression.  Norepinephrine  signals the body to react to short-term stress by increasing heart rate and blood pressure  Limited research suggests that high levels of norepinephrine are correlated with aggression  supported by the finding that certain drugs (e.g., reserpine) that reduce norepinephrine levels also reduce aggression  further investigation is needed to determine the exact role of norepinephrine in antisocial behaviour. 6. Psychophysiology and Crime:  A psychophysiological theory uses physiology (e.g., low resting heart rate) to explain psychological constructs (e.g., emotions, motivation, learning  These theories try to link measures of autonomic response (e.g., heart rate, electrodermal activity/galvanic skin response/skin conductance) to various measures along the antisocial spectrum.  Electrodermal activity (EDA) measures the amount of electrical current between two points on the skin.  Increases in heart rate and EDA are related to general emotional responses such as fear, anger, or anxiety Copyright © 2011 Pearson Canada Inc. 22 Psychology of Criminal Behaviour: A Canadian Perspective Chapter 2: Theories of Crime: Biological and Evolutionary Explanations  One of the most prominent psychophysiological theories is Gray’s arousal model based largely on animal models of behavior  Hypothesizes that personality, learning, motivation, and emotional responses are largely governed by two underlying biological systems of autonomic arousal: the behavioural activation system (BAS) and the behavioural inhibition system (BIS).  The BIS is conceptualized as an avoidance system responsible for inhibiting or stopping behaviour in the face of punishment  The BAS is an approach or reward-seeking system that responds to positive incentives/rewards  the BIS is linked to anxiety, the BAS is linked to impulsivity and sensation-seeking behaviour  hypothesized that antisocial individuals have underactive behavioural inhibition systems (are more fearless, less anxious, and less responsive to aversive cues  this fearlessness and absence of anxiety manifests in autonomic responses such as a low resting heart rate or low EDA.  Antisocial individuals have underactive behavioural activation systems and are prone to sensation-seeking and impulsive tendencies that tend to lead to antisocial behaviour one of the most comprehensive reviews of the literature on psychophysiological tests of antisocial behaviour found that there is a small effect for the relation between HR or EDA and various conceptualizations of antisocial behaviour (e.g., aggression, psychopathy/sociopathy, conduct problems); and this small effect is most evident for psychopathy when EDA is used as the measure of autonomic arousal (regardless of whether the paradigm involved “rest,” “task,” or “reactivity”).  This review supports idea some antisocial individuals, (psychopathic), show deficits in their behavioural inhibition system:: Did a faulty behavioural inhibition system (BIS) lead to psychopathic tendencies? Or did psychopathic tendencies lead to a faulty BIS?  In sum, while measures of autonomic arousal are small or possibly moderate correlates of antisocial behaviour, the predictive and/or causal status requires more research. 7. The Brain and Crime—Neuroimaging and Neuropsychology  The story of Phineas Gage was the first documented “natural experiment” linking the brain to personality and behaviour.  Scientists have accumulated much knowledge about the brain and antisocial behaviour since Gage’s unfortunate accident using brain imaging studies and neuropsychology Brain Imaging  Brain imaging (or “neuroimaging”) research examines the structural and functional characteristics of the brain B  Brain structure is typically studied with magnetic resonance imaging (MRI) and computed tomography (CT), while brain function is studied Copyright © 2011 Pearson Canada Inc. 23 Psychology of Criminal Behaviour: A Canadian Perspective Chapter 2: Theories of Crime: Biological and Evolutionary Explanations through positron-emission tomography (PET) and single photon emission computed tomography (SPECT)  Brain imaging studies are complex and diverse: involve assessing a small number of “known” antisocial individuals to a comparison group earlier studies compared the brain structures and/or functions of the two groups  more recent studies have compared brain function while the test subjects were engaged in some cognitive activity  a recent review by Raine and Yang (2006) summarizes the results and provides an integrated conceptual framework:  the study hypothesized that structural and/or functional damage to the areas of the brain posited to be responsible for moral reasoning and emotional regulation result in an “antisocial tendency.”  This antisocial tendency is thought to manifest in a variety of forms, ranging from violent and sexual offending to psychopathic tendencies and general criminality.  summary identified structural and/or functional deficits in four areas of the brain: 1. the frontal lobe—implicated in several higher order functions such as cognitive reasoning, planning, sound judgment, patience, abstract thought, moral reasoning, violence, and aggression regulation; 2. the temporal lobe—also implicated in the production and inhibition of aggression (includes the amygdala, specifically involved in emotional and fear situations; and the hippocampus, specifically involved in memory, learning, and emotion regulation); 3. the parietal lobe—integrates sensory information related to movement and space; and 4. the cingulated gyrus—the part of the brain that partially surrounds the corpus callosum (the juncture in the brain that joins the left and right hemispheres). Importantly, several of these structures are part of the interconnected limbic system (i.e., the amygdala, hippocampus, and cingulated gyrus)  In general, the limbic system is associated with emotion and the autonomic expression of emotion—faster heartbeat, faster respiration, trembling and sweating, and basic drives such as sex, hunger, thirst, and the “fight or flight” response  key conclusions: 1. structural and/or functional damage to the frontal lobe, specifically the pre-frontal lobe, is the most replicated brain imaging abnormality found in offenders to date. 2. the evidence is starting to suggest that structural/functional impairments to parts of the limbic system (e.g., the amygdala and the hippocampus) and the temporal lobe are also implicated in antisocial behaviour. 3. there is no single brain structure that is ultimately necessary for the development of antisocial behaviour; rather there are multiple Copyright © 2011 Pearson Canada Inc. 24 Psychology of Criminal Behaviour: A Canadian Perspective Chapter 2: Theories of Crime: Biological and Evolutionary Explanations potential contenders and as the number of deficits increases, so does the probability of antisocial behaviour. Neuropsychology  neuropsychology studies brain function indirectly: a battery of paper/pencil and/or motor tests designed to diagnose what part of the brain is malfunctioning  Experts in the field of neuropsychology have studied whether deficits in executive functioning (cognitive functioning involving future goal- oriented behaviour, purposive attention, organizational skills, and inhibitory control) are related to antisocial behaviour.  these functions have been associated with the frontal lobe, and perhaps other components of the brain such as the connector pathways  a recent meta-analytic study: A robust effect was observed, indicating that poor executive functioning is related to antisocial behaviour. 8. Other Biological Considerations—Pregnancy, Birth Complications, Toxins, and Diet:  Certain environmental insults change our biology in a manner that heightens our propensity toward antisocial behaviour.  Inadequate prenatal (during pregnancy) conditions, perinatal (during birth) complications, improper diet, and environmental toxins (e.g., lead) result in changes to our biology that may in turn make us more likely to engage in antisocial behaviour.  There is some evidence of a link between hypoglycemia (low blood sugar—known to result in panic, irritability, nervousness, and aggression: a double-blind study found that a program reducing sugar reduced antisocial behaviour by 48 percent.  Researchers have also investigated the impact of certain neurotoxins, namely lead, cadmium, and manganese, on brain development.  age 11, children with elevated lead levels exhibited significantly more antisocial behaviour than their “normal lead level” peers  Manganese is known to impact serotonin and dopamine levels and to somehow alter the levels of the monoamine oxidase (MAO) enzyme: children with learning problems, attention deficits, and attention deficit hyperactivity disorder (ADHD) had elevated levels of manganese.  diet-related research regarding the impact that vitamins, minerals, fat, fatty acids, food additives, and even food allergies can have on antisocial behaviour as well as the known precursors of antisocial behaviour—e.g., hyperactivity  abnormal fetal development due to a variety of factors—maternal smoking, drinking (Fetal Alcohol Spectrum Disorder), poor nutrition, trauma experienced by the mother, and birth complications may predispose an individual to antisocial behaviour.  hypoxia or lack of oxygen to the brain at birth can have a profound impact on development, increasing the probability of learning disabilities, impaired cognitive functioning, and intelligence: Copyright © 2011 Pearson Canada Inc. 25 Psychology of Criminal Behaviour: A Canadian Perspective Chapter 2: Theories of Crime: Biological and Evolutionary Explanations  Raine (1993) has hypothesized a direct link between birth complications and adult violence.  research has shown two things 1. the environment (e.g., positive parenting) can reverse the potentially deleterious effects associated with pregnancy and birth-related insults and thus serve to protect individuals from their “biology” 2) 2. the environment (e.g., poor parenting) can aggravate “biological risk,” such as children born with subtle neurological impairments (perhaps due to birth complications)  it is important to underscore the complex interactions occurring not only within the biological subsystems but also between them.  there are complex interactions occurring at the environmental level. e.g., the positive impact of “diet” on hyperactive children is magnified when accompanied by a supportive home environment
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