Genetic and environmental explanations of juvenile violence in advantaged and disadvantaged environments

This study tests the proposition derived from behavioral genetic theory that genetics and environmental variables have different effects across different environments. I examine the effects of intellectual imbalance [performance IQ (P) significantly greater than verbal IQ (V)] a variable assumed to be heritable to some extent, and love deprivation, a composite variable consisting of various indices of parental abuse and neglect, on violent delinquency within different socioeconomic status (SES) environments. The findings are consistent with behavioral genetic theory, in that love deprivation could not explain any unique variance in violent delinquency after P gt V explained all that it could in the advantaged environment (49.5%), and P gt V could not explain any unique variance in the disadvantaged environment after love deprivation explained all that it could (28.8%). It was also found that love deprivation explains a highly significant 30.5% of the variance in P gt V among SES-disadvantaged subjects, thus supporting those who posit that environmental disadvantages contribute significantly to intellectual imbalance. Violit summary: OBJECTIVE: The purpose of this study by Walsh was to test the proposition, based upon behavioral genetic theory, that genetic and environmental factors will exhibit differential effects upon violent delinquency across different environmental contexts. METHODOLOGY: The researcher employed a non-experimental case-study design, with a non-probability sample of 388 white juvenile delinquents who had been processed through an Idaho juvenile probation facility in the middle of the 1980's. Measures included a number of genetic as well as environmental factors, to examine their influences upon delinquency for subjects from three different socio-economic statuses. The genetic-related trait for this study was reported IQ, whilst the environmental factor was a measure of love deprivation. The IQ variable was more specifically defined as the difference between the subjects' reported performance IQ scores and their verbal IQ scores (a P > V intellectual imbalance). Love deprivation was measured using the Walsh and Petee love deprivation index. Seven indicators of love deprivation were used - physical abuse, psychological abuse, parental promiscuity, parental substance abuse, broken home, illegitimate birth and feeling unloved. The alpha reliability for this measure was somewhat questionable, at 0.62. Each subject's case history was assessed by the author for each of the seven indicators, with the subject being assigned the mean for each indicator that was derived from the initial professional rating. Socioeconomic status was determined via a composite measure of family income and occupational status of the head of the household. Three groups were differentiated - the homogeneously advantaged, the homogeneously disadvantaged, and a heterogeneous group for reference purposes. Violent delinquency was determined with the Andrew Violence Scale, with each incident being scored additively. Violence was defined as homicide, rape, robbery, aggravated assault, assault and battery. Analyses included Chi- Square, correlations and regressions. FINDINGS/DISCUSSION: The author found that there were five times more boys in the sample who had higher performance IQ scores than verbal IQ scores (P > V) than there were V > P boys. He suggested that the P > V profile thus appeared to be a marker of antisocial behavior, with the performance component being the active ingredient of the profile. Socioeconomic status (SES) had a significant but weak effect on P > V, with higher SES subjects showing a lesser difference in performance and verbal scores. For the whole sample, regardless of SES, love deprivation, P > V and SES showed a significant but modest relationship to violent delinquency. For the disadvantaged group, the mean of violent delinquency was almost twice that of the other two groups. This group also had the highest mean love deprivation scores, although the three groups did not differ on P > V. The author suggested that, consistent with behavioral genetic theory, the environmental variable of love deprivation impacted most significantly upon violence within the disadvantaged group, with the effect decreasing as SES environments improve. For the disadvantaged group, there was a high correlation between love deprivation and violence, whilst for the advantaged boys, P > V correlated strongly with violent behavior. Neither factor, however, strongly correlated with violence in the heterogeneous group. For the disadvantaged group, regression analysis showed that, after love deprivation explained all the variance it could (25.8%), P > V did not account for any unique variance. Conversely, for the advantaged group, love deprivation had no unique explanatory power after P > V accounted for all the variance that it could (49.5%). For the heterogeneous group, both variables were able to significantly, although weakly, predict violent delinquency (8.9%). The environmental variable, therefore, impacted much more strongly upon the disadvantaged than the advantaged boys - a finding that is consistent with behavioral genetic theory which stipulates that in lower SES environments, negative environmental influences will overwhelm any variance in individual differences in accounting for violent behavior. For the higher SES boys, individual differences, such as P > V, will have a larger impact upon such behavior patterns than will environmental factors. AUTHOR'S RECOMMENDATIONS: The author suggested that general theories of violent delinquency must take into account both environmental and individual differences, as well as interactions between the two variables. He advocated the use of twin studies to more precisely ascertain the influences of environmental and genetic factors upon violent delinquency. EVALUATION: This study presents an interesting examination of the differential effects of two types of variables upon violent behavior. However, one must question the internal validity of the study - did it measure what it was trying to measure? The reliance solely upon IQ for a measure of genetic influence, and upon love deprivation as a representative of all sorts of environmental factors, might not give an accurate picture of the role of the two types of factors in the development of violent behavior. The study may not have been measuring general effects of the two factors in violent delinquency, but may have actually been investigating only the role of IQ and love deprivation. Also, the secondary nature of the data limits the precision of the results - the author relied upon other people's versions of what each boy reported, and thus cannot be sure of the accuracy of the case histories. Whilst the analyses were appropriate to the investigation, the reporting of the findings was often confusing and unclear. Despite these limitations, the study might be useful as a basis for further research in the field. (CSPV Abstract - Copyright © 1992-2007 by the Center for the Study and Prevention of Violence, Institute of Behavioral Science, Regents of the University of Colorado) KW - Idaho KW - Family Environment KW - Domestic Violence Effects KW - Domestic Violence Victim KW - Child Abuse Effects KW - Child Abuse Victim KW - Child Abuse-Violence Link KW - Child Abuse-Delinquency Link KW - Child Neglect Victim KW - Child Neglect Effects KW - Love Deprivation KW - Juvenile Violence KW - Juvenile Offender KW - Violence Causes KW - Genetic Factors KW - Biological Factors KW - Environmental Factors KW - Socioeconomic Status KW - Offender Intelligence KW - Intelligence-Delinquency Link KW - Intelligence-Violence Link