Chapter 24: CRIMINALITY IN ADOPTEES AND THEIR ADOPTIVE AND BIOLOGICAL PARENTS: A PILOT STUDY by Barry Hutchings Sarnoff A. Mednick

What was the main goal of Hutchings & Mednick's study?

To examine the influence of biological (genetic) vs. adoptive (environmental) fathers on criminality in adoptees, using adoption as a natural experiment to separate heredity and environment.

Why is adoption considered a natural experiment in this context?

Because adoptees share genes with biological parents but environment with adoptive parents, allowing independent assessment of genetic and environmental influences.

What were the reasons for studying genetic factors in criminality?

1. Some specific biological factors may exist (e.g., organic psychoses, extra sex chromosomes).

2. Ignoring genetics confounds environmental studies.

3. Environmental changes can moderate genetic expression (example: height increase in Denmark).

4. Understanding biology can improve treatment programs.

What was the study population?

1,145 male adoptees born 1927-1941 in Copenhagen, ages 30-44 in 1971. Nonfamilial adoptions, full Danish national registers available.

How were nonadopted controls selected?

Individually matched by sex, age, father's occupational status, and residence.

Lifetime risk of male criminality in Denmark?

8.9%

Criminality rates in adoptees vs. nonadopted controls?

Adoptees: 16.2%, Nonadopted controls: 8.9%

Criminality rates in fathers (Table 2)?

Biological fathers: 30.8%

Adoptive fathers: 12.6%

Fathers of controls: 11.1%

Adoptee criminality by adoptive father criminality (Table 3)?

Adoptive father noncriminal: 14.0% adoptees criminal

Adoptive father minor offender: 9.2%

Adoptive father criminal: 21.7%

χ²(2) = 19.25, p < 0.001

Adoptee criminality by biological father criminality (Table 4)?

Biological father noncriminal: 16.5% adoptees criminal

Minor offense only: 10.0%

Criminal: 41.1%

χ²(2) = 16.91, p < 0.001

Combined effect of adoptive and biological fathers (Table 6, N=965)?

Criminality rises when either or both fathers are criminal, strongest effect from biological father.

Nonadopted controls' father-offspring criminality (Table 5)?

Nonadopted sons with criminal fathers: 21%

Minor offenders: 12.4%

Noncriminal fathers: 79% sons noncriminal

Association exists, but adoptees show stronger link with biological fathers.

What is the role of adoptive fathers' social class?

Predicts adoptee criminality independently of adoptive fathers' criminality.

Multiple regression analysis predicting adoptee criminality (Table 9)?

Adoptive father first:

1. Adoptive Father Criminal: F=5.70, p<0.025, R=0.103

2. Adoptive Father Social Class: F=13.00, p<0.001, R=0.184

3. Biological Father Criminal: F=16.88, p<0.001, R=0.252

4. Biological Father Social Class: F=3.13, NS, R=0.263

Biological father first:

1. Biological Father Criminal: F=19.56, p<0.001, R=0.187

2. Biological Father Social Class: F=5.04, p<0.025, R=0.210

3. Adoptive Father Criminal: F=4.14, p<0.05, R=0.227

4. Adoptive Father Social Class: F=10.00, p<0.01, R=0.263

ANOVA: Regression F=9.886, p<0.001

Key findings from regression analysis?

Biological father criminality is a strong predictor, independent of adoptive father.

Adoptive father social class also predicts, minor independent effect of adoptive father criminality.

Effects of biological and adoptive fathers are partially independent.

Limitations of the study:

Selective placement - biological and adoptive families matched by social class (r=0.22, p<0.001).

Screening - children and parents carefully selected.

Timing of adoption - earliest transfer at 4 months may miss critical periods.

Definition of criminality - administrative/legal records only, excludes undetected crimes.

Implications of findings:

Supports genetic influence on criminality.

Environmental factors (adoptive father, social class) also contribute.

Suggests a cumulative genetic disadvantage model: genetic predispositions + environment influence likelihood of criminality.

Does this study support genetic determinism?

No. Genetics increases risk but does not make criminality inevitable; environment can moderate expression.

How can this research inform policy or interventions?

Helps design offender treatment and prevention programs by considering both genetic predispositions and environmental modification.