1.1 Basic Concept

TwinLife sets out to take a look at the biological origin as well as the social origin of social inequality (Figure 1). Using the data of identical and fraternal twins as well as their families, the impact of genetic differences on certain behavior can be determined. Furthermore, environmental characteristics such as the socio-economic status (SES), family structure and home environment, relations among family members as well as characteristics of the neighborhood are observed.
Figure 1. Basic concept and six domains of social inequality.
Social inequality is divided into six areas (see Figure 1) that reach from education and labor market attainment to health, psychopathology and deviant behavior.

Skill formation and education

This area contains e.g., the level of education, educational aspirations, and achievement motivation in addition to cognitive abilities and their development.

Career, labor market attainment, and welfare

This domain includes the perceived security of the workplace, job satisfaction, commitment to work, current occupation, and current position as well as income or, if applicable, the receipt of social benefits.

Political and social integration and participation

The characteristics of the social environment of every person such as the support by family, friends, and spouses are covered in this area. Furthermore, social and political commitment and social resources are of particular interest.

Subjective perception of quality of life

This category comprises, e.g., a person’s self-esteem, global life satisfaction as well as their satisfaction concerning specific areas.

Physical and psychological health

Assessments of general health in terms of diseases, but also subjectively perceived impairments as well as information on health behaviors are covered in this area.

Psychopathology and deviant behavior

Criminal or delinquent behavior as well as the degree of internalizing and externalizing problem behavior are surveyed in this domain.