Table 2.

Assumptions of the adoption design.

Adoption Design Assumption	Description	Measurement and Analytic Approach
Selective placement	Adoption agencies might systematically selectively place children into rearing families that are similar to the linked biological parents, or that reflect systematic efforts to counter the possible environment provided by biological parents with adoptive families unlike them	Measure key personality or contextual variables in birth and adoptive parents that are relatively stable and unlikely to change over time/due to environmental influences. Then examine birth parent-adoptive parent correlations. Significant correlations would be evidence of selective placement
Adoption openness	Birth parents might have contact with the adoptive parents or the adopted child. This contact could influence the behaviors of the adoptive family, causing similarities between the adopted child and their birth parents that are due to postnatal environments rather than to genetic or prenatal exposures	Repeated assessments of contact and openness from both adoptive and birth families, longitudinally. Then include a construct of adoption openness in analytic models to control for possible effects of adoption openness
Expectancy effects	Adoptive parents might gain knowledge of qualities of the birth parents, even if there is no direct contact, that can influence their expectations of the adopted child’s behavior and characteristics. This could inflate estimates of genetic influences on child characteristics when adoptive parent report is used	Repeated assessments of knowledge from both adoptive and birth families, longitudinally. Include this aspect in the adoption openness construct. Other analytic strategies are using observational data and teacher-report data of child characteristics, and directly measuring adoptive parents’ expectations and beliefs about the level of influence that genetics have on specific child characteristics
Research team bias	Research team members who have knowledge of both the adoptive and birth parents within a family could inadvertently influence the behaviors and expectations of research participants.	Eliminated this potential threat by using separate research team members to evaluate birth parents and to evaluate rearing families and the adopted child, within a given family.