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Selective placement

In [[Adoption study|adoption studies]], '''selective placement''' refers to the practice by which [[adoption agencies]] tend to deliberately match certain characteristics of an adopted child's adopted parents with those of his or her biological parents. This practice has important implications in behavioural genetics and adoption research as it blurs the distinction between genetic and environmental influences on particular behaviours and traits, making it increasingly difficult to determine whether they originated from nature (biological parents genotype) or nurture (the environment they’re exposed to){{Cite journal |last=Dick |first=Danielle M. |date=2011 |title=Gene-environment interaction in psychological traits and disorders |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC3647367/ |journal=Annual Review of Clinical Psychology |volume=7 |pages=383–409 |doi=10.1146/annurev-clinpsy-032210-104518 |issn=1548-5951 |pmc=3647367 |pmid=21219196}}.

Methodological impact

When selective placement occurs, it results in a correlation between the rearing environments of biological relatives being raised in different homes. It has the potential to bias the conclusions of such studies, because twins who were reared in separate environments may in fact have been reared in much more similar environments than assumed. This can result in an inflated estimate of [[heritability]]. {{Cite journal |last=Leve |first=Leslie D. |last2=Neiderhiser |first2=Jenae M. |last3=Ge |first3=Xiaojia |last4=Scaramella |first4=Laura V. |last5=Conger |first5=Rand D. |last6=Reid |first6=John B. |last7=Shaw |first7=Daniel S. |last8=Reiss |first8=David |date=February 2007 |year= |title=The early growth and development study: a prospective adoption design |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC4169207/ |journal=Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies |chapter= |volume=10 |issue=1 |pages=84–95 |doi=10.1375/twin.10.1.84 |issn=1832-4274 |pmc=4169207 |pmid=17539368}}{{Cite journal |last=Kamin |first=Leon J. |last2=Goldberger |first2=Arthur S. |date=February 2002 |title=Twin Studies in Behavioral Research: A Skeptical View |url=https://ui.adsabs.harvard.edu/abs/2002TPBio..61...83K/abstract |journal=Theoretical Population Biology |language=en |volume=61 |issue=1 |pages=83–95 |doi=10.1006/tpbi.2001.1555}}{{Cite book |last=Eysenck |first=Hans Jürgen |url=https://books.google.co.uk/books?id=ka_gAwAAQBAJ&printsec=frontcover#v=onepage&q&f=false |title=The Structure and Measurement of Intelligence |publisher=Transaction Publishers |isbn=978-1-4128-3923-5 |language=en}}

This affects adoption research as its primary aim is to disentangle the effects of genetics and environment with the fundamental assumption of adoption studies being that they are ‘natural experiments’. Selective placement violates this. The resulting resemblance from selective placement between child and adoptive parent may be incorrectly attributed to the environment, similarly, the resemblance between child and birth parents - due to genetics - may be attributed solely to genetics, without accounting for matched environments. Substantial biases arising from selective placement can be drawn from adoption studies and failure to account for them could distort conclusions made about the roles of genetic and environmental influences, for instance, resulting in biased heritability coefficients.

The methodological impact {{Cite journal |last=Rhea |first=Sally-Ann |last2=Bricker |first2=Josh B. |last3=Wadsworth |first3=Sally J. |last4=Corley |first4=Robin P. |date=February 2013 |title=The Colorado Adoption Project |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC3817005/ |journal=Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies |volume=16 |issue=1 |pages=358–365 |doi=10.1017/thg.2012.109 |issn=1832-4274 |pmc=3817005 |pmid=23158098}}of selective placement differs between culture, time-period or country. For instance, adoption systems are not uniform, there are different placement rules, degrees of matching and levels of record-keeping. Some placements may be intentional with children being matched on every variable such as ethnicity, religion and social class, whereas, in others, placement may be more random or shaped by practical constraints such as availability of adoptive families and legal restraints{{Cite journal |last=Cadoret |first=Remi J. |date=1995 |title=Adoption Studies |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC6875765/ |journal=Alcohol Health and Research World |volume=19 |issue=3 |pages=195–200 |issn=0090-838X |pmc=6875765 |pmid=31799970}}. Selective placement is context-dependent, this means that the degree to which it is used reflects the level of bias introduced.

Measuring and correcting for selective placement

Researchers identify the use of selective placement through calculations of correlations between the traits of birth parents and adoptive parents. The correlation coefficient tells the researcher the degree to which matching of characteristics has occurred, for instance, if selective placement hasn’t occurred, it’ll be close to zero. Characteristics that are commonly matched on and are referred to in the studies within this article are socioeconomic levels, educational and occupational status, and physical characteristics such as hair and eye colour .

Selective placement must be controlled for in statistical analysis to calculate accurate heritability estimates. This is achieved by researchers including measures of adoptive parents traits as covariates {{Cite journal |last=Klahr |first=Ashlea M. |last2=Burt |first2=S. Alexandra |last3=Leve |first3=Leslie D. |last4=Shaw |first4=Daniel S. |last5=Ganiban |first5=Jody M. |last6=Reiss |first6=David |last7=Neiderhiser |first7=Jenae M. |date=March 2017 |title=Birth and Adoptive Parent Antisocial Behavior and Parenting: A Study of Evocative Gene-Environment Correlation |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC5749403/ |journal=Child Development |volume=88 |issue=2 |pages=505–513 |doi=10.1111/cdev.12619 |issn=1467-8624 |pmc=5749403 |pmid=27716897}} when predicting the extent of genetic influences. More advanced methods such as path analysis models derived from Van Eerdewegh (1982) allows researchers to separate the various sources of resemblance to reduce bias in estimates of genetic and environmental influences.

Issues in older studies

Issues of selective placement in older studies include them primarily focusing “on the birth-mother” when matching characteristics. Details about the adopted infant such as gestational age and early health status were neglected from the focus of previous studies. They also primarily took into account education or occupation as the variables to match adopted parents on. This information was obtained solely from the birth parents and not their parents. This poses a flaw as the majority of birth parents were young and therefore are in a dynamic state of “educational and occupational status”, inevitably meaning that their eventual “socioeconomic status” may differ notably from their status at the time of the adoption. To overcome this, it may be beneficial to predict this ultimate status through the status of the birth parents’ own parents. {{Cite web |last=Teasdale |first=T.W. |last2=Owen |first2=D.R. |year=1979 |title=Heredity and familial environment in intelligence and educational level — A sibling study |url=https://www.tandfonline.com/action/cookieAbsent |access-date=2026-04-18 |website=www.tandfonline.com |pages=1-6 |doi=10.1080/19485565.1979.9988356?needAccess=true}}

There is evidence, as illustrated in Farber’s book ‘Identical Twins Reared Apart: A Reanalysis’ that selective placement was a major [[Confounding factor|confound]] in many early studies of twins reared apart. {{Cite book |last=Moore |first=David S. |url=https://books.google.co.uk/books?id=GkMJDdcL7QUC&redir_esc=y |title=The Dependent Gene: The Fallacy of "Nature Vs. Nurture" |date=2003-02-05 |publisher=Macmillan |isbn=978-0-8050-7280-8 |language=en}}

Evidence for and against selective placement

Some adoption studies report little or no evidence of selective placement. {{Cite journal |last=Stunkard |first=Albert. J |last2=Sorenson |first2=Thorkild I. A. |last3=Hanis |first3=Craig |last4=Teasdale |first4=Thomas W. |last5=Chakraborty |first5=Ranajit |last6=Schull |first6=William J. |last7=Schulsinger |first7=Fini |date=August 1987 |title=Genetic contributions to human fatness: an adoption study |url=https://psychiatryonline.org/doi/10.1176/ajp.144.8.1003 |journal=American Journal of Psychiatry |volume=144 |issue=8 |page= |pages=1003–1008 |doi=10.1176/ajp.144.8.1003}}{{Cite journal |last=Miles |first=Donna R. |last2=Carey |first2=Gregory |date=1997 |title=Genetic and environmental architecture on human aggression. |url=https://doi.apa.org/doi/10.1037/0022-3514.72.1.207 |journal=Journal of Personality and Social Psychology |language=en |volume=72 |issue=1 |pages=207–217 |doi=10.1037/0022-3514.72.1.207 |issn=1939-1315}}{{Cite journal |last=Duyme |first=M. |last2=Dumaret |first2=A. C. |last3=Tomkiewicz |first3=S. |date=1999-07-20 |title=How can we boost IQs of "dull children"?: A late adoption study |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC17595/ |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=96 |issue=15 |pages=8790–8794 |doi=10.1073/pnas.96.15.8790 |issn=0027-8424 |pmc=17595 |pmid=10411954}}For instance, in the Colorado Adoption Project, a large-scale longitudinal study conducted by Plomin et.al in 1975 {{Cite journal |last=Leve |first=Leslie D. |last2=Neiderhiser |first2=Jenae M. |last3=Shaw |first3=Daniel S. |last4=Ganiban |first4=Jody |last5=Natsuaki |first5=Misaki N. |last6=Reiss |first6=David |date=2013-02 |title=The Early Growth and Development Study: a prospective adoption study from birth through middle childhood |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC3572752/ |journal=Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies |volume=16 |issue=1 |pages=412–423 |doi=10.1017/thg.2012.126 |issn=1832-4274 |pmc=3572752 |pmid=23218244}} researchers observed if selective placement had been used through correlating birth parent and adoptive family characteristics. The study specifically focused on “traits” unlikely to be influenced by evocative gene-environment correlations, such as “self-worth/executive function/temperament.” From the “132 comparisons” between birth and adoptive parents traits, it was found that  only 3 were statistically significant at p<0.05.” This indicates minimal selective placement.

Contrarily, some earlier studies did employ selective placement . For instance, Cadoret’s 1995 ‘Adoption Studies’ article recognises that certain studies matched on “hair and eye colour”; additionally, “an adoption agency might estimate a child’s “potential” from birth-parent characteristics (e.g., education or socioeconomic level) and place the child according to some expectation of future performance.”

In a 1979 study by Ho et al. examining selective placement directly, it was reported that a generally low level of selective placement in adopted children for either physical or behavioral traits took place. The authors concluded that to the extent that selective placement occurred for such traits, "our data suggest that it is based largely on characteristics of the birth father," rather than those of the adoptee{{Cite journal |last=Ho |first=Hsiu‐zu |last2=Plomin |first2=Robert |last3=DeFries |first3=J. C. |date=1979-03-01 |title=Selective placement in adoption |url=https://doi.org/10.1080/19485565.1979.9988356 |journal=Social Biology |volume=26 |issue=1 |pages=1–6 |doi=10.1080/19485565.1979.9988356 |issn=0037-766X |pmid=538462}}. Similarly, Carey (2003) concluded that selective placement was "moderate" for physical characteristics and typically "small or nonexistent" for behavioral characteristics. This shows that selective placement still appears to have operated in particular domains - in some traits more than others.

Selective placement of different traits

'''Cognitive characteristics'''

Selective placement on cognitive abilities e.g. IQ is prevalent in Freeman et. al’s 1928 study. Even though no cognitive data was available from birth parents, except from if they had a ‘mental defect’ or ‘moral defect’, the Stanford-Binet IQ scores for the adopted-away children were available to adoption agency workers prior to placement. In cases where the children were old enough for these scores to be meaningful (40% were above 4 years old), the information may have influenced adoption decisions.{{Cite journal |last=Hardy‐Brown |first=Karen |last2=Plomin |first2=Robert |last3=Greenhalgh |first3=John |last4=Jax |first4=Karen |date=April 1980 |title=SELECTIVE PLACEMENT OF ADOPTED CHILDREN: PREVALENCE AND EFFECTS |url=https://acamh.onlinelibrary.wiley.com/doi/10.1111/j.1469-7610.1980.tb00026.x |journal=Journal of Child Psychology and Psychiatry |language=en |volume=21 |issue=2 |pages=143–152 |doi=10.1111/j.1469-7610.1980.tb00026.x |issn=0021-9630}}

'''Physical characteristics'''

Selective placements were not restricted to cognitive characteristics, but also physical characteristics, specifically, “hair and eye colour”. The process of matching on phenotypes could have possible evolutionary explanations, such as the “paternal resemblance hypothesis”. Herring acknowledges this hypothesis in his journal article, it states that adult men will favour children who look like them. This is due to men investing in children who they are not biologically related to doesn’t enhance their reproductive success and therefore their passing on of genetic material. Hence, men are predisposed to subconsciously care for children whom they look similar to,{{Cite journal |last=Herring |first=David J. |date=2003 |title=Child Placement Decisions: The Relevance of Facial Resemblance and Biological Relationships |url=https://www.jstor.org/stable/29762823 |journal=Jurimetrics |volume=43 |issue=4 |pages=387–414 |issn=0897-1277}} although this interpretation remains debated.

'''Behavioural characteristics'''

Lastly, selective placements on behavioural characteristics include “educational level and occupation”.In addition to the birth parents educational level/occupation being recorded, their own parents characteristics were also measured. A large scale study by Teasdale 1979 also shows similar correlations between adoptive father and birth parents on occupational status emphasising how widespread this method is. The average correlations for comparisons between birth and adoptive parents are 0.19 for educational levels and 0.13 for occupation These moderate but non-zero correlation coefficients highlight that the socioeconomic and behavioural patterns of birth parents are somewhat used in selective placements.

Limitations

These findings must be interpreted with caution as studies revolving around selective placements have limited validity due to the quality of records available to research the traits of birth parents. For instance, in early adoption studies, researchers had to rely on incomplete agency files and secondarily recorded correlations between adoptive and birth parents . Also, due to confidentiality {{Cite journal |last=Lo |first=Albert Y. H. |last2=Grotevant |first2=Harold D. |last3=McRoy |first3=Ruth G. |date=2019 |title=Ethical Considerations in Adoption Research: Navigating Confidentiality and Privacy Across the Adoption Kinship Network |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC6785193/ |journal=Adoption Quarterly |volume=22 |issue=1 |pages=75–93 |doi=10.1080/10926755.2018.1488328 |issn=1092-6755 |pmc=6785193 |pmid=31598062}}, arranging data collection from a wide range of sources about the birth parents poses a technical difficulty. So, it is challenging to recognise how much selective placement has actually been done.

Drawing back to how the mechanisms of adoption studies are not uniform, generalisability is an issue when acknowledging how different time periods, religions, cultures, agencies vary the scale and nature of selected placements. Establishing causation is also challenging as the effects of selective placement cannot be illustrated in isolation with certainty due to the range of overlapping processes {{Cite web |title=Sage Journals: Discover world-class research |url=https://journals.sagepub.com/action/cookieAbsent |access-date=2026-04-19 |website=Sage Journals |language=en |doi=10.1177/0956797620904450 |pmc=7238511 |pmid=32302253}}that can lead to resemblance between adopted and biological families e.g. shared social backgrounds, pre- adoption experiences etc. (uncontrolled confounds). Therefore, selective placement should be considered as one of several potential sources of bias, rather than a sole explanation for this bias.

References

# Dick, Danielle M. (2011). "Gene-environment interaction in psychological traits and disorders". ''Annual Review of Clinical Psychology''. '''7''': 383–409. [[Doi (identifier)|doi]]:10.1146/annurev-clinpsy-032210-104518. [[ISSN (identifier)|ISSN]] 1548-5951. [[PMC (identifier)|PMC]] 3647367. [[PMID (identifier)|PMID]] 21219196.
# Leve, Leslie D.; Neiderhiser, Jenae M.; Ge, Xiaojia; Scaramella, Laura V.; Conger, Rand D.; Reid, John B.; Shaw, Daniel S.; Reiss, David (February 2007). "The early growth and development study: a prospective adoption design". ''Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies''. '''10'''(1): 84–95. [[Doi (identifier)|doi]]:10.1375/twin.10.1.84. [[ISSN (identifier)|ISSN]] 1832-4274. [[PMC (identifier)|PMC]] 4169207. [[PMID (identifier)|PMID]] 17539368.
# Kamin, Leon J.; Goldberger, Arthur S. (February 2002). "Twin Studies in Behavioral Research: A Skeptical View". ''Theoretical Population Biology''. '''61''' (1): 83–95. [[Doi (identifier)|doi]]:10.1006/tpbi.2001.1555.
# Eysenck, Hans Jürgen. ''The Structure and Measurement of Intelligence''. Transaction Publishers. [[ISBN (identifier)|ISBN]] [[Special:BookSources/978-1-4128-3923-5|978-1-4128-3923-5]].
# Rhea, Sally-Ann; Bricker, Josh B.; Wadsworth, Sally J.; Corley, Robin P. (February 2013). "The Colorado Adoption Project". ''Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies''. '''16'''(1): 358–365. [[Doi (identifier)|doi]]:10.1017/thg.2012.109. [[ISSN (identifier)|ISSN]] 1832-4274. [[PMC (identifier)|PMC]] 3817005. [[PMID (identifier)|PMID]] 23158098.
# Cadoret, Remi J. (1995). "Adoption Studies". ''Alcohol Health and Research World''. '''19''' (3): 195–200. [[ISSN (identifier)|ISSN]] 0090-838X. [[PMC (identifier)|PMC]] 6875765. [[PMID (identifier)|PMID]] 31799970.
# Klahr, Ashlea M.; Burt, S. Alexandra; Leve, Leslie D.; Shaw, Daniel S.; Ganiban, Jody M.; Reiss, David; Neiderhiser, Jenae M. (March 2017). "Birth and Adoptive Parent Antisocial Behavior and Parenting: A Study of Evocative Gene-Environment Correlation". ''Child Development''. '''88''' (2): 505–513. [[Doi (identifier)|doi]]:10.1111/cdev.12619. [[ISSN (identifier)|ISSN]]1467-8624. [[PMC (identifier)|PMC]] 5749403. [[PMID (identifier)|PMID]] 27716897.
# Teasdale, T.W.; Owen, D.R. (1979). "Heredity and familial environment in intelligence and educational level — A sibling study". ''www.tandfonline.com''. pp. 1–6. [[Doi (identifier)|doi]]:10.1080/19485565.1979.9988356?needAccess=true. Retrieved 2026-04-18.
# Moore, David S. (2003-02-05). ''The Dependent Gene: The Fallacy of "Nature Vs. Nurture"''. Macmillan. [[ISBN (identifier)|ISBN]] [[Special:BookSources/978-0-8050-7280-8|978-0-8050-7280-8]].
# Stunkard, Albert. J; Sorenson, Thorkild I. A.; Hanis, Craig; Teasdale, Thomas W.; Chakraborty, Ranajit; Schull, William J.; Schulsinger, Fini (August 1987). "Genetic contributions to human fatness: an adoption study". ''American Journal of Psychiatry''. '''144''' (8): 1003–1008. [[Doi (identifier)|doi]]:10.1176/ajp.144.8.1003.
# Miles, Donna R.; Carey, Gregory (1997). "Genetic and environmental architecture on human aggression". ''Journal of Personality and Social Psychology''. '''72''' (1): 207–217. doi:10.1037/0022-3514.72.1.207. ISSN 1939-1315.
# Duyme, M.; Dumaret, A. C.; Tomkiewicz, S. (1999-07-20). "How can we boost IQs of "dull children"?: A late adoption study". ''Proceedings of the National Academy of Sciences of the United States of America''. '''96''' (15): 8790–8794. doi:10.1073/pnas.96.15.8790. ISSN 0027-8424. PMC 17595. PMID 10411954.
# Ho, Hsiu‐zu; Plomin, Robert; DeFries, J. C. (1979-03-01). "Selective placement in adoption". ''Social Biology''. '''26'''(1): 1–6. doi:10.1080/19485565.1979.9988356. ISSN 0037-766X. PMID 538462.
# Carey, Gregory (2003). ''Human Genetics for the Social Sciences''. SAGE. ISBN 978-0-7619-2345-9.
# Hardy‐Brown, Karen; Plomin, Robert; Greenhalgh, John; Jax, Karen (April 1980). "SELECTIVE PLACEMENT OF ADOPTED CHILDREN: PREVALENCE AND EFFECTS". ''Journal of Child Psychology and Psychiatry''. '''21'''(2): 143–152. [[Doi (identifier)|doi]]:10.1111/j.1469-7610.1980.tb00026.x. [[ISSN (identifier)|ISSN]] 0021-9630
# Herring, David J. (2003). "Child Placement Decisions: The Relevance of Facial Resemblance and Biological Relationships". ''Jurimetrics''. '''43''' (4): 387–414. ISSN 0897-1277.
# Lo, Albert Y. H.; Grotevant, Harold D.; McRoy, Ruth G. (2019). "Ethical Considerations in Adoption Research: Navigating Confidentiality and Privacy Across the Adoption Kinship Network". ''Adoption Quarterly''. '''22''' (1): 75–93. doi:10.1080/10926755.2018.1488328. ISSN 1092-6755. PMC 6785193. PMID 31598062.
# Cheesman, Rosa; Hunjan, Avina; Coleman, Jonathan R. I.; et al. (2020). "Comparison of Adopted and Nonadopted Individuals Reveals Gene–Environment Interplay for Education in the UK Biobank". ''Psychological Science''. '''31''' (5): 562–574. doi:10.1177/0956797620904450.