Editing Twin study (section)

=== Criticisms of statistical methods ===
[[Peter Schönemann]] criticized methods for estimating [[heritability]] developed in the 1970s. He has also argued that the heritability estimate from a twin study may reflect factors other than shared [[genes]]. Using the statistical models published in [[John C. Loehlin|Loehlin]] and Nichols (1976),<ref>{{cite book | last1 = Loehlin | first1 = John C. | author-link1 = John C. Loehlin | last2 = Nichols | first2 = Robert | title = Heredity, environment, & personality: a study of 850 sets of twins | publisher = [[University of Texas Press]] | location = [[Austin, Texas|Austin]] | year = 1976 | isbn = 978-0-292-73003-8 | jstor = 2826060 | url = https://archive.org/details/heredityenvironm0000loeh }}</ref> the narrow HR-heritability of responses to the question "did you have your back rubbed"  has been shown to work out to .92 heritable for males and .21 heritable for females, and the question "Did you wear sunglasses after dark?" is 130% heritable for males and 103% for females.<ref>{{Cite journal | last1 = Schönemann | first1 = Peter H. | author-link1 = Peter Schönemann| title = On models and muddles of heritability | journal = [[Genetica]]| volume = 99 | issue = 2–3| pages = 97–108| doi = 10.1023/A:1018358504373 | year = 1997 | pmid = 9463078| s2cid = 37292855 }}</ref><ref>{{cite conference | last1 = Schönemann | first1 = Peter H. | author-link1 = Peter Schönemann | year = 1995 | title = Totems of the IQ Myth: General Ability (g) and its Heritabilities (h<sup>2</sup>, HR) | conference = 1995 Meetings of the American Association for the Advancement of Sciences }}</ref> Critics also contend that the concept of "heritability" estimated in twin studies is merely a statistical abstraction with no relationship to the underlying DNA<ref>{{Cite journal |last1=Pam |first1=A. |last2=Kemker |first2=S. S. |last3=Ross |first3=C. A. |last4=Golden |first4=R. |date=July 1996 |title=The "Equal Environments Assumption" in MZ-DZ Twin Comparisons: an Untenable Premise of Psychiatric Genetics? |journal=Acta Geneticae Medicae et Gemellologiae: Twin Research |language=en |volume=45 |issue=3 |pages=349–360 |doi=10.1017/S0001566000000945 |pmid=9014000 |s2cid=34798197 |issn=0001-5660}}</ref> and that the [[statistical]] underpinnings of twin research are invalid. Statistical critiques argue that [[heritability]] estimates used for most twin studies rest on restrictive assumptions that are usually not tested, and if they are, they are often contradicted by the data.

==== Responses to statistical critiques ====

Before computers, statisticians used methods that were computationally tractable, at the cost of known limitations. Since the 1980s these approximate statistical methods have been discarded. Modern twin methods based on [[structural equation modeling]] are not subject to the limitations and heritability estimates such as those noted above are mathematically impossible.<ref>M. C. Neale, S. M. Boker, G. Xie and H. H. Maes. (2002). Mx: Statistical Modelling. ''Journal''.</ref>
Critically, the newer methods allow for explicit testing of the role of different pathways and incorporation and testing of complex effects.<ref name=Neale1996 />