before I had to go out - this paper and other things I was looking at seem to use the Minnesota Twins study carried out in 1990.
The twins, all male and in their early 30s, were asked how often they currently went to religious services, prayed, and discussed religious teachings. This was compared with when they were growing up and living with their families. Then, each participant answered the same questions regarding their mother, father, and their twin.
The twins believed that when they were younger, all of their family members - including themselves - shared similar religious behaviour. But in adulthood, however, only the identical twins reported maintaining that similarity. In contrast, fraternal twins were about a third less similar than they were as children.
"That would suggest genetic factors are becoming more important and growing up together less important," says team member Matt McGue, a psychologist at the University of Minnesota. So, so far, one measure of "religiosity" would seem to be how often one continues to hew to the religious teaching one received as a child?
Then I saw five categories, as described here:
http://books.google.com/books?id=N6RtrzRvhh8C&pg=PA57&lpg=PA57&dq=minnesota+twins+study+religion&source=bl&ots=VcyJhPFy4G&sig=oB-JQt7VfQHG779vYZ1YhCKyPHs&hl=en&ei=AKtETbPsDYWglAeClZAG&sa=X&oi=book_result&ct=result&resnum=8&ved=0CFQQ6AEwBw#v=onepage&q=minnesota%20twins%20study%20religion&f=false1. religious fundamentalism
2. religious occupational interests
3. religious interest subscale (vocational interest inventory)
4. religious leisure time interests
5. religious values scale
This, of course, still does not provide definitions for the terms - is Calvinist prayer and Buddhist meditation perceived as the same thing when the two belief systems vary so much - as in one presents a monotheistic paternal figure to whom one prays while the other promotes detachment from the material world and embraces the belief that it is not necessary to believe in a god in order to pray/meditate... so I also wonder if all the (male) twins in the study were also all white Calvinists... and if they all hailed from and lived in an area of the country without much cultural diversity...
anyway, was looking around here and there, wondering about the information because, honestly, I have to wonder what it means to claim religion - does that include those religions that believe in ancestor spirits - not a "god" that exists outside of the human scale of life? and if not - how is the study representative of anyone other than the white calvinists living in a sort of mono-cultural petri dish? - if that's what they were?
could "religiosity" mean, cognitively, the human attempt to create meaning in random patterns is the same as a religious belief? and if not, why not? and wouldn't the human attempt to fit into a culture would be part of this cognitive processing - esp. a mono-culture?
The God Gene talks about "religiosity" as "self-transcendance" vs. self-absorption. That doesn't describe anything religious, per se. That could also be the experience of taking LSD, for example. So, do those who ingested LSD at some point and felt more connected to their fellow humans b/c of have a comparable religiosity "gene" as those who attend a church that insists on a set of doctrinal positions? or is "self-transcendence" a measure of "leisure time" activities that relate to religious institutions only.
A number of studies have suggested that religious tendencies are related to our genetic endowment. Twin studies, like the University of Minnesota twin studies3, suggest that there is a genetic contribution to the likelihood of church attendance or the tendency to have self-transcendent experiences.4 Consistent with these twin studies, studies comparing actual genes and behavior have found a correlation between the presence of a gene variant called VMAT2 and a self-report test of self-transcendence.5 The presence of this gene was significantly correlated with the subscale of the test measuring “self-forgetfulness”, but was less well correlated with scales involving transpersonal identification or mysticism. A similar correlation has been found between measures of self-transcendence and a genetic marker for the dopamine transport molecule. 6 One geneticist claimed that such results are an indication of genetic determination of brain wiring specifically subserving religiousness.7 However, there is nothing in the measures that might not also be related to non-religious self-transcendence or self-forgetfulness in other domains of life, and it is as yet unknown all that these genes might influence in other non-religious psychological and social domains. http://www.issr.org.uk/neuroscience-of-religion.asp...neurological disorders, like epilepsy, also factor into the experience of "communion with the divine" and/or "self-transcendence" and hallucinatory experiences that are categorized as "religious." what is the heritability in twins for epilepsy and other disorders and how would that relate to a study generalizing about religious experience... and, again, would identical twins be more likely to have the same brain abnormalties - rather than fraternal twins?
just some questions this whole assertion raises for me.
I would like for those who make this claim to state what the term means - because, again, at this time it means whatever someone wants it to mean - even when people use the studies while talking about the issue.