One example I found was an experiment to test the variations in resource expenditure for different grandparents. Dekay (1995). The evolutionary model they used precisely predicted the pattern of resource expenditure. Maternal grandmothers contributed most, followed by maternal grandfathers, followed by paternal grandmothers followed by paternal grandfathers.
You make it seem like this is an exception to the rule. Reading through an ev. psych textbook, I am constantly surprised by the clever experiments I never would have thought of to test evolutionarily based predictions. The predictions themselves are impressive.
One example I found was an experiment to test the variations in resource expenditure for different grandparents. Dekay (1995). The evolutionary model they used precisely predicted the pattern of resource expenditure. Maternal grandmothers contributed most, followed by maternal grandfathers, followed by paternal grandmothers followed by paternal grandfathers.
I think this is an excellent example to serve as a focus of arguments for and against evolutionary psychology. The idea here is not to praise or critique this particular piece of research, but rather to discuss what kinds of things good scientific researchers might do with this subject matter vs the things that sloppy researchers might do. The cited paper is not available online, but a later survey paper by the same author gives the rough outline.
As I understand it, DeKay is suggesting that differential care for grandchildren is a (genetic?) fact of human nature. And that the explanation for this differential can be found in the fact that some “fathers” are actually cuckolds, together with the standard evolutionary theory of inclusive fitness (aka kin selection). The empirical part of the research examines a sample of grandparents and finds that the predicted differential grandchild-care behavior is actually observed.
knb finds this research to be “clever”, “surprising”, and “impressive”. I, on the other hand, am more skeptical. Since we don’t have the actual research paper, we can’t criticise the actual research, but we can ask the kinds of questions that an evolutionary biologist might ask if it had been submitted for peer review to a biology journal.
First a scientist would want to know what other hypotheses had been considered and then empirically rejected. For example, might the results tell us something about culture (social norms) rather than about human nature. The scientist would want to make sure that the empirical sample of grandparents was taken from a broad diversity of human cultures and hence that a “human nature” label is not mistakenly being attached to a parochial cultural trait.
Besides culture and genetics, another possible explanatory factor for human behavior is rational self interest. I would want to know whether any of the sampled grandparents had any reason to rationally suspect that they were not true ancestors.
Another alternate hypothesis would be that the modern western cultural practice of divorce with maternal custody might have something to do with this—particularly when one party moves to another town. I would want to know how the research compensated for this. Otherwise, an attractive alternative hypothesis is that grandparent care happens because/when such care is solicited by the primary care-giver, and that primary caregiver usually solicits assistance from her own primary caregiver.
Since the proposed explanation is that the differential evolved by natural selection, driven by the probability that the nominal parent is not the genetic parent, I would want to have measurements of the differential taken in two populations with different values of the probability. For example, compare a population in which, for many generations, it has been the case that a nominal father has only a 15% chance of not being the genetic father, with a different population in which the probability of cuckoldry is more like 30%.
I would also like to see some results comparing adoptive vs genetic parentage. This kind of data might tease out which hypothesis regarding the causation behind the behavior (genetic, cultural, or rational) is more likely. In particular, this kind of data might show whether a propensity to care for grandchildren is a genetic trait, (passed on to genetic children), or a cultural trait (passed on to adopted children as well).
Ok, those are some of the issues that an evolutionary scientist would expect to see addressed in a paper purporting to be about evolutionary science. Does the cited research deal with these issues? I don’t know, but if anyone here has read the paper, I would be curious.
I would also like to see some results comparing adoptive vs genetic parentage.
This doesn’t relate to the grandparents thing, but I think most research has shown that parental investment is highest for adopted children, followed by biological children, followed by stepchildren.
I quickly googled this, because I was suspicious whether these results did properly control for socioeconomic factors. Apparently, they did. But the first google hit suggested another huge complication. This paper suggests that adopted children get more parental investment because they require more parental investment. That is, because they are often problem kids.
Differential parental investment in families with both adopted and genetic children
Kyle Gibson
Abstract
Stepchildren are abused, neglected and murdered at higher rates than those who live with two genetically related parents. Daly and Wilson used kin selection theory to explain this finding and labeled the phenomenon “discriminative parental solicitude.” I examined discriminative parental solicitude in American households composed of both genetic and unrelated adopted children. In these families, kin selection predicts parents should favor their genetic children over adoptees. Rather than looking at cases of abuse, neglect, homicide and other antisocial behavior, I focused on the positive investments parents made in their children as well as the outcomes of each child. The results show that parents invested more in adopted children than in genetically related ones, especially in educational and personal areas. At the same time, adoptees experienced more negative outcomes. They were more likely to have been arrested, to have been on public assistance and to require treatment for drug, alcohol or mental health issues. They also completed fewer years of schooling and were more likely to divorce. In adoptive families, it appears that “the squeaky wheel gets the grease.” Parents invest more in adoptees not because they favor them, but because they are more likely than genetic children to need the help. I conclude that discriminative parental solicitude differs in adoptive and step households because adoptive families generally result from prolonged parenting effort, not mating effort like stepfamilies.
One example I found was an experiment to test the variations in resource expenditure for different grandparents. Dekay (1995). The evolutionary model they used precisely predicted the pattern of resource expenditure. Maternal grandmothers contributed most, followed by maternal grandfathers, followed by paternal grandmothers followed by paternal grandfathers.
You make it seem like this is an exception to the rule. Reading through an ev. psych textbook, I am constantly surprised by the clever experiments I never would have thought of to test evolutionarily based predictions. The predictions themselves are impressive.
One example I found was an experiment to test the variations in resource expenditure for different grandparents. Dekay (1995). The evolutionary model they used precisely predicted the pattern of resource expenditure. Maternal grandmothers contributed most, followed by maternal grandfathers, followed by paternal grandmothers followed by paternal grandfathers.
Edit: Apparently I like to repeat myself. : )
I think this is an excellent example to serve as a focus of arguments for and against evolutionary psychology. The idea here is not to praise or critique this particular piece of research, but rather to discuss what kinds of things good scientific researchers might do with this subject matter vs the things that sloppy researchers might do. The cited paper is not available online, but a later survey paper by the same author gives the rough outline.
As I understand it, DeKay is suggesting that differential care for grandchildren is a (genetic?) fact of human nature. And that the explanation for this differential can be found in the fact that some “fathers” are actually cuckolds, together with the standard evolutionary theory of inclusive fitness (aka kin selection). The empirical part of the research examines a sample of grandparents and finds that the predicted differential grandchild-care behavior is actually observed.
knb finds this research to be “clever”, “surprising”, and “impressive”. I, on the other hand, am more skeptical. Since we don’t have the actual research paper, we can’t criticise the actual research, but we can ask the kinds of questions that an evolutionary biologist might ask if it had been submitted for peer review to a biology journal.
First a scientist would want to know what other hypotheses had been considered and then empirically rejected. For example, might the results tell us something about culture (social norms) rather than about human nature. The scientist would want to make sure that the empirical sample of grandparents was taken from a broad diversity of human cultures and hence that a “human nature” label is not mistakenly being attached to a parochial cultural trait.
Besides culture and genetics, another possible explanatory factor for human behavior is rational self interest. I would want to know whether any of the sampled grandparents had any reason to rationally suspect that they were not true ancestors.
Another alternate hypothesis would be that the modern western cultural practice of divorce with maternal custody might have something to do with this—particularly when one party moves to another town. I would want to know how the research compensated for this. Otherwise, an attractive alternative hypothesis is that grandparent care happens because/when such care is solicited by the primary care-giver, and that primary caregiver usually solicits assistance from her own primary caregiver.
Since the proposed explanation is that the differential evolved by natural selection, driven by the probability that the nominal parent is not the genetic parent, I would want to have measurements of the differential taken in two populations with different values of the probability. For example, compare a population in which, for many generations, it has been the case that a nominal father has only a 15% chance of not being the genetic father, with a different population in which the probability of cuckoldry is more like 30%.
I would also like to see some results comparing adoptive vs genetic parentage. This kind of data might tease out which hypothesis regarding the causation behind the behavior (genetic, cultural, or rational) is more likely. In particular, this kind of data might show whether a propensity to care for grandchildren is a genetic trait, (passed on to genetic children), or a cultural trait (passed on to adopted children as well).
Ok, those are some of the issues that an evolutionary scientist would expect to see addressed in a paper purporting to be about evolutionary science. Does the cited research deal with these issues? I don’t know, but if anyone here has read the paper, I would be curious.
This doesn’t relate to the grandparents thing, but I think most research has shown that parental investment is highest for adopted children, followed by biological children, followed by stepchildren.
I quickly googled this, because I was suspicious whether these results did properly control for socioeconomic factors. Apparently, they did. But the first google hit suggested another huge complication. This paper suggests that adopted children get more parental investment because they require more parental investment. That is, because they are often problem kids.
Differential parental investment in families with both adopted and genetic children
Kyle Gibson
Abstract
Stepchildren are abused, neglected and murdered at higher rates than those who live with two genetically related parents. Daly and Wilson used kin selection theory to explain this finding and labeled the phenomenon “discriminative parental solicitude.” I examined discriminative parental solicitude in American households composed of both genetic and unrelated adopted children. In these families, kin selection predicts parents should favor their genetic children over adoptees. Rather than looking at cases of abuse, neglect, homicide and other antisocial behavior, I focused on the positive investments parents made in their children as well as the outcomes of each child. The results show that parents invested more in adopted children than in genetically related ones, especially in educational and personal areas. At the same time, adoptees experienced more negative outcomes. They were more likely to have been arrested, to have been on public assistance and to require treatment for drug, alcohol or mental health issues. They also completed fewer years of schooling and were more likely to divorce. In adoptive families, it appears that “the squeaky wheel gets the grease.” Parents invest more in adoptees not because they favor them, but because they are more likely than genetic children to need the help. I conclude that discriminative parental solicitude differs in adoptive and step households because adoptive families generally result from prolonged parenting effort, not mating effort like stepfamilies.
I don’t have journal access—does it discriminate between from-infancy adoptees and adoptees from foster homes?
Very good question, but I don’t have journal access either.
There are quite a few studies relating to this—I posted some as children of the mother-comment.
Some starting points
“Grandparental investment as a function of relational uncertainty and emotional closeness with parents”
http://www.springerlink.com/content/8e2cwq89br0mhn88/
“Differential Investment Behavior between Grandparents and Grandchildren: The Role of Paternity Uncertainty”
http://www.epjournal.net/filestore/EP076677.pdf
“An Evolutionary Perspective on Parental and Grandparental Investment (2010)”
http://www.narcis.info/publication/RecordID/oai%3Adspace.library.uu.nl%3A1874%2F40155
“LINEAGE BASED DIFFERENCES IN GRANDPARENTAL INVESTMENT: EVIDENCE FROM A LARGE BRITISH COHORT STUDY”
http://www.staff.ncl.ac.uk/daniel.nettle/jbs.pdf