Поиск по сайту




Пишите нам: info@ethology.ru

Follow etholog on Twitter

Система Orphus

Новости
Библиотека
Видео
Разное
Кросс-культурный метод
Старые форумы
Рекомендуем
Не в тему

список статей


Sex difference in attitudes toward paternity testing

Lisa S Haywarda, Sievert Rohwerb

1. Methods

1.1. Surveys

1.2. Main effects on survey response

1.3. Motivation

2. Results

2.1. Sex difference

2.2. Other effects

3. Discussion

Acknowledgment

References

Copyright

Rearing children is a considerable investment. Men who raise unrelated offspring will likely achieve lower fitness than men who administer parental solicitude with discrimination. Thus, selective pressure for mechanisms ensuring certainty of paternity is expected. Evidence of a long history of such selection is apparent in sex differences in patterns of sexual jealousy Buss et al., 1992, Daly et al., 1982, Geary et al., 1995, domestic agonism Burch & Gallup, 2000, Flinn, 1988, ascriptions of paternal resemblance Daly & Wilson, 1982, McLain et al., 2000, Regalski & Gaulin, 1993, and emotional responses to phenotypic resemblance (Platek, Burch, Panyavin, Wasserman, & Gallup, 2002). Although it could be argued that for every man who suffers the costs of being cuckolded there is a man who benefits, there is no evidence of selective pressure having acted on the male psyche to motivate men towards protecting the ambiguity of paternity (but see Section 3).

Women, on the other hand, have almost certainly evolved mechanisms of protecting ambiguity about their offspring's paternity. Having the ability to fallaciously convince a man of his relatedness to her offspring could benefit a woman in a number of situations. For example, Trivers (1985) argues that women historically have had limited choice in marriage partner, and even where they can exercise choice, monogamy, or limited polygyny constrains their choice of mates (Wright, 1994). In such cases, the ambiguity of paternity may allow a female to exercise choice of a genetic sire for her offspring other than her husband. Hrdy (1981) argues that cryptic ovulation is a product of such a selective force: Women have prolonged sexual receptivity and give no overt signal of ovulation because they benefit from the resultant opportunity to elicit solicitude from as many sexual partners as they can convince have fathered their child. Studies conducted in Europe and North America suggest that women have children sired by men other than their partners in from 1% to 10% of births, with the highest rates reported in two studies of families of low socioeconomic status (reviews and references in Macintyre & Sooman, 1991, Cerda-Flores et al., 1999). Therefore, it should be in the best interests of women to protect the ambiguity of paternity rather than risk facing abandonment or infanticide (Daly & Wilson, 1988).

We administered surveys designed to test the hypothesis that men would be more in favor of genetic paternity testing than women. We also tested two secondary hypotheses.

First, we hypothesized that sex differences in attitude would be less marked among respondents of high economic class. Drawing on Hrdy's theory Hrdy, 1981, Diamond, 1997 that women may use ambiguity about paternity to elicit solicitude from men who may have fathered their child, we reasoned that women with fewer economic resources may be relatively likely to seek copulations (and associated solicitude) from men other than their primary partner, and hence relatively inclined to protect the ambiguity of their children's paternity (see Cerda-Flores et al., 1999), while women of greater means may have more to gain by proving paternity and insuring the parental investment of their partners. It is also possible that women seek extra-pair copulations more for good genes than for resources, in which case we would expect to see no effect of income or even that fewer women in high-income brackets favor paternity tests (if they are more likely to have married for resources than for genes). Some evidence that extra-pair copulations are especially likely to occur near ovulation supports the idea that women seek sires for offspring in extra-pair copulations (Bellis & Baker, 1990).

We reasoned that attitudes of men might vary with economic class in a corresponding manner. Men with few resources would worry more about their wives' fidelity, given the greater incentive for their wives to seek extra-pair copulations. Furthermore, men with ample resources have more sexual partners (Pérusse, 1993) and may wish to avoid providing the paternal investment that results of paternity tests might demand.

Secondly, we hypothesized that the sex difference in attitudes toward paternity testing would be less marked among single than married respondents because single men might fear that the results of paternity tests would make them accountable for unwanted pregnancies while single women might hope that such tests could insure them paternal investment.

1. Methods

1.1. Surveys

We obtained completed surveys aimed at investigating attitudes toward hospital practices surrounding birth from 733 adults, of whom 655 were enrolled in classes (in sociobiology, geology, psychology, and sociology) at the University of Washington, Seattle, or Highline Community College. To prevent class subject material from affecting responses, surveys were administered early in the term in sociobiology courses. To diversify the pool of respondents, we also obtained completed surveys from 78 adults outside a Washington state driver's licensing office and at the gates of the Seattle-Tacoma International Airport. Surveys requested information about respondent's age, sex, marital status, number of children, income bracket, parent's income bracket, partner's income bracket, and income bracket of partner's parents and were completed voluntarily and anonymously.

The question about paternity testing was as follows:


1.Should hospitals routinely include paternity exclusion tests for newborns? (Paternity exclusion tests verify whether the mother's partner is the child's father.)To conceal our aim in administering the survey, we also included the following questions about practices surrounding birth on 563 surveys (all surveys except the 170 used for the analysis of motives—see below):

2.Should fathers be present during births? (By present, we mean present in the delivery room under normal circumstances.)

3.Should mothers be allowed to have labor induced to conveniently schedule births? (Convenient scheduling does not include inducing labor for health reasons.)

There were four versions of the survey; one with question 1 alone (n=170); one with the questions in order 1, 2, and 3 (n=107); one with the order 2, 1, and 3 (n=222), and one with the order 3, 1, and 2 (n=234).

1.2. Main effects on survey response

Respondents were asked their age, marital status, and to place themselves in one of the following income categories: less than US$30 thousand a year, US$30–50 thousand a year, US$50–100 thousand a year, US$100–300 thousand a year, or more than US$300 thousand a year. For college-aged students, parents' income was taken to represent income category. Married respondents were assigned to the category for their combined household income. There was no difference in distribution among income categories between sexes (χ2=6.07; p=.19). Logistic regression and likelihood ratio tests were used to test for effects of sex, source (college student taking the survey as part of a class or public), marital status, income, age, and proceeding question on attitudes towards paternity testing, as well as for all possible pairwise interactions. For the analysis of framing effects (order of questions), we treated the four versions of the survey separately. Thirteen respondents did not provide complete information on their surveys. In addition, 170 respondents received a different version of the survey to look at motivations (see below), which did not ask about income. Therefore, sample size for the logistic regression was 550 (317 women and 233 men).

1.3. Motivation

A subset of respondents comprised of 65 University of Washington students in an introductory human behavior and evolution class and 105 students in a sociobiology class were asked to explain their responses to the target question about paternity (at the beginning of the quarter before course material could affect response). These 170 students were not asked about other hospital practices or their income.

Certification of Exemption was obtained from the Human Subjects Division of the University of Washington for all surveys administered to the public.

2. Results

2.1. Sex difference

Of the 294 men who answered our survey, 148 (50.3%) were in favor of the routine administration of paternity exclusion tests, compared to 141 (32.1%) of the 439 women favored the test. This sex difference is highly significant (p<.0001).

2.2. Other effects

Marital status, income, and age did not affect attitudes toward paternity testing (p=.49, .68, and .32, respectively). Nor were there any significant framing effects of proceeding question or survey context (administered in a college class or solicited from the general public) (p=.10 and .11, respectively). Degrees of freedom and G2 values for each main effect are presented in Table 1. There were no significant pairwise interactions.

Table 1.

Logistic likelihood ratio tests for main effects on attitudes toward paternity testinga

Main effect df G2 p
Sex 1 21.80 <.0001
Source 1 2.70 .100
Marital status 1 0.47 .492
Income 4 2.32 .678
Age 1 1.00 .316
Preceding question 3 6.09 .107
a

In another logistic regression analysis, interactions between main effect variables did not approach significance; thus, we eliminated interactions for this analysis.

3. Discussion

The results of this study indicate that males are indeed more in favor of the routine administration of paternity tests than women. The observed sex difference was highly significant for both married and unmarried respondents and did not change with income. However, the restricted income range in our sample and the paucity of individuals with high incomes made our data poorly suited for testing the hypothesis that attitudes would vary with income level. Given the tendency for women in the lowest socioeconomic classes in Mexico (Cerda-Flores et al., 1999) and Chicago (Sahacht & Gershowitz, 1963) to show high levels of nonpaternity, it is perhaps also likely that almost all the college students that we surveyed should be considered to have incomes too high for an effect of income to have been revealed by our data. More importantly, if women have affairs primarily to improve the heritable component of their offspring's fitness, rather than to acquire resources, our prediction should not be supported.

Attitudes toward paternity testing did not differ significantly among married and unmarried respondents, perhaps because we asked about the routine administration of paternity tests. A question about general practices could fail to reveal differences between married and single women if single women respond as though they will become married women.

We were surprised that only 50% of males surveyed were in favor of routine paternity testing. To explore why half of our male respondents objected to routine paternity testing, we asked a subset of respondents (including 53 men) to elaborate on the reasoning behind their answer. Of the 28 men opposed to routine paternity testing in this subsample, only three stated that they thought the test should be optional and one that it was a waste of state resources; no other ethical or pragmatic reasons were offered for opposition to the test. To our great surprise, 18 of the 28 males opposed justified their answer with statements to the effect that “ignorance is bliss,” and six more specified that the test was an invasion of privacy. Thus, 24 of the 28 men opposed to testing specifically expressed what seemed to be a preference for preserving the ambiguity of paternity. Perhaps a “polymorphism” among men in their attitude toward routine paternity testing implies a mixed strategy among males, suggesting that in our evolutionary history cuckoldry was common. If this were true, then for some males ignorance of cuckoldry could yield higher returns than discovering cuckoldry and abandoning the possibility of future children with the current partner. Similarly, an attitude of “ignorance is bliss” could protect a male's own children from the detrimental effects of the violence or abandonment that might result from certain knowledge of cuckoldry. Alternatively, some males must benefit from conceiving children with women who are socially partnered to other men. For either or both of these reasons, selection may have favored a proclivity to protect ambiguity of paternity as a feature of some male psyches. This begs the question of “Whose ignorance is bliss?” We speculate that few males are likely to sire extra-pair offspring, while many are potential victims of cuckoldry. If this is true, then an “ignorance is bliss” strategy likely has more to do with cutting potential losses associated with certain knowledge of a partner's infidelity.

In conclusion, we have shown that among our pool of mostly college student respondents, men favored paternity testing more than women in accordance with our hypothesis. We found no support for our secondary hypotheses about how attitudes would vary with income or marital status. We think examining attitudes across a broader spectrum of the population might reveal interesting patterns suggestive of ways that male and female reproductive strategies vary with personal situation. The split in men's attitudes toward paternity testing (about half in favor and half opposed) suggests that their attitudes towards ambiguity of paternity could be situation dependent in ways that relate to advantages associated either with remaining ignorant of a partner's cuckoldry or with cuckolding others.

Acknowledgements

Jon Herron enthused about this study. Zachary Folk, Luke Butler, and Davidson Dodd helped administer surveys. Margo Wilson alerted us to the problem of framing effects. Jon Herron and members of the Rohwer lab commented on the manuscript. Martin Daly provided very valuable suggestions for analysis and revision. Eric Buhle provided statistical consulting.

References

Bellis & Baker, 1990 1.Bellis MA, Baker RR. Do females promote sperm competition? Data for humans. Animal Behaviour. 1990;40:997–999. CrossRef

Burch & Gallup, 2000 2.Burch RL, Gallup GG. Perceptions of paternal resemblance predict family violence. Evolution and Human Behavior. 2000;21:429–435.

Buss et al., 1992 3.Buss DM, Larsen R, Westen D, Semmelroth J. Sex differences in jealousy: evolution, physiology, and psychology. Psychological Science. 1992;3:251–255. CrossRef

Cerda-Flores et al., 1999 4.Cerda-Flores RM, Barton SA, Marty-Gonzalez LF, Rivas F, Chakraborty R. Estimation of nonpaternity in the Mexican population of Nuevo Leon: a validation study with blood group markers. American Journal of Physical Anthropology. 1999;109:281–293. MEDLINE | CrossRef

Daly & Wilson, 1988 5.Daly M, Wilson M. Evolutionary social psychology and family homicide. Science. 1988;242:519–524. MEDLINE

Daly et al., 1982 6.Daly M, Wilson M, Weghorst SJ. Male sexual jealousy. Ethology and Sociobiology. 1982;3:11–27.

Daly & Wilson, 1982 7.Daly M, Wilson MI. Whom are newborn babies said to resemble?. Ethology and Sociobiology. 1982;3:69–78.

Diamond, 1997 8.Diamond J. Why is sex fun?. New York: Basic Books; 1997;.

Flinn, 1988 9.Flinn MV. Mate guarding in a Caribbean village. Ethology and Sociobiology. 1988;9:1–28.

Geary et al., 1995 10.Geary DC, Rumsey M, Bow-Thomas CC, Hoard MK. Sexual jealousy as a facultative trait: evidence from the pattern of sex differences in adults from China and the United States. Ethology and Sociobiology. 1995;16:355–383.

Hrdy, 1981 11.Hrdy SB. The woman that never evolved. Cambridge, MA: Harvard University Press; 1981;.

Macintyre & Sooman, 1991 12.Macintyre S, Sooman A. Non-paternity and prenatal genetic screening. Lancet. 1991;338:869–871. MEDLINE | CrossRef

McLain et al., 2000 13.McLain DK, Setters D, Moulton MP, Pratt AE. Ascription of resemblance of newborns by parents and nonrelatives. Evolution and Human Behavior. 2000;21:11–23.

Pérusse, 1993 14.Pérusse D. Cultural and reproductive success in industrial societies: testing the relationship at the proximate and ultimate levels. Behavioral and Brain Sciences. 1993;16:267–322.

Platek et al., 2002 15.Platek SM, Burch RL, Panyavin IS, Wasserman BH, Gallup GG. Reactions to children's faces: resemblance affects males more than females. Evolution and Human Behavior. 2002;23:159–166.

Regalski & Gaulin, 1993 16.Regalski JM, Gaulin SJC. Whom are Mexican infants said to resemble? Monitoring and fostering paternal confidence in the Yucatan. Ethology and Sociobiology. 1993;14:97–113.

Sahacht & Gershowitz, 1963 17.Sahacht LE, Gershowitz H. Frequency of extra-marital children as determined by blood groups. In: Proceedings of the Second International Congress of Human Genetics, Vol. II. Rome: Instituto G. Mendel; 1963;p. 894–897.

Trivers, 1985 18.Trivers R. Parental investment and sexual selection. In:  Campbell B editors. Sexual selection and the descent of man, 1871–1971. Chicago: Aldine Press; 1985;p. 136–179.

Wright, 1994 19.Wright R. The moral animal. New York: Vintage Books; 1994;.

a Department of Biology, University of Washington, Seattle, WA 98195, USA

b Burke Museum and Department of Biology, University of Washington, Seattle, WA 98195, USA

Corresponding author. Tel.: +1-206-543-7623; fax: +1-206-616-9155

PII: S1090-5138(04)00024-8

doi:10.1016/j.evolhumbehav.2004.04.001



2007:11:13