Pregnancy from rape

Pregnancy is a potential result of rape. It has been studied in the context of war, particularly as a tool for genocide, as well as other unrelated contexts, such as rape by a stranger, statutory rape, incest, and underage pregnancy. Although claims have been made to the contrary, the current scientific consensus is that rape is as likely to lead to pregnancy as consensual sexual intercourse.^[1][2]

Rape can cause difficulties during and after pregnancy, with potential negative consequences for both mother and child. Medical treatment following a rape includes testing for, preventing, and managing pregnancy. A woman who becomes pregnant after a rape may face a decision about whether to have an abortion, give the child up for adoption, or raise it. In some countries where abortion is illegal even after rape and incest, over 90% of pregnancies in children 15 and under are due to rape by family members.^[3]

The false belief that pregnancy can almost never result from rape was widespread for centuries. In Europe, from medieval times well into the 1700s a man could use a woman's pregnancy as a legal defense to "prove" that he could not have raped her, since her pregnancy was thought to mean that she had enjoyed the sex and therefore consented to it. In recent decades, several pro-life politicians and organizations who oppose legal abortion in cases of rape have advanced claims that pregnancy very rarely arises from rape, and that the practical relevance of such exceptions to abortion law is therefore limited or non-existent.^[4][5][6]

Rape-pregnancy rates

Three Young White Men and a Black Woman (1632) by Christiaen van Couwenbergh. See Treatment of slaves in the United States.

Any female capable of ovulation may become pregnant after rape by a fertile male. Rape conception happens between 25,000 and 32,000 times each year in the U.S. In a three-year longitudinal study of 4,000 American women, physician Melisa Holmes estimated from data from her study that forced sexual intercourse causes over 32,000 pregnancies in the United States each year.^[7] That study revealed that among women aged 12–45, pregnancy occurred in 5% of victims of rape.^[8] A 1987 study also found a 5% pregnancy rate from rape among 18- to 24-year-old college students in the US.^[9] A 2005 study placed the rape-related pregnancy rate at around 3–5%.^[10] Physician Felicia H. Stewart and economist James Trussell estimated that the 333,000 assaults and rapes reported in the US in 1998 caused about 25,000 pregnancies, and up to 22,000 of those pregnancies could have been prevented by prompt medical treatment, such as emergency contraception.^[11] A study of Ethiopian adolescents who reported being raped found that 17% subsequently became pregnant,^[12] and rape crisis centres in Mexico reported the figure the rate of pregnancy from rape at 15–18%.^[13] Estimates of rape-related pregnancy rates may be low since the crime is under-reported, resulting in some pregnancies from rape not being recorded as such.^[10]

Sociobiologists and evolutionary psychologists have hypothesized that causing pregnancy by rape may be a mating strategy in humans, as a way for males to ensure the survival of their genes by passing them on to future generations.^[14] Randy Thornhill and Craig T. Palmer are key popularizers of this hypothesis. They assert that most rape victims are women of childbearing age and that many cultures treat rape as a crime against the victim's husband. They state that rape victims suffer less emotional distress when they are subjected to more violence, and that married women and women of childbearing age experience less psychological distress after a rape than do girls, single women or post-menopausal women.^[15] Rape-pregnancy rates are crucial in evaluating these theories, because a high or low pregnancy rate from rape would determine whether such adaptations are favored or disfavored by natural selection.^[16]

There is debate as to whether conception rates are higher from rape or consensual sex. Psychologist Robert L. Smith states that some studies have reported "unusually high rates of conception following rape".^[17] He cites a paper by C.A. Fox and Beatrice Fox, reporting that biologist Alan Sterling Parkes had speculated in personal correspondence that "there is a high conception rate in rape, where hormonal release, due to fear or anger, could produce reflex ovulation".^[18] Smith also cites veterinary scientist Wolfgang Jöchle, who "proposed that rape may induce ovulaton in human females".^[19][20] Literary scholar Jonathan Gottschall and economist Tiffani Gottschall argued in a 2003 Human Nature article that previous studies of rape-pregnancy statistics were not directly comparable to pregnancy rates from consensual intercourse, because the comparisons were largely uncorrected for such factors as the use of contraception. Adjusting for these factors, they estimated that rapes are about twice as likely to result in pregnancies (7.98%) as "consensual, unprotected penile-vaginal intercourse" (2–4%). They discuss a variety of possible explanations and advance the hypothesis that rapists tend to target victims with biological "cues of high fecundity" and/or subtle indications of ovulation.^[16]

In contrast, psychologists Tara Chavanne and Gordon Gallup Jr., citing unpublished dissertations by Rogel and Morgan,^[21][22] argued that female adaptations reduce the likelihood of rape during fertile periods.^[23] A 1995 study of women who became pregnant after rape found that 60% had been impregnated during consensual intercourse.^[8] Anthropologist Daniel Fessler disputed these findings, saying, "analysis of conception rates reveals that the probability of conception following rape does not differ from that following consensual coitus".^[24]

Statutory rape, incest and underage pregnancy

In 1995–96, the journal Family Planning Perspectives published a study by the Guttmacher Institute, a sexual health research and policy organization, on statutory rape (sexual intercourse with a minor) and resulting pregnancies. It drew on other research^[25][26] to conclude that "at least half of all babies born to minor women are fathered by adult men", and that "although relatively small proportions of 13–14-year-olds have had intercourse, those who become sexually active at an early age are especially likely to have experienced coercive sex: Seventy-four percent of women who had intercourse before age 14 and 60% of those who had sex before age 15 report having had a forced sexual experience". Because of difficulties in bringing such cases to trial, however, "data from the period 1975–1978 ... indicate that, on average, only 413 men were arrested annually for statutory rape in California, even though 50,000 pregnancies occurred among underage women in 1976 alone."^[27] In that state, it was found that two thirds of babies born to school-age mothers were fathered by adult men.^[25]

Sexual abuse early in life can lead young women to feel a lack of control over their sexual lives, decrease their future likelihood of using contraceptives such as condoms, and increase their chances of becoming pregnant or acquiring sexually transmitted infections.^[13] A 2007 paper by Child Trends^[28] examined studies from 2000 to 2006 to identify links between sexual abuse and teenage pregnancy, starting with Blinn-Pike et al.'s 2002 metastudy of 15 studies since 1989.^[29] It found that childhood sexual abuse has a "significant association" with adolescent pregnancy. Direct connections have been demonstrated both by retrospective studies examining antecedents to reported pregnancies and prospective studies, which track the lives of sex abuse victims and "can be helpful for determining causality".^[28]:3 The more severe forms of abuse, such as rape and incest, entail a greater risk of adolescent pregnancy.^{[28]:4[30][31]} Although some researchers suggest that pregnancy could be a choice made to escape a "bad situation", it may also be "a direct result of unwanted intercourse", which one study found to be the case for about 13% of participants in a Texas parenting program.^[28]:4[32]

In Nicaragua, between 2000 and 2010, around 172,000 births were recorded for girls under 14, representing around 13% of the 1.3 million births during that period. These were attributed to poverty, laws forbidding abortion for rape and incest, poor sex education, lack of access to justice, and beliefs held in the culture and legal system.^[3][33] A 1992 study in Peru found that 90% of babies delivered to mothers aged 12–16 were conceived through rape, typically by a father, stepfather, or other close relative.^[3][34] In 1991 in Costa Rica, the figure was similar, with 95% of adolescent mothers under 15 having become pregnant through rape.^[3][35]

Many of the youngest documented birth mothers in history experienced precocious puberty and were impregnated as a result of rape, including incest. The youngest, Peruvian Lina Medina, was impregnated when she was four and had a live birth in 1939, at age five.^[36]

Rape in war and conflict

Forced prostitution was used by the Japanese Army during World War II. Rangoon, Burma. 8 August 1945. A young ethnic Chinese woman who was in one of the Imperial Japanese Army's "comfort battalions" is interviewed by an Allied officer.

Rape has been used as a weapon of psychological warfare for centuries, to terrorize, humiliate, and undermine the morale of the enemy. Rape was also used as an act of ethnic cleansing to produce babies that share the perpetrators' ethnicity.^[37] Forced pregnancy has been noted in places including Bangladesh, Darfur, and Bosnia.^[38] More broadly, pregnancy commonly results from wartime rape that was perpetrated without the intention of impregnating the enemy, as has been found in conflicts in East Timor, Liberia, Kosovo, and Rwanda.^[38] Gita Sahgal of Amnesty International commented that, rather than being primarily about "spoils of war" or sexual gratification, rape is often used in ethnic conflicts as a way for attackers to perpetuate social control and redraw ethnic boundaries.^[39] Children may be born to women and girls forced to "marry" abductors and occupiers; this happened in the Indonesian occupation of East Timor and in the Lord's Resistance Army's conflict in Uganda.^[40]

Rape during war is recognized under United Nations Security Council Resolution 1820 as a war crime and a crime against humanity.^[41] "Forced pregnancy" is specifically enumerated as a war crime and crime against humanity in the Rome Statute, which was the "first international criminal tribunal ever officially to criminalize forced pregnancy".^[42]

Children born as the result of wartime rape may be identified with the enemy and grow up stigmatized and excluded by their communities; they may be denied basic rights or even killed before reaching adulthood.^[38] Children are particularly at risk for such abuse when they are visibly identifiable as sharing half their ethnicity with the occupying forces, as in the case of half-Arab children of Darfuri women raped by janjaweed soldiers as part of the war in Darfur.^[43] Children of war rape are also at risk due to neglect by traumatized mothers unable to provide sufficient care.^[43]

Rape of Nanking

In 1937 the Japanese army took over Nanking, which at the time was the capital of China. In the resulting seven-week occupation known as the Rape of Nanking, as many as 80,000 people were raped.^[44] Chinese women and girls of all ages were raped, mutilated, tortured, sexually enslaved, and killed; unknown numbers of them were left pregnant.^[44] Many pregnant Nanking women killed themselves in 1938, and others committed infanticide when their babies were born.^[44] During the rest of the 20th century there was no record of any Chinese woman acknowledging her child as having been born as a result of the Rape of Nanking.^[44]

Bosnian War

During the 1992–95 Bosnian War, pregnancy from rape was used to perpetrate genocide. There were reports of deliberately created "rape camps" intended to impregnate captive Muslim and Croatian women. Women were reported to have been kept in confinement until their pregnancies had advanced beyond a stage at which abortion would be safe.^[45] In the context of a patrilineal society, in which children inherit their father's ethnicity, such camps were intended to create a new generation of Serbian children.^[45] The women's group Tresnjevka claimed that more than 35,000 women and children were held in such Serb-run camps.^[46][47][48] Estimates range from 20,000^[49] to 50,000^[50] victims.^[51][52][53] Feryal Gharahi of Equality Now reported:

"Families were separated, and women and children were kept in the gym, where all of the women and girls over ten years old were raped in the first few days.... There are rape camps all over the country. Thousands of women are being raped and killed. Thousands of women are pregnant as a result of rape. Over and over again, everywhere I went in Bosnia-Herzegovina and in Croatian refugee camps, women told me stories of abomination – of being kept in a room, raped repeatedly and told they would be held until they gave birth to Serbian children." ^[54]

After the Bosnian War, the International Criminal Court updated its statute to prohibit "confin[ing] one or more women forcibly made pregnant, with the intent of affecting the ethnic composition of any population".^[55]

Treatment and outcomes

Immediate post-rape treatment protocols call for medical professionals to assess the likelihood that a victim will become pregnant in their assessment of the physical damage done to the woman. Protocol calls for gaining a history of the use of contraceptives, as a woman's use of birth control pills or other contraceptives before a rape affect her chance of becoming pregnant.^[56] Treatment protocols also call for clinicians to provide access to emergency contraception and counseling on abortion in countries where it is legal.^[57] High-dose estrogen pills were tried as an experimental treatment after rape in the 1960s, and in 1972 Canadian physician A. Albert Yuzpe and his colleagues began systematic studies on the use of ethinyl estradiol and dl-norgestrel to provide emergency contraception after an assault. These treatments reduced the rate of pregnancy after rape by 84%.^[58] This method is now called the Yuzpe regimen.^[59] Before being treated with pregnancy prevention measures, a rape victim is given a HCG pregnancy test to determine whether she was already pregnant before the rape.^[60]

When being discharged from emergency care, clinicians provide information about pregnancy as well as other complications such as infection and emotional trauma.^[60] While a woman who has become pregnant during the past 48 hours will test negative for pregnancy in an HCG pregnancy test (unless she was already pregnant before the rape), pregnancy resulting from the rape can be detected at the two-week followup visit.^[61]

Decisions of whether to end a rape-related pregnancy or carry it to term, and whether to keep the child or give it up for adoption can be severely traumatizing for a woman.^[62] Abortion rates for pregnancies due to rape vary significantly by culture and demographics; women who live in countries where abortion is illegal must often give birth to the child or secretly undergo a dangerous, back-alley abortion.^[13] Some women do not wish to get abortions for religious or cultural reasons.^[63] In a third of cases, rape-related pregnancies are not discovered until the second trimester of pregnancy, which may reduce a woman's options, particularly if she doesn't have easy access to legal abortion or is still recovering from the trauma of the rape itself.^[64] A 1996 study of thousands of US women showed that, of pregnancies resulting from rape, 50% were aborted, 12% resulted in miscarriage, and 38% were brought to term and either given up for adoption or raised.^[8] Peer-reviewed studies have reported from 38% of American women to 90% of Peruvian adolescents carrying the pregnancy to term.^[7][65] In Lima, Peru, where abortion is illegal, 90% of girls aged 12 to 16 who became pregnant through rape carried the child to term.^[65] Of all children born, 1% are put up for adoption; the number of children conceived from rape who are given up for adoption was found to be about 6% in one study and 26% in another.^[66] When a mother commits neonaticide, killing an infant younger than 24 hours old, the child's birth being the result of rape is a main cause, although other psychological and situational factors are generally present.^[67] Some people turn to drugs or alcohol to cope with emotional trauma after a rape; use of these during pregnancy can harm the fetus.^[68]

Children of rape

For a mother who raises a rape-conceived child, both the traumatic effect of the rape and the child's blood relationship to the rapist can create significant psychological problems for both mother and child.^[66][69] If a woman decides to keep and raise the child, she may have difficulty accepting it, and both mother and child face ostracism in some societies.^[70]

Mothers may also face legal difficulties. In most US states, the rapist maintains parental rights.^[69] Research by legal scholar Shauna Prewitt indicates that the resulting continued contact with the rapist is damaging for women who keep the child. www.hopeafterrapeconception.org ^[69] She wrote in 2012 that in the US, 31 states allow rapists to assert custody and visitation rights over children conceived through rape.^[69]

History

Children whose births result from rape have been killed by their mothers at various times in history; during ancient and medieval times, such infanticide was not prohibited (however penance was expected of these mothers in medieval Europe).^[64]

Law

In contrast to the modern scientific consensus that rape-induced pregnancies are no less likely than any other, beliefs that rape could not lead to pregnancy were widespread in both legal and medical opinion for centuries.^[71][72] Galen, an ancient Greek physician, believed that a woman must experience pleasure to release "seed" and become pregnant, and could not derive such pleasure from nonconsensual sex.^[73] Galen's thinking influenced understanding from medieval England to Colonial America.^[73]

The Ancient Greek physician Galen's belief that women could not conceive without pleasure influenced medical and legal thinking for centuries.

The Ancient Greek philosopher Aristotle also believed that female pleasure played a central role in conception.^{[citation needed]} Female reproduction was, in many ways, viewed through the lens of male reproductive processes, imagining that female organs functioned as inverted versions of male organs, and hence orgasm was required for conception.^[71]

Centuries later, in medieval Europe, the belief that pregnancy could not occur without consent was still standard; in fact, conception by a woman was considered a legitimate defense against charges of rape.^[72] The belief was codified in the medieval British law texts Fleta^[71] and Britton. Britton states:

"If the defendant confesses the fact, but says that the woman at the same time conceived by him, and can prove it, then our will is that it be adjudged no felony, because no woman can conceive if she does not consent."^[74]

Medieval literary scholar Corinne Saunders acknowledged a difficulty in determining how widely held was the belief that pregnancy implies consent, but concluded that it influenced "at least some justices", citing a 1313 case in Kent.^[75]

By the late 1700s, scientists no longer universally accepted the view that pregnancy was impossible without pleasure, although this view was still common.^[76] A 1795 British legal text, Treatise of Pleas of the Crown, disparaged the belief's legal utility and its biological veracity:

"Also it hath been said by some to be no rape to force a woman who conceives at the time; for it is said, that if she had not consented, she could not have conceived, but this opinion seems very questionable, not only because the previous violence is no way extenuated by such a subsequent consent, but also because, if it were necessary to shew that the woman did not conceive, the offender could not be tried till such time as it might appear whether she did or did not..."^[72][77]

The 1814 British legal text Elements of Medical Jurisprudence by Samuel Farr claimed that conception "probably" could not occur without a woman's "enjoyment", so that an "absolute rape" was unlikely to lead to pregnancy.^[71][78] On the other hand, in the US, in an 1820 court case in the Arkansas Territory, a man plead innocent to rape charges because the victim became pregnant, but the court rejected the argument:

"The old notion that if the woman conceive, it could not be a rape, because she must have in such case have consented, is quite exploded. Impregnation, it is well known, does not depend on the consciousness or volition of the female. If the uterine organs be in a condition favorable to impregnation, this may take place as readily as if the intercourse was voluntary."^[79]

Islamic law

Historian Ian Talbot has written about how countries with Quran-based Islamic codes on rape and pregnancy use Sura An-Nur, verse 2, as a legal basis: "The law of evidence in all sexual crimes required either self-confession or the testimony of four upright (salah) Muslim males. In the case of a man, self-confession involved a verbal confession. For women however medical examinations and pregnancy arising from rape were admissible as proof of self-guilt."^[80]

Opposition to legal abortion

Pregnancy from rape is an ethical and moral issue in the context of opposition to legal abortion. In recent decades, claims of the improbability of rape-induced pregnancy, reminiscent of historical beliefs,^[2][71] have again begun to play a role in political discourse surrounding abortion regulation in cases of rape, particularly in the United States.^[2][6]

Claims that rape reduces the chance of pregnancy have at times been made by referring to the fact that chronic stress can reduce a woman's fertility over a long term. However the current scientific consensus is that this is specific to long-term stress—the acute stress reaction that occurs during rape cannot "shut down ovulation that has already begun".^[1][2] In a 1972 article, physician and anti-abortion activist Fred Mecklenburg argued that pregnancy from rape is "extremely rare", adding that a woman exposed to the trauma of rape "will not ovulate even if she is 'scheduled' to".^[81] Blythe Bernhard wrote in The Washington Post, "That article has influenced two generations of anti-abortion activists with the hope to build a medical case to ban all abortions without any exception."^[82] John C. Willke, a former president of the National Right to Life Committee and a general practitioner with training in obstetrics, has published similar statements since 1985.^[5][6] In a 2012 interview he said, "This is a traumatic thing – she's, shall we say, she's uptight. She is frightened, tight, and so on. And sperm, if deposited in her vagina, are less likely to be able to fertilize. The tubes are spastic." These assertions were disputed by a number of gynecology professors.^[5] A 1997 book published by the group Human Life International (which opposes legal abortion in all cases, including rape) claims that several studies performed in the 1970s show that only 0.08% of rapes result in pregnancy, and alternatively offers an estimate of 0.8% from other data. The same book dismisses contrary statistics, claiming that "the women who obtain abortions for 'rape' are almost always lying".^[4]

Related views have also been expressed by pro-life groups outside the United States. The United Kingdom pro-life group Society for the Protection of Unborn Children similarly claims that rape-pregnancy is "extremely rare", in part because the "trauma of being raped makes it difficult for fertilisation or implantation to occur".^[83] The Irish pro-life group Youth Defence published claims on its web site that "trauma from the rape may bring into play some natural defence mechanisms that reduce the likelihood of pregnancy", but removed these statements in 2012 following the Akin controversy, explaining that the group now deemed them "unreliable".^[84] The Irish group Precious Life published claims that "the trauma of sexual assault is likely to inhibit ovulation" and "the rate of pregnancy arising from sexual assault is 0.1%".^[85] Other groups that say rape prevents ovulation include the Australian group Pro-Life Victoria,^[86] and the group Pro-Life Philippines.^[87] The Austrian group Jugend für das Leben (Youth for Life) writes that "pregnancies after rape are extremely rare" because "protective mechanisms" from the stress of rape will "almost always prevent conception".^[88]

In the US, several politicians in the Republican Party have advanced claims that pregnancy from rape is rare. Pennsylvania state representative Stephen Freind claimed in 1988 that the odds of a pregnancy resulting from rape were "one in millions and millions and millions".^[89][90] James Leon Holmes published a letter in 1980 stating, "concern for rape victims is a red herring because conceptions from rape occur with approximately the same frequency as snowfall in Miami".^[91] Holmes apologized for this remark in 2003 after he was nominated as a United States federal judge. (He was confirmed in 2004).^[91][92] In 1995, North Carolina House of Representatives member Henry Aldridge remarked during a debate to eliminate a state abortion fund for poor women: "The facts show that people who are raped – who are truly raped – the juices don't flow, the body functions don't work and they don't get pregnant. Medical authorities agree that this is a rarity, if ever."^[93][94] In 1998, Arkansas state senator Fay Boozman lost a campaign for a US Senate seat after remarking that fear-induced hormonal changes made rape victims unlikely to become pregnant. He later apologized and eventually called the claim a mistake, but the controversy was renewed in 1999 when he was appointed director of the Arkansas Department of Health by then-governor Mike Huckabee.^[95][96] During his campaign in the United States Senate election in Missouri, 2012, US Representative Todd Akin commented on abortion exceptions for rape victims: "I understand from doctors, that's really rare. If it's a legitimate rape, the female body has ways to try to shut that whole thing down."^[97] The comment was widely criticized,^{[98][99][100][101][102]} and Akin apologized, saying he "misspoke". Akin's suggestion that rape is unlikely to result in pregnancy was defended by some prominent individuals and groups which oppose legal abortion.^{[5][103][104]} A SurveyUSA poll one day after Akin's comments reported that 76% of Missouri adults disagreed with Akin, 13% agreed with the statement and 11% were unsure (±3.8%).^[105]

See also

• Effects and aftermath of rape
• Reproductive coercion
• Unintended pregnancy

References

Bibliography

• R. Charli Carpenter (25 June 2007). Born of War: Protecting Children of Sexual Violence Survivors in Conflict Zones. Kumarian Press. ISBN 978-1-56549-237-0. Retrieved 15 February 2013. 
• de Brouwer, Anne-Marie (20 October 2005). Supranational Criminal Prosecution of Sexual Violence: The ICC and the Practice of the ICTY and the ICTR. Intersentia nv. ISBN 978-90-5095-533-1. Retrieved 31 January 2013. 
• Hazelwood, Robert R.; Burgess, Ann Wolbert (2009). Practical Aspects of Rape Investigation: A Multidisciplinary Approach. CRC Press. ISBN 978-1-4200-6504-6. Retrieved 29 January 2013. 
• Jenkins, Jon L.; Braen, G. Richard (1 August 2004). Manual of Emergency Medicine, 5e. Lippincott Williams & Wilkins. ISBN 978-0-7817-5035-6. Retrieved 15 February 2013. 
• Krug, Etienne G.; World Health Organization (2002). World Report on Violence and Health. World Health Organization. ISBN 978-92-4-154561-7. Retrieved 15 February 2013. 
• Price, Sally (2007). Mental Health in Pregnancy and Childbirth. Elsevier Health Sciences. ISBN 978-0-443-10317-9. Retrieved 15 February 2013. 
• Smith, Merril D. (2004). Encyclopedia of Rape. Greenwood Publishing Group. ISBN 978-0-313-32687-5. Retrieved 29 January 2013. 

Further reading

• Beebe, DK (1991). "Emergency management of the adult female rape victim". American Family Physician 43 (6): 2041–6. PMID 2042547. 
• Campbell, R; Bybee, D (1997). "Emergency medical services for rape victims: Detecting the cracks in service delivery". Women's Health 3 (2): 75–101. PMID 9332152. 
• Krueger, Mary M. (1988). "Pregnancy as a result of rape". Journal of Sex Education & Therapy 14 (1): 23–7. 
• Lathrop, Anthony (1998). "Pregnancy Resulting from Rape". Journal of Obstetric, Gynecologic, & Neonatal Nursing 27 (1): 25–31. doi:10.1111/j.1552-6909.1998.tb02587.x. PMID 9475124. 
• McFarlane, J. (2007). "Pregnancy Following Partner Rape: What We Know and What We Need to Know". Trauma, Violence, & Abuse 8 (2): 127–34. doi:10.1177/1524838007301222. PMID 17545570. 
• Sutherland, Sandra; Scherl, Donald J. (2010). "Patterns of Response Among Victims of Rape". American Journal of Orthopsychiatry 40 (3): 503–11. doi:10.1111/j.1939-0025.1970.tb00708.x. PMID 5422298.