The following is an article from the Annals of Improbable Research.
A pointed look at an emerging field of research
by Alice Shirrell Kaswell, Improbable Research staff
with finger drawings from Jackson’s Gymnastics for the Fingers and Wrist, N. Trubner & Co., London, 1865
Fingers are hot in the research world. Here is a quick tour of what scientists say they have discovered. The study of finger lengths is now the basis of many academic careers. So many studies have been published that the field—it seems no exaggeration to call it a field—has produced several celebrities. For a look at some of the top personalities, see “Finger Celebrities” elsewhere in this issue of the Annals of Improbable Research.
The Big Idea, and the Rise of the Finger
Until recently, people who did research on fingers either measured them or, if they were broken, repaired them. Then came an idea about what fingers might mean. Here is the idea in a six-part nutshell:
1. The body’s many hormones—chemical messengers—are involved in many things that happen in your body during fetus-hood, childhood and adolescence. These many things happen at various times, in various ways.
2. Each of these hormones has many different effects. Scientists have noticed some of these effects, and understand a few of them at least a little bit.
3. Testosterone is one of the many hormones.
4. Maybe testosterone somehow, at some time, affects how long various fingers grow.
5. Maybe the relative lengths of someone’s fingers tells something about how much testosterone was in the body at some point early in their life.
6. Maybe the amount of testosterone in someone’s body at some point early in their life affects lots of other things.
This simple idea is often credited to Dr. John Manning of the University of Liverpool. Dr. Manning is now one of the world’s great finger research celebrities (see “Finger Celebrities” elsewhere in this issue).
The rest of this article is a too-quick look at what researchers have done with this idea, and at some other finger research. But first, a mention of the way finger-length research was done before the coming of the idea.
Differences Long Unnoticed and/or Ignored
In 1952, V. Rae Phelps, at the University of Texas and at Tulane University, compiled a capsule history of early finger findings, waxing nearly poetic about the researchers’ many missteps and mistakes.
“Relative Index Finger Length as a Sex-Influenced Trait in Man,” V. Rae Phelps, American Journal of Human Genetics, vol. 4, no. 2, 1952, pp. 72-89. Professor Phelps reports:
One of the most frequently reported normal variations in the human hand is the length of the index finger as compared with the ring finger. Ecker (1875) noted that three manifestations of relative finger length may be discerned in the living model: index finger shorter than ring finger; index finger equal in length to ring finger; and index finger longer than ring finger. Many of the earlier workers failed to recognize this variability in relative index finger length. Gerdy (1829) stated that the index finger is always shorter than the ring finger, while according to Carus (1853) and Humphry (1861), the index finger exceeds the ring finger in length. Langer (1865) declared that the index finger is shorter than or nearly equal to the ring finger. Alix (1867), Grining (1886), Baker (1888), Schultz (1926), and Wood-Jones (1920, 1941) point out that although the index finger is usually shorter than the ring finger, it may in certain instances exceed the length of the ring finger….
* * *
Several scientists have looked at little fingers.
Is Little-Finger Length a Family Legacy?
“Inheritance Study of the Little Finger Length,” Inderjit S. Bansal, Human Genetics, vol. 4, no. 2, June 1967, pp. 183–6. The author, at the University of Delhi, India, reports:
An attempt has been made to see whether the length of the little finger (based upon its approach to the last interphalangeal joint of the ring finger) follows any hereditary pattern in its transmission. For this 100 biological families along with their offsprings have been analysed. Results show that heredity certainly plays a role for this trait.
Is Little-Finger Length a Family Legacy?
“Hereditary Transmission of Finger Length Ratios” [article in German], H.D. Rosler, Acta Gerontologica, vol. 7, no. 3, July 1958, pp. 361–82.
* * *
Some have looked at other fingers. F. Holik and O. Slaby went further then most.
The Sixth Finger
“Rudiment of the sixth finger” [article in Czech], F. Holik and O. Slaby, Acta Chirurgiae Orthopaedicae et Traumatologiae, vol. 21, no. 4, August 1954, pp. 124–7.
* * *
Much research has been devoted to the index finger, and to finger-pointing.
Proudly Noted Extra Index Fingers
“Note on Duplication of the Index Finger,” Michael Burman, Journal of Bone and Joint Surgery, vol. 54, 1972, p. 884. The author explains:
[A published study by a Dr. Wood] found 145 patients with polydactyly in the records of the University of Iowa Hospitals.... A duplication of the little finger occurred in sixty-two, of the thumb in 101, of the ring finger in twenty-six, the long finger in eight, and of the index finger in seven. This is the only series with so many cases of double index. Wood found no other direct references to this anomaly of double index finger in the English literature. He believed it to be “a previously undescribed congenital anomaly of the hand.” [But this] anomaly has been described before.... I give here the references on doubling of the index finger found in my own study of polydactyly.
Inhuman Finger-Pointing (Chimpanzees)
“Differences Between Chimpanzees (Pan troglodytes) and Humans (Homo sapiens) in the Resting State of the Index Finger: Implications for Pointing,” Daniel J. Povinelli and D. Richard Davis,
Journal of Comparative Psychology, vol. 108, no. 2, pp. 134–9. The authors, at the University of Southwestern Louisiana, report:
In contrast to humans, chimpanzees (Pan troglodytes) do not develop a pointing gesture with the index finger and rarely point by gesturing with hands or arms.... In this article we report the existence of a difference in the resting morphology of the index finger in humans and chimpanzees. We speculate on how this species difference may be related to species differences in pointing with the index finger.
Inhuman Finger-Pointing (Baboons)
“Relative Digit Lengths and Testosterone Levels in Guinea Baboons,” J.R. Roney, J.C. Whitham, M. Leoni, A. Bellem, N. Wielebnowski and D. Maestripieri, Hormones and Behavior, vol. 45, no. 4, April 2004, pp. 285–90. The authors, at the University of Chicago, report:
A growing body of literature suggests that the ratio of the lengths of the second to fourth digits on human hands is sexually dimorphic and associated with prenatal exposure to gonadal hormones, circulating serum testosterone, and a number of psychological and behavioral measures. Little research has investigated digit ratios in nonhuman species. In the present study, we investigated sex differences in digit ratios and their possible association with serum testosterone in a captive group of Guinea baboons (Papio papio).
Inhuman Finger-Pointing (Frogs)
“Pointing the Way: The Distribution and Evolution of Some Characteristics of the Finger Muscles of Frogs,” Thomas C. Burton, American Museum Novitates, no. 3229, June 10, 1998.
In-Human Finger Pointing (Lincoln)
“Good Samaritan Surgeon Wrongly Accused of Contributing to President Lincoln’s Death: An Experimental Study of the President’s Fatal Wound,” J.K. Lattimer and A. Laidlaw, Journal of the American College of Surgeons, vol. 182, no. 5, May 1996, pp. 431–48. (Thanks to John Dudley for bringing this to our attention.) The authors, who are at the College of Physicians and Surgeons of Columbia University, in New York City, explain that:
BACKGROUND: When President Abraham Lincoln was shot in the back of the head at Ford’s Theater in Washington, D.C., on April 14, 1865, he was immediately rendered unconscious and apneic. Doctor Charles A. Leale, an Army surgeon, who had special training in the care of brain injuries, rushed to Lincoln’s assistance.... In February 1995, an article in a popular magazine alleged that Doctor Leale had caused further (fatal) damage to Lincoln’s brain by thrusting his finger into the brain through the bullet hole.... CONCLUSIONS: The wound made by John Wilkes Booth’s derringer ball in Lincoln’s brain was devastating; it was clearly the cause of his death. Good Samaritan surgeon Leale has been falsely accused of contributing to Lincoln’s death.
The Meaning of the Finger (1)
“L’index significant (The Pointed Index Finger)” [article in French], G. Calbris, Études de Linguistique Appliquée, no. 35, July–September 1979, pp. 91–109.
In the framework of a study of nonverbal communication, the various meanings attached to the pointed index finger are analyzed. The question is raised as to what extent the findings hold for cultures other than French.
The Meaning of the Finger (2)
“Relation Between Index-Finger Extension and the Acoustic Quality of Cooing in Three-Month-Old Infants,” Masataka Nobuo, Journal of Child Language, vol. 22, no. 2, June 1995, pp. 247–57. The author explains:
Reports on two studies that looked at the spontaneous face-to-face interaction of three-month-old infants with their mothers. Facial and manual actions, gaze direction, and vocalizations were coded. Results showed a correlation between index-finger extensions and syllabic sounds, suggesting a strong connection between speech and the pointing gesture long before the infant can actually talk.
* * *
Research has probed not only the meaning of the finger, but also some of its uses.
The Uses of the Finger: Depressing
“Index Finger—A Tongue Depressor,” N. Islam, Journal of the Association of Physicians of India, vol. 34, no. 7, July 1986, p. 531.
* * *
Other research has aimed for better ways to observe the finger.
Looking at the Finger: Plethysmograph
“A Controlled Temperature Plethysmograph for the Index Finger,” A. D. M. Greenfield and J. T. Shepherd, Proceedings of the Physiological Society, vol. 11, nos. 3–4, April 1, 1950, pp. 40–1.
The authors, at the Queen’s University of Belfast, explain:
This plethysmograph was designed for an investigation in which it was desired to make observations on the finger at controlled temperatures, and with various heads of external pressure up to 35 cm. of water.
* * *
The Finger-Length Proportion Studies (and Their Lingo)
The numerous studies about relative Finger-Length Proportions are the crown jewels of modern finger research, according to those who do the studies. Here are some of them. Others are described in the article “Finger Celebrities.”
A key piece of lingo is the phrase “2D:4D.” This is a ratio of two numbers: the length of the second finger to the length of the fourth finger. This ratio is, reportedly, freighted with significance.
Some researchers also discuss a related notion called “fluctuating asymmetry,” or “FA.” There are many definitions for this reportedly fascinating concept. One definition, perhaps typical, says that fluctuating asymmetry “represents non- directional deviations from perfect symmetry in morphological characters.”
Women’s Ability to Read Maps
“Spatial Navigation Related to the Ratio of Second to Fourth Digit Length in Women,” Árpád Csathó, Anikó Osváth, Kázmér Karádi, Éva Bicsák, John Manning and János Kállai, Learning and Individual Differences, vol. 13, 2003, 239–49. The authors, variously at the University of Pécs, Hungary and at the University of Liverpool, report:
In this study, the 2D:4D ratio was measured in a sample of 46 female university students. The subjects’ place learning ability was tested in a real arena maze (RAM). Our results tend to support an association between prenatal gonadal hormone concentration and some aspects of spatial navigation.
Women’s Ability to Read Maps and Use Numbers
“Second-to-fourth Digit Length, Testosterone and Spatial Ability,” Petra Kempel, B. Gohlke, J. Klempau, P. Zinsberger, M. Reuter and J. Hennig, Intelligence, vol. 33, no. 3, May–June 2005, pp. 215–30. The authors, at the University of Giessen, Germany, find that, on tasks such as reading a map:
Females who exhibit a “male-like” finger length ratio pattern, which is associated with a higher prenatal level of testosterone, outperform females who display higher digit ratios on numerical as well as on spatial abilities.
Marks of Male University Students
“Examination Marks of Male University Students Positively Correlate with Finger Length Ratios,” Maria Romano, Barbara Leoni and Nicola Saino, Biological Psychology, vol. 71, no. 2, February 2006, pp. 175–82.
Manual Labor and Finger Proportion
“Finger Length Proportion and Manual Labor” [article in German], H.D. Rosler, Internationale Zeitschrift für angewandte Physiologie, einschliesslich Arbeitsphysiologie, vol. 16, no. 5, 1957, pp. 434–52.
Finger Lengths and Handwriting Style
“Do Differences in Sex Hormones Affect Handwriting Style? Evidence from Digit Ratio and Sex Role Identity as Determinants of the Sex of Handwriting,” John R. Beech and Isla C. Mackintosh, Personality and Individual Differences, vol. 39, no. 2, July 2005, pp. 459–68. (Thanks to John Bell for bringing this to our attention.)
Fingering the Father
“The Diagnostic Value of the Finger Length Proportion in Paternity Determination” [article in
German], H.D. Rosler, Deutsche Zeitschrift für die gesamte gerichtliche Medizin, vol. 48, no. 1, 1958, pp. 73–9.
Fingering the Fetus
“The Digital Formula in Japanese Fetus. I. Study on the Relative Length Between the Index Finger and the Ring Finger,” K. Minami, Okajimas Folia Anatomica Japonica, vol. 24, no. 3, August 1952, pp. 137–8.
Sporting Ability in Women
“The Big Finger—The Second to Fourth Digit Ratio is a Predictor of Sporting Ability in Women,” S.N. Paul, B.S. Kato, J.L. Hunkin, S. Vivekanandan and T.D. Spector, British Journal of Sports Medicine, vol. 40, 2006, pp. 981–3. (Thanks to David Talbot for bringing this to our attention.) The authors, at St Thomas’ Hospital, London, report:
Methods: Hand radiographs from 607 women (mean age 54 years) were used to estimate 2d:4d. Ranking of sports ability was on a scale (1–5).
Conclusions: These results suggest that a low 2d:4d ratio is related to increased female sports ability. It can be postulated that this ratio may predict potential sports ability.
Attractiveness, Attractiveness, Attractiveness
“Relative Digit Lengths Predict Men’s Behavior and Attractiveness During Social Interactions with Women,” J.R. Roney, and D. Maestripieri, Human Nature, vol. 15, no. 3, 2004, pp. 271–82. The authors, at the University of Chicago, report:
Our results confirm that male 2D:4D was significantly negatively correlated with women’
s ratings of men’s physical attractiveness and levels of courtship-like behavior during a brief conversation.
Sexual Orientation, Sexual Orientation, Sexual Orientation
“Fluctuating Asymmetry, Second to Fourth Finger Length Ratios and Human Sexual Orientation,” Q. Rahman, Psychoneuroendocrinology, vol. 30, 2005, pp. 382–91. The author, at the University
of East London, reports:
Homosexual men and women had significantly lower right hand 2D:4D ratios (even after controlling for handedness, height and weight differences) in comparison to heterosexuals.
Finger Lengths and Erotic Role Preferences of Gay Men
“Digit Ratios, Childhood Gender Role Behavior, and Erotic Role Preferences of Gay Men,” Matthew H. McIntyre, Archives of Sexual Behavior, vol. 32, no. 6, December 2003, pp. 495–7. The author, at Harvard University, explains:
Digit lengths were measured on photocopies from the most proximal crease to tip. All photocopies were then remeasured by a second rater.
Participants also completed items about their three most recent relationships or sexual encounters. Items included a general estimate of the frequency of their taking a “top” or “bottom” role in anal sex, their stated preference in that relationship, and the length of the relationship. In addition, subjects estimated their frequency of taking a top or bottom role in anal sex during masturbation fantasies. The variable used to describe “receptivity in anal intercourse” is the sum of the relative frequency of the bottom role in fantasies and in the three relationships averaged together.
Semen, Semen, Semen
“Are Body Fluctuating Asymmetry and the Ratio of 2nd to 4th Digit Length Reliable Predictors of Semen Quality?”, Renee C. Firman, Leigh W. Simmons, James M. Cummins and Phillip L. Matson,
Human Reproduction, vol. 18, no. 4, 2003, pp. 808–12. The authors, at the University of Western Australia and at nearby institutions, report:
Comparison of our data with previous studies suggests that the putative relationship between semen quality and 2D:4D may have been driven by the inclusion of severely oligozoospermic men within the original subject group. Our sample included men with equally high 2D:4D ratios but who had normal semen. Thus, the 2D:4D ratio may not reliably indicate poor semen quality.
“Finger-Length as an Index of Assertiveness in Women,” G.D. Wilson, Personality and Individual Differences, vol. 4, 1983, pp. 111–2.
The Aggressiveness of Unbalanced People
“Fluctuating Asymmetry Predicts Human Reactive Aggression,” Zeynep Benderlioglu, Paul W. Sciulli and Randy J. Nelson, American Journal of Human Biology, vol. 16, no. 4, 2004, pp. 458–69. (Thanks to Martin Gardiner for bringing this to our attention.)
* * *
Many finger-related studies occupy their own categories. Here are some examples.
The Index-Finger Formula
“Size of External Genital Organs and Somatometric Parameters Among Physically Normal Men Younger Than 40 Years Old,” E. Spyropoulos, D. Borousas, S. Mavrikos, A. Dellis, M. Bourounis and S. Athanasiadis, Urology, vol. 60, no. 3, September 2002, p. 485. (Thanks to Kathleen O’Malleyand Len Jaffe for bringing this to our attention.) The authors, who are at the Naval and Veterans Hospital of Athens, Greece, report that:
Fifty-two physically normal men, 19 to 38 years old, underwent tape measurements of penile dimensions in the flaccid-stretched state (total, shaft, glanular lengths), penile shaft volume calculation, and ultrasonographic testicular volume estimation.... Age and somatometric parameters were not associated with the size of the genitalia, excluding the index finger length, which correlated significantly with the dimensions of the flaccid, maximally stretched, penis.
A Finger-fore Gone
“Biting Off More Than You Can Chew: A Forensic Case Report,” J.R. Drummond and G.S. McKay,
British Dental Journal, November 13, 1999, p. 466. The authors, who are at the University of Dundee, explain:
A case is reported where a forefinger is ‘amputated’ by a human bite. This type of extreme biting injury is uncommon and probably represents tearing by the premolar teeth rather than a clean bite by incisor teeth.
The Midas Rough Touch
“Contamination by Human Fingers: The Midas Touch,” R. Gwozdz and F. Grass, Journal of Radioanalytical and Nuclear Chemistry, vol. 259, no. 1, 2004, pp. 173–6. (Thanks to Tom Gill for bringing this to our attention.) The authors, who are at Atominstitut der Österreichischen Universitäten, Vienna, Austria, explain that:
Wear and abrasion of various surfaces are constant processes in daily life, and commonly include interaction between human fingers and surfaces of every conceivable material. New methods for investigation of trace transfer processes by human fingers are described. Results of transfer for commonly used metals such as gold, silver, zinc, cadmium, tin, cobalt, nickel, chromium and iron are presented. Relationship between transfer of metals by touch and the general problem of purity in analytical activities is briefly discussed.
Constipation Without Fingerprints
“Childhood Constipation is Not Associated with Characteristic Fingerprint Patterns,” C.R. Jackson, B. Anderson and B. Jaffray, Archives of Disease in Childhood, vol. 88. 2003, pp. 1076–7. (Thanks to Scott A. Norton for bringing this to our attention.) The authors, who are at the University of Newcastle upon Tyne, UK, conclude that:
Fingerprint patterns are not associated with severe childhood constipation.
Finger Licking While Paging Through the Clinical Chart
“Pertinacious Habit on a Rehabilitation Unit: Repetitive Finger Licking While Paging Through the Clinical Chart,” M.M. LaBan, et al., American Journal of Physical Medicine and Rehabilitation, vol. 83, no. 1, 2004, pp. 75–8. (Thanks to Leigh Tooth for bringing this to our attention.) The authors, who are at William Beaumont Hospital, Royal Oak, Michigan, explain that:
A survey was performed to determine the frequency of unrecognized repetitive licking of fingers while reviewing hospital charts by various healthcare professionals who, by this habit, may be putting themselves at risk of acquiring a nosocomial infection.... Of the 50 healthcare professionals surveyed, five (10%) admitted to habitual repetitive licking of fingers while reviewing charts. In addition, 30 (60%) of those surveyed had observed other professionals doing so. Forty-seven (94%) acknowledged that they did not routinely wash their hands after reviewing the charts, potentially placing themselves at risk of acquiring a nosocomial infection. As an immediate consequence of this study, staff members have been encouraged to wash their hands before and after reviewing a patient’s chart.
This article is republished with permission from the September-October 2007 issue of the Annals of Improbable Research. You can download or purchase back issues of the magazine, or subscribe to receive future issues. Or get a subscription for someone as a gift! Visit their website for more research that makes people LAUGH and then THINK.