The Matilda effect is a type of bias.  The Matilda effect is when a woman scientist does something but people think a man scientist did it.  Sometimes people do this on purpose, for example when a professor steals a female student's research and puts his own name on the paper.  Sometimes people do this without thinking about it.

History
Suffragist and abolitionist Matilda Joslyn Gage (1826–98) was the first person to write about this effect.  She wrote an essay, "Woman as Inventor." It was first published as a tract in 1870 and in the North American Review in 1883.  The term "Matilda effect" was started in 1993 by science historian Margaret W. Rossiter.

Rossiter wrote about several times the Matilda effect had happened in real life.  Trotula (Trota of Salerno), a 12th-century Italian woman physician, wrote books which, after her death, were rewritten with male authors' names on them.  Nineteenth- and twentieth-century cases of the Matilda effect include those of Nettie Stevens, Lise Meitner, Marietta Blau, Rosalind Franklin, and Jocelyn Bell Burnell.

Comparison
The Matilda effect was compared to the Matthew effect. The Matthew effect is when a famous scientist gets more credit than a less famous scientist even if they both did the same work.

Research 
In 2012, two woman researchers from Radboud University Nijmegen did a study.  They looked at men and women who were being picked to be professors at universities.  They found the people choosing who would become a professor were affected by whether the person they were looking at was a man or a woman. Another study in Italy Italian and another in Spain showed the same thing.
However, some other studies found no difference between the number of times men and woman researchers' papers had been named as sources in other papers.

Swiss researchers found that when people in mass media, for example newscasters, want to put a scientist on their show, they talk to male scientists more than to female scientists.

According to one U.S. study, "although overt gender discrimination generally continues to decline in American society," "women continue to be disadvantaged with respect to the receipt of scientific awards and prizes, particularly for research."

Examples 
Examples of women to whom to the Matilda effect happened:
  Theano of Crotone, (6th century BC) - early philosopher who did work in mathematics, but people thought her husband, father, or teacher had done all the work (depending on the source)  Pythagoras
 Trotula (Trota of Salerno, 12th century) – Italian physician, author of works which, after her death, people said had really been written by men.  Some people were so against women being teachers and healers that they said Trotula had never really lived. At first, people said her husband and son wrote her work, but later, monks confused her name for that of a man. She is not in the "Dictionary of Scientific Biography"
 Jeanne Baret (1740–1807) – French botanist, first woman to have traveled all the way around Planet Earth. Partner and collaborator of the botanist Philibert Commerson, she joined the expedition of Louis-Antoine de Bougainville disguised as a man. They collected the first specimens of Bougainvillea plants. Most botanical discoveries have been attributed to  Commerson alone, after whom about a hundred of species have been named. She was immortalized for the first much later with the description of  in 2012.
 Nettie Stevens (1861–1912) – Discoverer of how chromosomes make living things male and female.   Her studies of mealworms showed for the first time that a living thing's sex is caused by its chromosomes and not by its environment. Stevens greatly influenced the scientific community's transition to this new idea: chromosomal sex determination. However, Thomas Hunt Morgan, a distinguished geneticist at the time, is generally credited with this discovery. Even though she did a great deal of work in genetics, Stevens' contributions to Morgan's work are often disregarded.
 Mary Whiton Calkins (1863–1930) – Harvard University Discovered that stimuli that were given to a test subject at the same time as other stimuli would be easier for that person or animal to remember. She also found that subjects remembered things better if they saw or otherwise experienced them for a longer time. Georg Elias Müller and Edward B. Titchener used Calkins' research findings for their own work without giving her any credit.
 Gerty Cori (1896–1957) – Nobel-laureate biochemist, worked for years as her husband's assistant, even though they were both equally qualified for the job.
 Rosalind Franklin (1920–58) – Now recognized as an important part of the 1953 discovery of DNA structure. Francis Crick and James Watson both won the 1962 Nobel Prize, and they did not tell people how they had used Franklin's research findings to help their own work. In 1968, Watson talked about how important Franklin was in his book The Double Helix).
 Marthe Gautier (born 1925) – She helped discover that Down syndrome is caused by a problem with the 21st chromosome. People used to think Jérôme Lejeune did it alone.
 Marian Diamond (born 1926) – Working at the University of California, Berkeley, discovered brain plasticity.  Before that, scientists thought the brain was not plastic. When her 1964 paper was about to be published, she saw that the names of her two secondary teammates, David Krech and Mark Rosenzweig, had been placed before her name, and her name was only there in parentheses.  She protested that she had done the essential work described in the paper, and her name was then put in first place without parentheses.  This problem is in a 2016 documentary film, My Love Affair with the Brain: The Life and Science of Dr. Marian Diamond.
Harriet Zuckerman (born 1937) – Zuckerman was also credited by husband Robert K. Merton as co-author of the concept of the Matthew effect.
 Programmers of ENIAC (dedicated 1946) – Several women did large parts of this project: Adele Goldstine, Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Wescoff, Fran Bilas and Ruth Lichterman, but most histories of ENIAC have not talked about what they did. Instead, they focus on hardware accomplishments rather than software accomplishments.

Times men scientists had Nobel Prizes when women scientists did not:
 In 1934, the Nobel Prize in Physiology or Medicine was awarded to George Whipple, George Richards Minot, and William P. Murphy. They said their female co-worker, Frieda Robscheit-Robbins should have gotten it with them but didn't because she was a woman. Whipple shared the prize money with her because she was co-author of almost all of Whipple's scientific papers.
 In 1944 the Nobel Prize in Chemistry was given to Otto Hahn as the sole recipient. Lise Meitner had worked with Hahn and had laid the theoretical foundations for nuclear fission (she coined the term "nuclear fission"). Meitner was not recognized by the Nobel Prize Committee, partly due to her gender and partly due to her persecuted Jewish identity in Nazi Germany. She was affected by the Law for the Restoration of the Professional Civil Service, which prohibited Jews from holding government-related positions, including in research. Initially, her Austrian citizenship shielded her from persecution, but she fled Germany after Hitler's annexation of Austria in 1938.
 In 1950, Cecil Powell received the Nobel Prize in Physics for his development of the photographic method of studying nuclear processes and for the resulting discovery of the pion (pi-meson). Marietta Blau did pioneering work in this field. Erwin Schrödinger had nominated her for the prize along with Hertha Wambacher, but both were excluded.
 In 1956, two American physicists Tsung-Dao Lee and Chen Ning Yang, predicted the violation of the parity law in weak interactions and suggested a possible experiment to verify it. In 1957, Chien-Shiung Wu performed the necessary experiment in collaboration with National Institute of Standards and Technology and showed the parity violation in the case of beta decay.  The Nobel Prize in Physics in 1957 was awarded to the male physicists and Wu was omitted. She received the Wolf Prize in 1987 in recognition for her work.
 In 1958, Joshua Lederberg shared a Nobel Prize in Physiology or Medicine with George Beadle and Edward Tatum. Microbiologists Joshua Lederberg and his wife Esther Lederberg, along with Beadle and Tatum, developed replica plating, a method of transferring bacterial colonies from one petri dish to another, which is vital to current understanding of antibiotic resistance. However, Esther Lederberg was not recognized for her vital work on this research project; her contribution was paramount to the successful implementation of the theory. Furthermore, she did not receive recognition for her discovery of the lambda phage or for her studies on the F fertility factor that created a foundation for future genetic and bacterial research.
 In the late 1960s, Jocelyn Bell Burnell (born 1943) discovered the first radio pulsar.  For this discovery, in 1974 a Nobel Prize in Physics was awarded to her supervisor Antony Hewish and to Martin Ryle, citing Hewish and Ryle for their pioneering work in radio-astrophysics.  Jocelyn Burnell was left out.  A Ph.D. student at the time of her discovery, she felt the intellectual effort had been mostly her supervisor's; but her omission from the Nobel Prize was criticized by several prominent astronomers, including Fred Hoyle.  Iosif Shklovsky, recipient of the 1972 Bruce Medal, at the 1970 International Astronomical Union's General Assembly.

Other
Ben Barres (1954–2017), a neurobiologist at Stanford University Medical School.  Barres is a trans man, meaning Barres was raised with a female gender role. He began to live as a man when he was 42 years old.  Barres said people thought his research was better when they thought he was a man than when they thought he was a woman.  Someone even said "His work is much better that his sister's" because they thought "Barbara Barres" was his sister and not his own old name. This is one time when the Matilta effect worked on the same person at different times in that person's life.

Related pages
 History of science
 History of technology
 Logology (science of science)
 Matthew effect
 Sociology of science
 Women in science

References 

Feminism