William Stern (psychologist)
William Stern (29 April 1871 – 27 March 1938), born Louis William Stern, was a German psychologist and philosopher. He is known for the development of personalistic psychology, which placed emphasis on the individual by examining measurable personality traits as well as the interaction of those traits within each person to create the self. Stern also coined the term intelligence quotient, or IQ, and invented the tone variator as a new way to study human perception of sound. Stern studied psychology and philosophy under Hermann Ebbinghaus at the University of Berlin, and quickly moved on to teach at the University of Breslau. Later he was appointed the position of professor at the University of Hamburg. Over the course of his career, Stern wrote many books pioneering new fields in psychology such as differential psychology, critical personalism, forensic psychology, and intelligence testing. Stern was also a pioneer in the field of child psychology. Working with his wife, Clara Joesephy, Stern kept meticulous diaries detailing the lives of their 3 children for 18 years. He used these journals to write several books that offered an unprecedented look into the psychological development of children over time.
William Stern was born on April 29, 1871 in Berlin, Germany to Rosa and Sigismund Stern. The couple named their only child Louis William, but he later dropped his first name and was known simply as William. Stern’s father owned a small design studio in Berlin, although the business was not very successful. When Sigismund died in 1890, he left his family very little money, and William, who was studying at university, had to take up tutoring to support his sickly mother until her death in 1896. 
Stern met his future wife, Clara Joseephy, while on a bicycle ride through Berlin. Joseephy’s parents were unhappy with the match, as Stern had little money, but Clara persisted despite her parents’ disapproval and the two married early in 1899. They had their first daughter, Hilde, on April 7, 1900, which began the Stern’s 18-year long project in child development. The couple also had a son, Günther, in 1902 and another daughter, Eva, in 1904. 
Stern spent the final five years of his life in exile due to the increased antisemitism in Germany. He spent one year in Holland before moving to America to accept a job as a professor at Duke University, despite knowing little English. Stern died suddenly on March 27, 1938 of coronary occlusion. 
Stern studied at the University of Berlin where he studied under the guidance of Hermann Ebbinghaus. He received his PhD in 1893. He then taught at the University of Breslau for 19 years, from 1897 to 1916. From 1916 to 1933 he was appointed Professor of Psychology at University of Hamburg. After the rise of the Nazi power he left to teach at Duke University where he was appointed Lecturer and Professor until he died of a heart attack in 1938 .
Work in Child Development
Stern greatly influenced the area of child development with the work done by him and his wife. He used his three children, Hilde, Gunther, and Eva, as subjects, studying the development of language as well as other aspects of child development that they observed. His children were born in 1900, 1902, and 1904 respectively, and Stern and his wife started the journaling from the day each were born up until they were 12, 10, and 7. The data that they recorded included reactions, babbling, the ability to recall events, lying, moral judgement, and even systematic recording sessions where the child would elicit story narratives and descriptions with one parent while the other jotted down the notes. Through their observations Stern found what is called "game theory", which is that child's play is necessary for the personal development of a child.
During Stern's time, many other psychologists were working on ways to qualitatively assess individual differences. Alfred Binet and Théodore Simon, for instance, were developing tests to assess the mental age of children in order to identify learning disabilities, but lacked a standardized way to compare these scores across populations of children. Stern suggested a change in the formula for intelligence, which has previously been calculated using the difference between an individual's mental age and chronological age. Instead, Stern proposed dividing an individual’s mental age by their chronological age to obtain a single ratio. This formula was later improved by Lewis Terman, who multiplied the intelligence quotient by 100 to obtain a whole number.
Stern, however, cautioned against the use of this formula as the sole way to categorize intelligence. He believed individual differences, such as intelligence, are very complex in nature and there is no easy way to qualitatively compare individuals to each other. Concepts such as feeble mindedness cannot be defined using a single intelligence test, as there are many factors that the test does not examine, such as volitional and emotional variables.
Stern invented the tone variator in 1897, which allowed him to study human sensitivity to changes in sound. Whereas his predecessors had limited themselves to studying thresholds and noticeable differences using constant, discrete stimuli, Stern studied the continuous change of one stimulus into the next. 
- General Psychology from the Personalistic Standpoint (1938)
- * Stern, William (1914) [1912 (Leipzig: J. A. Barth, original German edition)]. Die psychologischen Methoden der Intelligenzprüfung: und deren Anwendung an Schulkindern [The Psychological Methods of Testing Intelligence]. Educational psychology monographs, no. 13. Guy Montrose Whipple (English translation). Baltimore: Warwick & York. LCCN 14010447. OCLC 4521857. Retrieved 15 June 2010.
- Werner Deutsch (1991), "Über die verbogene Aktualität W. Sterns"
- Lamiell, James T. (2003), Beyond Individual and Group Differences, Sage Publications
- Lamiell, James T. (2010), William Stern (1871-1938): A Brief Introduction to His Life and Works, Lengerich/Berlin (Pabst Science Publishers), p. 172, ISBN 978-3-89967-589-4
- Lamiell, J. T. (2012). Introducing William Stern (1871–1938). History of Psychology, 15(4), 379-384.
- Kreppner, K. (1992). William L. Stern, 1871-1938: A neglected founder of developmental psychology. Developmental Psychology, 28(4), 539-547.
- Lamiell, James T. (2012). "6". In Wertheimer, Michael; Kimble,, Gregory A.; Boneau, Alan. Portraits of Pioneers in Psychology, Volume 2. Psychology Press. pp. 73–85. ISBN 9781135691059.
- Allport, Gordon (Oct. 1938). "William Stern: 1871-1938". The American Journal of Psychology. 51 (4): 770–773.
- "Tone variator". Brass Instrument Psychology. University of Toronto. URL accessed 2018-10-12.
- Lamiell, James (2003). Beyond Individual and Group Differences. Sage Publications. pp. 2–6. ISBN 9780761921721.
- Lamiell, James (2003). Beyond Individual and Group Differences. Sage Publications. pp. 5–6. ISBN 9780761921721.
- Allport, Gordon (Oct 1938). "William Stern: 1871-1938". The American Journal of Psychology. 51 (4): 772–773. Retrieved 16 October 2018.
- T., Lamiell, James (2010). William Stern (1871-1938) : a brief introduction to his life and work. Lengerich: Pabst Science Publishers. ISBN 9783899675894. OCLC 660502562.
- "Some Philosophical and Historical Considerations Relevant to William Stern's Contributions to Developmental Psychology". econtent.hogrefe.com. 2009. doi:10.1027/0044-3409.217.2.66. Retrieved 2018-12-06.
- Lamiell, James (2003). Beyond Individual and Group Differences. Sage Publications. pp. 55–82. ISBN 9780761921721.
- Lamiell, James (2003). Beyond Individual and Group Differences. Sage Publications. pp. 61–62. ISBN 9780761921721.
- "Stern Variator, Tone Variator". Brass Instrument Psychology at the University of Toronto.