Joseph Jastrow (January 30, 1863 – January 8, 1944) was an American psychologist, noted for inventions in experimental psychology, design of experiments, and psycho-physics. Jastrow was one of the first scientists to study the evolution of language, publishing an article on the topic in 1886. He also worked on the phenomena of optical illusions, and a number of well-known optical illusions (such as the Jastrow illusion) were either discovered or popularized in his work. Jastrow believed that everyone had their own, often incorrect, preconceptions about psychology.  One of his goals was to use the scientific method to identify truth from error, and educate the layperson, which he did through speaking tours, popular print media, and radio. 
Jastrow was born in Warsaw, Poland. A son of Talmud scholar Marcus Jastrow, Joseph Jastrow was the younger brother of the orientalist, Morris Jastrow, Jr. Joseph Jastrow came to Philadelphia in 1866 and received his bachelors and master's degrees from the University of Pennsylvania. During his doctoral studies at Johns Hopkins University, Jastrow worked with C. S. Peirce on experiments in psycho-physics that introduced randomization and blinding for a repeated measures design.  [a] From 1888 until his retirement in 1927, Jastrow was a professor at the University of Wisconsin–Madison, where he advised Clark L. Hull. He was a lecturer at the New School of Social Research from 1927 to 1933.
Jastrow was head of the psychological section of the World's Columbian Exposition in 1893. He collected "psychophysical and reaction time data" from thousands of attendees. He was one of the charter members of the American Psychological Association, and became its president in 1900. 
Jastrow was noted for his outreach in popular media, exposing the general public to research in psychology. He gave public lectures, and published articles in popular magazines, including Popular Science, Cosmopolitan, and Harper's Monthly.  Jastrow also wrote Keeping Mentally Fit, a syndicated column that appeared in 150 different newspapers.
Jastrow was one of the founding members of the American Society for Psychical Research, in order to study the "mesmeric, psychical, and spiritual". The early members of the society were skeptical of paranormal phenomena. Jastrow took a psychological approach to psychical phenomena, believing that it was foolish to separate "... a class of problems from their natural habitat...". By 1890 he had resigned from the society. He became an outspoken critic of parapsychology. Psychical researchers were rarely trained psychologist, and Jastrow thought their research lacked credibility.  Given the lack of evidence of psychical phenomena, he believed psychologists should not prioritize disproving them.  In his book The Psychology of Conviction (1918) he included an entire chapter exposing Eusapia Palladino's tricks.
Jastrow was a leading figure in the field of anomalistic psychology. His book Fact and Fable in Psychology (1900) debunked the claims of all kinds of occultism including Spiritualism, New Thought, Theosophy and Christian Science. Jastrow approached the occult in a scientific manner. He wanted to understand why people were attracted to it, how it gained a foothold in society, and what evidence its supporters used.  Jastrow wrote that many people considered coincidence, dreams, and premonitions as sources of information above science.  He thought the role of scientist was to help the public understand truth from fiction, and to prevent the spreading of erroneous beliefs. 
Use of analogy in society
Jastrow thought that analogies represented a more primitive way of interpreting the world.  He gave many examples of cultures that acted analogously, including the "Zulu chewing a bit of wood to soften the heart...", and the "Illinois Indians making figures of those whose days they desire to shorten, and stabbing these images in the heart."  Jastrow also wrote about different cultures that ate certain animals to gain their physical attributes.  Jastrow saw this tradition still persisted in his day, through superstitions, rituals, and folk medicine.  The underlying motivation for this mentality, Jastrow wrote, was that "one kind of connection... will bring it to others." 
Jastrow was interested in perception, especially eyesight. He thought that eyesight was more complex than a camera, and that the mental processing of images was central to our interpretation of the world.  Jastrow illustrated this fact through many optical illusions, including the rabbit-duck illusion. He believed that what people saw also depended on their emotional state and their surroundings. 
To detect unconscious movement of the hand, Jastrow invented a machine he called the automagraph.  He found that when a subject was asked to concentrate on an object, their hand moved unconsciously in that direction.  The magnitude of the effect varied across individuals, especially in children, where the movement was more random. 
Dreams of the blind
Jastrow found that people that had lost their eyesight after age six still were able to see in their dreams, and that people that had lost their eyesight before the age of five could not.  This same difference in perception and age was true for people with partial vision loss.  Jastrow concluded that sight was not innate, and that significant mental development occurred between ages five and seven.  He noted that hearing, not sensation, was the primary sense of the blind, in both waking and dream.  He collected first-hand accounts of dreams from visually impaired individuals, including Helen Keller. 
His publications include:
- Charles Sanders Peirce and Joseph Jastrow (1885). "On Small Differences in Sensation". Memoirs of the National Academy of Sciences 3: 73–83.
- Time Relations of Mental Phenomena (1890)
- Epitomes of Three Sciences (1890)
- Fact and Fable in Psychology (1900)
- The Subconscious (1906)
- The Qualities of Men (1910)
- Character and Temperament (1914)
- "Charles Peirce as a Teacher" in The Journal of Philosophy, Psychology, and Scientific Methods, v. 13, n. 26, December, 723–726 (1916). Google Books and text-string search.
- The Psychology of Conviction (1918)
- The House that Freud Built (1932)
- Wish and Wisdom: Episodes in the Vagaries of Belief (1935)
- Story of Human Error (1936)
- Hull 1944, p. 581.
- Jastrow 1900, p. vii.
- Kimble, Wertheimer, White 2013, p. 78.
- * Charles Sanders Peirce and Joseph Jastrow (1885). "On Small Differences in Sensation". Memoirs of the National Academy of Sciences 3: 73–83.
- Hacking, Ian (September 1988). "Telepathy: Origins of Randomization in Experimental Design". Isis 79 (3): 427–451. doi:10.1086/354775. JSTOR 234674. MR 1013489.
- Stephen M. Stigler (November 1992). "A Historical View of Statistical Concepts in Psychology and Educational Research". American Journal of Education 101 (1): 60–70. doi:10.1086/444032.
- Trudy Dehue (December 1997). "Deception, Efficiency, and Random Groups: Psychology and the Gradual Origination of the Random Group Design". Isis 88 (4): 653–673. doi:10.1086/383850. PMID 9519574.
- Hull 1944, p. 582.
- Kimble, Wertheimer, White 2013, p. 82.
- Kimble, Wertheimer, White 2013, p. 86.
- Hull 1944, p. 582,584.
- Kimble, Wertheimer, White 2013, p. 84.
- John F. Oppenheimer. (1971). Lexikon des Judentums. Bertelsmann. p. 321. ISBN 978-3570059647
- Wade Pickren, Alexandra Rutherford. (2010). A History of Modern Psychology in Context. Wiley. ISBN 978-0470276099
- Jastrow 1900, p. 50.
- John Melton. (1996). Psychical Research in Encyclopedia of Occultism & Parapsychology. Gale Group. ISBN 978-0810394865
- Jastrow 1900, p. 54.
- Paul Kurtz. A Skeptic's Handbook of Parapsychology. Prometheus Books. p. 551. ISBN 978-0879753009
- Jastrow 1900, p. 74.
- Joseph Jastrow. (1918). The Psychology of Conviction. Houghton Mifflin Company. pp. 101-127
- Leonard Zusne, Warren H. Jones. (1989). Anomalistic Psychology: A Study of Magical Thinking. Psychology Press. pp. 10-12. ISBN 978-0805805086
- Jastrow 1900, p. 4,13-14.
- Jastrow 1900, p. 40.
- Jastrow 1900, p. 46.
- Lawrence R. Samuel. (2011). Supernatural America: A Cultural History. Praeger. pp. 9-10. ISBN 978-0313398995
- Jastrow 1900, p. 238.
- Jastrow 1900, p. 240.
- Jastrow 1900, p. 242.
- Jastrow 1900, p. 253.
- Jastrow 1900, p. 275.
- Jastrow 1900, p. 295.
- Jastrow 1900, p. 294-296.
- Kimble, Wertheimer, White 2013, p. 79.
- Jastrow 1900, p. 312-313.
- Jastrow 1900, p. 332-333.
- Jastrow 1900, p. 342.
- Jastrow 1900, p. 343-344.
- Jastrow 1900, p. 369.
- Jastrow 1900, p. 364.
- Jastrow 1900, p. 353-358.
- Jastrow, Joseph (1900). Fact and fable in psychology. Houghton, Mifflin and Co.
- Hull, Clark L. (Oct 1944). "Joseph Jastrow: 1863-1944". The American Journal of Psychology 57. Retrieved Nov 2, 2014.
- Gregory A. Kimble; Michael Wertheimer; Charlotte White (31 October 2013). Portraits of Pioneers in Psychology. Psychology Press. pp. 75–87. ISBN 978-1-317-75992-8.
- Works written by or about Joseph Jastrow at Wikisource
- Media related to Joseph Jastrow at Wikimedia Commons
- Rabbit-Duck Illusion
- Duck-rabbit and Rabbit-duck (after Wittgenstein)
- Mind Tricks for the Masses, On Wisconsin magazine article
- Joseph Jastrow's biography at University of Wisconsin - Madison's Psychology Department
|9th President of the American Psychological Association