Joseph Jastrow (January 30, 1863 – January 8, 1944) was a Polish-born American psychologist, noted for inventions in experimental psychology, design of experiments, and psychophysics.
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.