The study is an investigation of the origins of psychophysics and experimentalpsychology. According to historians of psychology. FrancisBacon had the most crucial influence in the history of the experimentalmethod, because he emphasized the importance of induction, skepticism,quantification, and observation. The present study, however,attempts to show that Ibn al-Haytham laid the foundations of the aboveaspects of the experimental method. Furthermore, a number of historiansof psychology believe that Fechner was the founder of psychophysicswith his application “Filements of Psychophysics” in 1860.This study shows that in the eleventh century, Ibn al-Haytham made anoriginal contribution to the study of vision, wherein his psychophysicsborrowed its structure from physics and its spirit from psychology.Several aspects of visual perception were investigated by him, includingsensation (which occupies a central place in psychophysics), variationsin sensitivity, perception of colors. sensation of touch, perceptionof darkness, the psychological explanation of moon illusion, and binocularvision. This study presents five experiments by Ibn al-Haythamregarding the errors of vision, which is called in contemporary psychology“visual illusion.” These experiments have been applied andverified in Bahrain from both the physical and psychological perspectives.Finally, the study concludes that Ibn al-Haytham deserves the title“founder” of psychophysics as wellp the “founder” of experimentalpsychology. In this respect. Kitab ul-Manazir by Ibn al-Haytham.which appeared in the fmt half of the eleventh century, and not the“Elements of Psychophysics” by Fechner. which was published in thenineteenth century, marks the official “founding” of psychology,because it provides not only new concepts and theories but new methodsof measurement in psychology.
The horizon line, linear perspective, interposition, and background brightness as determinants of the magnitude of the pictorial moon illusion