SCIENCE PHOTO LIBRARY SCIENCE PHOTO LIBRARY
Thaler sensory illusion, 19th-century artwork. The experimenter is placing cold and warm silver coins on a man's forehead. The cold object feels heavier than the warm one. This sensory illusion, named for a silver coin known as a thaler, involves sensory receptors and thermoreception and mechanoreception. The phenomenon was identified in the 1830s by German physician Ernst Heinrich Weber (1795-1878). Artwork from the 14th volume (second period of 1894) of the French popular science weekly 'La Science Illustree'.
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