Stephen Louis Macknik is an American neuroscientist and science writer. He is a Professor of Ophthalmology, Neurology, and Physiology & Pharmacology at the State University of New York, Downstate Medical Center, where he directs the Laboratory of Translational Neuroscience. His work has delved into understanding how the brain processes visual information and how illusions can reveal insights into neural mechanisms. Macknik's studies on attentional mechanisms have provided valuable insights into how our brains filter and prioritize sensory information.