Individual infrared cone reflectance responds idiosyncratically to visible light stimulation (See also Visualization 1 (5.5MB, mp4) ). A) A 58x58 µm cropped section of an image of the cone mosaic exposed to a two-second, 390 nW/degree2 (2.2·104 cd/m2) 550 nm stimulus in subject 11015. B) Cones’ reflectance signals responded to the stimulus in a highly variable manner. Some cones increased their reflectance (orange profile) in response to the stimulus, others decreased their reflectance (purple profile), and some oscillated (cyan profile). C) The reflectance response of a single cone was also heterogeneous across trials. While the reflectance in the first trial increased (orange profile), following trials decreased (purple profile), increased (red, blue profiles), and showed minimal to no change (green profile). Stimulus duration indicated by the black bar. Scale bar is 15µm.