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Stuart Anstis, Don Macleod; Fluttering hearts: a new analysis. Journal of Vision 2004;4(8):211. doi: 10.1167/4.8.211.
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© ARVO (1962-2015); The Authors (2016-present)
In the fluttering hearts illusion, red hearts or spots oscillating on a blue surround in dim light appears to flutter or float around on the surround; particularly at an eccentricity of 5 to 20, a retinal region rich in both rods and cones. We propose that a moving red spot is seen first by the cones as lighter than the surround, and then ∼50 ms later by the more sluggish rods as apparently darker than the surround, because rods are more sensitive to red than to blue light (the Purkinje shift). The interplay between asynchronous and contrast-reversed rod and cone images generates the illusion. A dim red spot, 18 eccentric, that circled around a fixation point appeared be followed by an illusory “dark twin”. This twin lagged because the rods were sluggish, lagging the cone response by 50 ms, and it was dark because rods are insensitive to red. Conversely a circling dim blue spot had an illusory “light twin” following it. An oscillating red spot on a blue surround looked light in foveal vision, dark at eccentricities >10, and apparently fluttering at intermediate eccentricities, where the lagging dark rod image overlaid the light cone image. Conversely an oscillating blue spot looked dark in foveal vision, light in eccentric vision, and apparently fluttering in between. Similarly, a pattern of light red stripes and dark blue stripes can undergo a surprising motion reversal at mesopic light levels. The pattern jumped to the right through half a stripe width (90 phase angle). In cone vision, the jump to the right was seen correctly. But at mesopic intensities, frame #1 was seen first by the cones, and then after 50ms by the rods, with a brightness reversal, with the blue stripes looking lighter than the red. When the cones then saw frame #2, the light (blue) stripes appeared to jump to the left, into the light (red) stripes. The intensity range that gave this motion reversal was identical to the range that gave fluttering hearts.
NIH grant EY01711-028
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