RF, special edition: perception
"An ambiguous figure in which the brain switches between seeing a rabbit and a duck. The duck-rabbit was 'originally noted' by American psychologist Joseph Jastrow. Jastrow used the figure, together with such figures as the Necker cube and Schröder stairs, to point out that perception is not just a product of the stimulus, but also of mental activity. Jastrow's cartoon was based on one originally published in Harper's Weekly (Nov. 19, 1892, p. 1114) which, in turn, was based on an earlier illustration in Fliegende Blätter, a German humor magazine (Oct. 23, 1892, p. 147). Interestingly, children tested on Easter Sunday are more likely to see the figure as a rabbit, whereas when tested on a Sunday in October, they tend to see it as a duck."
2. Is it a young woman or an old woman?
"'Our cortex is already changing the raw visual information before that information gets into our consciousness,' Voytek concluded. You're not only seeing what is actually before you; you're seeing what your brain is telling you is there. Specifically, the cortex is sending a cascade of predictions about what should be seen at all the different layers of complexity. So what travels back up from the eyes is not raw visuals of the environment, but how the world deviates from what the brain is expecting."
3. Is it red in white light or white in red light?
"Perception solves an underdetermination problem. The perceptual system estimates environmental conditions, such as the shapes, sizes, colors, and locations of distal objects. It does so based upon proximal stimulations of sensory organs. The proximal stimulations underdetermine their environmental causes. For instance, a convex object under normal lighting generates retinal stimulations ambiguous between at least two possibilities: that the object is convex and that light comes from overhead; or that the object is concave and that light comes from below. Similarly, light reflected from a surface generates retinal stimulations consistent with various colors (e.g. the surface may be red and bathed in daylight, or the surface may be white and bathed in red light). In general, then, retinal input underdetermines possible states of the distal environment. We cannot yet program a computer that solves this underdetermination problem. The perceptual system solves it quickly, effortlessly, automatically, and reliably. How?"
4. Is it the same in space as it is on earth?
"On Gemini 10, Michael Collins and John Young used a color patch kit like this to give scientists a known set of colors to compare with those seen in space. Attached to a long arm, the color patch could be photographed to determine if the camera or anything in space changed color perception. The actual experiment used in space did not return and the Museum's collection includes two back-up units, of which this is one."
5. Will computers think the dress is gold and white or black and blue?
"In this lecture I summarise the basic model of colour image formation which teaches that the colours recorded by a camera depend equally on the colour of the prevailing light and the colour of objects in the scene. Building on this, some of the fundamental ideas of colorimetry are discussed in the context of colour correction: the process whereby acquired camera RGBs are mapped to the actual RGBs used to drive a display. Then, we discuss how we can remove colour bias due to illumination. Two methods are presented: we can solve for the colour of the light (colour constancy) or remove it through algebraic manipulation (illuminant invariance). Either approach is necessary if colour is to be used as a ‘descriptor’ for problems such as recognition and tracking."
If you have no idea why there are all these perception links in the newsletter: get to know the dress.
Today on Fusion: Killer robots are as big a problem as overpopulation on Mars, Baidu chief scientist and AI-builder Andrew Ng tells us.
Today's 1957 American English Usage Tip:
diplomat(ist). The shorter form is standard in the US, though the longer is often used by extension for 'one wh is artful or tactful in meeting situation.' The longer form is standard Brit.
The Credits
1. mathworld.wolfram.com 2. theatlantic.com 3. philosophy.ucsb.edu 4. airandspace.si.edu 5. mi.eng.cam.ac.uk
How the World Deviates