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New theories on #theDress shed light on spatial filtering
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Erica L. Dixon and Arthur G. Shapiro used a series of experiments to show how the 2015 dress phenomenon may be explained by variations in a simple spatial filter that extracts relevant information from the environment.
In early 2015, a photo of a dress was posted to the blogging site Tumblr and went viral. The author of the post said that she and her friends were debating over the color of the dress – some of them saw it as blue and black and some of them saw it as white and gold. In a later post, she said that she had seen the dress in person and that it was blue and black.
To date, the theories for the dress phenomenon have relied on a strong role for perceptual inferences, like color constancy, according to researchers.
The underlying assumption to color constancy is reflectance.
Researchers proposed an alternative type of invariance across illumination conditions where an object that appears to vary in color under blue, white or yellow illumination does not change color in the high spatial frequency region.
In the first experiment, which used 21 individual photos of the dress, each filter size for each illuminant was represented. The results confirmed the researchers’ prior observations that adding a yellow illuminant creates a shift toward reports of white-gold, and adding a blue illuminant creates a shift toward reports of blue-black.
The second and third experiments measured the effects of filtering and dress similarity. The dress under the original illuminant was paired with either the dress under the blue illuminant (experiment 2) or paired with the dress under the yellow illuminant (experiment 3), with the pairings done across all filter sizes.
They found that regardless of group or illumination condition, removing a higher proportion of low spatial frequencies increased rankings of dress similarity.
The results of the first three experiments suggest that individual differences in the perception of the dress could be related to variation in the processing of low spatial frequency contact within the image, according to researchers.
In experiment 4, researchers explored differences between observers’ perception of the color of the original dress image and measurements of contrast sensitivity.
Observers in the white-gold group have a higher average contrast sensitivity than observers in the blue-black group at low spatial frequencies. A two-tailed, independent-samples t test across all conditions showed significant differences for 0.25 and 1 cycles per degree.
While there was no significant difference in the location of peak sensitivity, there was a significant difference for maximum contrast sensitivity between groups, with white-gold observers having an average of 3.95 to the blue-black observers’ average of 3.04.
Their results support the hypothesis that under some conditions, high spatial frequency content remains invariant to changes in illuminant, they wrote.
Measurements of luminance and color that disregard spatial frequency scale are often incomplete and can mislead what the visual system is capable of encoding, they continued.
The researchers are not suggesting that a single spatial filter is a complete explanation of color constancy and the dress, they said. They believe that measurements of luminance and color that disregard spatial frequency scale are often incomplete and can mislead what the visual system is capable of encoding.
“There is a wealth of information in the stimulus that many standard proposals of color constancy seem to ignore; in addition to high spatial frequency content, there are other types of information that the visual system can extract from the environment,” they wrote. – by Abigail Sutton
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