[HN Gopher] The non-Riemannian nature of perceptual color space ...
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       The non-Riemannian nature of perceptual color space (2022)
        
       Author : cpach
       Score  : 23 points
       Date   : 2024-07-31 08:45 UTC (2 days ago)
        
 (HTM) web link (www.pnas.org)
 (TXT) w3m dump (www.pnas.org)
        
       | bbor wrote:
       | The paper in PDF:
       | https://www.pnas.org/doi/pdf/10.1073/pnas.2119753119?downloa...
       | there's a lot of math symbols but IMO the usage is pretty
       | straightforward for anyone familiar with linear algebra and
       | proofs.                 Ramsay (30) suggests that the principle
       | of diminishing returns or its opposite may have been spuriously
       | identified by otherresearchers (daringly including his PhD
       | advisor, Helm) because of experimental procedures (successive
       | intervals, paired compar-isons) ill suited to the task. Indeed,
       | open-ended and criterion-dependent tasks give less accurate
       | measures of similarity because of individual factors and the
       | difficulty of the task...       Instead, we use a more reliable
       | two-alternative forced choice (2AFC) task, where the participant
       | simply answers the following question: "Which is more different?"
       | Specifically, we use a triad arrangement of stimuli with the
       | reference in the middle and one test on either side. Each of 320
       | triads covering the neutral axis was judged by at least 250
       | different participants in a crowdsourced study on Amazon
       | Mechanical Turk (MTurk) (52).*
       | 
       | The core of it seems strong, IMO. I would have liked a bit more
       | cognitive science / philosophy to distinguish between an ideal
       | color space and whatever imperfect model is created by individual
       | human's neural software, and skipping Goethe and Schopenhauer in
       | the intro was downright criminal, but that's more on me than
       | them.
       | 
       | Color has long been a convenient "entry point" into the study of
       | human unconscious and subconscious data transformations, most
       | notably through Wittgenstein's musings about red squares. I look
       | forward to this technique being extended to other spaces, even
       | ones as abstract as "moral space" or "valence space"!
        
       | piannucci wrote:
       | I love the drama of how the abstract is written, but TBH I don't
       | think this is a surprise. I believe it's well-known among color
       | theorists that large perceptual distances are inconsistent with
       | sums of small differences. So maybe the most generous thing to
       | say here is, good on them for bringing awareness of this subtlety
       | to a broader audience.
        
       | jimsimmons wrote:
       | Is it non Riemann or non Eucliden
        
         | OvbiousError wrote:
         | Both
        
       | Sniffnoy wrote:
       | While this phrases things in terms of Riemannian geometry, it
       | seems to me like this is really about more fundamental metric
       | properties, but I find its terminology a bit unclear. Would it be
       | correct to summarize this as saying is that color space is not a
       | length space / geodesic space? (See e.g.
       | https://en.wikipedia.org/wiki/Intrinsic_metric )
       | 
       | (Yes "length space" (or "path space") and "geodesic space" are
       | not exactly the same thing, but "length space but not geodesic
       | space" doesn't exactly seem like a very likely possibility.)
        
       | ucarion wrote:
       | > Consequently, we need to adapt how we model color differences,
       | as the current standard, DE, recognized by the International
       | Commission for Weights and Measures, does not account for
       | diminishing returns in color difference perception.
       | 
       | This isn't to reduce the notability of the article, but isn't
       | BIPM's interest in any color-perception stuff basically limited
       | to making lightbulbs roughly equally bright? (i.e.
       | https://en.wikipedia.org/wiki/Luminous_efficiency_function) I
       | guess I don't see how even nonlinearity in perceptual space
       | matters for that purpose.
        
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