The quote in bold above is from a series of editorial essays Richard L Gregory wrote in 2006 in Perception. I am currently on a snowboarding spell in the Swiss Alps, alone, and took along a number of printouts I had had sitting for reading on my desk for a long time; they have aged well :). The #bayesian  interpretation of perception was first introduced to my in a talk by Heinrich Bülthoff, and I find it explains quite a number of perceptual phenomena like those I collect here http://michaelbach.de/ot/. Richard makes the point that a number of visual illusions are not explained by prior probability at all, for instance all where perceptual constancies are at play (e.g. Ponzo). My hypothesis here is that in the visual processing chain the information from the world is first lost to a large degree (e.g. loosing 3D, stereoscopy notwithstanding and much more), and in order to reconstruct an “inner world”, good enough for scene understanding and action planning, Bayes comes into play but only after certain constancies have been invoked.

   It should be quite interesting to check every visual phenomenon for applicability of the Bayesian interpretation. Richard started that with a table on p432 http://dx.doi.org/10.1068/p3504ed which, frankly, I do not fully understand. The more I think about it, the more this sounds like a full research programme. As it happens, today I also found the well-done Bayes explanation: http://oscarbonilla.com/2009/05/visualizing-bayes-theorem/
       You may wonder what the image below has to do with it all. Well, it was taken at Bernd Lingelbach's “Scheune” where Richard and Priscilla brought, among many ideas-turned-into-educational-experiments, a picture frame. On the right is the original painting “Escaping Criticism” by Pere Borrell del Caso (1835-1910), a beautiful and witty trompe l’œil painting, self referential on more than one level. On the left you can see me attempting to replicate that with Richard's frame. Less than a year later Richard died, and we lost a brilliant, warm-hearted, and inspiring colleague.

    To end on a lighter note: It's nice for me to have some free time vacationing, thoughts rummage around, ending up in the happy musings like the above.