On 17/02/2008, Mike Tintner <[EMAIL PROTECTED]> wrote: > Hope I'm not covering old ground, but I'm wondering whether any one is > interested and would like to comment on Marr's idea of vision involving a > primal sketch at a basic level. I'm interested, despite much ignorance here, > because it links to the image schemas of Lakoff and co..
As far as I know nobody has ever succeeded in implementing Marr's theory. When you begin to start implementing it you soon realize that the nice edge based primal sketches, such as the ones which appear in that paper, are unrepresentative of the general case. In many cases the edge features do not exist, or they exist only in your mind and not in the original pixel data. My main criticism of many such vision theories is that they simply fail to close the loop. Typically they assume that vision is a bottom up process, i.e. that things exist objectively within the data which the system is simply measuring and passing up to higher cognitive levels. Unfortunately this is rarely the case, and perception is as much of a creative process as it is one of passively recording information. In a closed loop system what you have is a synchronisation between data streams. In part the brain is trying to find the best model that it can and superimpose that onto the available data (hence the perception of lines which don't really exist), and in part the low level data helps to create and maintain the higher level models. The brain creates multiple competing interpretations of the data, and yet at any point in time only one of these makes it into the arena of consciousness. Hence in surrealist double images your mind will sometimes flip between possible interpretations. I remember there were some demonstrations in Christof Koch lectures which show this nicely. In one you see what appears to be a rotating sphere made from dots, and your brain will sometimes filp between interpreting that the pattern is rotating in one direction or the opposite direction. ------------------------------------------- agi Archives: http://www.listbox.com/member/archive/303/=now RSS Feed: http://www.listbox.com/member/archive/rss/303/ Modify Your Subscription: http://www.listbox.com/member/?member_id=8660244&id_secret=95818715-a78a9b Powered by Listbox: http://www.listbox.com
