From owner-cse575-fa08-list@LISTSERV.BUFFALO.EDU Tue Oct 28 11:16:42 2008 Date: Tue, 28 Oct 2008 11:16:30 -0400 From: "William J. Rapaport" Subject: 575: Perceiving the Future To: CSE575-FA08-LIST@LISTSERV.BUFFALO.EDU ------------------------------------------------------------------------ Subject: Perceiving the Future ------------------------------------------------------------------------ Here's the citation on the paper that argues that we perceive neither the (immediate) present nor the (very recent) past, but the future (they call it "perceiving the present", but it's really the very near future as measured from the time of the stimulus): Changizi, Mark A.; Hsieh, Andrew; Nijhawan, Romi; Kanai, Kanai; & Shimojo, Shinsuke (2008), "Perceiving the Present and a Systematization of Illusions", Cognitive Science 32(3) (April): 459-503 http://www.informaworld.com/smpp/content~content=a793175124~db=all~order=page And here's the crucial passage (Sect. 2.1): "Computation necessarily takes time and, because visual perceptions require complex computations, it is not surprising to learn that there is an appreciable latency--on the order of 100 msec--between the time of the retinal stimulus and the time of the elicited perception....Neural delays of this size are significant, for an observer can move a distance of 10 cm in that time even at a relatively slow walk; or, consider reaching out to grab a 1-meter distant object translating in front of an observer at 1 meter per second; if an observer did not have perceptual compensation mechanisms, then by the time he perceives the object, the object will be roughly 6 degrees displaced from its perceived position, making it nearly impossible to plan and execute appropriate behavioral reaching for a catch. Therefore, it is reasonable to expect that the visual system will have been selected to have compensation mechanisms by which it is able to, via using the stimulus occurring at time t, generate a perception at time t+100 msec that is probably representative of the scene as it is at time t+100 msec. In short, we should expect that visual systems have been selected to "perceive the present," rather to perceive the recent past."