Displacement thresholds for coherent apparent motion in random dot-patterns.
نویسندگان
چکیده
Two correlated random-dot patterns (A and B) were generated on a CRT screen and presented in rapid alternation; (B) was shifted horizontally by varying amounts in relation to (A) so that coherent apparent motion was seen. We found that larger shifts were tolerated if (i) the stimulus onset asynchrony (SOA) was longer; (ii) if the patterns were optically blurred; and (iii) if there were fewer dots on the screen. Hence apparent motion in random-dot patterns may involve a global pattern matching operation as in stereopsis. Two uncorrelated random-dot patterns were alternated to produce incoherent dynamic "noise". A low spatial frequency sine wave grating was then projected on this "noise" and moved in step with the alternating random-dot patterns. This resulted in "motion-capture"--i.e. all the dots now seemed to move synchronously with the moving grating. The effect could not be obtained with high spatial frequency gratings or with stationary dots. As a tentative solution to the "correspondence problem" it is suggested that low spatial frequencies are matched first and these matches impose constraints on subsequent high frequency matches--thus allowing the system to home in on a unique solution.
منابع مشابه
What is Noise for the Motion System?
Motion coherence thresholds in random-dot patterns have been widely adopted as a measure of performance in visual motion processing. However, there has been diversity in the type of "noise" in which a coherent motion signal has to be detected. Here we compare coherence thresholds for three ways of creating motion noise: dots replotted in random positions in each new frame; dots with a set displ...
متن کاملThe effects of age on the spatial and temporal integration of global motion
The purpose of this study was to determine the relative contributions of local element speed and/or spatial displacement to age-related deficits in global motion processing. Motion coherence thresholds (79% correct) were measured for discriminating the direction of translational random dot kinematograms (RDKs) as a function of dot speed and spatial displacement across the adult lifespan (20-79 ...
متن کاملPerception of coherent motion in random dot displays by pigeons and humans.
Pigeons and humans were required to discriminate coherent from random motion in dynamic random dot displays. Coherence and velocity thresholds were determined for both species, and both thresholds were found to be substantially higher for pigeons than for humans. The results are discussed with reference to differences in motion processing in mammals and birds. It is suggested that the inferior ...
متن کاملDiscrimination of spatial displacements by patients with retinitis pigmentosa
We compared maximum displacement thresholds (Dmax) with minimum displacement thresholds (Dmin) in patients with retinitis pigmentosa (RP) in order to characterize the nature of their visual disability, as well as to assess possible models of foveal vision loss. Thresholds for discriminating the direction of the spatial displacement of random dot patterns were measured in a group of 20 patients ...
متن کاملIN APPAREhT MOTION
A region in an alternated pair of random-dot patterns was uniiormty displaced. It U:E perceiled ‘1s a segregated. coherently moving shape only if the displacement was smdii. The hmit on the displacement was Its absolute size (maximum about 15’) rather than the number of elements’ widths. Segregation due to apparent motion did not occur if the two patterns were exposed to diKerent eyes. These co...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Vision research
دوره 23 12 شماره
صفحات -
تاریخ انتشار 1983