Seventeen years of research of cyclopean perception — that is now called early vision — is reviewed particularly from a point of view to be of interest to physicists and engineers. Recent neurophysiological findings show neurons at the input stage to the cortex (layer IVB in VI) that fire for dynamic random-dot stereograms. So, global stereopsis is an early (bottom-up) process and as shown psychophysically is not influenced by semantic (top-down) processes. A new experiment, based on depth-from-shading processes, also shows that global stereopsis occurs first. Here is thus a model system where psychological phenomena [level-i] can be linked to neurophysiological events [level(i-1)]. Several cooperative and noncooperative models of global stereopsis are also discussed and since they are quite robust, only psychobiological evidence can decide which of them are likely to be used in human and monkey vision.