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6.2 The quantum approach
6.3 The circuit theory approach
6.4 The element contribution theory
6.5 The inhibition theories
6.6 VISTARAQ
References
7. MODELLING OF VISION. 2: A VERSATILE PHYSICALLY-BASED
MODEL
It can be seen from the survey of the more comprehensive models of vision
covered in Chapter 6 that there is a wide divergence of opinion as to the basic
functions, even for the simplest of detection tasks. The effect of stimulus
differential energy is variously considered to be predominantly associated with
the centre of the stimulus, as in the element contribution theory, or the edge, as
in the inhibition theories. Transmission of data is implied to be by D.C. coupling
in some cases, by A.C. coupling in others, particularly by Schade. The temporal
storage of data is also variously described. Whilst some models explicitly imply a
signal / noise situation, others do not. The inhibition theories do not appear to be
related to threshold performance, nor the threshold models to known edge
phenomena. Some models in their most refined forms do not appear to be able
even to predict the full range of thresholds for simple circular stimuli, whilst
others require complex empirical variations of various constants in order to
provide a good prediction of these same simple data. Only the element
contribution theory is positively shown to have the ability to predict multiple
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