A geometrical description of visual sensation

Bart Ons, Paul Verstraelen

The following are some oversimplified verbal definitions regarding sensation and perception, which however might be not entirely useless, even if only by keeping them somewhere in the back of our heads while scientifically studying perception and sensation within the field of psychology. A sensation is the observation made when observing something. In particular, a visual sensation is the observation of light energy when looking at something. A perception is the appreciation made of a sensation. In particular, a visual perception is what we see when looking at something: in early vision this refers to what could be called instinctive perceptions and in cognitive vision this refers to possibly various ways of thinking about or interpreting the naked perceptions made in early vision. In [1] [2] [3] [4] essentially perception is defined via the Casorati curvature of sensation, or, more precisely, "early" human perceptions are defined as the most rudimentary, the most intuitive surface curvatures of human sensations, whereby the latter are defined to be human observations as described in detail by Koendernik and van Doorn basically for all most natural human observations, and, in particular, very concretely for visual human observations, in [5] [6] [7]. The main purpose of the present article is to bring a kind of refinement to Koenderink and van Doorn's description of human visual observation in order to take into account the factual anisotropy which hereby occurs, most dramatically illustrated by the different evaluations of geometrically equal lengths in the horizontal and vertical directions, respectively, cfr. [8] [9], which horizontal-vertical visual effect for instance can be observed pretty distinctly in the following 1858 figure of W. Wundt (see Figure 1). For most visual perceptions, this amendment to the isotropic phenomenology of human visual sensations is not of crucial importance from practical points of view, but, still, for quite a number of visual perceptions it is rather significant to properly take into account the above anisotropy. In any case, in Section 1, from [5] we will briefly recall some elements concerning the nature of visual observation following J. Koenderink and A. van Doorn. This presentation will not be done in a subtle way. We will take the most naive possible approach to this matter, referring the reader who is in need for a more serious treatment to [5] [6] [7]. Next, in Section 2, we will at first recall some basic facts related to visual anisotropies due to M. Borisavljević [10], and in this context also will consider some studies of G. Fechner and A. Fick; (in these respects, [11] could be mentioned here as a reference with many references showing some psychologists' kinds of ways of relating to the golden numbers $\varphi = (\sqrt 5 - 1)/2$ and $\Phi = (qrt 5 + 1)/2$). And, then, we will introduce a scientific description of visual sensation which, at least qualitatively and at present, seems to be most realistic and natural. This new geometrical model for human visual sensation was inspired by the results of some experiments from Ons whereby the horizontal-vertical visual effect plays a role of crucial importance, as is reported on in [15].