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J Drösler

Publications and source records attributed to J Drösler.

7 recordsLinked to original sources
PubMed2000

An n-dimensional Weber Law and the Corresponding Fechner Law.

Weber's law of 1834, DeltaS/S=c for the just noticeable difference (jnd), can be written as S+DeltaS=kS, k=1+c. It follows that the stimulus decrement required to elicit one jnd of sensation is S-DeltaS*=k(-1)S. If generalized for two stimulus dimensions and two corresponding response dimensions, Weber's law would have to state such equations for all directions of change in the plane. A two-dimensional Weber law with exactly these properties is realized by [S(x)+DeltaS(x)(straight theta), S(y)+DeltaS(y)(straight theta)]=[k(sin(straight theta))S(x), k(cos(straight theta))S(y)] which determines the stimulus coordinates for all stimuli just noticeably different from the stimulus (S(x), S(y)) in all directions 0</=straight theta</=2pi. Fechner's problem now is understood as finding a transformation of the plane which maps the set of stimuli one jnd apart from the standard stimulus onto a unit circle around the standard stimulus' image. This transformation (R(2)(+)-->R(2)) is [x, y]mapsto[log(k)(x), log(k)(y)]. The solution is generalized to arbitrarily many dimensions by substituting the sin and cos in the generalized Weber law by the standard coordinates of a unit vector. Copyright 2000 Academic Press.

Journal Article↗
PubMed1992

[A study of perspective vision].

The present study describes the structure of monocular depth perception using an experimental basis. It regards the traditional theory of perspective, which is a subset of descriptive geometry, only as a construction guide for flat, albeit depth eliciting, visual stimuli. The investigation starts with a definition of structure as a set with an automorphism on it. In the present context the projection of the physical stimuli onto the retina provide a suitable ground set. After suitable confinement of the stimuli to a horizontal plane, the effects of eye and head movements of the subject can be represented as projective mappings of the retinal image onto itself. The present approach represents these as visual automorphisms. They are each characterized by a special visual invariance. The automorphisms form a group which comprises the affine, the affine unimodular and the orthogonal groups (in this order) as subgroups. Experimental studies of the different invariants of these subgroups as well as the consideration of other empirical observations lead to the conclusion that the structure of monocular space perception is characterized by the affine unimodular subgroup of the projective group. There are indications that the phenomena of size constancy can be represented by affine unimodular maps instead of orthogonal (metric) maps as sometimes has been conjectured.

Attention↗
PubMed1979

Relativistic effects in visual perception of real and apparent motion.

Timing in the visual field is regarded as an additive conjoint measurement structure, psychophysical extension of stimulus path as an extensive measurement structure. These two sets of postulates lead to the derivation of an essential maximum for velocity perception. Apparent phi motion perception under strictly stationary stimulus conditions is described as relative motion of the first stimulus' psychophysical mapping with respect to a moving perceptual subsystem. The essential maximum of velocity modifies the relative motion postulate: relativistic dilatation of seen length of path is predicted. Testable properties of the model, comparison with experimental data from "real" motion and apparent phi motion perception are discussed.

Humans↗