The evolution of visual pigment spectral sensitivities is probably influenced by the reflectance spectra of surfaces in the animal's environment. These reflectances, we conjecture, fall into three main classes: i. Most inorganic and many organic surfaces, including tree bark, dead leaves and animal melanin pigmentation, whose reflectance increases gradually… (More)
Contrary to the orthodox view that optical image quality should "match" the photoreceptor grain, anatomical data from the eyes of various animals suggest that the image quality is significantly superior to the potential resolution of the cone mosaic in most retinal regions. A new theory is presented to explain the existence of this relation and to better… (More)
Information about the visual angle size of objects is important for maintaining object constancy with variations in viewing distance. Although human observers are quite accurate at judging spatial separations (or cross-sectional size), they are prone to error when there are other spans nearby, as in classical illusions such as the Müller-Lyer illusion. It… (More)
The nature of redundancy in visual images is discussed and the methods of removing statistical redundancies are considered. It is demonstrated that local spatial frequency analysis is a highly successful method and it is thus argued that this determines the choice of representation of the visual image by the simple cells of the visual cortex.
Although irregularity in a sampling array reduces the Moire effects caused by undersampling, it makes interpolation more sensitive to noise. The advantages of irregularity are considered with this in mind.
Automated image processing has the potential to assist in the early detection of diabetes, by detecting changes in blood vessel diameter and patterns in the retina. This paper describes the development of segmentation methodology in the processing of retinal blood vessel images obtained using non-mydriatic colour photography. The methods used include… (More)
The optical geometry of the eye of the American garter snake suggests a highly pronounced Stiles-Crawford effect occurs at the level of its cone photoreceptors. However, it is demonstrated here that inner segments of the cones in this species have a high density of microdroplets, up to 0.1 microns in diameter, which increases the refractive index of the… (More)
Recently it has been reported that the visual cortical cells which are engaged in cooperative coding of global stimulus features, display synchrony in their firing rates when both are stimulated. Alternative models identify global stimulus features with the course spatial scales of the image. Versions of the Munsterberg or Café Wall illusions which differ… (More)
Artificial intelligence (AI) research is fast approaching, or perhaps has already reached, a bottleneck whereby further advancement towards practical human-like reasoning in complex tasks needs further quantified input from large studies of human decision-making. Previous studies in psychology, for example, often rely on relatively small cohorts and very… (More)
The Santa Fe Artiicial Stock Market 13, 4] is an agent-based artii-cial model in which agents continually explore and develop expectational models, buy and sell assets based on the predictions of those models that perform best, and connrm or discard these models based on their performance over time. The purpose of this paper is to classify the diierent… (More)