THE INFLUENCE OF LIGHT-DARK ADAPTATION AND LATERAL INHIBITION ON PHOTOTAXIC FORAGING - A HYPOTHETICAL ANIMAL STUDY

Vision did not arise and evolve merely so that individuals might ''see '' things but rather so that they might act on and interact with their habitat. Thus it might be misleading to study vision without looking also at its natural coupling to vital action. Here we investigate this problem in a simulation study of the simplest kind of visually guided foraging by a species of two-dimensional hypothetical animal called t he (diurnal) paddler. in a previous study, we developed a hypothetical animal called the archaepaddler, which used positive phototaxis to fo rage for autoluminescent prey in a totally dark environment (the deep sea). Here we discuss possible visual mechanisms that allow (diurnal) paddlers to live in shallower water, foraging for light-reflecting pre y in ambient light. The modification consists of two stages. in the fi rst stage, Weber adaptation compresses the retinal illumination into a n acceptable range of neural firing frequencies. In the second stage, high-pass filtering with lateral inhibition separates background respo nses from foreground responses. We report on a number of parameter stu dies conducted with the foraging diurnal paddler, in which the influen ce of dark-light adaptation and lateral inhibition on foreground-backg round segregation and foraging performance (''fitness'') are quantifie d. If is shown that the paddler can survive adequately for a substanti al range of parameters that compromises between discarding as much unw anted visual (background) information as possible and retaining as muc h information on potential prey as possible. Parameter values that opt imize purely visual performance, such as foreground-background segrega tion, are not always optimal for foraging performance, and vice versa. This article shows that studies of vision might indeed require more s erious consideration of the goals of vision and the ethogram of the st udied organisms than has been customary.