José Alexsandro da Silva

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The results of two types of experiments are reported. In 1 type, Ss matched depth intervals on the ground plane that appeared equal to frontal intervals at the same distance. The depth intervals had to be made considerably larger than the frontal intervals to appear equal in length, with this physical inequality of equal-appearing intervals increasing with(More)
The question of how perceived extents are related to the corresponding physical extents is a very old question that has not been satisfactorily answered. The common model is that perceived extent is proportional to the product of image size and perceived distance. We describe an experiment that shows that perceived extents are substantially larger than this(More)
Scales for perceived egocentric distance produced by three psychophysical methods in four ranges of distances were compared. It was found that (a) the exponents produced by ratio and fractionation methods are in good agreement; (b) the exponents of both these methods were larger than those produced by magnitude estimation; (c) an increase in range of(More)
By means of the method of fractionation, scales for subjective distance were derived from five different types of judgment accomplished with two ranges of distance estimated in a large open field. It was found (a) that the scales for subjective distance are to a considerable extent influenced by ways of obtaining the judgments, (b) that the scales are(More)
We conducted two psychophysical experiments to investigate the relationship between processing mechanisms for exocentric distance and direction. In the first experiment, the task was to discriminate exocentric distances. In the second one, the task was to discriminate exocentric directions. The individual effects of distance and direction on each task were(More)
Two triangulation methods for measuring perceived egocentric distance were examined. In the triangulation-by-pointing procedure, the observer views a target at some distance and, with eyes closed, attempts to point continuously at the target while traversing a path that passes by it. In the triangulation-by-walking procedure, the observer views a target(More)
Five age levels (6, 8, 10, 12 years, and adults, N = 127) estimated distance in a large open field by the fractionation method. Scales for subjective distance were derived for each group. It was found that (a) the adults differed from all the other groups, (b) the 12-year-olds differed from the six-year-olds, (c) all the exponents were smaller than 1, (d)(More)
Schistosomiasis mansoni is an endemic disease in Brazil. Cases of nervous system schistosomiasis have been referred in our medical literature for the past forty years. In this report five cases of schistosomiasis of the spinal cord are studied. A review of the literature has been made and some clinical, laboratory and therapeutical aspects are discussed.