RESUMO
The inside of a picture of a uniformly gray tube drawn with black circles appears lighter than the outside. Coren and Komoda, who first described this illusion, argued that observers take illumination into account to infer that the inside is lighter. That is, the inside of the tube should receive less illumination than the outside but reflects the same amount of light into the eyes. Observers, therefore, infer that it must be lighter. The inside of a gray tube drawn with white circles should appear lighter as well according to this account, but the experiments reported here show that the outside appears lighter in such a tube. We believe that depth perception is involved in this illusion but that lightness constancy is not.
Assuntos
Sensibilidades de Contraste , Percepção de Profundidade , Ilusões Ópticas , Reconhecimento Visual de Modelos , Humanos , Iluminação , Orientação , PsicofísicaRESUMO
A method for the freehand drawing of anaglyphs is described. Usually textbooks cover the topic of stereopsis in an abstract way, making it difficult for students to grasp. The present method enables students to draw anaglyphs by hand and should make the concept of binocular disparity more easily learned.
Assuntos
Atenção , Percepção de Profundidade , Orientação , Reconhecimento Visual de Modelos , Desempenho Psicomotor , Disparidade Visual , Percepção de Cores , Aprendizagem por Discriminação , HumanosAssuntos
Aprendizagem por Discriminação , Ilusões , Percepção de Movimento , Ilusões Ópticas , Orientação , Fixação Ocular , HumanosRESUMO
Two experiments concerning induced movement are reported. The hypothesis was that when outline inducing frames were used, object-relative displacement was modified by two variables, adjacency and apparent speed. Adjacency is directly related to the magnitude of induced movement. Small outline frames are high in adjacency, and so small frames should be powerful generators of induced movement. On the other hand, several investigators have found the speed of the inducing frame to be inversely related to the magnitude of induced movement. It is hypothesized here that this effect of speed was determined by apparent speed (not real speed), and if so, since small objects appeared to move faster than large ones, a small outline frame should be a relatively weak generator of induced movement. In the first experiment, this hypothesis was tested using single inducing frames. In the second experiment, this hypothesis was tested using two inducing frames presented simultaneously. The implications of these experiments were discussed with regard to other theories of induced movement.
Assuntos
Percepção de Forma , Ilusões , Percepção de Movimento , Ilusões Ópticas , Discriminação Psicológica , Humanos , Orientação , Percepção de TamanhoRESUMO
Two instances of a new illusion of motion were discovered. In the first, when observers tracked a spot of light moving vertically in a field of stationary vertical lines, the lines appeared to move in the same direction as the spot. If observers did not track the spot, the lines appeared stationary. The second instance was designed to see if the same illusion would occur when the spot appeared to move as a result of induced motion. In this display a vertically moving grid of horizontal lines surrounded a stationary vertical line. A stationary spot of light could be projected on the line. If the subject fixated the spot, both spot and line appeared to move against the grid. If the spot was absent, the line appeared to move along with the grid. The implications of this illusion for theories of induced motion are discussed.