Ilusöes: o olho mágico da percepçäo / Illusions: a window into perception

A percepçäo é a construçäo ativa de um estado neural que se correlaciona a elementos biologicamente relevantes do ambiente. Esta correlaçäo, longe de estabelecer uma representaçäo fiel do mundo, guia nossas açöes na elaboraçäo de comportamentos adaptativos, sendo, portanto, condicionada por fatores evolutivos. Já que a construçäo de um percepto é um processo intrinsecamente ambíguo, discrepâncias perceptivas podem surgir a partir de condiçöes idênticas de estimulaçäo. Essas discrepâncias säo denominadas ilusöes, e se originam dos mesmos mecanismos fisiológicos que produzem a nossa percepçäo cotidiana. Derivando de diferentes fatores, tais como ópticos, sensoriais e cognitivos, as ilusöes visuais säo instrumentos úteis na exploraçäo das bases fisiológicas da percepçäo e de sua interaçäo com o planejamento e execuçäo de açöes motoras. Aqui, examinamos as origens biológicas das ilusöes visuais e algumas de suas relaçöes com aspectos neurobiológicos, filosóficos e estéticos

A combination of focusing and defocusing through yoga reduces optical illusion more than focusing alone.

The degree of optical illusion was assessed using standard Muller-Lyer lines in two groups (yoga and control) of thirty subjects each. All subjects were between eighteen and forty two years of age. The difference between the reading at which the lines were actually equal and the reading at which the subject felt them to be equal, was noted as the degree of illusion ("di"). Each subject was assessed at the beginning and end of a month. During the month the yoga group received training in yoga, while the control group carried on with their usual routine. At the end of the month the yoga group showed a significant (two factor ANOVA, Tukey test, P < .001) decrease in the "di" (86%), whereas the control group showed no change. The improvement following yoga could be attributed to the combination of focusing and defocusing involved in yoga practice, as these factors are known to influence the "di". Previous results which mentioned a 79% decrease in "di" with focusing alone, provided a comparison.