Employees of the State University of New York College of Optometry investigated the cause of the visual illusion that was first discovered by Galileo Galilei. The study was published Feb. 10, 2014 in the edition of Proceedings of the National Academy of Sciences.
Optical illusion makes considered Venus (lowest point) is bigger than Jupiter (top point)
Optical illusion makes considered Venus (lowest point) is bigger than Jupiter (top point)
Neuroscientists have found an explanation of optical illusion, first described by Galileo 400 years ago during the observation of the planets of the Solar System it. By studying the planets through a telescope and with the naked eye, the astronomer was surprised to see that in the first case, the apparent size of Venus is less than the size of Jupiter, and in the second case - on the contrary.
"Galileo was the first to suggest that our eyes distort the reality", - said Dr. Jose Manuel Alonso from the College of Optometry in New York (USA). Galileo found that distortion occurs in the human eye. Bright planets observed directly on a dark background seem to gain more and radiant crown, which makes for Galileo Venus eight times larger than Jupiter, despite the fact that when viewed through a telescope, Jupiter appeared four times more. In the future, many astronomers have noted that the angular resolution when viewed with the naked eye above for faint objects than bright. Galileo wrote that this is "or from the fact that their light is refracted on the moisture, which covers our pupil, or due to the fact that it is reflected from the edges of the eyelids, and then scattered by the pupil or by some other reason. "
The reason turned out to be really in the man, the physiological reasons blur bright objects have tried to explain many scientists, including the famous German doctor and physicist Hermann Helmholtz.
Helmholtz was closer to the truth, realizing that the increase in the apparent size of bright objects related to our perception of light signals, not the optics of the eye.
"Our research has shown that the perception that Helmholtz explained this phenomenon - the nonlinear response of the visual system, when objects are visible on a dark background," - said Alonso, author of the article published in the journal Proceedings of the National Academy of Sciences.
In their experiments, the researchers tested the activity of neurons in the thalamus and the cerebral cortex responsible for the perception of light in cats, monkeys, and humans, using implanted electrodes.
At the time of the experiment to humans and animals, which were under anesthesia, showed three types of image: the dark figures on a light background, bright shapes on a dark background, as well as light and dark figures on a gray background.
Today we know that a person perceives the bright and dark signals (no light) with the help of the so-called on and off-channel in the retina and the optic thalamus. By measuring electrical signals from these channels, the researchers found that the off-neurons react predictably and linearly on the appearance of dark figures on a light background: the sharper the contrast between figure and background, the more active the neurons. However, on-the neurons responded to an increase in the brightness of light objects on a dark background disproportionately.
In other words, with the same contrast of figure and ground the second option gives you more excited neurons.
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According to researchers, this explains the asymmetry in our assessment of the size of bright and faint objects, and this feature has arisen in the course of evolution is not just.
"When you're in a very dark place, it allows you to see the weakest light sources" - said Alonso.
Once it used to help people detect danger in the dark. However, in the afternoon, on the contrary, view this property allows us to see fine details of the dark for a bright background. The same effect also plays a role in everyday life, every woman knows that her slender dark clothing, smoothing figure flaws. Now, this is a scientific explanation: a dark figure on a light background gives the excited neurons less than the figure of light on a dark background.
The researchers believe that their discovery will help better understand the nature of diseases such as nearsightedness
