It is true that some of us can actually see sounds. It was discovered that this “weirdness” may take place in cases when the parts of the brain associated with vision are small. This discovery is connected with a strategy used by the brain when the vision may be impaired, the study adds.
Scientists paid a little more attention to the sound caused by the illusion of flash. When a flash is followed by two beep sounds, people sometimes can also see two consecutive fictitious flashes.
Experiments in the past revealed that there are significant differences among people when it comes to
how prone they are to this illusion. “Some see the fictitious flash every time the flash followed by two beeps, while others never see the second flash,” say the researchers. These differences may be related to the anatomy of the brain among these two groups of people. To give an answer, Benjamin de Haas and his colleagues of the University of London analyzed the brain of 29 volunteers using a CT scanner.
On average, the volunteers saw the fictitious flash in 62% of repetitions of the experiment, although some saw it only in 2% of the total time, while some others saw it in 100% of the experiment.
“When we all are looking at the same thing at the same time, we expect that the perception of things will be alike. However, the results have shown that this is not really true in all cases, since the perception is related to the particular anatomy of the brain,” the researchers write.
“The representation in the brain of the things that the eye sees is quite satisfactory, but far from perfect, since there is an uncertainty about the visual representations, especially when things happen quickly, such as instantly switching flash. We assume that this kind of uncertainty is greater in a brain that has less proportion of neurons in areas associated with the function of vision, just like a camera that has fewer pixels and captures images of lower resolution. ”
“Thus smaller visual areas of the brain use the available information they can get from hearing. In the physical world, the sources of light and sound are often alike.” Yet there is much material to be studied to understand the cause of this illusion. For example, only a quarter of these differences can be explained by the brain anatomy. Further research will attempt to answer whether the relation between the size of the visual cortex and visual perception is associated with this illusion or with other audiovisual hallucinations.