When you see a black cat while the friend with you is sure there isn’t one, it can be scary. But don’t be afraid, this doesn’t mean there is a witch or ghost, and it doesn’t mean you have a mental illness.
Feedforward and feedback
Normally when you see something, the neurons at the back of your brain first extend forward and quickly send the visual signals to the frontal cortex. This process is called feedforward. Then, the neurons send the visual signals back. In this process called feedback, you realize what you just saw.
When you don't see what you actually saw, scientists call it a “crash in visual processing.”
Crash in visual processing
Although human brain can deal with at most 70 images per second, your brain may be poor at detecting targets that appear too close together. In order to further explore this phenomenon, scientists designed a series of experiments.
The researchers recruited a group of participants and let them see images of natural scenes at a rate of 12 per second. After showing them all the pictures, the researchers asked them how many images contained animals and what animals were they. It turns out that the participants could hardly tell the correct answers.
When multiple targets are presented in quick temporal succession, the brain is busy processing the feedback signals of the first target as well as the feedforward signals of the second target. When the two processes crash and interfere with each other, it affects your cognition toward both targets.
Moreover, when the researchers reduced the interference between the feedforward and feedback process, the participants performed better in cognizing the targets.
To conclude, your brain is like a hard-working worker. When he is asked to do more jobs than he can handle in a very short period of time, he has no choice but to go on strike. But this study also suggests that scientists may use these findings to improve learning and cognizing in humans.