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Scientists help explain visual system's remarkable ability to recognize complex objects
From MedicalXpress:
How is it possible for a human eye to figure out letters that are twisted and looped in crazy directions, like those in the little security test internet users are often given on websites?
It seems easy to us—the human brain just does it. But the apparent simplicity of this task is an illusion. The task is actually so complex, no one has been able to write computer code that translates these distorted letters the same way that neural networks can. That's why this test, called a CAPTCHA, is used to distinguish a human response from computer bots that try to steal sensitive information.
...
For example, a neuron might respond to a bit of the curve in the number 5 in a CAPTCHA image, no matter how the 5 is situated within its receptive field. Researchers believed that neuronal translation invariance—the ability to recognize any stimulus, no matter where it is in space—increases as an image moves up through the visual processing hierarchy.
"But what both studies show is that there is more to the story," she says. "There is a trade off between the complexity of the stimulus and the degree to which the cell can recognize it as it moves from place to place."
more ...
It seems easy to us—the human brain just does it. But the apparent simplicity of this task is an illusion. The task is actually so complex, no one has been able to write computer code that translates these distorted letters the same way that neural networks can. That's why this test, called a CAPTCHA, is used to distinguish a human response from computer bots that try to steal sensitive information.
...
For example, a neuron might respond to a bit of the curve in the number 5 in a CAPTCHA image, no matter how the 5 is situated within its receptive field. Researchers believed that neuronal translation invariance—the ability to recognize any stimulus, no matter where it is in space—increases as an image moves up through the visual processing hierarchy.
"But what both studies show is that there is more to the story," she says. "There is a trade off between the complexity of the stimulus and the degree to which the cell can recognize it as it moves from place to place."
more ...
