It has long been assumed that the brain doesn't develop just because of genetic programming, but that it's affected by what we experience through our senses.
Yet not until now has anyone been able to come up with solid proof.
Research recently published in the scientific journal Nature provides some insight into neuroplasticity - the idea that the brain is not static, but that its neurons and pathways are constantly changing throughout a person's life, based on what's going on around them.
Tests to see how neurons are formed were carried out on 13 young mice and 18 older mice by researcher Owen Ko Ho, 27, and teams at Chinese University of Hong Kong and University College London.
Their study looked at how areas of the brain processing visual information are affected in the absence of light, colour, movement and other stimuli that come with being able to see.
"If you deprive [baby mice] of sight, their brains don't form the neuron circuits [that mature mouse brains have]," said Ko.
Older mice, he said, have more pathways between cells that do a similar job, but for blind infant mice, the part of the brain that deals with processing visual information has more random connections. He said that proved external stimuli were needed for the brain to develop.
"If we understand how the brain changes in response to stimuli, we're in a much better position to help diseased brains. Some people recover well after suffering from strokes, others don't do so well, so understanding why that's the case, we can help them better," said Professor Yung Wing-ho, of Chinese University's biomedical sciences school.
He is an adviser to Ko but was not involved in the study.
"But when and how it will be used? I think we're still far away," he said.