A team of neuroscientists at the Massachusetts Institute of Technology (MIT) believe that they have come up with the answer to an age-old philosphical riddle. If a blind person were suddenly able to see, would he be able to recognize by sight the shape of an object he previously knew only by touch? The question was originally formulated in 1668 by the British politician and scientist William Molyneux in a letter to John Locke and has been discussed ever since. The empiricists favoured the nurture idea, whilst the nativists have been more inclined to believe in an innate knowledge. John Locke himself was a firm believer that the knowledge was acquired through experience.
First broadcast on RFI in April 2011. Listen here
Recent developments in technology have enabled this theory to be put to the test. Richard Held and Pawan Sinha at MIT carried out an experiment on a group of Indian children between the ages of 8 and 17 who were blind from birth. Once they had their sight restored, they were asked to see if they could differentiate between simple geometric shapes by sight alone. The results published in Nature Neuroscience show that those tested were unable to correlate a tactile sense of a cube or sphere with a visual one.
“Initially these newly sighted people could not recognise what they saw from their previous experience of what they had touched. But within a week or so they were doing that correctly,” said the lead author of the project Richard Held. Although they did not bring anything new to Locke’s analysis, it did show a remarkable plasticity of the brain even after the first years of life.
“The fact that these children are able to acquire the mapping so rapidly – in the matter of a week or so – it provides us some guidelines as to what kind of mechanisms might be at play in developing this mapping,” says the senior authour Pawan Sinha.
He explains that there were doubts wether the brain would be able to make use visual information, even if the eye is optically corrected, if it had been deprived of this sense in the first years of life.
“It suggests to us possible mechanisms for how this kind of mapping across the senses might be established and that is very interesting not just from the perspective of the touch to vision mapping but other kinds of cross-modal mapping as well.”
Sinha explains that when Molyneux framed this question it was “the heyday of the debate between the empiricists who favoured the nurture idea and the nativists who were more inclined to innate knowledge.”
This results of this experiment are clearly in favour of the nurture as opposed to nature argument.
“I think he would be very happy about the initial findings that the transfer was not immediate as he himself believed that, said Held responding to how Molyneux himself would respond to the findings. “I think he would be very pleased.”