In 1688, the Irish philosopher William Molyneux sent a letter to his colleague John Locke submitting to him a thought experiment which has occupied both philosophers and scientists ever since. The question was very simple: if a person born blind – and able to differentiate objects (for example a cube and a sphere) by touch, – sees one day, will he be able to recognize these same objects only by looking at them?
The two correspondents at the time concluded that the person would not succeed. For Molyneux, although the person had acquired the experience of touch, if they regained sight without having experienced the connection between touch and sight, it would be impossible for them to pass the test. This questioning was central for Locke and his empirical philosophical colleagues, because responding positively to Molyneux’s question confirms the existence of an innate idea, of a common space between the senses. Responding negatively supports the argument that these knowledge gains come from experiential learning. Despite Locke and Molyneux’s clear opinion, thinkers such as Voltaire or Diderot continued to look into the question, without anyone really succeeding in providing a definitive answer.
Then, going beyond the epistemological and philosophical framework, it ends up interesting neuroscience researchers. For them too, the stake was important: a positive answer would imply the existence of cerebral biological afferents – that is to say specific nervous pathways connecting the different sensory areas – that we would have from birth.
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Learned or innate ability?
In 2003, Pawan Sinha, professor at the Massachusetts Institute of Technology (MIT), and member of the Prakash project, which works on blindness problems, developed a protocol to try to provide a definitive answer. He first identified people who could meet Molyneux’s criteria. Five patients, aged between 8 and 17, blind from birth, were going to have an operation to acquire total sight. They were chosen to participate in the experiment. Within 48 hours of the surgeries performed between 2007 and 2010, teams of Richard Held, a colleague of Sinha, applied the famous protocol and presented them with objects. The results confirmed the philosophers’ intuition: the participants had managed to identify from a distance what was shown to them, with a success rate of 58%, which was hardly better than chance. It seemed to suggest that the correspondence between touch and sight was a learned ability. However, Held’s team didn’t stop there and decided to retake the test five days, seven days and then five months later. The results in these cases were significantly better and the success rates were as high as 80-90%! This meteoric improvement contradicted our philosophers and seemed to indicate that at least some form of biological wiring was already present – but unused – in the brains of these people. This function simply needed a relatively short period of time to get started. The interdependence between our senses therefore seemed to be a factor quite ingrained in our biology.
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This thought experiment, as well as its resolution, shows how important transdisciplinarity between science and philosophy is for both disciplines. A question asked in the 17th century has helped 21st century neuroscientists better understand our perception and the connections between our senses. We have an unfortunate tendency to separate areas that are interested in humans. The collaboration between these disciplines is an asset that should not be overlooked. Moreover, for the anecdote, in 2020, researchers in entomology – the branch of zoology whose object is the study of insects – even studied the Molyneux problem in a population of bumblebees to see if they had an internal representation of the objects they touched or saw, and the bugs passed the test! Transdisciplinarity can give quite surprising results and that is what makes it so precious.
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