I am looking for a way to verify a claim that I read that it takes 40 days of repetition to create or lay down a neuron tract in the brain ( I suspect) in order to form an automatic habit. I realize it is complex but I wonder why it is 40 days, not say, 28.
I don't have any neurological problem or medical issues. I am writing an introduction to a self help book which makes the claim of 40 days. I want to verify it or at least have an idea that it is true.
Can you point me to the experiments that suggest a 40 day time period for neuron tract development? Is that something PubMed would have?