If your album is like mine, in the Four Planes of Development, there is a mention of how the term Sensitive Period came to be. In both my Primary and Elementary Theory Albums, it is stated that Maria Montessori got the term from Hugo de Vries. Hugo is said to have been a biologist and studied mutation in the Porthesia Butterfly. I just came across this blog post and wanted to share. “Sensitive Periods: Hugo de Vries, Jacques Loeb, and the Porthesia Larvae” was written by Uma Ramani in 2015. It is interesting and informative and shares the investigative work done to uncover the true history behind the story. She shares information that disclaims the Montessori version of Dr. Hugo de Vries work with Porthesia butterflies. Because Uma did not go further into where the term Sensitive Periods actually came from, I did a bit of my own research.
The term Sensitive Period is not associated with either Hugo de Vries or Jacques Loeb in Wikipedia. Hugo de Vries still contributed some very interesting things to the world, it is just entirely different than we were told. Hugo de Vries coined the term “pangenes” which throughout time was shortened to genes. According to Wikipedia, Hugo de Vries postulated that different characters have different hereditary carriers. He specifically postulated that inheritance of specific traits in organisms comes in particles, which he referred to as pangenes. He was also responsible for The Mutation Theory, a two-volume publication for the argument that evolution may occur more frequently with large scale changes than via gradualism as described by Charles Darwin. Jacques Loeb was a famous scientist in the early 1900s. According to the Encylopedia Brittanica: “Through his work with bringing about the development of sea urchin larvae from unfertilized eggs by exposing them to controlled changes in their environment. Loeb’s work was significant in showing that the initiation of cell division in fertilization was controlled chemically and was in effect separate from the transmission of hereditary traits. Loeb also is remembered for his work on the physiology of the brain, animal tropisms (involuntary orientations), regeneration of tissue, and the duration of life. He is noted for his arguments in favour of mechanism, the belief that the phenomena of life can be explained in terms of physical and chemical laws.”
I then searched for Sensitive Periods in Wikipedia, which is nested under Critical Period. Neither Jacques Loeb or Hugo de Vries are listed. Maria Montessori gets one sentence: “Dr. Maria Montessori was one of the earlier educators who brought attention to this phenomenon and called it “Sensitive Periods”, which is one of the pillars of her philosophy of education.” After an extensive though certainly not exhaustive search, I can not find any history of the term Sensitive Period that is not related to Montessori. In many of the pages I looked at, the term Sensitive Period is synonymous with the term Critical Periods.
So what we are left with then is a mystery. Where did Maria Montessori get the term Sensitive Period? It may have been Jacques Loeb though the term Sensitive Period is not mentioned in his Biographical Memoir published by the National Academy of Sciences. Several articles I read cite his work involving the Porthesia butterfly in which he referred to the caterpillars sensitivity to light in the beginning of their life.
Please let me know if you find anything else!