Benjamin Spock's wrote a book called The Common Sense Book of Baby and Child Care, which is one of the best-selling books of the twentieth century, selling half a million of copies in the six months after its initial publication in 1946, and 50 million by the time of Spock’s death in 1998, with multiple translation in more than 30 languages. Mothers were eager to take advises from Spock’s expertise, especially when Spock emphasizes that, above all, parents should have confidence in their abilities and trust their instincts.
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So many people took Spock's advice because the book was written in a friendly and encouraging tone, so Spock positioned himself in the role of mentor but not with an academic approach, but instead with an approach that was trustworthy. Spock’s reassuring advice make parents trust their instincts.