Readability - Early Children's Readability Formulas

Early Children's Readability Formulas

In 1923, school teachers Bertha A. Lively and Sidney L. Pressey published the first reading ease formula. They had been concerned that science textbooks in junior high school had so many technical words. They felt that teachers spent all class time explaining their meaning. They argued that their formula would help to measure and reduce the “vocabulary burden” of textbooks. Their formula used 5 variable inputs and 6 constants. For each thousand words, it counted the number of unique words, the number of words not on the Thorndike list, and the median index number of the words found on the list. Manually applied, it took three hours to apply the formula to a book.

After the Lively–Pressey study people tried to find formulas that were 1. more accurate and 2. easier to apply. By 1980, over 200 formulas were published in different languages.

In 1928, Carleton Washburne and Mabel Vogel created the first of the modern readability formula. It was validated by using an outside criterion, and correlated .845 with test scores of students who read and liked the criterion books. It was also the first to introduce the variable of interest to the concept of readability.

Between 1929 and 1939, Alfred Lewerenz of the Los Angeles School District published several new formulas.

In 1934, Edward Thorndike published a formula of his own. He wrote that word skills can be increased if the teacher brings in new words, and repeats them, often. In 1939, W.W. Patty and W. I Painter published a formula for measuring the vocabulary burden of textbooks. This was the last of the early formulas that used the Thorndike vocabulary-frequency list.