The cognitive benefits of reading are well-established, and countless scientific studies conducted over the years have demonstrated how beneficial this complex cognitive process is to one’s psychological well-being.

According to the South African College of Applied Psychology, studies have shown that reading boosts creativity, increases empathy for others, improves mental flexibility, stimulates the brain, and unlocks creativity.

There is certainly is no better way to gain a larger vocabulary than by reading, but only a few studies have explored the relationship between reading and vocabulary in prepubescent children. A new Ohio State University study explores just that — the relationship between children’s vocabulary and reading, in children younger than 5-years-old.

The study found that children whose parents read them five age-appropriate books a day (containing between 140 and 228 words, on average) enter kindergarten with a vocabulary potentially richer for 1.4 million words.

Authored by Jessica Logan, Laura Justice, Melike Yumus, and Johana Chaparro Moreno, and published in the online edition of The Journal of Developmental and Behavioral Pediatrics, “When Children Are Not Read to at Home” investigates the “correlational and causal influences” of reading on children’s vocabulary development.

For the study, the researchers — in collaboration with the Columbus Metropolitan Library — identified the 100 most circulated board books and picture books. They randomly selected 30 books from the list, counting how many words each of them had — the picture books (for preschoolers) contained 140 words on average, and board books (for toddlers and infants) contained an average of 228 words.

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Using this information, and assuming that kids would be read board books up until the age of 3-years-old and picture books up until the age of 5-years-old, Ohio State University researchers calculated how many words a child would hear from birth until entering kindergarten.

The calculations show that children whose parents read them five books a day hear over 1.4 million words before entering kindergarten.

Kids who have their parents read them one book a day hear 296,600 words before entering kindergarten. Children whose parents read them between three and five books a week hear 169,520 words, and children whose parents read to them one or two books a week hear 63,570 words before starting kindergarten.

Children who are never read to hear only 4,662 words before the age of 5, according to the researchers’ calculations.

“Kids who hear more vocabulary words are going to be better prepared to see those words in print when they enter school. They are likely to pick up reading skills more quickly and easily. The word gap of more than 1 million words between children raised in a literacy-rich environment and those who were never read to is striking,” lead author Jessica Logan explained in a statement.