I FUCKING LOVE THE SUMMARY

Summary: Russian children’s books focus more heavily on negative human emotions, such as anger, sadness, and fear than books US parents are likely to expose their young children to.

Because three paragraphs down it says the following about American books vs Russian books

Yankee:

“In the U.S., there’s an emphasis on the value of positive emotions—such as happiness or pride,” says Amy Halberstadt, co-author of a paper describing both studies and a professor of psychology at North Carolina State University.

Russian:

“In Russia, there’s more nuance,” says Yulia Chentsova-Dutton, corresponding author of the paper and an associate professor of psychology at Georgetown University. “Russian culture seems to value all emotions—including negative emotions—and it is important to learn from these emotions.

Long story short, showing children the broad range of human emotions helps them understand and deal with their emotions in a more positive manner than only showing a narrower range.