1. The study aimed to establish receptive and productive vocabulary norms for emotion-descriptive language in children aged 18 months to 6 years.
2. The researchers found that children's understanding of emotion-descriptive language increased with age, with the most significant growth occurring between ages 3 and 4.
3. Productive use of emotion-descriptive language also increased with age, but at a slower rate than receptive understanding. Girls tended to have a larger productive vocabulary for emotion-descriptive language than boys.
Unfortunately, the article text is not provided in this prompt, so a detailed critical analysis cannot be conducted.