Answer:
Claim 1:
There is evidence to suggest that vocabulary exposure has decreased in teenagers between 1984 and 2012. A study published in the journal Child Development in 2019 found that teenagers' vocabulary knowledge has declined over the past several decades. The study analyzed data from three nationally representative samples of American high school students collected between 1972 and 2013. The results showed that students in the later samples performed worse on vocabulary tests than those in the earlier samples. The researchers attributed this decline to a decrease in reading for pleasure, which they argue is the primary way that teenagers acquire new vocabulary.
Claim 2:
There is limited evidence to support the claim that teenagers in 1984 had a higher literacy achievement than teenagers in 2012. Several studies have compared literacy achievement across different cohorts of students, but the results are mixed and depend on the specific measures used. For example, a study published in the journal Reading Research Quarterly in 2016 found that the reading achievement of high school students in 2012 was not significantly different from that of students in 1971, after controlling for demographic factors. However, another study published in the same journal in 2017 found that the reading comprehension of middle school students had declined between 1971 and 2012. These mixed findings suggest that it is difficult to make a definitive claim about changes in literacy achievement over time.