Final answer:
Dr. Darden is using cross-sectional research to compare memory recall between young adults and older adults, and she should find a higher proportion of positive memories in the older adults due to the positivity effect.
Step-by-step explanation:
Dr. Darden is using the cross-sectional research method to assess the proportion of positive statements in the recall protocols of young adults and older adults. In this approach, different age segments of the population are compared at the same time, which allows for gathering data without the long-term commitment required for longitudinal studies. However, it can be influenced by cohort effects, which are the differences resulting from individuals in different age groups having varied social and cultural experiences. Based on the text's discussion and general findings in developmental psychology, Dr. Darden should find that older adults tend to recall a higher proportion of positive memories, a phenomenon known as the positivity effect. This effect suggests that as people age, they tend to remember more positive than negative information.