The three types of research methods are each presented in a rectangular section inside the image. Text under the title “Research Methods in Developmental Psychology” reads “Developmental psychologists use several research methods to study changes that occur with age. Imagine you want to know whether using social media helps protect against feelings of loneliness over time. How would you design a study to measure that? Let’s compare methods.” Directly to the right of the text is the section for longitudinal research methods. Text explains that longitudinal methods measure a single group at different points in time, and provides the following example: “Researchers follow a sample of participants, interviewing them every decade for a total of three measurements. As they age, participants report lower levels of loneliness than expected. But because the study is longitudinal, we can’t eliminate the possibility that this particular group of participants is less lonely because of some historically specific effect.” Below this text is an illustration of a longitudinal sample group, Group 1. The illustration is an arrow with three dates on it. At 2005, Group 1 is 20 years old, at 2015, it is 30 years old, and in 2025 it is 40 years old. Text below the illustration explains that the benefits and problems of this method. The benefit is that it can track age-related changes. The problems are that measured changes could be specific to the particular group of participants, and that it takes a long time, leading some participants to drop out before the study is complete. The second type of research method is cross-sectional. Text explains that Cross-sectional research methods measure groups of people of different ages (for example, 20 -, 40-, and 60-year-olds) at a single point in time, and provides the following example: “Researchers interview participants in three different age groups: 20-, 40-, and 60- year-olds. The oldest group reports higher levels of loneliness. But because the study is cross-sectional, we can’t be sure if this finding reflects a cohort effect, in which differences may be due to age or to common experiences within the group, as opposed to developmental changes in physical, cognitive, or socioemotional functioning. Under this text is an illustration, showing the three groups (of 20-, 40-, and 60-year-olds), all in 2015. Text below the illustration explains the benefits and problems of this method. The benefits are that it allows comparison between age groups, and that it can be completed relatively quickly. The problem is that it is susceptible to the cohort effect. The third type of research method is cross-sequential. Text under the title explains that cross-sequential methods measure groups of people of different ages, following them across different points in time, and provides the following example: Researchers interview participants from three age groups every decade for a total of three measurements. This results in data showing how social media use and loneliness change within each group as they age. Under this text is an illustration, showing three groups of people, each a different age, at three different dates. Group 1 is 20 years old in 2005, 30 years old in 2015, and 40 years old in 2025. Group 2 is 40 years old in 2005, 50 years old in 2015, and 60 years old in 2025. Group 3 is 60 years old in 2005, 70 years old in 2015, and 80 years old in 2025. Text below the illustration explains the benefits and problems of this method. The benefits are that it shows changes within individuals and between groups, and that it better addresses the cohort effect. The problems are that it requires substantial resources and many participants, and that it takes a long time, leading some participants to drop out before the study is complete.