Which of the following scenarios would be classified as research with human subjects?

The correct answer is the scenario where a developmental psychologist videotapes interactions among toddlers and caregivers. This situation involves the direct observation and interaction of individuals as subjects within a research context. Human subjects are defined as individuals from whom data is collected through intervention, interaction, or identifiable private information. In this case, the toddlers and caregivers are being observed in real-time, allowing researchers to gather data regarding their behaviors and interactions.

The other scenarios do not fit the broader definition of research involving human subjects. Analyzing existing literature does not involve gathering new data from individuals but rather synthesizes already published information. The case study involving interviewing patients may seem related to human subjects but often does not qualify unless it involves systematic data collection beyond routine clinical practices. Finally, distributing a survey anonymously online does not involve identifiable data which limits the interaction with human subjects, as it retains anonymity and may not align with traditional definitions of research involving direct engagement or interaction.