What characterizes the research methods that do not involve direct manipulation of subjects?

The research methods that do not involve direct manipulation of subjects are characterized by naturalistic observation. This approach involves watching and recording behaviors in their natural context without interfering in any way. It allows researchers to collect data on how animals interact with their environment and each other in realistic settings, gaining insights into their behavior that might not be possible in an experimental setup.

Naturalistic observation is valuable because it captures the complexities of animal behavior as they occur organically, which can lead to a more authentic understanding of that behavior. This method is especially beneficial in studies where manipulation could alter the behavior of the subjects or the dynamics of the environment, allowing for a more accurate portrayal of the subjects' actions and interactions.

In contrast, other methods mentioned, such as controlled experimentation, involve manipulating variables to observe effects, and thus, are not representative of a non-manipulative approach. Rigid control of variables is a hallmark of experimental designs, which aim to isolate the effects of specific factors. Statistical analysis is a quantitative method used to interpret data but does not pertain specifically to the manipulation or observation of subjects directly.