Final answer:
Unobtrusive research involves indirect observation methods like erosion measures and accretion measures, which examine wear and buildup, respectively, to study behaviors or patterns without disturbing subjects.
Step-by-step explanation:
Unobtrusive research is a research method that does not require direct interaction with the subjects, and thus it does not alter the behavior of those being studied. Two common physical traces of unobtrusive research are erosion measures and accretion measures. Erosion measures involve assessing physical wear or degradation of an object or area to make inferences about patterns of use or interaction, such as the worn steps of a public building indicating high traffic. On the other hand, accretion measures look at the buildup of materials, like layers of paint in a graffiti-covered alley, to analyze change over time without impacting the social dynamics of the environment.