Final answer:
The unobtrusive method described by Wells and colleagues (1966) involves observing undisturbed subjects in natural settings. This method, known as naturalistic observation, aims for high ecological validity by ensuring behaviors are observed without participants being aware of the observation.
Step-by-step explanation:
Wells and colleagues (1966) describe the unobtrusive method as those in which undisturbed subjects are observed in natural settings. This approach is commonly known as naturalistic observation and is used in fields such as psychology, sociology, and anthropology to study behavior in its natural environment. The aim is to gather data that has high ecological validity and to observe participants who are behaving as they normally would, without the influence of being consciously observed, which can affect their behavior. For instance, in the example provided, observers used subterfuge by having a classmate pretend to put in contact lenses while secretly recording handwashing behavior. This approach makes it possible to observe real behaviors, increase the validity of the information collected, and enhance the ability to generalize findings to real-world settings.