The difficulty with studying human behaviour is that you can never be sure that you are getting accurate results. I have a background in qualitative research but it can be frustrating to hear that your interviews are biased or that people are not giving you accurate responses because they are afraid of what you will think of them. Even in quantitative methods there are many criticisms. For survey research some people may check off what they wish applied to them. For example, if you are asking how many hours of television a person watches per day he/she may answer fewer hours than are actually watched because he/she plans to cut down on hours of television watched. Sometimes this really bothers me. My friends who are in science roll their eyes when they speak about social science. I want my research to be taken seriously and to seem credible.
I was, therefore, intrigued to read Knight's section on unobtrusive methods. It is interesting to think of doing a study without leaving a mark. You're simply making observations. The researcher cannot influence subjects under these circumstances. Knight says that most researchers choose not to use unobtrusive methods but I think there might be something very valuable to them. I am not sure if they would make scientists take us more seriously, but they definitely are able to get around some of the criticisms with many social science methods.