SUMMARY OF CHAPTER 5
Unobtrusive measures such as physical traces and archival data are important alternatives to direct observation and surveys. Physical traces are the remnants, fragments, and products of past behavior. Physical-use traces are based on the accumulation of evidence (accretion measures) or are the result of selective wear (erosion measures). Furthermore, use traces can either result naturally, without any intervention by the investigator, or be planned by the investigator. Physical traces may provide important nonreactive (unobtrusive) measures of behavior and can be used as the sole dependent variable or in combination with other measures of behavior. Multimethod approaches to the study of behavior are particularly recommended because they reduce the chance that results are due to some artifact of the measurement process. In obtaining physical traces, an investigator must be aware of possible biases in the way in which traces accumulate or survive over time.
Archival data are found in records and documents that recount the activities of individuals, institutions, governments, and other groups. These sources of information are valuable because they provide a way of investigating the external validity of laboratory findings, assessing the effect of a "natural treatment" (such as a political assassination), analyzing the content of communications, and describing trends. Archival records are nonreactive measures of behavior and, like physical traces, can be used in multimethod approaches to hypothesis testing. The analysis of archival data typically requires some form of content analysis, a process that can involve problems of sampling and coding that are not unlike those that arise in the analysis of narrative records (see Chapter 3). Problems of selective deposit and selective survival must be investigated when archival data are used, and evidence should be presented showing that observed relationships are not spurious.
Unobtrusive measures can be an important alternative to more intrusive methodologies, permitting psychologists to do research on important issues with minimal risk to the participants.