Rationale

The problem of reactivity (people changing their behavior because they know they are being observed) does not arise when unobtrusive measures of behavior such as physical traces are used.

The investigation of physical traces represents a valuable component of the multimethod approach to hypothesis testing.

Types of Physical Traces

Two categories of physical traces are "use traces" and "products."

Use traces reflect the physical evidence of use (or nonuse) of items, and can be measured in terms of natural or controlled use.

By examining the products people own or the products produced by a culture, researchers test hypotheses about attitudes and preferences.

Problems and Limitations

Before concluding that a measure of physical traces is a valid indicator of behavior or attitudes, a researcher should make sure no sources of bias exist.

Validity of physical-trace measures can be ascertained by examining converging evidence.

Rationale

Archival data comprise the records or documents of the activities of individuals, groups, institutions, and governments.

Archival data are used to test hypotheses as part of the multimethod approach, to establish the external validity of laboratory findings, and to assess the effects of natural treatments.

Archival data represent a rich, plentiful source of observations for psychological studies.

Types of Archival Data

Types of archival data include running records, news media, and other types of records; archival data can consist of public or private documents.

Content Analysis

Content analysis refers to the process of making inferences based on objective coding of archival records. Steps for content analysis include identifying a relevant source of archival data, sampling data from the records, and then coding the contents of the records.

Coding in content analysis involves classifying events and behaviors from archival records into clearly defined categories and recording the amount of time or words devoted to events and behaviors.

Trained coders use rating scales to make qualitative judgments about the contents of archival records.

Problems and Limitations

Archival data may be biased due to selective deposit and selective survival.

Selective deposit occurs when biases influence what information is recorded (deposited) in an archival record, or whether a record is made at all; selective survival occurs when archival records are missing or incomplete.

Archival records are subject to errors and changes in record-keeping procedures.

Although archival data are considered nonreactive, reactivity can influence the production of archival records; this is particularly true for public records.

When interpreting the results of correlational analyses of archival data, researchers must be alert to the possibility of spurious relationships.

Ethical Issues and Unobtrusive Measures

Unobtrusive measures such as physical traces and archival data represent an important research method for psychologists to fulfill their ethical obligation to improve individual and societal conditions.