Which of the following is an example of observer drift?

• A. A school psychologist consistently codes behaviors using the same criteria
• B. A researcher doubles the observation period to increase reliability
• C. An observer is trained with updated criteria but applies them consistently
• D. A school psychologist unintentionally changes the standards being used to code a behavior over time

Answer: (D)

Observer drift happens when the standards for recording behavior slowly shift over time, even though the procedure isn’t officially changed. This means an observer begins applying slightly different thresholds or criteria as time goes on, leading to data that aren’t directly comparable across time points. In this scenario, the observer unintentionally changes the standards used to code a behavior as time passes, which is exactly drift. Reliability and validity suffer because the same behavior might be coded differently at different times. By contrast, consistently applying the same criteria keeps data stable; extending the observation period can affect reliability but doesn’t imply changing how behaviors are coded; and updating criteria while applying them consistently still maintains standardized procedures across time. Observer drift is a key threat to measurement accuracy in behavioral observation, and regular reliability checks help prevent it.