Which of the following best describes a fatigue effect in an experiment?

In a within-subjects design, a fatigue effect is considered a confounding variable because it introduces an alternative explanation for why a participant's performance might decline across experimental conditions.

A researcher is investigating how room lighting affects typing accuracy using a within-subjects design. Arrange the following events to illustrate how a fatigue effect would typically manifest and impact the validity of this study.

A researcher examines how font size affects reading speed using a within-subjects design. All participants read a passage in 10pt font first, 12pt second, and 14pt third. The researcher observes that reading speed is significantly slower in the 14pt condition than in the others. Match each component of this experiment to its functional role in the context of the fatigue effect.

A fatigue effect can be triggered by mental boredom or tiredness, even if the participant does not experience physical exhaustion.

To demonstrate your understanding of the fatigue effect in psychological research, match each conceptual aspect of the phenomenon with its correct description.

A critic reviews a within-subjects study and determines that the researcher's conclusion—that the final memory task was inherently the most difficult—is invalid because the experimental session lasted three hours without breaks. The specific internal validity threat that the critic would cite to justify rejecting this conclusion is the _____ effect.