Sequence Effects

Sequence effects are potential confounding influences in experiments where subjects are exposed to multiple conditions. Sequence effects refer to potential interactions among conditions of an experiment based on the sequences these treatments are presented. Sequence effects are distinct from order effects, where the actual order of conditions influences the outcome, and carryover effects, where subjects are permanently changed by the manipulation. To illustrate the differences among sequence, order, and carryover effects, imagine an experiment where subjects are asked to pick up and guess the weight of different objects [Page 1341]on multiple daily sessions. A sequence effect would be the perceived weight of a given object being influenced by whether a light or heavy object was handled just before. In contrast, an order effect would be ...