Alternating Treatments Design

It shows differential effect through separation of data paths rather than a phase shift. By rapidly alternating two or more conditions in a counterbalanced order and plotting each as its own series, the design reveals whether one condition's outcomes consistently sit above the other's. A stable, replicated vertical gap between the paths — with little overlap — indicates that the treatments produce different results for that individual, because the rapid alternation holds time, context, and the person constant across conditions.

Multitreatment interference is carryover, where exposure to one condition alters how the individual responds in another, so the alternated treatments no longer reflect their isolated effects. Because the ATD interleaves conditions closely in time, an effect of treatment A may persist into a treatment B session and shrink or distort the difference between paths. Researchers guard against it by choosing treatments unlikely to carry over, counterbalancing thoroughly, and, when interference is suspected, interpreting the comparison cautiously or isolating conditions to verify their separate effects.

Choose the ATD when your question is comparative — which of several treatments is better — and when you do not want to withdraw an effective treatment to baseline, since the ATD compares conditions directly through alternation. Choose a reversal design when you want to demonstrate that a single intervention controls the behavior and when the behavior can ethically and practically return toward baseline. The ATD is faster for head-to-head comparisons but assumes minimal carryover, whereas the reversal design isolates one treatment's effect through repeated on-off demonstrations.