An alternating treatment design ATD also known as a multielement design involves rapidly alternating two or more interventions within a single participant often in a single setting to compare their effects on a target behavior While ATDs are excellent for quickly comparing the relative effectiveness of multiple interventions and can effectively demonstrate functional relationships their primary limitation is susceptibility to multiple treatment interference or carryover effects If the effects of one intervention linger and impact the clients response to a different intervention applied subsequently it becomes difficult to isolate the true effect of each intervention The text highlights this stating if one intervention is going to impact the other one whats going to happen well thats going to impact our fidelity right its going to impact our functional relation In such cases the data paths may become intertwined making it challenging to differentiate the specific impact of each intervention thus undermining the designs ability to demonstrate clear experimental control Other designs like a multiple baseline design might be more appropriate when carryover effects are a significant concern