How to Be RAD: Repeated Acquisition Design Features that Enhance Internal and External Validity

Area of Science:

• Behavioral Science
• Research Methodology
• Psychology

Background:

• The Repeated Acquisition Design (RAD) is a single-case research design (SCRD) valuable for measuring rapid, irreversible skill acquisition.
• RAD is sensitive to immediate changes in learning rate or accuracy, making it useful in human and animal studies.
• However, RAD faces criticism regarding threats to internal validity and has been overlooked in SCRD standards.

Purpose of the Study:

• To address limitations in the Repeated Acquisition Design (RAD).
• To propose a set of 15 quality indicators for RAD studies.
• To enhance causal inference and external validity in RAD research.

Main Methods:

• A review of contemporary RAD usage was conducted.
• A set of 15 quality indicators for RAD studies was developed.
• Guidelines for interpreting RAD study effects and evidence strength were proposed.

Main Results:

• The proposed indicators include foundational elements and features to strengthen causal inference and external validity.
• Contemporary RAD use was analyzed to demonstrate how these features improve study rigor.
• Suggested guidelines for interpreting RAD effects and evidence were provided.

Conclusions:

• Implementing the proposed quality indicators can enhance the rigor of RAD studies.
• These indicators provide a framework for improving the validity and utility of RAD.
• The guidelines aim to support researchers in maximizing the potential of the RAD for robust learning research.