Scale-type rules about permissible operations never crossed into political science and economics.

Evidence

Adding not only makes the 0–1 indicators ordinal, but makes them interval. This arises because addition is not a permissible mathematical operation on nominal or ordinal variables. … The classics of measurement of the 1960s in psychology (e.g., Suppes and Zinnes 1963) discussed at some length these issues of permissible mathematical operations depending on scale type. However, (1) these discussions did not seem to make it into more distant disciplines like political science and economics, and (2) have probably been dropped over the decades in psychology methods classes. — Gary Goertz, Social Science Concepts and Measurement, 831

Categorization

• XREF: Connects to your reading on measurement theory and to critiques of quantitative political science methodology.
• DEEPTHINKING: Raises a larger question: what other foundational insights died in their home discipline before reaching others, and how much of current practice rests on such silent amnesia?