Interpreting an interaction term assumes zero is a meaningful value of the other variable.

Evidence

Typically, the interpretation is that β1 is the impact of X1 when X2 = 0. This then assumes obviously that X2 = 0 really means something. If X2 is an interval variable then X2 = 0 is completely arbitrary (see Friedrich 1982 and Allison 1977). — Gary Goertz, Social Science Concepts and Measurement, 847

Categorization

• DEFINE: Pins down why the standard reading of interaction coefficients fails for interval variables.