Simple descriptive, numerical, and visual analogue scales are unidimensional, as they only assess pain intensity, and universal, as they are understood in any language or culture.
These scales were developed to assess pain in humans from self-report and then adapted for use in animals with an observer. The value “0” (absence of pain) is arbitrary, as you never know if the animal does not feel pain.
Simple Descriptive Scale
1 – No pain
2 – Mild pain
3 – Moderate pain
4 – Intense pain
Numerical Scale: ordinal numbers from 0 (no pain) to 10 (worst possible pain).
Visual analogue scale
