Animal welfare science uses behavioural, physiological, and cognitive indicators to assess welfare states, and advances in methodology are improving our ability to measure both negative and positive welfare.
Welfare science methodology has advanced substantially from simple symptom observation to multi-domain assessment incorporating physiological and cognitive indicators. Cognitive bias paradigms that measure animals' tendency to make optimistic or pessimistic judgements in ambiguous situations provide a window into their affective states that observation alone cannot access. Physiological markers including cortisol, telomere length, and immune function provide objective welfare indicators. The challenge is developing practical, on-farm welfare assessment tools that use validated indicators without requiring laboratory analysis. Progress in wearable sensor technology and computer vision analysis is beginning to make continuous welfare monitoring feasible at farm scale.