The animal’s underlying emotional state, distinct from any specific behavioural response.

Affective states range from positive (calm, engaged, curious, anticipating reward) to negative (fearful, anxious, frustrated, depressed, in pain). Welfare science has increasingly focused on assessing affective state directly, recognising that an animal can perform behaviours that look fine while in a poor underlying state, or perform behaviours that look problematic while in a reasonable underlying state.

The concept matters for welfare assessment because the animal’s experience is the welfare outcome that matters most. Physical health, environmental conditions, and behavioural opportunities are all important, but they matter ultimately because of their effect on how the animal feels and experiences their life. An animal in poor physical condition who nonetheless has a positive affective state is in different welfare territory than an animal in good physical condition but a negative affective state.

Assessing affective state in non-verbal animals is methodologically challenging but has become substantially more feasible with recent research. Methods include behavioural observation (using validated ethograms for the species), physiological measurement (heart rate variability, vagal tone, cortisol patterns), and cognitive bias testing (assessing whether the animal interprets ambiguous information optimistically or pessimistically).

The two-dimensional framework of valence (positive vs negative) and arousal (high vs low) is commonly used to describe affective state. Different combinations of valence and arousal correspond to different recognisable emotional states across species: high arousal + positive valence (excitement, play); low arousal + positive valence (contentment, relaxation); high arousal + negative valence (fear, anxiety); low arousal + negative valence (depression, withdrawal).

The understanding of animal affective states continues to develop and remains contested in some respects. The basic premise that animals have affective states worth assessing scientifically is now broadly accepted across welfare science, even if the methods for assessing them continue to be refined.