Table 1 Definitions of feline primary emotions

Fear

Negative emotional state [19] caused by immediate perceived danger or the threat of danger [20] and manifested as vigilance and attempts to withdraw or escape [21].

Anger/Rage

Negative emotional state [22] caused by the frustrated desire to perform actions/achieve goals [12] (including escape or exploration) or by competition for resources [23]. Manifested as aggression or the threat of aggression [22].

Joy/Play

A high intensity positive emotional state [24], which may be internally motivated [23]. Manifested as non-functional behaviours involving physical activity (locomotor play), interaction with other individuals (social play), or interaction with objects (object play) [25, 26].

Contentment

A positive emotional state caused by the fulfilment of the animal’s needs and desires and an acceptance of their current state [27]. Manifested as resting [28], calm [29], and affiliative behaviour [29].

Interest

A positive emotional state [28], caused by the presence of a novel stimulus or stimulus of salience and/or anticipation of engagement [30]. Manifested as attention and orientation to the stimulus [30, 31] and/or seeking behaviours [12, 13].