A central issue in the study of animal welfare is how and when animals suffer. Understanding and alleviating poor welfare states, and providing resources that allow for positive experiences, may be considered an ethical imperative. Approaches to understanding affective state have often focused on behavioral changes associated with adverse or challenging events. For example, changes in time budgets (e.g., feeding, activity, play, and social behavior) have been observed in calves around disbudding and during illness. Body posture, movement of specific body parts, and pain-face or grimace scales are also increasingly studied. Preference and motivation tests can tell us how animals perceive and value different resources and opportunities for behavioral expression, which is informative for managing animals to improve affective state. For example, animals are motivated to access resources which may alleviate negative states, such as shade in hot conditions. This can be assessed through short-term tests or by observing behavior and resource use over longer periods in normal housing. Other short-term tests can offer insights into an animal’s pervasive affective state (e.g., cognitive bias tests) or perception of stimuli as positive or negative (e.g., aversion races or conditioned place preference tests). Our ability to gain insight into an animal’s subjective experience remains subject to some limitations. Behavioral observation and testing often provide insight into only the valence (positive vs. negative) of emotions, which is important for welfare assessment but may not inform how to improve animal welfare. Further, whereas responses associated with presumed negative states have been well studied, we have limited means to evaluate positive states. Monitoring individual responses and understanding the scope of individual wants and needs also remains a challenge. Nonetheless, increasing use of automated technology and continuing study in this area, including recognition of how behavior patterns may be reflective of personality and individual ability to cope and respond to changes, is shedding new light on our understanding of animal emotions.