 [A]s people formulated and debated various proposals about what constitutes a satisfactory life for animals in human care, three main concerns emerged: (1) that animals should feel well by being spared negative affect (pain, fear, hunger etc.) as much as possible, and by experiencing positive affect in the form of contentment and normal pleasures; (2) that animals should be able to lead reasonably natural lives by being able to perform important types of normal behavior and by having some natural elements in their environment such as fresh air and the ability to socialize with other animals in normal ways; and (3) that animals should function well in the sense of good health, normal growth and development, and normal functioning of the body. (Fraser 2008: 70–71)