Satisfaction. Low-intensity positive states, where an individual shows subtle signs of comfort or satisfaction associated with a physical sensation or meeting a non-essential need. These might include comfortable bedding conditions, grooming or basking in the sun. Engagement is present but not overwhelming, allowing the individual to easily shift attention to other stimuli or activities as needed. 

Joy. Positive states involving greater engagement in rewarding activities. Individuals may display enhanced vigor in play, stronger social bonding, or more or active engagement in highly preferred activities, such as foraging. Behaviors indicative of joy suggest a greater focus on these positive experiences, although they do not exclusively dominate the individual’s attention. The individual’s behavior is noticeably directed towards maintaining or enhancing the positive experience. Physiological indicators may include heightened autonomic responses (e.g., heart rate).

Euphoria. Experiences in this category are intense and the primary focus of attention. Everything else might seem secondary. Euphoria might be observed in immersive play, mating rituals, or the pursuit and enjoyment of highly favored resources, such as a successful hunt. In some situations, this intense state might lead to spontaneous expressions of pleasure, such as vocalizations.

Bliss. At the peak of positive experiences, bliss represents a profound level of pleasure that pervades the individual’s sensory and emotional experience. It’s a sensation that transcends the ordinary. When experiencing bliss, the sensation of pleasure is so overwhelming that it eclipses other immediate needs or environmental stimuli for the duration of the experience. The world outside fades away as the individual is consumed by this all-encompassing state. Examples could be orgasmic states, reuniting with socially significant partners that are long missing, or the encounter of extremely positive conditions after prolonged periods of stress and hardship. Blissful states are expected to be rare and of short duration.