I saw the image below recently and was intrigued. Unfortunately I saw the image without context so I couldn’t figure out what to google to learn more. The other day, however, I ran into it again. Here’s the explanation I found:

Robert Plutchik considered there to be eight primary emotions – anger, fear, sadness, disgust, surprise, anticipation, trust, and joy. Plutchik proposed that these ‘basic’ emotions are biologically primitive and have evolved in order to increase the reproductive fitness of the animal. Plutchik argues for the primacy of these emotions by showing each to be the trigger of behavior with high survival value, such as the way fear inspires the fight-or-flight response.

Robert Plutchik’s Matrix of Emotions

Ten Postulates of Emotion

Plutchik’s psycho-evolutionary theory of basic emotions has ten postulates:

1. The concept of emotion is applicable to all evolutionary levels and applies to animals as well as to humans.
2. Emotions have an evolutionary history and have evolved various forms of expression in different species.
3. Emotions served an adaptive role in helping organisms deal with key survival issues posed by the environment.
4. Despite different forms of expression of emotions in different species, there are certain common elements, or prototype patterns, that can be identified.
5. There is a small number of basic, primary, or prototype emotions.
6. All other emotions are mixed or derivative states; that is, they occur as combinations, mixtures, or compounds of the primary emotions.
7. Primary emotions are hypothetical constructs or idealized states whose properties and characteristics can only be inferred from various kinds of evidence.
8. Primary emotions can be conceptualized in terms of pairs of polar opposites.
9. All emotions vary in their degree of similarity to one another.
10. Each emotion can exist in varying degrees of intensity or levels of arousal.