How do we think of mood and emotion, and are there "primary emotions" just as there are primary colours or do we need to think of each experience as unique? We have been wrestling with this question as long as we have been working with people with "mood disorders" and we recently spent several weeks thinking more about it and reading more of the literature about the physiology and psychology of emotion. There aren't clear answers but there are some conceptions of this topic that seem useful (Adachi 2008).
Discussion
Robert Plutchik has been one of the most articulate writers who support the notion that there are "primary emotions" from which all other emotions can be derived. His three-dimensional circumflex model (illustrated to the right) describes the relations among emotion concepts, which are analogous to the colours on a colour wheel. The cone's vertical dimension represents intensity, and the circle represents degrees of similarity among the emotions (Schinnerer 2007). The eight sectors are designed to indicate that there are eight primary emotion dimensions defined by the theory arranged as four pairs of opposites. In the exploded model the emotions in the blank spaces are the primary dyads—emotions that are mixtures of two of the primary emotions.
Other authors have also proposed the existence of a limited number of primary emotions. The table below (from Ortony and Turner, 2000) shows the authors and the emotions that they identified as "primary emotions" as well as the evidence that they cite in favour of their theory. As you will note there is a high degree of overlap across different authors, which suggests that there are at least some emotions that are shared. We have highlighted some of those shared "primary" emotions (Cooke 2009).
Mood
Moods are shorter-term emotional states, typically lasting hours, although they can last for days or longer. For example you may wake up feeling a bit down and stay that way for most of the day. We can be sent into a mood by an unexpected event, from the happiness of seeing an old friend to the anger of discovering betrayal by a partner (Clynes 2009). We may also just fall into a mood. Medical conditions such as depression are not really moods and are typically caused by a chemical imbalance in the brain. Moods can be caused by shorter-term chemical imbalances, for example brought on by a poor diet.
Emotion
Emotions as commonly experienced and discussed are different from moods and temperament in several ways. First, emotions tend to last for much shorter periods (Bouhuys 2005). The delight at being given a birthday present may subside in minutes as it is replaced by disappointment about a useless gift. Emotions thus tend to replace one another and it can be difficult to be both happy and sad (although we may have a good go at it).
Emotions also tend to be more extreme than moods and temperament, with higher highs and lower lows. We can become very angry very quickly, though it is difficult ...