Today, cognitive scientists try to link facial expressions to emotions in order to track the genetic and chemical pathways that govern emotion in the brain.
Until now they have focused on six basic emotions: happy, sad, fearful, angry, surprised and disgusted.
But restricting emotions to just six categories is like painting only using primary colours, said Martinez. The new study, published in the journal Proceedings of the National Academy of Sciences, has tripled the colour palette available to researchers.
In future, the computer model could aid the diagnosis and treatment of conditions such as autism and post-traumatic stress disorder (PTSD), said the researchers.
Here is the full list of emotional states identified by the scientists from facial expressions: Happy, sad, fearful, angry, surprised, disgusted, happily surprised, happily disgusted, sadly fearful, sadly angry, sadly surprised, sadly disgusted, fearfully angry, fearfully surprised, fearfully disgusted, angrily surprised, angrily disgusted, disgustedly surprised, appalled, hatred, awed.