- Species in the Star Trek universe tend to display at least basic emotions.
Some common emotions include:
- Fear (personified in The Clown)
- Hate (personified in Armus)
Despite their suppression of emotions Vulcans still have them. Sarek suffered from Bendii Syndrome, an illness which makes Vulcans lose their emotional control. (TNG: "Sarek") Tuvok even laughed when his identity was erased to make him a laborer on the Quarren homeworld. (VOY: "Workforce") There are even Vulcans who choose not to follow the path of logic like the V'tosh ka'tur and Sybok. (Star Trek V: The Final Frontier) In addition, surprise, combined with strong emotion, made Spock (who was half-Human as well as half-Vulcan) lose control for a brief moment. (TOS: "Amok Time")
Since Vulcans have the capability to exert a level of conscious control over virtually all of their body functions, they can actually manipulate the neural pathways that regulate and receive the balances of neurochemicals involved in emotion. This enables them to inhibit their brain from forming the neural impulses that create conscious emotional mental states, thereby actually suppressing their innate emotions. The psycho-suppression system in the Vulcan brain that endows Vulcans with this ability is located in the mesiofrontal cortex. (VOY: "Meld") The Vulcan ritual, known as the kolinahr, is designed to purge all remaining emotions in a Vulcan. (Star Trek: The Motion Picture)
Often, robots like the Pralor Automated Personnel Unit or other advanced artificial lifeforms like androids or exocomps can exhibit self awareness but don't have emotions. An exception is Data, who obtained an emotion chip from his creator, Dr. Noonian Soong, which allowed him to experience Human emotions. (TNG: "Brothers") After receiving the chip in 2371, he was initially unprepared for the unpredictable nature of emotions. However, that after having experienced 261 distinct emotional states, he felt he had learned how to control his feelings. (Star Trek Generations) Although he was able to switch his emotions off he chose to remove the emotion chip in 2375. (Star Trek: Insurrection)