Emotions are feelings which cannot be explained by logic according to Vulcans. Emotions experienced by Humans and other species include love, hate, fear, joy, anger, bliss, envy, and others.
Although all sentient species have emotions there are some who choose to suppress them.
- Based on the fact that every species in StarTrek seem to get angry or laugh surely one of the most basic emotions
The best known species who suppress their emotions are Vulcans. This is due to Surak, who believed that logic was the only way to lead his people out of the chaos that resulted when emotions controlled their behavior and caused destructive wars. Ultimately their logical thinking helped them leave their violent ways. The suppressing of emotions has to be learned by studying with a Vulcan master and must be maintained by meditations. (VOY:"Gravity")
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, Part I"). There are even Vulcans who choose not to follow the path of logic like Sybok. (Star Trek V: The Final Frontier)
Another species who seem to have no emotions are the Borg. A drone in the Borg collective shows no emotions when they assimilate others, however, the Queen can express them. (Star Trek: First Contact)
In general, 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. The exception is Data, who obtained an emotion chip from his creator, Dr. Noonien Soong which allowed him to experience Human emotions. (TNG:"Brothers") Although he was able to switch his emotions off he chose to remove the emotion chip in 2375. (Star Trek: Insurrection)
- Researchers presently believe that emotions are the first form of intelligence. The associations between emotions and events enabled early man to repeat rewarding events and avoid baneful ones. Modern theory holds that emotions are vitally important in making decisions for similar reasons.
- One famous example of emotional damage is railway worker Phineus Gage. In 1848, most of Gage's left frontal lobe (a part of his brain) was destroyed in a freak accident. Although he eventually recovered, his personality changed; he became emotionally labile and at the same time unable to settle on a course of action. Prior to his accident, he had neither of these problems. Other individuals with emotional problems have also been observed to have difficulty in decision making; they either cannot make decisions at all, or they make poor decisions even when they should be aware of the consequences.