Betazoids

Betazoids hail from the Federation member planet Betazed. A peaceful race that have developed highly telepathic abilities, the Betazoid people appreciate fine arts, literature, and philosophy. As all Betazoids are telepathic, they usually do not need to vocalize their thoughts to one another in order to communicate, but can do so for the benefit of offworlders. It is a natural ability, and likewise the strength of the skill varies from one to another. Most develop the ability in adolescence, but a few have congenitally active telepathic abilities that may cause severe mental problems due to their inability to screen out other peoples minds. Screening is a skill that is absolutely necessary for the well-being of a Betazoid,particularly for those with keen telepathic sensory skills. Externally, Betazoids are among the most humanoid species on record, and are indistinguishable from humans in every aspect but one, they have very black eyes and show no iris color. They can reproduce with humans, although this often dilutes the telepathic abilities of the offspring, case in point: Commander Deanna Troi. The children of such a union often develop empathic rather than full telepathic abilities, though they can still communicate telepathically with their Betazoid parent and a bonded mate. 
Full Betazoids are unable to read the minds of Ferengi, Breen, Ullians or Dopterians due to their unusual brain lobe formations, but some half Betazoids have been occasionally successful in sensing the emotions of these species. 
Society Betazoid society tends toward more formal and elaborate traditions and ceremonies than most cultures in their present evolutionary stage. Some of the rites often make the more conservative Federation offworlder uneasy at first, most notably the traditional wedding ceremony in which no clothing is to be worn. Though there are no official gender-based restrictions in place within Betazoid society, women have traditionally held many positions of authority. 
Betazoids are a race of pacific philosophers who are more likely to observe than act, and consequently have little use for weapons or even defense systems. Their planetary defense system were outdated the moment they were finally in place and proved to be quite useless with the Dominion . Nonetheless they are considered a major world of the Federation and their fall during the Dominion war in 2374 struck home the devastation that had eaten away at the Federation's formerly secure borders.
The Betazoid brain contains the paracortex, which is a lobe devoted specifically to telepathy. While most Betazoids develop their telepathic powers at the onset of adolescence, and they gradually develop after that, a small number are born fully telepathic, although no one knows exactly why. Betazoids born with their telepathic abilities fully developed almost never lead normal lives - they are constantly bombarded with the thoughts of others around them, and drive themselves to distraction attempting to block out the never-ending telepathic "attack". The opposite, Betazoids can be born without any telepathic ability, leading to sociopathic behavior. 
Even if we are very similar physically, the REM frequency of sleeping Betazoids is different from that of most humanoids. The gestation period for Betazoids is typically 10 months and at around age 40, Betazoid females enter a period of increased sexual desire called "the phase". A Betazoid woman's sex drive will typically quadruple in intensity during the phase.