A sixth sense is a sense beyond the conventionally accepted five physiological senses of sight, hearing, smell, taste, and touch. Many people use the term to describe an especially sensitive sense of intuition or perception that allows people to predict events or pick up on subtle cues that others miss. People also sometimes describe extra-sensory perception (ESP) as a sixth sense, stressing the idea that it is paranormal in nature.
In fact, researchers have discovered several physiological senses beyond the well-known five. For example, equilibrioception, the human sense of balance, is sometimes termed a sixth sense. Researchers have also discovered a special structure in the nose called the vomeronasal organ which appears to pick up on specific hormone signals. In 1999, researchers at Harvard suggested that humans might have communicated with hormone signals at some point in their evolutionary history.
True physiological sixth senses aside, some people believe that the more ephemeral version of this sense allows people to predict the future, sometimes with varying degrees of success. When someone has an especially prescient hunch, for example, someone may say that he or she has “a sixth sense.” It is also used to explain paranormal phenomena like clairvoyance, the believed ability to see into the future. In this sense, people may also use the term “second sight” to describe it.
Numerous studies have been conducted on extra-sensory perception, to discover whether or not people really can predict things. Most of these studies have concluded that, in the sense of a prediction or hunch which cannot be explained with rational means, the sixth sense does not exist. However, some people are very good at identifying subtle cues in a situation which they can use to their advantage, and people with less perceptive personalities might mistake this skill as something paranormal.
One of the most common pieces of evidence mustered to support the idea of the sixth sense is an apocryphal story about a friend of a friend who “got a bad feeling” and acted on it, avoiding some calamitous fate. This is an example of a cognitive bias known as the confirmation bias, which leads people to discard data that does not confirm their beliefs. For every bad feeling that pays off, in other words, people have many more bad feelings and hunches that never amount to anything, but they forget about them and focus on the one that confirmed their belief in uncanny intuition.