NARRATOR: Humans have many senses, the ability to receive and respond to stimuli. In addition to the five traditional senses, sight, hearing, taste, smell, and touch, we have a sense of balance, called the vestibular sense, and a sense of body position and movement called kinesthesia. Together, our senses help us navigate the world.

LINDA BARTOSHUK: The senses give us information about the environment to help us survive. Without sensory input we would die very quickly. The senses are what tell us about the world we live in.

NARRATOR: Of the five traditional senses, the human brain prioritizes vision and hearing. But all our senses interact and influence one another, what's known as sensory integration. The connection between smell and taste is a good example.

LINDA BARTOSHUK: We're now understanding things about taste and smell that are almost up to our sophisticated friends in audition and vision.

NARRATOR: Humans have thousands of taste buds, the specialized receptors for catching food chemicals. Each taste bud response to one of the five basic tastes, sweet, salty, sour, bitter, and umami, or savory.

LINDA BARTOSHUK: Taste is hardwired into the brain. You are born loving sweet and hating bitter, that's really important for survival. A newborn baby already knows bitter is bad, sweet is m dilute salt is good, acid strong is bad.

NARRATOR: When we smell something, combinations of chemicals in odor molecules stimulate receptors at the top of the nose. The brain then pieces this pattern of activation together into a unique scent.

LINDA BARTOSHUK: Smell plays a very important part inside the mouth, and it's integrated with taste in the brain into flavor. Bacon is made up of many different odors. And there are many different receptors that went into producing the template of bacon. But you recognize bacon immediately and you can treat it like a unit.

NARRATOR: People often associate a specific scent with a specific person or place, contributing to the strong link between scent and memory.

LINDA BARTOSHUK: Many people have had the experience of smelling something and being taken back to their childhood. This is almost certainly a survival characteristic, because you smell something that's associated with good and you remember it with pleasure. You can smell something associated with a bad experience and really remember it with extreme displeasure.

NARRATOR: Our sense of touch is made up of four basic sensations, pressure, warmth, cold, and pain. Pain is the body's alarm system, alerting us that something is not right. Sensitivity to pain depends on different factors, some we can control and some we can't. According to gate control theory, the spinal cord acts as a gate that lets in certain signals and blocks others to determine what the brain interprets as pain. Thus pain, like all our senses, exists at least partly in the mind.