It's pretty hard to imagine someone drooling over most of these pictures. But chances are each of them has at least one fan. Taste can be very, very subjective.

"The sense of taste is a sensory system like the eye," Ilene Bernstein, Ph.D., a professor of psychology at the University of Washington, explained. "The tongue is sensitive to different tastes -- sweet, sour, bitter, or salty. Taste as a sense is the perception of a combination of these chemical signals on the tongue."

While it may sound simple, taste involves so much more than these four categories that we learned about in grade school. From genes, to environment, to a fifth taste referred to as umami, experts say there are a lot of factors that determine whether or not we like what we're biting into.

Taste is a combination of how food smells, looks, and sounds. When we eat celery, for example, it has to crunch. When we drink espresso, we expect a certain aroma. Plus, how a person perceives taste also has to do with nature and nurture.

"Taste is a product of our genes and our environment," Leslie J. Stein, Ph.D., from the Monell Chemical Senses Center in Philadelphia, said. "Our food preferences are determined by multiple factors, including genes, experience, and age."

Genes play their part by giving a person a predetermined preference and our environment is a factor in learning new tastes.

"Research has demonstrated that our genes help to determine how we detect the basic tastes by influencing the configuration of taste receptors," Stein continued. "Part of why you might like broccoli while your best friend finds it bitter is because you have different genes, which code for different bitter receptors."

Similarly, "Experience is also an important determinant of food preferences," says Stein. "For example, infants and young children need to learn what foods are safe to eat. Even before birth, information about specific flavors of mothers' diets passes to infants through amniotic fluid."

But genetics and upbringing aside, it sometimes seems as if everyone has at least a little bit of a sweet tooth.

"I would say that as a species, almost everyone has some degree of a sweet preference," Bernstein said. "We are born having automatic positive responses to sweetness."

However, when it comes to salt preference, an unlikely factor plays a role.