The things we see and experience in our everyday lives, though they seem quite real to us, may not be real at all. Beau Lotto, PhD, explained: “Our brains did not evolve to sense reality; they evolved to give us what is useful for our survival.” A panel discussed the role that our five senses — smell, taste, sight, hearing and touch — play in making sense of the world. They also explored our brains’ inherent quirks that can sometimes trick those senses.
At a World Science Festival, in front of a packed auditorium at John Jay College, a group of scientists presented the audience with a series of visual and auditory illusions. The crowd tried to guess the perceived brightness of two sets of squares, and the words spoken in a garbled bit of audio. Audience members largely guessed wrong, setting the stage for a lively discussion about the mechanisms behind these mind-bending tricks.
Dr. Seth argued that the way our brains attempt decipher these illusions should be considered a feature, not a bug. “They should not be viewed as quirks or mistakes,” he said, “but rather an intriguing window into how we perceive the world at all times.”
“In fact, smell itself is an illusion,” added Dr. Lomvardas, who studies the science of our sense of smell. “The scents that enter our nose are just combinations of chemicals. And those chemicals do not have any inherent meaning. Instead, our brains choose to assign meaning to them. This is why, a scent that is pleasing to one person may be revolting to another.”
Whether reality is indeed an illusion perpetuated by our brains, as Dr. Hoffman proposed, remains to be seen. But the reality that we experience each and every day is what we must use to survive in our environment. To that end, the panel then turned their focus to the biological mechanisms that guide our senses.
What Guides our Senses?
One of the central questions here revolved around how our brains combine real-time sensory information — what we see, touch, taste, hear and smell — with our memories and previous experiences.
“Sometimes the [sensory] evidence you have to work with is bad, such as if it is dark and you’re trying to make out a particular shape,” said Dr. Constantinople. In those cases, she said, it may be better to rely more heavily on our previous experiences than senses.
Our senses themselves also often work in concert, which is critical to survival. To demonstrate this, Dr. Lomvardas called four volunteers from the audience. Given blind folds and nose plugs, the volunteers were fed peanut butter, strawberries and onions in sequence and asked to guess what they ate. Without the aid of their eyes, nose or fingers, the volunteers often guessed wrong.
“This illustrates just how important sight, smell and touch is to our ability to taste our food,” said Dr. Lomvardas.
As a follow up, Dr. Lomvardas then demonstrated how our senses can be tricked. He gave another volunteer a tablet that dissolved in her mouth. After donning a blind fold and nose plugs, she was asked to take a sip of a mystery liquid. She described the drink as sweet, “like sweetened lemonade.” In fact, the volunteer had been sipping sour vinegar.
The mystery tablet, it turned out, containing the chemical miraculin. Miraculin suppresses the tongue’s sour taste buds and boosts the sweet. This means that even the sourest of drinks, in this case, vinegar, tastes sweet — if only temporarily.
Senses Can Play Off Each Other
Synesthesia exists in about 4% of the population, and occurs when one sense actually triggers another. The most common type of this condition is called grapheme-color synesthesia, in which a person will always associate letters or words with a specific color. While the precise mechanisms that drive synesthesia are not yet known, Dr. Seth said that some evidence has suggested that this condition may in fact be present in all of us from birth, and is something that we “grow out of” as we get older.
As the evening concluded, the focus returned to fundamentals of the brain itself. And while the debate over the brain’s perception of reality may be unresolved, the panel were in awe of the feats that the brain can accomplish.
Indeed, the brain guides our most complex feelings of love, hate, guilt, morality — even the nature of our own reality. “But at the end of the day,” concluded Dr. Lomvardas, “our brains are simply a collection of cells, sending electrical signals back and forth to each other.”