Sensation and Perception
Just as a smartphone has "keys" that allow the input of information into your favorite apps—you know, the finest (um, Shmoopiest) ones in all the land—the human body has systems that interpret information from the outside world and "does things" with those signals.
Smart things. Usually.
The eyes see glaring morning sunlight, the nose smells the post-workout socks living at the bottom of your locker and plotting to take over the world, the ears hear the cacophony of your dad singing his favorite historically infused disco jam in his morning shower, the taste buds hate to taste the wretchedness of Brussels sprouts...
These inputs are all stimuli to which we respond. The fancy term for this process is transduction, where signals become neural impulses. These impulses zip along the speed lane of the nerve highway to the brain.
Adjusting to that runner's olfactorally awful sock? That feedback is called sensory adaptation. Putting on loud music to take your mind off the smell? That's called sensory habituation.
Psychologists often measure the trade-offs between what our senses tell us to do (you hear, "It's not you; it's me") and what we perceive to be happening (you think, "it's definitely me; maybe it's time to take a shower").
In this section, we'll be exploring the five senses, sensory disorders, and the dual roles of attention and culture in perceiving and processing those inputs.
Study Break
"Perception is a clash of mind and eye, the eye believing what it sees, the mind seeing what it believes." – Robert Brault
Thresholds and Signal Detection Theory
Have you ever wondered how your brain smells? No, not the thought of actually sniffing the contents of your cranium, because ew. (Although one guy did go on a road trip with Albert Einstein's brain. We bet they squabbled over who got to deejay.) We're talking about the way your brain actually receives, processes, and then tells you about external stimuli. For example, how can we hear music on the radio or see the double yellow lines on the road clearly enough to drive a car?
First, sensation is the detection of outside stimuli by special receptors on our bodies.
Perception is what we do with those sensations, how our minds process them, and how we create meaningful interactions. Or, more simply put, what we do with the inputs from outside stimuli.
Our bodies have developed specific sensory receptors, such as taste buds on the tongue, rods and cones in the eye, and hair cells in the ear, that are capable of receiving some form of energy from the world and transducing it—or turning it into an electrical signal that the brain can understand.
What stimuli do our bodies perceive in a world that is jam-packed with it? How do we choose and prioritize in the onslaught?
Thresholds
Not every stimulus can be perceived by the body. We need a minimum threshold of energy or stimulus that we must receive before our body's sensors can determine that, yes, the bus is coming at us at 75 miles per hour, so we should...um, move, probably.
The absolute threshold is the smallest level of stimulus that must reach the receptors before a person can detect it. A tiny whiff of perfume or cologne from down the hall, for example, and your nose knows your crush around the corner (and that you're probably going to embarrass yourself in one of a million horrifying ways in about five seconds). The absolute threshold of sound is the quietest noise you would be able to hear in a silent room.
