Read Psychology for Dummies Online
Authors: Adam Cash
Tags: #Psychology, #General, #Body; Mind & Spirit, #Spirituality
Psychology for Dummies (14 page)
Sound travels in waves and is measured by its
amplitude
or
wave size
and
frequency
or
number of waves per unit time
. Each of these translates into a psychological experience: Amplitude determines loudness (my neighbor’s rock band), and frequency provides pitch or tone (the screeching lead singer of my neighbor’s rock band). The structures of the ear are specifically designed to transduce, or convert, sound-wave energy into neural energy.
A sound first enters the ear as it is funneled in by the
pinna.
Our crumpled-up outer ear is designed as a “sound scoop.” As the wave passes through the ear canal, it eventually reaches the eardrum, or the
tympanic membrane.
The vibrating eardrum shakes three little bones
(malleus, incus,
and
stapes,
Latin words for
hammer, anvil, and stirrup),
which amplifies the vibration.
After the sound wave reaches the inner ear, the
cochlea,
auditory transduction occurs. The cochlea contains the hardware for the transduction process. The cochlea is filled with fluid, and its floor is lined with the
basilar membrane.
Hair cells
(they actually look like hairs) are attached to the basilar membrane. The sound waves coming into the inner ear change the pressure of the fluid inside the cochlea and create fluid waves that move the basilar membrane. Movement of the basilar membrane causes the hair cells to bend, which starts the transduction ball rolling. When the hair cells bend, their chemical properties are altered, thus changing their electrical polarity. As I discuss in Chapter 3, when a cell’s polarity is altered, it is in a position to fire and send a neural signal. The sound waves, now turned into neural electrochemical energy, travel to the
auditory cortex
(the part of the brain responsible for hearing)
for perceptual processing.
The sense of touch includes sensing pressure, temperature, and pain. Specialized cells in the skin sense touch, which send a signal to the spinal chord and then on to the brain. In this case, transduction in touch is a physical or mechanical process; it’s much more straightforward than the chemical transduction in the eye for vision. When heat, cold, or weight stimulates touch receptors in the skin, this sends a neural signal toward the brain, much the same way that the hair cells of the inner ear operate. The pressure leads directly to a neural signal.
Pain is a special case for the sense of touch because it would be hard to avoid harm and survive in this world without our sense of pain. How do I know fire can damage my flesh and possibly lead to death? Because it hurts when I touch it. Pain is an important signal that something is harming, damaging, or destroying the body.
A-delta fibers
and
C fibers,
two specific nerve fibers located throughout our skin, signal pain to the brain. A-delta fibers carry sharp sensations and work rapidly, sending swift signals to the brain. C fibers send signals of chronic and dull pain and burning sensations.
I’ve played sports most of my life, and one thing is for sure — pain tolerance is always an issue. “No pain, no gain!” I’d hear in practice every day. I’ve had to play through many an injury, and it really hurt! Some people seem to have a really high threshold for pain. The
gate-control theory of pain
states that pain signals must pass through a gate in the spinal cord that “decides” which signals will get through to the brain and which ones will not. If another sense is using the pain pathways, the pain signal may not reach the brain. Also, there might be competing signals coming from another body part toward the gate, thus inhibiting the pain signal from traveling up to the brain. If you’ve ever rubbed your thigh while your ankle aches, it seems to help. That’s because the rubbing signal (pressure) from the thigh is competing for access through the gate with the pain signal from the ankle. That’s amazing! I’m always blown away by the complexity of the human body.
Our sense of smell is called
olfaction.
Sometimes I can smell my neighbor’s barbecue on the weekend. I have that experience because little particles from the cooking food,
volatile
chemical particles,
have become airborne and traveled over to the smell receptors in my nose. Inside my nose are thousands of olfactory receptors that can sense tens of thousands of different odors.
The molecules from the volatile chemicals cause a chemical change in the receptors in my nose, which sets the transduction process in motion. The chemical energy is then converted into neural energy by the receptor cells, and a signal is sent to the
olfactory bulb
in my brain where the signal is processed. The olfactory bulb also connects with the part of my brain that involves emotion. Some researchers think that this connection is why smells can activate emotional memories from time to time.
There’s been a lot of talk about
pheromones
scents that animals send out as signals to other animals, during mating season, for example. Some companies have marketed pheromone products for humans, especially for those men out there desperate to find a date. Do humans really produce pheromones? The research jury is still out, but a few recent findings seem to suggest that we do. One thing is for sure though: Pheromones or no pheromones, the perfume and cologne industries seem to be on to something!
Gustation
refers to our sense of taste. Taste is a chemical sense made possible by the chemical receptors on our tongues known as
taste buds.
All tastes are variations on four themes: sweet, sour, bitter, and salty. We have approximately 10,000 taste buds. The taste buds react to the molecules of the food, which again converts chemical energy into neural energy and sends that information to the area of the brain involved in analyzing taste information.
Obviously, the world we’re in touch with through our senses is a lot more complex than just a bunch of singular sounds, smells, tastes, and other sensations. We hear symphonies, not just notes. We see fireworks, not just single photons of light. We indulge our taste buds with scrumptious meals, not just salty, sour, bitter, and sweet tastes. We can thank the ability of perception for all of these pleasures.
Perception
is the process of organizing, analyzing, and providing meaning to the various sensations that we are bombarded with on a daily basis. If sensation provides us with the raw material, perception is the final product.
There are two popular views of this complex process:
Ecological view:
This idea states that our environment provides us with all of the information that we need to sense the world; very little interpretation or construction is needed. For example, when I perceive a tree, it’s not because I’ve constructed a perception of it in my mind. I perceive the tree because the tree has provided me with all of the necessary information to perceive it as it is.
Constructionist view:
In this view, the process of perception relies on previous knowledge and information to construct reality from fragments of sensation. We are not just passive recipients of sensory information. We are actively constructing what we see, hear, taste, and so on.
Regardless of whether you’re an ecologist or a constructionist, there are some basics to the process of perceiving. If sensation is the process of detecting specific types of energy in our environments, how do we know which information is worth detecting and which is just background noise? After all, we couldn’t possibly respond to every bit of sensory energy around us. We’d easily be overwhelmed with all the roaring traffic, howling wind, bustling pedestrians, and other stuff around us. The good news is that our perceptual systems have a built-in system for determining what information should be or is actually detectable.
The concept of an
absolute threshold
refers to the minimum amount of energy in the environment that a sensory system can detect. Each sensory system has an absolute threshold below which energy does not warrant or garner perceptual attention.
Another determinant of whether a stimulus is detected or not comes from
Weber’s law,
which gives the idea of the
just-noticeable difference (JND).
Each sensory system determines a constant fraction of intensity for each form of energy that represents the smallest detectable difference between energy intensities. The idea is that a stimulus has to exceed the JND in order for it to be detectable; otherwise, it will go unnoticed because the difference is too small.
Yet, another theory known as
signal-detection theory
takes a slightly more complicated look at the problem. An overwhelming amount of the environmental energy around us is considered background noise. When we encounter a stimulus, called the
signal,
it’s analyzed based on our individual
sensitivity
and
response criterion.
Based on the sensitivity and response criterion of their individual sensory systems, people can either correctly detect a stimulus
(hit),
fail to detect a signal when there is one
(miss),
detect a signal when there isn’t one
(false alarm),
or report no signal when there isn’t one
(correct rejection).
Our individual biases and motivations determine our response criterion and play a role in whether we make an accurate detection or not. So, when people think I’m not listening to them, it’s not my fault. I’m not detecting their signal because my response criterion is set not to respond to anyone talking to me at that moment. I’m an innocent victim of my perceptual processes.
The perceptual system is not made up of a bunch of arbitrary rules and random processes. Psychologists and other researchers over the years have discovered a number of principles that guide the way our perceptual systems organize all the information that we receive from our sensory systems:
Figure-Ground:
Information is automatically divided into figure and ground, or immediate and background. The information that is figural is more obvious, and the ground is less meaningful.
If you focus on, or
make figural,
the white area, all you see is a shapely vase. If you focus on the black areas, making them figural, you can see two faces looking at each other.
Grouping:
This large category contains principles that are used to determine whether stimuli belong in a group with similar stimuli.
•
Proximity:
Stimuli that are close together in space are perceived to belong together.
•
Common fate:
Stimuli that move in the same direction and at the same rate are grouped together.
•
Continuity:
Stimuli that create a continuous form are grouped together.
•
Similarity:
Similar things are grouped together.
Closure:
This principle is the tendency to fill in missing information to complete a stimulus.
Most psychologists today are in the
constructionist
camp. (See the “Finishing the Product: Perception” section earlier in this chapter.) They view perception as a process of building the things we perceive of reality out of fragments of information. We are born with some of the rules for organizing information, but a few other factors can influence the way we perceive things.
Our experiences have a powerful impact on how we perceive things. The concept of
perceptual set
tries to capture this idea, an expectation of what I will perceive. We use cues from context and experience to help us understand what we are seeing. For example, if I am driving down the street and see someone in a police uniform standing next to someone’s car window, I assume that he is making a traffic stop. I could actually be seeing a person in a police uniform asking for directions, but my experience tells me otherwise.
Another powerful influence on how we perceive things is the culture that we live in. A good example of the role cultural influences play in our perceptions involves figuring out a story line based on a series of pictures. Consider that I have five pictures, each containing a different piece of a puzzle that, when viewed in sequence, can tell a story. The story that I think the pictures are telling might be different if I’m from a different culture. For example, I’m looking at a series of pictures that show a woman carrying a bag, a picture of her crying, a man approaching her, and a picture with her bag missing. What’s going on here? I might see a woman who is upset because she dropped her bag and a man who is coming to help her. Or, I might see a woman crying out of fear because a man is coming to steal her bag. Depending upon my culture or subculture, not to mention my experience, I could see two very different stories.
Illusions and magicPerceptual illusions are a consequence of the organizing principles of our perceptual systems. We might see things that aren’t really there or see things moving when they’re motion- less. Illusionists, such as magicians, use these perceptual organizing rules against us. They have a keen understanding of how our perceptual systems work, and they take advantage of this knowledge to carry out their tricks.
