Module 6 – SensationPsychology 120

Outcomes: In this module the student will:

  1. Discover the basic principles associated with sensation.
  2. Learn how each of our senses contributes to our sensations. (visual system, auditory system, taste, smell, touch and body)

Module Notes: In this module you will be filling in missing information from your text. Start on page 95.

Introduction

Think for a minute, while sitting in your seat…..we know we can see things, but what can you hear, what can you smell, what can you feel?

Sensation is awareness of the world around you. Your NS sorts through all the incoming sensory information by using bottom-up processing, a form of information processing that analyses the raw stimuli entering through your many sensory systems. The analysis of sensory information that takes place during bottom-up processing is part of perception. Ex: sensation allows you to know that an object is a red sphere, it feels cold in your hand, it smells sweet, it sounds crunchy. Analysis of this bottom-up stream of data leads to the perception that you are eating an apple.

Perception is also influenced by top-down processing, information processing that draws upon our experiences and expectations to interpret incoming sensations. See slide.

Sensation and perception cannot be separated because these processes blend together in our everyday experiences.

Sensation is governed by basic principles that determine how we process stimulation from the environment.

Basic Principles

  1. Thresholds: an edge or a boundary

Absolute Threshold: minimum amount of stimulation needed to detect a particular stimulus. See page 96 for examples.

Difference Threshold: also called the JND; the minimal difference to detect that two stimuli are not the same; the smallest detectable change in a stimulus. Ex: How much does the room have to cool down before you notice it is too cold? How much does the music have to go up to realize it is too loud?

Can Subliminal Messages Improve Your Memory? See p. 97

  1. Signal Detection Theory:predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulus(noise). Signal detection depends on three things.

They are: 1.

2.

3.

This grew out of the Cold War as a way of improving our ability to detect incoming nuclear warheads in time to respond appropriately. National security depends on accurate signal detection.

Signal detection formulas consider three kinds of variables:

1.______- how bright is the blip on the radar screen?

2.______- how much distracting noise is there in the room with the radar equipment?

3.______- is the operator properly trained and motivated?

  1. What happens when we detect a stimulus continuously? Sensory Adaptation: When we filter out non-changing aspects of our environments. When stimulus is constant and unchanging, you eventually fail to respond because you usually don’t need to. Ex: dive into a pool of cold water….what happens? What are some things that show sensory adaptation?
  1. Selective Attention: focusing conscious awareness on a particular stimulus to the exclusion of others.

Think of how many stimulus are competing for your attention right now? What do you see when you look at the following? Selective attention to a small number of stimuli lets you function in a busy, noisy world.

THE VISUAL SYSTEM

Even nocturnal creatures depend on the low level of light available to their eyes at night. Light enters the eye as waves of electromagnetic energy . Your visual system has two different types of receptor cells, rods and cones, to change light energy into nerve impulses that the brain can interpret.

Rods:

Cones:

What is a blind spot?

Ewald Hering proposed an opponent-process theory, that color is processed in opponent pairs (red-green, yellow-blue, black-white). Light that stimulates one half of the pair, blocks the other half. So, you can see red OR green at any one spot at any given time but not both simultaneously. Think about it….red and green combine to form violet, but not reddish green! See diagram in book p. 106 (6.10)

THE NATURE OF SOUND

Sound is vibration. Feel your vocal cords when singing or talking. Vibrations are sent to your ear in pulses of air molecules. It can also travel in your bones, in water, etc. As you get older you gradually lose your ability to hear higher-pitched sounds.

Pitch:

Hertz:

Decibels:

See diagram on p. 108. Notice that any prolonged sound exceeding 85 dB can produce hearing loss! The hearing loss won’t be noticeable on a day-to-day basis, but exposure to any loud prolonged noise, will produce gradual, irreversible hearing loss.

Sound localization: knowing where a sound is coming from….to the left, to the right, in front of you, in back of you. Sounds signify important environmental events, such as danger. There are two important

cues in locating sound sources:

Step 1:

Step 2:

OTHER SENSES

Vision and hearing are vital senses. They are also the best understood. But what would life be like with no ability to taste or smell? Would you want to prepare meals? What if you lost the sense of touch? You would lose good touch like a good hug, but you would also lose the ability to detect pain. Wouldn’t that be great? Or would it? What about your sense of balance? Could you walk?

TASTE

Taste is a chemical sense. Receptor cells are located on the surface of your tongue and respond to the chemical structure of the food you eat. They can detect 5 tastes: ______, ______, ______, ______, ______. Babies have some natural abilities.

Taste receptors can be damaged by heat and tobacco smoke. But they get replaced in a few days.

We don’t all have the same sensitivity to taste. About a quarter of the population are supertasters! They experience tastes, especially bitter, more intensely than most of us do. They were the poison detectors of ancient civilization. Another quarter of the population are nontasters. They taste things less intensely than most of us. They do well in food shortage times where they are more willing to eat anything, no matter how bad it tastes. Eeeewww!

SMELL

Smell is also a chemical taste. Molecules given off by certain foods circulate in the air. See the diagram in your book, page 113. Taste and smell interact to produce flavor. So, when you have a cold or you plug your nose you probably can’t detect a flavor. If you plugged your nose and ate a starburst candy, what will happen? Explain.

Flavor is also connected to appearance. That’s why restaurants make food look nice! Feel or texture is as well. That’s why Ms. Blake doesn’t like shellfish. It might taste good but the smell and texture is repulsive to her.

TOUCH

Your skin is embedded with receptors that respond to various kinds of stimulation. The basic skin senses are ______, ______, ______and ______.

Your experience of other skin sensations flows from various combinations of these four basic skin senses.

What’s an itch?______

What is Hot a combination of?______

What is wetness a combination of?______

What is pain? Explain the gate-control theory:

Why is pain not only bottom-up processing but also top-down processing?

BODY SENSES

Most of us have the basic five senses, but two additional body senses are critically important to our functioning.

  1. Kinesthetic sense:
  1. Vestibular sense:

MODULE 7 – PERCEPTION

Have you ever tasted something that someone liked but you found it disgusting? Our perception of things can be quite different from the perception of others. Perception is a top-down processing system. Our experiences and expectations influence our perceptions as we organize and interpret incoming sensory information.

Gestalt Organizational Principles

Gestalt psychologists emphasize that the whole is greater than the parts. They believe this is how human perception occurs. We don’t focus on discrete, individual stimuli in our environment; rather we group them into more meaningful units.

Figure-ground Principles:

Gestalt psychologists pointed out that we naturally organize our environment into figure-ground relationships. We organize the visual field into objects (the figures) that stand out from their surroundings (the ground). The tendency to perceive figure and ground is not exclusively visual. We strive to identify the figure in other contexts as well, such as the predominant taste in a casserole, or the melody in a song.

Grouping Principles:

Gestalt psychologists also believed people are predisposed to organize stimuli by grouping them into understandable units. Several principles guide the way we group stimuli:

Similarity:

Proximity:

Closure:

Continuity:

Depth Perception

Try and imagine how difficult it would be if you couldn’t see in three dimensions or judge distance. Would you be able to operate your car? Probably not. Sports would also be impossible. Many other things would also be impossible. Is depth perception a result of nature or nurture? Read about the visual cliff p. 122. Working together your eyes and brain use a number of tricks to create third dimensions.

Some depth cues are binocular cues, which use both eyes, and monocular cues, requiring only one eye.

Binocular Cues: A good example of this for us is the view master toy you might have used as a child. The toy’s design relies on the binocular depth cue known as retinal disparity. Explain this:

Retinal disparity is most effective when viewing items close to you.

Another example of a binocular cue is convergence. Explain this:

Also, this is most effective at short distances.

Monocular Cues: People who have lost vision in one eye cannot use the above cues. They can calculate depth accurately using monocular cues, which continue to operate with the use of one eye. Artists can trick our two dimensional retinas into seeing three dimensional on a two dimensional canvas. There are several of those cues.

Relative size:

Relative motion:

Interposition:

Relative height:

Texture gradient:

Relative clarity:

Linear perspective:

Perceptual Constancy

One of the amazing qualities of human perception is perceptual constancy, perceiving the size, shape and lightness of an object as unchanging even as the image of the object on the retina of the eye changes. Imagine how scary the world would be if we did not have perpetual constancy! There are three main kinds of perpetual constancy.

1.

2.

3.

Perpetual Set

Do you have a favorite tv show? Are you ever disappointed when you watch it? Probably not. You expect it to be great because you love it. Perpetual set is a mental predisposition to perceive something one way and not another. It is a clear example of top-down processing. You can predispose someone into seeing something a certain way. This “power of suggestion” produced by perpetual set influences us in many ways. Six times as many preschoolers think French fries taste better when served in a Macdonald’s container instead of a white bag. Can you think of any other examples? Have you ever been told that playing a record backwards produces a message?
Have you heard of people seeing pictures of Jesus in pancakes? Or Pepsi cola symbols on lobsters?

Illusions

Perceptual illusions fascinate all of us. We can be tricked into misinterpreting sensory stimuli. Illusions provide clues to how our sensory and perceptual systems work. For many types of illusions, some basic perceptual principles help create the illusion.

Explain the following types of illusions and determine which principle underlies it.

Muller-Lyer Illusion:

Ames Room Illusion:

Gestalt Closure Illusion:

Light illusions:

Perception is the road we follow to make sense of the world. The constant stream of sensory input that bombards us is meaning unless we can interpret it properly.