Unit 4 Processes of Sensation
Overview
In Unit 4, we will explore processes of sensation; in Unit 5 we will examine perception. Sensation and perception are different yet unified processes. The world outside of the human body is full of sensory information – phenomena we can see, hear, touch, taste, and smell. A walk around Trinity Western University can ignite your perceptions with the shadows of lofty coniferous and flowering cherry trees, the sounds of geese honking, and the warming, fragrant air of a spring morning. The body has developed two specialized mechanisms to make sense of this abundance of information – sensation and perception. The textbook (Krause et al., 2018) defines sensation as the process of detecting external events with sense organs and turning those stimuli into neural signals. Perception involves attending to, organizing, and interpreting stimuli that we sense. At the sensory level, the sound of someone’s voice is simply air particles pushing against the eardrum, and the sight of a person is merely light waves stimulating receptors in the eye. All of this raw sensory information is then relayed to the brain, where perception occurs. Perception includes organizing the different vibrations of the eardrum in a way that allows you to recognize them as a human voice and linking together the stimulation of groups of receptors in the eye into the visual experience of seeing someone walking toward you (Krause et al., 2018). Our sensation and perception affect every aspect of what we can detect and how we experience it in this wonderful world.
Learning Outcomes
When you have completed this unit, you should be able to:
- Describe the key terminology relating to sensation and perception, the eye and vision, ear, hearing, and the vestibular system, and of touch and chemical senses.
- Explain stimulus thresholds, the principles of Gestalt psychology, how visual information travels from the eye through the brain to give us the experience of sight, and colour visions.
- Apply your knowledge of signal detection theory to identify hits, misses, and correct responses in examples.
- Analyze claims that subliminal advertising can influence your behaviour, how we perceive objects and faces.
- Apply your knowledge to explain how we perceive depth in our visual field, sound localization, touch, and how to determine whether you or someone you know is a “supertaster.”
- Describe the different characteristics of sound and how it correspond to perception, how the vestibular system affects our sense of balance, how pain messages travel to the brain, and the relationship between smell, taste, and food flavour experience.
- Analyze how musical beats are related to movement, and how different senses are combined together.
Activity Checklist
Here is a checklist of learning activities you will benefit from in completing this unit. You may find it useful for planning your work.
Learning Activities
- Read and Reflect – Chapter 4
- Review the Unit 4 – Course Notes (found on Course Notes tab)
- Complete the Subliminal Manipulation activity
- Complete the Colour Deficiencies and Colour Blindness activity
- Complete the How the Ear Works activity.
- Complete the All About Pain activity
Note
The course units follow topics in the textbook, Revel for An Introduction to Psychological Science by Krause et al. (4th Edition). For each unit, please read the pertinent chapter(s) before completing the assessment for the unit.
4.1 Thresholds of Perception
Thresholds of Subliminal Perception
The simplest way to distinguish sensation (the topic of this chapter) from perception (the topic of the next chapter) is to think of physical versus mental processes. The physical processes involved in processing a stimulus, such as pressure waves of a certain frequency, we call sensation. The mental response to the stimulus, perhaps interpreting it as a familiar voice, we call perception.
We consider sensation to be a “bottom-up” process because it starts with basic physical stimuli and moves up the sensory system to stimulate higher mental processes of interpretation. The mental processing of perception we call a “top-down” process because it starts with higher level mental processes, such as memories and expectations that lead us to recognize the physical sensation as a familiar voice.
The bottom-up processes of sensation obviously affect what we perceive since our sensory apparatus registers only a certain amount and type of the vast array of physical stimuli around us. Visual or auditory impairment will limit our perceptions even more. Some psychologists emphasize bottom-up processes and even consider perception itself to be primarily a bottom-up process.
On the other hand top-down processes also influence what we perceive. You may have had the experience of hearing your name above the din of a crowded and noisy room even though it was spoken no louder than all the other sounds of conversation. This “cocktail party effect” occurs because your higher mental processes are tuned to receive certain information more readily.
Activity: Read and Reflect
Take a moment to read through chapter 4 of your textbook and review the Course Notes for this unit. Consider how some of the themes and concepts you read about apply to what you have learned in this section.
Activity: Subliminal Manipulation
Subliminal Perception
What does all this have to do with thresholds and subliminal perception? Well first of all we should note that “limen” is another word for threshold. Since a threshold for perception is the minimum level at which a stimulus can be perceived, subliminal perception, means sub-threshold perception—a contradiction in terms! In practice, however, we use the term subliminal perception to refer to situations where a stimulus too weak to be noticed nevertheless has a measurable effect on subsequent behavior. So subliminal perception, or subliminal influence, is a bottom-up process whereby an undetectable stimulus influences us. Sound scary? Many people thought so when James Vicary claimed, in 1957, that he had influenced movie-watchers to drink Coke and eat popcorn without their awareness. Along with these claims, came equally strong denials that any such thing was possible. As usual, the truth was somewhere in the middle. The below links provide more information around Vicary’s claims, general information about subliminal perception, and some experiments for you to try:
- Popcorn Subliminal Advertising
- Investigating Subliminal Persuasion
- Subliminal Perception: Facts and Fallacies
After you complete the reading, consider the following questions:
- Of what value are thresholds? (Hint: What would it be like without them?)
- What do you know about thresholds that would make subliminal influence difficult?
- Why do claims of subliminal influence attract so much attention?
Be prepared to share your thoughts and insights with other members of the class
4.2 Vision
The Visual System
Most people enjoy the function of their vision everyday without putting much thought into the complex and integrative processes that are taking place neurologically for them to have sight. The visual system has many different parts that work together to produce an uninterrupted visual perception. The part of the visual system that most people are familiar with are the eyes. Visual data collected by a variety of cell then converge on the optic nerve. The optic nerves are connecting pathways that first go through the optic chiasm, where they divide and partially cross over to the contralateral side of the brain and then progress towards an area of the thalamus, known as the lateral geniculate nucleus (LGN). From the LGN the sensory information travels to the primary visual cortex in the occipital lobe and then to other parts of the brain for further processing and integration. Due to this activity, you are able to rapidly take in information from your visual field. To learn more about the visual system (and other senses), complete with illustrations, check out this site:
Activity: Colour Deficiencies and Colour Blindness
“More correctly called color vision deficiency, color blindness describes a number of problems in identifying various colors and shades. Abnormal color vision may vary from only a slight difficulty distinguishing among different shades of the same color to the rare inability to distinguish any colors.” The following sites will allow you test to see if you have a color vision deficiency and to see what a person with a color vision deficiency sees. Try the following:
After you complete the reading, consider the following questions:
- Some people do not know they are colorblind until they take a test for colorblindness. Sometimes this is not until they are adults. How do you know you are not colorblind (assuming you have not taken a colorblindness test)?
- What would you do to adapt if you lost your ability to see colors? If you know someone who is colorblind, describe how it has affected this person’s life.
Be prepared to share your thoughts and insights with other members of the class
4.3 Hearing
The physiology of hearing is very complex. The ear is designed to gather sound waves. Once those sound waves enter your ear canal a host of processes takes place that eventually results in hearing. The purpose of hearing is to imbue the sound waves with some sort of meaning. The meaning the sounds can influence our thoughts, emotions and our actions in various ways. For example, have you ever noticed that your voice seems to sound different when you hear it recorded? Why is that? The answer is that we normally hear our voice through the bones in our head as well as through the air. What we hear is quite different from what other people hear. You can demonstrate sound waves traveling through the head by taking a vibrating object, such as a fork which has been struck on a table, and placing it on the bone behind the ear—or even better, between the teeth.
When Beethoven became deaf, he is reported to have “listened” to piano playing by placing one end of his walking stick against the piano and clenching the other end of it between his teeth.
Activity: How the Ear Works
We being this activity by learning how the ear actually works. This following resources will not only provide an in-depth description of how the ear works, but it will also provide you with some illustrations and videos to ensure you accurately understand. Take a look:
Next, take a look at the following video. After looking at how the ear works, this video shows you a way to turn anything into a loudspeaker for those hard of hearing:
[Watch: How To Turn Anything Into A Speaker!] (https://www.youtube.com/watch?v=I1shcxHWQas){target=“_blank”}
After exploring the information above, consider the following questions:
- Hearing is sometimes called “the social sense.” Why might loss of hearing be more psychologically significant than even loss of vision?
Be prepared to share your thoughts and insights with other members of the class
4.4 Pain
Have you ever heard the statement that, “pain is all in your head”? What do you think about that statement? Well we do have an area of the brain known as the somatosensory cortex that receives and processes all sorts of touch information. However, to feel pain a number of process need to take place in your brain and body. Physiologically speaking, we experience pain through cells called nociceptors that leads to the process of nociception. Nociceptors are receptors that initiate pain messages that travel to the central nervous system. Nociceptors are located on nerve endings that can be found on our skin, teeth, corneas, and internal organs. Nociception is the activity of nerve pathways that respond to uncomfortable stimulation —for example, to sharp stimulation, such as a pin prick, or to extreme heat or cold (Krause et al., 2018). What is more is that our experience of pain is also influenced by memory, expectations, attention, stress, and negative emotions. As you’ve seen with vision and hearing, touch and pain are also very complex systems
Activity: All About Pain
By this point in your life, you have probably experienced pain in many different capacities. Below are a variety of resources intended to help you learn more about different types of pain. While you are not required to read each resource, it is suggested that you pick a few of personal interest to learn more and help you better understand the topic of pain.
After reading through these topics, consider the following question:
- What is the strangest or most surprising thing you have seen so far about pain?
Be prepared to share your thoughts and insights with other members of the class
Assessment
Refer to the course schedule for graded assignments you are responsible for submitting. All graded assignments, and their due dates, can be found on the “Assessment” tab.
In addition to any graded assignments you are responsible for submitting, be sure to complete all the Learning Activities that have been provided throughout the content - these are intended to support your understanding of the content.
Checking your Learning
Before you move on to the next unit, you may want to check to make sure that you are able to:
- Describe the key terminology relating to sensation and perception, the eye and vision, ear, hearing, and the vestibular system, and of touch and chemical senses.
- Explain stimulus thresholds, the principles of Gestalt psychology, how visual information travels from the eye through the brain to give us the experience of sight, and colour visions.
- Apply your knowledge of signal detection theory to identify hits, misses, and correct responses in examples.
- Analyze claims that subliminal advertising can influence your behaviour, how we perceive objects and faces.
- Apply your knowledge to explain how we perceive depth in our visual field, sound localization, touch, and how to determine whether you or someone you know is a “supertaster.”
- Describe the different characteristics of sound and how it correspond to perception, how the vestibular system affects our sense of balance, how pain messages travel to the brain, and the relationship between smell, taste, and food flavour experience.
- Analyze how musical beats are related to movement, and how different senses are combined together.