Chapter 3 Sensation and Perception Lectures

[Ready for Fall 2026]

Updated: 2026-09-02 3:5s8 PM CDST

• When you smell for a living (p. 101)
  • Anosmia is when one cannot smell.
  • For some people, Covid altered or eliminated their sense of smell
  • Helene Barre, a winemaker, lost her sense of smell due to Covid.
  • Many people are in jobs that demand that they have a normal sense of smell
  • FYI, a few minutes ago I was outside and smelled rain coming before the drops fell
  • As you will see in this chapter, humans sense of smell is the least understood of the senses.
• HOW WE SENSE AND PERCEIVE THE WORLD (p. 86)
• Bottom up processing
  • Sensors detect sensations and transmit those to the brain
• Top down processing
  • The brain, via its previous experience, attempts to perceive a previous situation
• Look at the figure below
  • a) is what I first sensed one night coming home on US 371 S from Prescott.
    • That was bottom up
  • But, in a flash, I perceived it as a funny 18 wheel truck's back door
    • That was top down
  • b) is when I passed the truck
    • It was not a funny door, it was a tower
    • When I first looked at it, my brain could not interpret it quickly.
    • When I passed all of the sensations made sense.

• PSYCHOLOGICAL INQUIRY (p. 104): Old Woman or Young Woman
  • Reversible Illusions
    • Old Woman and Young Woman: This is a similar reversible illusion to the one in the text. It's impossible to see them both at the same time.
  Psychophysics
  • Thresholds: absolute and relative (JND)
  • Ernst Weber and Gustav Fechner: Fathers of psychophysics
  • Know the definition of perception: the process of organizing and interpreting sensory information
  • Sensation is the immediate detection of a stimulus, e.g., the first instant you notice pain
  • Subliminal perception has never been satisfactorily demonstrated.
• Physical Forces and Associated Sensory Systems
  • Light, sound, dissolved chemicals, volatile chemicals, mechanical stimuli, gravity and acceleration, magnetic fields, electrical fields, echolocation
  • The process of sensation and perception starts with the sensory receptors identified above.
  • Humans do not have receptors that detect the last threemay
  • Synesthetes may perceive more than one perception modality simultaneously, e.g., shapes plus sounds
• Comparative Sensory Systems
  • Deers and orange: deer can detect orange but rely on other senses more
  • Body odor: human's odor detection is suppressed culturally via deodorants, perfumes, and colognes, but odor preferences vary culturally
  • Rat's eyes/pigeon's eyes: rats have no cones, pigeons have no rods
  • Transducers: all sense organs transduce (convert) physical energy into neural activity
• Perception
  • Attention
    • Selective: focusing on one stimulus and not paying attention to others.
    • Inattentional blindness: not perceiving an aspect of a percept while focusing on another (look for the gorilla) Video
      • Simon's videos demonstrate how selective our perception can be.
    • Adaptation: after exposure to a weak, repetitive stimulus people quit paying attention to it.
  • Stimulus Factors in Perception: Read how stimulus characteristics such as change, novelty, optimal complexity (e.g., "over my head" or "too simple"), repetition, intensity, contrast, and movement affect perception.
  • Individual Factors in Perception: In addition, everyone perceives the world differently. Examples include individual interests, motivation, and experience.
  • Perceptual Set
    • Demo: read what is on the following page be sure to scroll down to see the second example.
      • Read them word for word.
      • Use your browser's Back button to return to this page.
      • ARE YOU SURE YOU READ WHAT YOU THINK YOU DID? CHECK AGAIN.
        • What is a "the the bird?"
        • How can you walk "though the woods?"
      • Notice how your expectations altered your perceptions.
        • In the first case you missed a word
        • In the second case you added a letter
  • Depth Perception
    • Monocular Cues: These cues for depth perception only require one eye to work. Of course, they work with two eyes as well. They are: linear perspective, texture, haze, interposition, relative size and accommodation.
    • Binocular Cues: There are two binocular cues. Retinal disparity (aka stereoscopic vision) is the most powerful of all of the depth perception cues. Binocular convergence is the other. It is the cue provided by the eyes rotating inward as an object approaches the face.
    • Motion Parallax: Refers to relationship of known object size, nearness, and perceived velocity.
  • Visual Constancies
    • Size, shape, color (brightness). Again, previous knowledge profoundly affects perception.
  • Gestalt Principles of Perception
    • Gestalt Psychology: A type of psychology that originated in Germany in the 1930s that did much work in rules of perception
    • Phi (QuickTime Movie)
    • Explanation: Wertheimer discovered the phi phenomenon (apparent movement) while riding on a train.
    • No one knows exactly what Wertheimer observed in 1910 through the train window as he was traveling from Vienna to begin a vacation.
      • One version (Hunt, 2007) states that he noticed that the more distant telegraph poles, houses, and hilltops along the route seemed to be speeding along with the train.
      • He realized the “movement” he was observing had to be somehow coming from his brain.
      • To an observer outside the train, all of those stimuli would appear stationary.
    • Figure-Ground and Camouflage: the more pronounced the difference between an object and its surround, the more perceptible it is. That is strong figure ground. But, when the object can no be easily discerned from its background it is hard to perceive. Camouflage is the intentional attempt to destroy the figure-ground relationship.
    • Closure: Look at the figure, none of them are triangles, but they are perceived as such. Perceptually, the triangle is such a prominent gestalt and it is nearly impossible not to see it.
    • Proximity: Look at the figure. There are 16 squares, but the perception depends on the distance between them.
    • Similarity: Look at the figure, the gestalt rule here is to perceived similar stimuli as belonging together.
    • Continuity1 and Continuity2: Look at both of these. The two figures in the first one will be linked together and see what happens. The original two stimuli are now hard to perceive.
  • Auditory Habituation: low intensity, repetitive sounds tend to be no longer noticed (e.g., perceived).
  • Illusions
    • Muller-Lyer and Muller-Lyer (solution) Look at both. This is a powerful illusion.
    • Devils' Pitchfork: Another powerful illusion. Count the tines on the left and their base on the right.
• PSYCHOLOGICAL INQUIRY : Priming and Magic (p. 109)
  • Notice how magicians prime, or give implicit cues to audience members hoping to influence their responses.
    • Subliminal Perception (p. 109)
      • "limen" is another word for "threshold"
      • So, subliminal means below the threshold
      • The APA's Dictionary of Psychology notes:
        • Subliminal perception is the registration of stimuli below the level of awareness, particularly stimuli that are too weak (or too rapid) for an individual to consciously perceive them.
        • There has been much debate about whether responses to subliminal stimuli actually occur and whether it is possible for subliminal commands or advertising messages to influence behavior.
        • Experimental evidence indicates that subliminal commands may not directly affect behavior but may prime later responses
• Signal Detection Theory
  • The APA's Dictionary of Psychology notes:
    • Signal Detection Theory (SDT) is a body of concepts and techniques from communication theory, electrical engineering, and decision theory that were applied during World War II to the detection of radar signals in noise.
    • These concepts were applied to auditory and visual psychophysics in the late 1950s and are now widely used in many areas of psychology.
    • An important methodological contribution of SDT has been the refinement of psychophysical techniques to permit the separation of sensitivity from criterial, decision-making factors.
    • SDT has also provided a valuable theoretical framework for describing perceptual and other aspects of cognition and for quantitatively relating psychophysical phenomena to findings from sensory physiology.
  • Example
    • Someone calls your name and you respond: Hit (correct)
    • Someone calls your name and you do not respond: Miss (mistake))
    • You believe someone called your name (they did not) and you respond: False Alarm (mistake)
    • No one called your name and you did not respond: Correct Rejection (correct)
• THE VISUAL SYSTEM (p. 97)
  • Vision
    • Light
      • Electromagnetic radiation visible to human eye
      • ROY G. BIV is the acronym for the colors visible to humans
        • Red
        • Orange
        • Yellow
        • Green
        • Blue
        • Indigo
        • Violet

  See how tiny the visible spectrum is? It is that thin, white line below:

from: https://www.livescience.com/50678-visible-light.html

• Eye Diagram: Know the parts of the eye: cornea, lens, pupil, rods, cones, and fovea.
  • Retina
  • Fovea
  • Blind spot is where the neurons leave the eye
  • Presbyopia is the aging and hardening of the lens. That makes the focal length longer and leads to the purchase of reading glasses
• Rods and Cones
  • Distribution in human eye/function (many more rods than cones)
  • Function of each
• Dark Adaptation
  • Red light: has lower energy and dark adaptation is thus quicker from red light than from white light
  • Time: night vision takes about 30 minutes
  • Night blindness: some humans have no rods and thus little night vision
  • Graph the lower the curve, the better the night vision
• Higher Level Processing
  • Feature detectors: parts of brain that detect specific visual stimuli
  • The cortical cell shown in the diagram above shows that the feature detector cell fires maximally when the visual stimulus is vertical. Other feature detectors fire when stimulated by dots or lines at different angles.
• Color Vision
  • Trichromatic Theory (Young-Helmholtz): red, green, blue cones
  • Opponent Process (Hering): red-green, blue-yellow, black-white cones
  • Type of color blindness
    • Red-Green is most common
    • Total color blindness
  • Stroop effect: takes more time to name colors when the words are them selves color names: e.g., RED vs RED (answers should be the color names: red, blue
    • See page 111

THE AUDITORY SYSTEM (p. 112)

• The Nature of Sound and How We Experience It
  • Physical Dimensions, Perceptual Dimensions, and Form of Sound Waves
• Amplitude: distance from top to bottom of peaks.
  • Measured in decibels.
  • Perceived as loudness.
• Frequency: distance from peak to peak in sound waves.
  • Measure in Hertz (cycles/second).
  • Perceived as tone
• Complex Sounds: Many frequencies blended together
  • Music is an example
  • Timbre is the perceptual quality of a sound wave
    • Responsible for difference in human voices and perception of same frequency from different musical instruments
• Ear Diagram
• The Ear
  • Know the structure and parts: outer: pinna, auditory canal; middle: eardrum, hammer, anvil, stirrup; inner: cochlea, vestibular organ
  • Medium: sound requires a medium (solid, liquid, gas) and sound cannot travel in a vacuum
  • Helium: inhale helium and speak normally, voice sounds higher because helium is a lighter element than air (nitrogen plus oxygen)
  • Your recorded voice?: recorded voice sounds strange because listeners hear themselves via the air and their facial bones
• Sound Localization
  • Pinnae: the outer ear structures. Some animals have moveable outer ears, humans do not.
  • Move head: in order to localize sounds, humans must move their heads so that sound enters on ear first and then the other. Sound is slow enough to hit one ear first and then the other. But, if the sound waves hit both ears simultaneously (e.g., when coming from front or back) sound localization is impossible.
  • Slow: comparared to the speed of light, sound is very slow.
  • Cocktail party phenomenon: hearing your name from another nearby source while attending to your own conversation
    • In other words, you are paying attention to more than the conversation you are in.
• Pony Express
  • Horse's ears: in this children's story a pony express rider escapes harm by watching his pony's ears and riding in the opposite direction the pony's ears point.

• Hearing Aids
• Cheap vs Expensive: the cheapest hearing aids amplify all frequencies; they are just louder. Expensive hearing aids, especially those using AI, can be programmed to only amplify frequencies that the hearer has difficulty hearing and by blocking the frequencies of background noises.

OTHER SENSES (p. 118)

• Skin Senses: Some consider the skin as the largest organ of the body. Detectors in the skin sense: touch, hot, cold, and pain.
  • Skin Diagram: the hypothetical diagram shows small patches of skin might be. Note that some areas of the skin are unable to sense any stimuli.
  • Brass Instrument Psychology
    • One place psychology started. Many early psychologists (late 19th century) focused on sensation and perception, and the instruments the used were largely made of brass.
  • Pain: read. Explains: free nerve endings, money spent on pain, role of the environment, physiology, analgesics, and anesthetics.
    • Gate theory: posits fast and slow pain pathways and "gate" that either allows pain signal through or not see video
    • Psychology of pain: WWII doctors discovered that soldiers traumatically wounded and brought to hospitals reported less pain than did their patients from civilian practice undergoing similar trauma (e.g., traumatic limb amputations). For those soldiers going to the hospital was better than staying in combat and possibly being killed. Consider civilians going to the hospital. That is very different because they view the hospital as a place where they will experience more, not less, pain.
• Chemical Senses
  • The Tongue: the tongue contains four separate areas (taste buds) to detect tastes plus an additional sensation: umami
    • Taste buds are housed on the tongue
  • The Four Tastes: the four basic tastes are: sweet, sour, salty, and bitter
    • Umami too: Umami is a brothy or meaty taste. Foods high in the amino acid glutamate provide the sensation. Examples include: parmesan cheese, seaweed, miso soup, and mushrooms.
  • The Nose: the nose is the organ of odor recognition. It is the least well known of the senses.
    • Odor Perception: One reason studying odor perception is difficult is because we possess few words that adequately describe odors. In Cain's (1982) participants were asked to identify odors from familiar sources. Johnson's Baby Powder and chocolate were the most recognized stimuli.
    • The sense of smell does not connect through the thalamus. All of the other senses do first connect to the thalamus.
    • The olfactory epithelium is where the sense organs for smell are located.
  • Savoring: Eating involves all of the senses. Imagine a plate of fajitas arriving at the table. It sizzles, smells, has visual appeal, is hot, and may be spicy enough to cause pain.
    • All senses involved
    • Disgust: One way to study savoring is to look at its opposite: disgust. Rozin has made a career out of studying disgust and offers examples of chocolate fudge shaped like dog droppings and rotting flesh. My disgusting example is bean dip. Like it? How about if its served in a diaper?
  • Your House Stinks!: It does, but sensory fatigue (adaptation) explains why its not perceived.
• The Kinesthetic and Vestibular Senses
  • Kinesthesis: This system consists of receptors in muscle fibers and joints that inform the location of body parts.
    • Demos:
      • 1) touch the tips of your two index fingers behind your head. Did they touch exactly together, or were they a little off.
      • 2) Close your eyes and touch the tip of your nose with your index fingers alternately. How close were you? No try it with both eyes open. Better, right? Both of these are examples of proprioreception.
    • Upright?: Kinesthesis also informs about being upright or tilted. Imagine walking uphill or downhill, how do you react?
    • Rod and frame test: The rod and frame test measures the possible discrepancy between gravitational and visual cues. People who respond more to the orientation of the room to perceive the upright are termed "field dependent" while people who respond more to gravity are called "field independent."
    • Phantom limb: Often, traumatic or surgical loss of limb is not noticed kinesthetically, meaning that the person still perceives the limb as attached and present. Itch and pain often accompany phantom limb. For example, a foot may no longer be attached but the person feels pain as if the foot were still there.
  • Vestibular System: The vestibular system is in the inner ear and senses acceleration, either due to gravity or to change in velocity. Children often spin until they can no longer remain upright. They fall and nystagmus takes place. That's the perception that the world is spinning around them. As a two-dimensional species, humans often get in trouble in 3D environments such piloting an airplane or scuba diving.
    • Balance: The vestibular system is one component of the human balance system. Sometimes, people will be unable to maintain their balance when they have a severe ear infection.
    • "Balance is achieved and maintained by a complex set of sensorimotor control systems that include sensory input from vision (sight), proprioception (touch), and the vestibular system (motion, equilibrium, spatial orientation); integration of that sensory input; and motor output to the eye and body muscles. Injury, disease, certain drugs, or the aging process can affect one or more of these components. In addition to the contribution of sensory information, there may also be psychological factors that impair our sense of balance." See Source of quote

SENSATION, PERCEPTION, AND HEALTH AND WELLNESS (p. 136)

• All of our senses require us to take care of them in order to not have them deteriorate or disappear.
  • We should:
    • Eat right to aid our vision
    • Not expose ourselves to loud noises
    • Enjoy observing the natural world