Chapter 6 Notes

### Chapter 6: Basic Concepts of Sensation and Perception

#### 6-1. Define sensation and perception, and explain what we mean by bottom-up processing and top-down processing.

- Sensation: The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

- Perception: The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

- Bottom-Up Processing: Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information. It involves processing sensory information as it is coming in.

- Top-Down Processing: Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.

#### 6-2. Identify the three steps that are basic to all our sensory systems.

1. Reception: The process of detecting physical energy (a stimulus) from the environment and changing it into neural signals.

2. Transduction: Converting the physical energy into a neural signal.

3. Transmission: Delivering the neural information to the brain to be processed.

#### 6-3. Distinguish between absolute thresholds and difference thresholds.

- Absolute Threshold: The minimum stimulus energy needed to detect a particular stimulus 50% of the time.

- Difference Threshold (Just Noticeable Difference, JND): The minimum difference between two stimuli required for detection 50% of the time; we experience the difference threshold as a just noticeable difference.

#### 6-4. Discuss how we are affected by subliminal stimuli.

- Subliminal Stimuli: Stimuli that are below the absolute threshold for conscious awareness. While they can influence feelings and thoughts temporarily, there is limited evidence to suggest that subliminal stimuli can produce powerful or enduring effects on behavior.

#### 6-5. Explain the function of sensory adaptation.

- Sensory Adaptation: The diminished sensitivity to a stimulus as a consequence of constant exposure to that stimulus. This allows us to focus on changes in our environment without being distracted by constant, unimportant background stimuli.

#### 6-6. Explain how our expectations, contexts, motivation, and emotions influence our perceptions.

- Expectations: Preconceptions and prior knowledge shape what we perceive. For instance, we might be more likely to see a shape as a letter of the alphabet if we expect to see a letter.

- Contexts: The surrounding environment can influence perception. For example, the same sound can be perceived differently depending on the context in which it is heard.

- Motivation and Emotions: Our desires and feelings can affect how we perceive stimuli. For example, a hill appears steeper when we are tired or carrying a heavy load.

### Vision: Sensory and Perceptual Processing

#### 6-7. Describe the characteristics of the energy that we see as visible light, and identify the structures in the eye that help focus that energy.

- Visible Light: A small portion of the electromagnetic spectrum that we can see, characterized by wavelengths between about 400 and 700 nanometers.

- Eye Structures:

- Cornea: The transparent outer covering of the eye; helps to focus incoming light.

- Pupil: The adjustable opening in the center of the eye through which light enters.

- Iris: The colored part of the eye, which controls the size of the pupil.

- Lens: The transparent structure behind the pupil that changes shape to help focus images on the retina.

- Retina: The light-sensitive inner surface of the eye, containing rods and cones plus layers of neurons that begin the processing of visual information.

#### 6-8. Describe how the rods and cones process information, as well as the path information travels from the eye to the brain.

- Rods: Photoreceptors in the retina that detect black, white, and gray; necessary for peripheral and twilight vision.

- Cones: Photoreceptors in the retina that detect fine detail and color, and function best in well-lit conditions.

- Pathway:

1. Light enters the eye and is focused on the retina.

2. Rods and cones convert the light energy into neural signals.

3. These signals are processed by bipolar and ganglion cells.

4. The axons of ganglion cells form the optic nerve, which transmits the information to the brain.

5. The optic nerve carries the visual information to the thalamus, and then to the visual cortex in the occipital lobe.

#### 6-9. Describe how we perceive color in the world around us.

- Trichromatic Theory: Suggests that the retina contains three types of color receptors (cones), each most sensitive to red, green, or blue. These receptors work together to produce the perception of color.

- Opponent-Process Theory: Proposes that we perceive color in terms of opposing pairs: red-green, blue-yellow, and white-black. Some neurons are excited by one color in the pair and inhibited by the other.

#### 6-10. Describe the location and function of the feature detectors.

- Location: Feature detectors are located in the visual cortex of the brain.

- Function: These neurons respond to specific features of a stimulus, such as shape, angle, or movement, and play a crucial role in visual perception.

#### 6-11. Explain how the brain uses parallel processing to construct visual perceptions.

- Parallel Processing: The brain's ability to process many aspects of a visual scene simultaneously. This includes processing information about color, motion, shape, and depth all at once to create a cohesive visual experience.

#### 6-12. Describe how Gestalt psychologists understood perceptual organization, and explain how figure-ground and grouping principles contribute to our perceptions.

- Gestalt Psychology: Emphasized our tendency to integrate pieces of information into meaningful wholes.

- Figure-Ground: The organization of the visual field into objects (figures) that stand out from their surroundings (ground).

- Grouping Principles: Methods by which our brains naturally organize stimuli into coherent groups, including proximity, similarity, continuity, closure, and connectedness.

#### 6-13. Explain how we use binocular and monocular cues to perceive the world in three dimensions, and describe how we perceive motion.

- Binocular Cues: Depth cues that depend on the use of two eyes, such as retinal disparity (the slight difference in images between the two eyes) and convergence (the inward angle of the eyes when focusing on a close object).

- Monocular Cues: Depth cues available to either eye alone, such as relative size, interposition, relative clarity, texture gradient, relative height, relative motion, linear perspective, and light and shadow.

- Motion Perception: Involves the brain interpreting signals from the visual system about changes in position over time, including the movement of objects and our own motion.

#### 6-14. Explain how perceptual constancies help us construct meaningful perceptions.

- Perceptual Constancies: Allow us to recognize objects as unchanging despite changes in illumination, distance, and angle of view. This includes:

- Shape Constancy: Perceiving the form of familiar objects as constant even when our retinas receive changing images of them.

- Size Constancy: Perceiving objects as having a constant size, even while our distance from them varies.

- Color Constancy: Perceiving consistent color in objects, even if changing illumination alters the wavelengths reflected by the object.

#### 6-15. Describe what research on restored vision, sensory restriction, and perceptual adaptation reveals about the effects of experience on perception.

- Restored Vision: Studies of individuals who gained sight after being blind from birth show that they can detect figure-ground relationships and distinguish colors, but often struggle with recognizing objects and faces.

- Sensory Restriction: Experiments with animals raised without exposure to certain stimuli (like light or patterns) show that sensory deprivation can result in lifelong deficits in sensory and perceptual capabilities.

- Perceptual Adaptation: The ability to adjust to an artificially displaced or even inverted visual field. Humans can adapt to changes in their visual environment, demonstrating the flexibility of the perceptual system.

### The Nonvisual Senses

#### 6-16. Describe the characteristics of air pressure waves that we hear as sound.

- Sound Waves: Variations in air pressure that create waves of compression and rarefaction. Key characteristics include:

- Frequency: Determines the pitch of a sound (measured in Hertz).

- Amplitude: Determines the loudness of a sound (measured in decibels).

- Timbre: The quality or color of a sound, allowing us to distinguish different sounds with the same pitch and loudness.

#### 6-17. Explain how the ear transforms sound energy into neural messages.

1. Sound waves enter the ear canal and cause the eardrum to vibrate.

2. Middle ear bones (ossicles - hammer, anvil, stirrup) amplify the vibrations and transmit them to the cochlea in the inner ear.

3. Cochlea: Fluid vibrations cause the basilar membrane to ripple, bending the hair cells lining its surface.

4. Hair cells convert these vibrations into electrical signals.

5. Auditory nerve transmits these signals to the brain's auditory cortex via the thalamus.

#### 6-18. Explain how we detect loudness, discriminate pitch, and locate sounds.

- Loudness: Detected by the number of activated hair cells in the cochlea.

- Pitch

:

- Place Theory: Different frequencies stimulate different places on the basilar membrane.

- Frequency Theory: The rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone.

- Sound Localization: Determined by the differences in the time and intensity of sound waves reaching each ear.

#### 6-19. Describe how we sense touch.

- Touch: Sensed through receptors in the skin that detect pressure, temperature, and pain. Signals from these receptors travel through the nervous system to the brain's somatosensory cortex.

#### 6-20. Describe the biological, psychological, and social-cultural influences that affect our experience of pain, and discuss how placebos, distraction, and hypnosis help control pain.

- Biological Influences: Include genetic differences, the presence of endorphins, and the functioning of the nervous system.

- Psychological Influences: Include attention to pain, learning based on experience, and expectations.

- Social-Cultural Influences: Include cultural attitudes toward pain and the presence of others.

- Pain Control:

- Placebos: Can trigger the brain's release of endorphins, which help alleviate pain.

- Distraction: Can reduce the perception of pain by diverting attention.

- Hypnosis: Can alter the perception of pain through suggestion.

#### 6-21. Explain how our senses of taste and smell are similar, and how they differ.

- Similarities: Both are chemical senses; they detect molecules in the environment (taste in food, smell in air).

- Differences:

- Taste: Involves receptor cells in taste buds on the tongue that respond to sweet, sour, salty, bitter, and umami.

- Smell: Involves receptor cells in the nasal cavity that detect airborne molecules, with the olfactory bulb processing the information.

#### 6-22. Explain how we sense our body’s position and movement.

- Kinesthesia: The system for sensing the position and movement of individual body parts through receptors in muscles, tendons, and joints.

- Vestibular Sense: The sense of body movement and position, including the sense of balance, provided by the inner ear's semicircular canals and vestibular sacs.

#### 6-23. Describe how sensory interaction influences our perceptions, and define embodied cognition.

- Sensory Interaction: The principle that one sense may influence another, such as the taste of food being influenced by its smell.

- Embodied Cognition: The influence of bodily sensations, gestures, and other states on cognitive preferences and judgments.

#### 6-24. List the claims of ESP, and discuss the conclusions of most research psychologists after putting these claims to the test.

- Claims of ESP: Include telepathy (mind-to-mind communication), clairvoyance (perceiving remote events), and precognition (perceiving future events).

- Research Conclusions: Most psychologists remain skeptical about the existence of ESP, citing a lack of replicable evidence and methodological issues in studies claiming to demonstrate ESP abilities.