Sensation and Perception in Psychology: Past Paper

Ch.3 Mod.8 – sensing the worls around us Sensation and Perception: Key Concepts  Sensation: Activation of the sense organs by a source of physical energy.  Perception: Sorting, interpretation, analysis, and integration of stimuli by the sense organs and brain.  Stimulus...

Ch.3 Mod.8 – sensing the worls around us Sensation and Perception: Key Concepts  Sensation: Activation of the sense organs by a source of physical energy.  Perception: Sorting, interpretation, analysis, and integration of stimuli by the sense organs and brain.  Stimulus: Energy that produces a response in a sense organ. Study Alert:  Sensation = Physical response (activation of sense organs).  Perception = Psychological response (interpretation by brain). Psychophysics: Study of the relationship between the physical aspects of a stimulus and our psychological experience of it. Senses Beyond the Five: Humans have more sensory abilities than just sight, sound, taste, smell, and touch. For instance:  Touch: Includes pain, pressure, temperature, vibration.  Vision: Has subsystems for day and night vision.  Hearing: Involves not only sound but also balance. ABSOLUTE THRESHOLDS:DETECTING WHAT’S OUT THERE/STIMULI  Absolute Threshold: The lowest intensity of a stimulus that can be detected by an organism. It is the stimulus intensity detected 50% of the time.  Noise: Background stimulation that interferes with the perception of other stimuli. It affects all senses, not just auditory. Key Concepts:  As the strength of a stimulus increases, the likelihood of detection increases gradually.  A small stimulus is often enough to produce a response(e.g., feeling a bee's wing from 1 cm away).  Sensitivity of Senses: Our senses are highly sensitive, and if they were any more acute, it could lead to distractions (e.g., hearing air molecules hitting the eardrum). Ideal vs. Real Conditions:  Absolute thresholds are measured under ideal conditions, but real-life conditions may involve noise, making detection harder. DIFFERENCE THRESHOLDS:NOTICING DISTINCTIONS BETWEEN STIMULI  Difference Threshold: o The smallest level of added or reduced stimulation required to sense that a change in stimulation has occurred. Also known as the just noticeable difference (JND). o The difference threshold is the minimum change needed to detect a difference between two stimuli. o The size of the change needed for detection depends on the initial intensity of the stimulus.   Weber’s Law: States that the just noticeable difference is a constant proportion of the intensity of the initial stimulus, rather than a constant amount. Applications:  In a quiet room, a cellphone ring is more noticeable than in a noisy room.  The moon appears dim in the late afternoon but brighter in the night sky due to relative intensity differences. Study alert: Remember that Weber’s law holds for every type of sensory stimuli: vision, sound, taste, and so on. SENSORY ADAPTATION:TURNING DOWN OUR RESPONSES Adaptation: An adjustment in sensory capacity after prolonged exposure to unchanging stimuli. Key Points:  Sensory Nerve Receptors: These receptors are most responsive to changes in stimulation, not constant stimulation. After prolonged exposure to a stimulus, the receptors become less responsive and stop firing messages to the brain.  Constant Stimulation: Does not produce a sustained reaction.  Example: In a movie theater, you initially notice the smell of popcorn, but after a few minutes, you barely notice it anymore due to sensory adaptation. Why It Happens:  Sensory receptors become less sensitive after repeated exposure to strong stimuli.  Adaptation allows the brain to mentally "turn down the volume" of constant stimuli, making them less noticeable over time. Examples of Sensory Adaptation:  Loud Tone: Repeated exposure makes the sound seem quieter.  Cold Water: Initially unpleasant, but the body adapts over time, and the cold becomes less noticeable. Contextual Influence:  Judgments of Stimuli: Our judgments are influenced by the context in which they are made. For example, lifting a small envelope with the same weight as a large one can make the small envelope seem heavier due to the context of its size. Mod. 9 -- vision VISION  Vision and Light o Vision begins with light, which is electromagnetic radiation. o Light is measured in wavelengths, which are the distances between peaks in lightwaves. o The human eye can detect a specific range of these wavelengths, called the visual spectrum, which includes the colors of the rainbow from violet to red.  Structure of the Eye:  Cornea: The transparent, protective outer layer of the eye that refracts light to focus it more sharply.  Iris and Pupil: The iris is the colored part of the eye, and the pupil is the dark hole in the center of the iris. The pupil’s size changes depending on the amount of light in the environment, dilating in dim light and contracting in bright light.  Lens: Located behind the pupil, the lens focuses light onto the retina by changing its thickness (a process called accommodation). It becomes flatter for distant objects and rounder for close objects.  Retina and Receptors:  1. The retina converts light into electrical impulses for transmission to the brain.  It has two types of light-sensitive receptor cells: o Rods: Cylindrical cells sensitive to dim light and responsible for peripheral and night vision. o Cones: Cone-shaped cells responsible for sharp focus, color perception, and vision in bright light. Cones are concentrated in the fovea, a sensitive area of the retina.  Dark Adaptation: The process of adjusting to low light, which takes longer for rods (20–30 minutes) than cones (a few minutes).  Neural Transmission: 2. When light stimulates rods and cones, it triggers a chemical change in their proteins (rhodopsin in rods) that generates neural responses. 3. These signals are passed to bipolar cells and then to ganglion cells. 4. The optic nerve, composed of ganglion cell axons, carries visual information to the brain.  There is a blind spot where the optic nerve exits the retina, as no rods or cones are present there.  Processing in the Brain: 5. The neural impulses travel through the optic nerve and meet at the optic chiasm, where the left and right visual fields are processed in opposite hemispheres of the brain. 6. Feature detectors in the brain process visual stimuli like shapes and patterns.  Peripheral Vision and Blind Spots: Peripheral vision allows us to see objects outside our main focus, and the blind spot is compensated for by surrounding information, allowing us to "fill in" the missing visual data automatically. COLOR VISION AND BLINDNESS  Normal Color Vision: A person with normal color vision can distinguish at least 7 million colors.  Color Blindness: o About 7% of men and 0.4% of women are color blind. o People with color blindness often see the world as dull and lacking contrast. o In the most common form of color blindness, red and green are indistinguishable, while other forms may cause difficulty in distinguishing between yellow and blue. In rare extreme cases, individuals see no color at all Theories of Color Vision There are two main theories that explain how humans perceive color:  Trichromatic Theory: o Proposed by Thomas Young and Hermann von Helmholtz in the 1800s. o Suggests that there are three types of cones in the retina, each responsive to different wavelengths of light:  Blue-violet cones  Green cones  Yellow-red cones o Color perception is influenced by the relative activation of these cones. For example, when we see a blue sky, the blue-violet cones are activated, and the other cones are less active.  o Limitation: The trichromatic theory struggles to explain the phenomenon of afterimages. When staring at a colored object (e.g., the U.S. flag), the colors in the afterimage appear different from the original. This suggests a flaw in the trichromatic model.  Opponent-Process Theory: o Proposed by Ewald Hering in the 19th century. o Suggests that color receptors are linked in pairs, working in opposition to each other:  Blue-yellow pairing  Red-green pairing  Black-white pairing o When an object reflects light that contains more blue than yellow, the blue receptors are stimulated, while the yellow receptors are inhibited. The object appears blue. o Afterimages: The opponent-process theory explains afterimages as a result of receptor fatigue. For example, staring at yellow reduces the sensitivity of the yellow receptors, causing the image to appear blue when looking at a white surface. This is temporary, as the receptors regain their ability to respond. Combined Insights: Both trichromatic and opponent-process theories contribute to our understanding of color vision:  Trichromatic processes operate in the retina, where the three types of cones respond to different light wavelengths.  Opponent mechanisms work both in the retina and in later stages of neural processing, explaining phenomena like afterimages and color contrasts. Study alert: Keep in mind that there are two explanations for color vision: trichromatic and opponent- process theories. APPROFONDIMENTI -A Graphic Designer How might you market your products to those who are color blind versus those who have normal color vision? Understanding Color Blindness for Marketing as a Graphic Designer Marketing products to people who are color blind versus those with normal color vision requires an approach that considers differences in color perception. Here’s how a graphic designer might tackle this challenge: Understanding Color Blindness 1. Types of Color Blindness: o Deuteranopia: Difficulty distinguishing between green and red. o Protanopia: Inability to distinguish red tones. o Tritanopia: Difficulty distinguishing between blue and yellow. o Achromatopsia: Total absence of color perception (rare). 2. Prevalence: About 8% of men and less than 1% of women have some form of color blindness. Marketing Strategies for Both Groups 1. Inclusive Design:  Use contrast in brightness instead of relying solely on color differences. For example, combine light and dark tones to highlight key elements.  Choose combinations visible to both color-blind individuals and those with normal vision, such as: o Blue and orange. o Purple and yellow.  Avoid problematic combinations like red-green or green-brown. 2. Patterns and Textures:  Use textures, lines, or patterns to differentiate elements instead of relying only on color. For example, use striped or dotted designs to distinguish different sections. 3. Test Your Design:  Use online tools to simulate how color-blind individuals perceive the design (e.g., Coblis or Adobe Color Accessibility Tools).  Ensure that critical information is recognizable even without color. 4. Clear Messaging:  Accompany color with text labels or symbols to enhance understanding (e.g., use icons alongside colors in charts or maps). 5. Appropriate Color Palettes:  Use universally distinguishable colors like blue or yellow.  For people with normal vision, leverage vibrant and eye-catching colors to grab attention. Practical Examples  For Color-Blind Audiences: o An infographic using shades of gray with different textures for categories. o A logo with strong brightness contrast or a monochromatic design.  For Normal Vision Audiences: o More complex designs with vivid colors and gradients, taking advantage of the full spectrum. Conclusion A well-thought-out design should work for both groups. Using contrast, textures, and clear messaging ensures that products are accessible to all, increasing their impact and marketing reach. Mod.10 – hearing and the other senses SENSING SOUND 1. Sound Localization  Definition: The process by which we identify the direction of a sound's origin.  Mechanism: 1. Outer ear,located on opposite sides of the head, aiding in localization. 2. Wave patterns enter each ear at slightly different times. 3. The brain uses timing discrepancies as clues. 4. Outer ears delay or amplify specific frequencies differently Structure of the Ear  Outer Ear: oFunction: Collects sound and funnels it into the auditory canal (acts as a reverse megaphone). o Auditory Canal: A tube-like passage leading to the eardrum.  Middle Ear: o Middle ear acts as a mechanical amplifier. o Eardrum:  Vibrates when hit by sound waves.  Vibrations increase with sound intensity.  Eardrum’s larger size compared to the oval window increases the force of sound waves o Bones of the Middle Ear:  Hammer, Anvil, Stirrup:  Act as levers to transmit and amplify vibrations.  Vibrations are transferred to the oval window. o Oval Window: A thin membrane connecting to the inner ear.  Inner Ear: o Function: Converts sound vibrations into neural signals for the brain. o Cochlea:  Coiled, fluid-filled structure.  Vibrates in response to sound. o Basilar Membrane:  Runs through the cochlea, dividing it into upper and lower chambers.  Contains hair cells. o Hair Cells:  Located on the basilar membrane.  Bend with cochlear vibrations, transmitting neural messages to the brain. The physical aspect of sound Sound Waves  Definition: Physical movement of air molecules in regular, wavelike patterns caused by vibrating sources.  Medium: is the technical term to describe the material (for example air, water, or any substance that allows the propagation of sound waves) that transmits sound waves. Frequency  Definition: Number of wave cycles per second.   Low Frequency: Low pitch, few wave cycles.  High Frequency: High pitch, many wave cycles.  Human Hearing Range: 20–20,000 cycles per second. Amplitude  Definition: Spread between peaks and valleys of air pressure in a wave.  Soft Sounds: Small peaks and valleys.  Loud Sounds: Large peaks and valleys.  Measured in Decibels: o Painful sounds >120 dB. Age & Frequency Sensitivity  Effect of Aging: Reduced ability to detect high-pitched sounds. Theories of Hearing 1. Place Theory: o Different areas of the basilar membrane respond to different frequencies. o High frequencies: Near oval window. o Low frequencies: Near cochlea’s inner end. 2. Frequency Theory: o Entire basilar membrane vibrates in response to sound. o Nerve impulses correspond to sound frequency. 3. Combination: o Place theory explains high frequencies. o Frequency theory explains low frequencies. o Medium frequencies use both. Auditory Processing  Auditory Cortex: o Transmits signals from the ear to the brain. o Neurons respond to specific sounds (e.g., tone, clicks).  Speech Perception: o Involves fine discrimination of similar sounds. o Recognizes voice, accent, emotional state. Echolocation  Definition: Using sound waves and echoes to locate objects.  Applications: Used by bats and visually impaired humans. Hyperacusis  Definition: Sensitivity to sounds tolerable to others.  Cause: Exposure to loud sounds.  Cure: None. Balance & Vestibular System  Structures Involved: o Semicircular canals: Contain fluid to detect rotational/angular movement.  o Otoliths: Motion-sensitive crystals that detect gravity and acceleration.  Function: Maintains balance.  Space Sickness: Weightless otoliths cause nausea in zero gravity. Study alert:Vestibular system and hearing have distinct functions. SMELL AND TASTE Smell  The human sense of smell—called olfaction—permits us to detect more than 10,000 separate smells.  Smells are strongly linked with memory.  The sense of smell is sparked when the molecules of a substance enter the nasal passages and meet olfactory cells, the receptor neurons of the nose.  Smell may also act as a hidden means of communication, through the release of pheromones. o -Chemicals that are secreted into the environment to produce a social response in members of the same species. o -The degree to which pheromones are part of the human experience remains an open question. Taste The sense of taste (gustation) involves receptor cells that respond to four basic stimulus qualities: sweet, sour, salty, and bitter. -A fifth controversial category, umami, involves food stimuli that contain amino acids. The receptor cells are located in roughly 10,000 taste buds. -These wear out and are replaced every 10 days or so. “Supertasters” are highly sensitive to taste. “Nontasters” are insensitive to taste. THE SKIN SENSES:TOUCH,PRESSURE,TEMPERATURE,PAIN  Skin senses: Touch, pressure, temperature, and pain.  Operate via nerve receptor cells located at various depths throughout the skin. Pain as a Skin Sense  Extensively researched due to its medical and survival importance.  Susceptibility varies by individual, influenced by: o Biological factors: Hormones, genes. o Psychological factors: Emotions, thoughts, previous experiences. o Cultural factors: Practices and rituals. Functions of Pain  Warns of bodily danger (e.g., burns, inflamed appendix).  Enhances appreciation of pleasure.  Promotes social bonding and empathy.  Increases vigilance toward the environment.  Warning signal for danger.  Encourages care and caution.  Facilitates bonding and empathy. Chronic Pain   Constant, intense pain disproportionate to injury.  Mild stimuli like touch or sound can cause excruciating pain. Gate-Control Theory of Pain  Mechanism: o Nerve receptors in the spinal cord open a "gate" to the brain. o Pain is experienced when the gate is open. o Certain receptors can close the gate, reducing pain.  Ways to Close the Gate: 1. Nonpainful stimuli (e.g., rubbing the skin, distracting activities like music). 2. Psychological factors:  Positive emotions.  Interpretation of events (e.g., childbirth pain moderated by joy). 3. Cultural factors:  Rituals like hookswinging in India (steel hooks cause no pain).  Acupuncture (stimuli may shut the gate).  Role of Endorphins: o Natural painkillers released by the body. o Reduce discomfort and enhance well-being. Gender and Pain  Women report greater sensitivity to pain than men.  Hormones linked to menstrual cycles affect pain intensity. Psychological Influences on Pain  Anxiety increases pain perception (e.g., at the dentist).  Soldiers in battle often feel no pain due to relief and survival instincts. Research Insights  fMRI studies: Participants can learn to control brain regions associated with pain to reduce its intensity. HOW OUR SENSES INTERACT Synesthesia  Definition: Stimulation of one sensory system involuntarily leads to an additional sensory response in a different sensory system (e.g., hearing a sound and seeing a color).  Causes (Hypotheses): o Unusually dense neural linkages between sensory areas. o Lack of neural controls inhibiting connections between sensory areas. o Genetic inheritance.  Rarity: A rare perceptual condition.  Example: People with synesthesia may perceive numbers in specific colors, aiding in tasks like identifying patterns. Illustration Example (FIGURE 6):  (a) Picking out numbers like "0s" among "8s" can be difficult.   (b) Synesthetic individuals perceive numbers in colors, making patterns easier to detect. Multimodal Perception  Definition: The brain collects information from individual sensory systems and integrates/coordinators it to form a cohesive understanding of the environment.  Examples: o Taste is influenced by texture and temperature.  Warm food perceived as sweeter (e.g., hot chocolate vs. cold chocolate milk). o Spicy foods stimulate pain receptors, similar to heat stimuli. Interactions Between Senses  Integration: Senses work together to build a unified perception of the world. o Brain imaging studies confirm this integration.  Universal Principles: Despite different stimuli, all senses react based on common principles (e.g., Weber’s law on sensitivity to changes in stimulus strength).  Purpose: o Translate environmental information into usable formats. o Navigate the world effectively and intelligently APPROFONDIMENTI - A Medical or Dental Services Provider How would you handle a patient who is anxiously awaiting treatment and complaining that her pain is getting worse? Handling an anxious patient who is awaiting treatment and complaining of worsening pain requires a combination of empathy, clear communication, and prompt action. Here's how I would approach the situation: 1. Acknowledge Their Feelings and Pain  Show Empathy: Begin by acknowledging their pain and anxiety. For example: o "I understand that you're in a lot of discomfort, and I want to assure you that we're here to help."  Validate Their Concerns: Let them know that their feelings are valid and important: o "It's completely normal to feel worried in this situation, and I’m sorry you're in so much pain." 2. Assess the Pain  Ask Specific Questions: Quickly assess the severity of their pain to determine if immediate intervention is needed: o "Can you describe your pain for me? Is it sharp, dull, or throbbing?" o "On a scale from 1 to 10, how bad is the pain right now?" o "Has anything made it better or worse since you arrived?"  Observe Body Language: Non-verbal cues like grimacing or restlessness can provide additional information about their pain level. 3. Provide Reassurance  Explain the Process: Reduce anxiety by explaining what’s happening and what will be done: o "We’re working as quickly as we can to get you treated. You’re our priority, and we’ll take care of you soon."  Be Honest About Timeframes: If there is a wait, set realistic expectations while showing you understand their urgency: o "There’s a short delay because we’re preparing everything for your treatment. We’ll start as soon as possible." 4. Offer Immediate Comfort Measures  Positioning: Help them find a comfortable position that may alleviate some of the pain.  Distraction Techniques: Engage them in light conversation to divert their focus from the pain, or provide reading materials or music, if available.  Apply Non-Invasive Relief (If Appropriate): o Offer a cold or warm compress if it is suitable for their condition. o If allowed, provide water or ensure they are hydrated (if it does not interfere with treatment). 5. Communicate With the Treatment Team  Prioritize Their Care: If the pain seems severe or worsening, inform the relevant medical or dental staff immediately so their treatment can be expedited.  Advocate for the Patient: Ensure the team is aware of the patient’s escalating pain and anxiety. 6. Use Anxiety-Reducing Techniques  Deep Breathing Exercises: Teach them a simple breathing technique: o "Let’s try this together: take a deep breath in through your nose for four seconds, hold it for four seconds, and then exhale slowly through your mouth."  Reassuring Statements: Let them know they are in capable hands: o "We have helped many patients in similar situations, and we’ll do everything we can to make you feel better soon." 7. Follow Up After Treatment  Check on Their Comfort: After the procedure, ensure they feel relieved and provide guidance for managing their recovery.  Give Clear Aftercare Instructions: Explain how to handle any residual pain and when to seek further help if needed. Why This Approach Works  Empathy builds trust and helps calm the patient.  Clear communication reduces anxiety by setting expectations and ensuring they feel informed.  Prompt action shows that their concerns are taken seriously and that you are prioritizing their well-being. This combination of strategies creates a supportive and professional environment where the patient feels cared for and reassured. -Managing Pain Are you one of the more than 116 million people in the United States who suffers from chronic pain? Psychologists and medical specialists have devised several strategies to fight pain. Among the most important approaches are these: Medication. Painkilling drugs are the most popular treatment in fighting pain. Drugs range from those that directly treat the source of the pain—such as reducing swelling in painful joints—to those that work on the symptoms. Medication can be in the form of pills, patches, injections, or liquids. In a recent innovation, drugs are pumped directly into the spinal cord. Nerve and brain stimulation. Pain can sometimes be relieved when a low-voltage electric current is passed through the specific part of the body that is in pain. For example, in peripheral-nerve stimulation, a tiny battery-operated generator is implanted in the lower back. In even more severe cases, electrodes can be implanted surgically directly into the brain, or a handheld battery pack can stimulate nerve cells to provide direct relief Light therapy. One of the newest forms of pain reduction involves exposure to specific wavelengths of red or infrared light. Certain kinds of light increase the production of enzymes that may promote healing Hypnosis. For people who can be hypnotized—and not everyone is susceptible—hypnosis can greatly relieve pain. In fact, it can affect the brain and spinal-cord functioning in injured people, actually improving their physical functioning Biofeedback and relaxation techniques. Using biofeedback, people learn to control what are usually involuntary functions such as heartbeat, respiration, blood pressure, and muscle tension. Through biofeedback, a person can learn to control the stimulus that is causing the pain. For instance, people with tension headaches or back pain can be trained to relax their bodies to bring themselves relief..Surgery. In one of the most extreme methods, specific nerve fibers that carry pain messages to the brain can be cut surgically. Still, because of the danger that other bodily functions will be affected, surgery is a treatment of last resort, used most frequently with dying patients Cognitive restructuring. Cognitive treatments are effective for people who continually say to themselves, “This pain will never stop,” “The pain is ruining my life,” or “I can’t take it anymore,” and are thereby likely to make their pain even worse. By substituting more positive ways of thinking, people can increase their sense of control—and actually reduce the pain they experience Mirror pain therapy. One surprising treatment for people who suffer from phantom-limb pain (in which a person with an amputated limb experiences pain where the missing limb used to be) employs mirrors. By using a mirror to make it appear that both limbs are intact, the brain of the amputee stops sending messages perceived as pain. Mod. 11 -- Perceptual Organization: Constructing Our View of the World Perception: a constructive process by which we go beyond the stimuli that are presented to us and attempt to construct a meaningful situation. THE GESTALT LAWS OF ORGANIZATION  Definition: A set of psychological principles describing how we organize bits and pieces of information into meaningful wholes.  Origins: Developed in the early 1900s by German psychologists studying patterns (gestalts).  Core Idea: Perception goes beyond individual elements, representing an active, constructive process in the brain.  Legacy of Gestalt: o Gestalt principles remain influential in understanding perception as an integrated and constructive process. o Example: Environmental stimuli are actively organized by the brain beyond individual sensory elements.  Key Laws of Organization 1. Closure: o We group elements to form enclosed or complete figures rather than open ones. o Example: Incomplete shapes are perceived as whole figures. 2. Proximity: o Elements closer together are perceived as grouped. o Example: Pairs of dots appear as groups instead of single dots. 3. Similarity: o Elements similar in appearance are grouped together. o Example: Horizontal rows of similar shapes (circles and squares) are perceived instead of vertical mixed columns. 4. Simplicity (Overriding Principle): o Patterns are perceived in the most basic, straightforward way possible.  o Example: A square with lines on two sides is seen as a whole figure, rather than as separate letters (W on top of M). Figures & Examples (Key Visuals):  Figure 2a: Demonstrates closure—we fill in gaps to perceive a complete figure.  Figure 2b: Shows proximity—dots close together form pairs.  Figure 2c: Illustrates similarity—rows of circles and squares are grouped by appearance.  Figure 2d: Highlights simplicity—a square with lines is preferred over a complex interpretation (W and M). Additional Insights:  Figure-Ground Ambiguity: o Example: Vase/profiles (Figure 1a) and Necker cube (Figure 1b). o Perception can shift based on ambiguous visual cues.  Active Perception: o Stimuli are perceived as a whole greater than the sum of their parts. o Example: A complex image of scattered dots can form a perceptual whole (e.g., a dog, Figure 3). TOP-DOWN AND BOTTOM-UP PROCESSING  Top-Down Processing:  Perception guided by higher-level knowledge, experience, expectations, and motivations.  Example: Filling in gaps in ambiguous stimuli (e.g., recognizing incomplete sentences). 1. Sentence: "Ca- yo- re-d t-is -en-en-e, w-ic- ha- ev-ry -hi-d l-tt-r m-ss-ng?" 2. Decoded: "Can you read this sentence, which has every third letter missing?"  Role of Context: 1. Context influences how we perceive objects. 2. Example (Figure 4):  First row perceived as "A, B, C, D, E, F."   Second row perceived as "9, 10, 11, 12, 13, 14." Bottom-Up Processing:  Perception starting with individual components of stimuli and progressing to the whole.  Example: Recognizing individual shapes that make up letters in a word.  Role in Perception: o Allows for recognition of the basic elements of stimuli (e.g., shapes and features of letters). o Fundamental for progressing to higher-level recognition. Interaction Between Top-Down and Bottom-Up Processing  Both processes occur simultaneously and interact: o Bottom-Up: Processes fundamental stimulus characteristics. o Top-Down: Applies higher-level knowledge to interpret stimuli.  Together, they allow us to: o Fill in gaps in ambiguous stimuli. o Make appropriate responses to environmental information.  Folk & Remington (2008): Explored interaction between top-down and bottom-up processes. DEPTH PERCEPTION:TRANSLATING 2-D TO 3-D Depth Perception: ability to view the world in three dimensions and perceive distance. Binocular Cues  Binocular Disparity:  Difference in images seen by the left and right eyes.  Function: 1. Brain integrates two images into one, recognizes differences to estimate distance. 2. Examples:  Objects closer have greater disparity (e.g., pencil closer to face).  Objects farther away have smaller disparity.  Studies: 1. Gillam, Palmisano, & Govan (2011). 2. Valsecchi et al. (2013). 3. Gao, Schneider, & Li (2017). Monocular Cues Definition:Cues permit us to obtain a sense of depth and distance with just one eye  Motion Parallax:  o Change in position of an object on the retina allows perception of movement. o Example:  In a moving car:  Objects closer than a focal point (e.g., tree) move backward faster.  Objects farther than a focal point move forward slower.  Relative Size: o Assumes that if two objects are the same size: o The object with a smaller retinal image is farther away.  Texture Gradient: o Details of distant objects are less distinct than those of closer objects.  Linear Perspective: o Distant objects appear to converge (e.g., railroad tracks joining in the distance). o Helps estimate distance with a monocular view. Key Points  Retina projects flat 2-D images, but the brain transforms these into 3-D perceptions.  Binocular cues rely on both eyes, while monocular cues work with just one eye.  Both types of cues help interpret the distance and depth of objects in our environment. PERCEPTUAL CONSTANCY Definition: our understanding that physical objects are unvarying and consistent even though sensory input about them may vary. It allows us to view objects as having an unchanging size, shape,color, and brightness, even if the image on our retina changes. MOTION PERCEPTION:AS THE WORLD TURNS Cues about perception of motion:  Movement of an object across the retina is perceived relative to some stable background.  If a stimulus is increasing in size, filling more of the visual field, we assume the stimulus is approaching.  We also factor information about our own head and eye movements.  Apparent movement: the perception that a stationary object is moving.  Occurs when different areas of the retina are quickly stimulated. PERCEPTUAL ILLUSION:THE DECEPTION OF PERCEPTIONS Visual illusions: physical stimuli that consistently produce errors in perception. Most explanations for visual illusions concentrate on either the physical operation of the eye or our misinterpretation of the visual stimulus. APPROFONDIMENTI 1. Cultural Differences in Perception  Drawing Reproduction (Deregowski, 1973): o Westerners see "impossible" 3D shapes in the drawing, making reproduction difficult.  o African tribes interpret it in 2D, allowing easy reproduction.  Depth Perception (Hudson, 1960): o Westerners assume smaller animals are farther due to depth cues. o African tribes may interpret the hunter aiming at the larger animal (elephant), not using depth cues in 2D drawings.  Conclusion: o Cultural differences in perception stem from learning and experience, not basic perceptual processes. 2. Subliminal Perception  Definition: o Perception of stimuli (e.g., words, sounds, smells) below conscious awareness.  Research Findings: o Subliminal primes (e.g., "smart" or "happy") can subtly influence impressions. o Subliminal messages (e.g., images of Coke and "thirst") can increase thirst but don’t strongly change behavior or brand preference.  Conclusion: o Subliminal perception can influence behavior slightly, but it doesn’t cause substantial changes unless motivation is already high. 3. Extrasensory Perception (ESP)  Definition: o Perception beyond known senses (e.g., telepathy, clairvoyance).  Belief vs. Skepticism: o Nearly half of the U.S. population believes in ESP. o Most psychologists reject it due to lack of credible evidence and inadequate research methodologies.  Debate: o Early 2000s studies claimed support for psi (information transfer without senses). o Criticized for flawed methods and lack of theoretical basis.  Conclusion: o No reliable scientific support for ESP, but research continues to explore the topic. Key Takeaway:  Perception is influenced by cultural, psychological, and motivational factors, but phenomena like ESP and subliminal messages remain scientifically unproven for major behavior changes.