Sensation & Perception 1A, 1D PDF

# Sensation and Perception ## Group 04 BS PSYC 1A BPSY50 **Group 04 BS PSYC 1A BPSY50** ## Sensation vs Perception ### Sensation - The process of how the sensory systems detect raw information into neural activity. - Bottom-Up Processing (information flows from the bottom-up): - Sensory rece...

# Sensation and Perception ## Group 04 BS PSYC 1A BPSY50 **Group 04 BS PSYC 1A BPSY50** ## Sensation vs Perception ### Sensation - The process of how the sensory systems detect raw information into neural activity. - Bottom-Up Processing (information flows from the bottom-up): - Sensory receptors detect the information or stimulus. - Information flows to the brain. - Example: - Up: Sensory receptors. - Down: Brain. ### Perception - The process of how the brain makes sense of that sensory information. - Top-Down Processing (information flows from the top-down): - The brain interprets information based on past knowledge and experiences. - Information flows from the brain to the senses. - Example: - Top: Brain. - Down: Sensory receptors. ## 1. Sensation ### How does sensing work? #### Sensory Receptors - Cells that detect signals, such as light, sound, touch, temperature, taste, and smell, relaying them to the brain. #### Transduction - The process of converting sensory signals into electrical signals that the brain can understand. ### The Five Senses - Sight - Hearing - Touch - Smell - Taste ## Psychophysics - The study of how physical stimuli affect our senses and perceptions. - **Absolute Threshold:** The minimum stimulation needed to register a particular stimulus, 50% of the time. - **Signal Detection Theory:** - A model for predicting how and when a person will detect a weak stimuli, partly based on context. - **Sensitivity:** The true ability of the individual to detect the presence or absence of signals. - **Response Bias:** A behavioral tendency to respond "yes" to the trials, which is independent of sensitivity. ## Difference Threshold - **Just Noticeable Difference (JND):** The minimum difference between a pair of stimuli that can be perceived under experimental conditions. ## Ernst Weber - A German physiologist and psychologist known for **Weber's Law.** ### **Weber's Law** - The ability to detect a difference in a stimulus depends on the original intensity of the stimulus. - Example: - You can hear a whisper in a quiet room, but in a loud room you would need to shout. ## 2. VISION: Seeing ### Vision - Our eyes take in sensory information that helps us understand the world around us. - The process of detecting the electromagnetic energy that surrounds us. - Only a small fraction of the electromagnetic spectrum is visible to humans. ### Electromagnetic Energy - Pulses of energy waves that can carry information from place to place. #### Wavelength - The distance between one wave peak and the next wave peak. <start_of_image>graphic: A graph showing the electromagnetic spectrum. It shows the different types of waves that can be found in the electromagnetic spectrum, including gamma rays, X-rays, ultraviolet, visible, infrared, microwave, and radio waves. The graph also shows the size of various objects, such as atomic nuclei, atoms, molecules, protozoans, pinpoints, honeybees, humans, and buildings. The x-axis shows the wavelength in meters from 10^-12 to 10^3. ### Eye Anatomy graphic: An illustration showing a cross section of a human eye. It shows the lens, pupil, iris, cornea, retina, blind spot, and optic nerve. #### Anatomy of the Visual System 1. **Light Waves:** Transmitted across the cornea and enter through the pupil. 2. **Pupil:** The pupil's size is controlled by muscles that are connected to the iris (the colored part of the eye). 3. **Lens:** Light crosses the lens and is focused on the fovea, which is part of the retina. 4. **Fovea:** Contains photoreceptors. 5. **Photoreceptors:** Connected to retinal ganglion cells, axons from these cells exit through the back of the eye where they form the optic nerve to send visual information to the brain. 6. **Optic Nerve:** Carries the visual information to the brain. #### Blind Spot - A point of no receptors, where information exits the eye, where we cannot respond to visual information. ### Parts of the Eye #### **Cornea** - A clear covering that protects the eye and begins focusing the incoming light. #### **Pupil** - A small opening in the center of the eye. #### **Iris** - The colored part of the eye that controls the size of the pupil by constricting or dilating in response to light intensity. #### **Lens** - Structure that focuses the incoming light on the retina #### **Retina** - The layer of tissue at the back of the eye that contains photoreceptor cells. #### **Fovea** - The central point of the retina. ### Photoreceptor Cells #### **Rods** - Scotopic (nighttime) vision. - Visual neurons that specialize in detecting black, white, and gray colors. - Work best in low light conditions. - High sensitivity. - Allows for low-acuity vision in dim light. - Involved in the perception of movement in our peripheral vision. - Located in the periphery of the retina. #### **Cones** - Phototopic (daytime) vision. - Visual neurons that are specialized in detecting fine detail and colors. - Work best in bright light conditions. - High-acuity color information. - Located in the fovea. graphic: An illustration showing rods and cones located on the retina of a human eye. It also shows a magnified view of one rod and cone with a description of each. ### **Optic Chiasm** - The optic nerve of each eye merges at the optic chiasm, an X-shaped structure just below the cerebral cortex. - Information from the right visual field is sent to the left hemisphere and information from the left visual field is sent to the right hemisphere. - This information is then sent to the occipital lobe for processing. graphic: An illustration of the human brain showing the optic nerve crossing at the optic chiasm. It also shows the path of visual information as it travels from the eye through the optic nerve, optic chiasm, and optic tract to the brain. ### **Visual Pathways** - After being processed in the occipital lobe, visual information exits and goes through two different pathways. #### **Dorsal Stream** - This pathway sends information to the parietal lobe, which is important for using visual information to form movements. - Also known the "how" pathway as it helps us with location in space and how we might interact with a particular visual stimulus. #### **Ventral Stream** - This pathway sends information to the temporal lobe, which is important for identifying details of objects. - Also known as the "what/where" pathway as it helps us with object recognition and object identification. graphic: An illustration showing two pathways of visual information as it travels from the eye to the brain. ### **Visual Accommodation** - The process of changing the curvature of the lens to keep the light entering the eye focused on the retina. #### **Normal Vision** graphic: An illustration of a normal eye showing how light enters the eye and is focused on the retina. #### **Nearsightedness** (Myopia) - It is difficult to see objects that are far away. - The visual image is focused in front of the retina. - This is usually caused by the eyeball elongating over time. graphic: An illustration of a nearsighted eye showing how light enters the eye and is focused in front of the retina. #### **Farsightedness (Hyperopia) - It is difficult to see objects that are close up. - The visual image is focused behind the retina. - This is usually caused by the eyeball shortening. graphic: An illustration of a farsighted eye showing how light enters the eye and is focused behind the retina. ### **Optic Nerves** - Collection of millions of ganglion neurons that sends vast amounts of visual information, via the thalamus, to the brain. graphic: An illustration of a human eye with optic nerve fibers in the back of the eye. It also shows a close-up of the optic nerve fibers and how they transmit information from the eye to the brain. ### **Perceiving Colors** #### **Hue** - Shade of a color. - Conveyed by the wavelength of light that enters the eye. - Shorter wavelengths = blue - Longer wavelengths = red graphic: An illustration showing a spectrum of visible light from 400 nm to 780 nm. #### **Young-Helmholtz Trichromatic Color Theory** - Proposes that color perception is the result of the signals sent by the three types of cones, whereas the opponent-process color theory proposes that we perceive color as three sets of opponent colors: red-green, yellow-blue, and white-black. graphic: An illustration of three types of cones in the retina of the human eye. #### **Color Blindness** - Inability to detect either green and/or red colors. graphic: An illustration showing the difference between a normal eye and a colorblind eye. #### **Opponent-Process Theory** - Proposes that we analyze sensory information not in terms of three colors but rather in three sets of "opponent colors": red-green, yellow-blue, and white-black. graphic: An illustration showing three sets of opponent colors: red-green, yellow-blue, and white-black. ### **Perceiving Form** #### **Gestalt** - The "whole is more than the sum of its parts." - Complete jigsaw puzzles. - Rather than looking at each piece as an individual unit, they form meaningful relationships between the pieces to see the big picture more quickly and efficiently. graphic: An illustration showing a completed jigsaw puzzle with the text, “The whole is different than the sum of its parts.” and below the text is “verywell.” ### **Perceiving Depth** #### **Depth Perception** - The ability to perceive three-dimensional space and to accurately judge distance. graphic: An illustration showing a person looking at a series of squares, with the image becoming smaller as the squares go back in space. #### **Visual Cliff** - A mechanism that gives the perception of a dangerous drop-off, in which infants can be safely tested for their perception of depth. graphic: An illustration showing a visual cliff with a small child at the edge of a platform looking into the drop-off. ### **Depth Cues** - Our depth perception is the result of depth cues. - A message from our bodies and the external environment that supply us with information about space and distance. #### **Binocular Depth Cues** - Depth cues created by retinal image disparity—that is, the space between our eyes, and thus which require the coordination of both eyes. graphic: An illustration showing a pair of human eyes looking forward at a house in the distance. There are lines connecting the eyes to specific parts of the house. #### **Convergence** - The inward turning of our eyes that is required to focus on objects that are less than about 50 feet away from us. graphic: An illustration of a person looking at an object with their eyes converging on the object. #### **Monocular Depth Cues** - Depth cues that help us perceive depth using only one eye. graphic: An illustration of a person with one eye covered looking at an object. #### **Monocular Cues** - Linear Perspective - Height in the visual field - Interposition - Texture Gradient - Relative Size graphic: An illustration with six boxes showing different monocular cues and how they work. ### Perceiving Motion #### **Beta Effect** - The perception of motion that occurs when different images are presented next to each other in succession. graphic: An illustration showing a series of four squares with white dots on a blue background. The white dots are in different positions in each square. #### **Phi Phenomenon** - We perceive a sensation of motion caused by the appearance and disappearance of objects that are near each other. graphic: An illustration of a series of eight squares with a black shark in each square. The shark is in a slightly different position in each square. ## 3. AUDITION: Hearing ### **Audition** - The ability or process of hearing, which allows individuals to detect and interpret sound. - One of the five senses that plays a crucial role in recognizing, understanding, and responding to various sounds in our environment. graphic: An illustration showing a human ear with sound waves passing through the ear canal. ### **Hearing** - The process of detecting sound waves through the ear and interpreting them in the brain, allowing us to perceive and respond to sounds in our environment. #### **Frequency** - The number of vibrations or cycles a sound wave completes per second, measured in Hertz (Hz). #### **Amplitude** - The height or strength of a sound wave, which indicates the amount of energy the wave carries. #### **Decibel (dB)** - Unit of measurement used to express the intensity or loudness of sound ### **Ear Anatomy** graphic: An illustration showing a cross section of a human ear, including the outer ear, middle ear, and inner ear. It also includes labeling for the pinna, ear canal, eardrum, ossicles, semicircular canals, cochlea, oval window, and saccule. #### **Anatomy of the Auditory System** - The ear is made up of three main parts, each essential for hearing. - **Outer Ear** - **Pinna** - The external part of the ear that captures sound waves and funnels them into the ear canal. - **Ear Canal** - A passage that directs the sound waves toward the eardrum. - **Eardrum (Tympanic Membrane)** - A thin membrane that vibrates in response to sound waves, transmitting the vibrations to the middle ear. - **Middle Ear** - **Ossicles** - Three small bones—malleus, incus, and stapes—that amplify and transmit the vibrations from the eardrum to the inner ear. - **Inner Ear** - **Oval Window** - A membrane that connects the middle ear to the inner ear, receiving vibrations from the stapes and triggering fluid movement in the cochlea. - **Cochlea** - A spiral-shaped structure filled with fluid, where sound vibrations are transformed into electrical signals. - **Organ of Corti** - Located within the cochlea, it contains hair cells that convert vibrations into electrical impulses, which are sent to the brain through the auditory nerve. ### **Temporal Theory** - The frequency of sound is represented by the firing rate of sensory neurons. - Limitation: The firing rate of neurons cannot account for the full range of frequencies. ### **Place Theory** - Different areas of the basilar membrane are sensitive to different frequencies of sound. - The base of the membrane reacts to high frequencies, while the tip responds to low frequencies. ### **Combining Both Theories** - Both theories explain different aspects of how we perceive pitch. - The rate of action potentials can explain frequencies up to around 4000 Hz. - Pitch is encoded using the amount of stimulation on the basilar membrane. ### **Sound Localization** - Sound localization involves two types of cues to determine the source of sound. #### **Monaural Cues** - One ear: These cues are based on the information from a single ear. - How it works: Each ear interacts with incoming sound waves in a unique way, allowing the ear to assess the direction and distance of sounds. #### **Binaural Cues** - Two ears: These cues use both ears to locate the sound on the horizontal plane. - How it works: Binaural cues rely on differences in sound patterns reaching each ear, which include: #### **Interaural Level Difference (ILD)** - The sound is louder in the ear closer to the sound source due to the attenuation of the sound wave as it passes through the head. #### **Interaural Timing Difference (ITD)** - A slight delay in the time it takes for the sound to reach each ear. The ear closer to the source hears the sound slightly earlier. - Together, these cues allow the brain to determine the location of a sound based on intensity and timing differences between the two ears. ### **Hearing Problems or Loss** #### **Conductive Hearing Loss** - Occurs when there is a problem with the vibration of the eardrum or the movement of the ossicles. - Often be treated with hearing aids that amplify sound waves, making it easier for the eardrum to vibrate and the ossicles to move. #### **Sensorineural Hearing Loss** - Happens when there is a failure to transmit neural signals from the cochlea to the brain. - Can be caused by conditions like Meniere's disease, which leads to the degeneration of inner ear structures. ## 4. GUSTATION: Tasting ### **Gustation** - Also referred to as taste. - One of the five senses and involves the perception of flavors from substances in the mouth. - The human tongue contains taste buds that can detect five basic tastes: sweet, salty, sour, bitter, and umami (savory). - These taste buds send signals to the brain, enabling us to experience and differentiate various flavors. graphic: An illustration of a human tongue with the text, “Gustation” above it. ### **Anatomy of a Tongue** #### **Taste Pore** - A tiny opening on the tongue’s surface that allows food and beverage molecules to enter and interact with sensory cells inside the taste buds. #### **Taste Receptor Cells** - Respond to different taste qualities, such as sweet, sour, bitter, salty, and umami. - They send signals to the brain, triggering the sensation of taste. #### **Nerves** - Transmit signals from the taste receptor cells to the brain, allowing it to process and recognize various tastes. #### **Tongue Surface** - Essential for taste, it contains taste buds located within papillae, which are small structures on the tongue that house the taste receptors. graphic: A cross section of a taste bud in the tongue. ## 5. OLFACTION: Smelling ### **Olfaction** - The sense of smell. - A chemical sensation of gaseous odorants. graphic: An illustration of the front of a person’s face showing their nose and mouth. #### **Chemoreceptors** - The chemical receptors of the olfactory and taste. #### **Volatile** - Gaseous state. ### **The Process of Olfaction** 1. **Nasal Cavity:** Contains a thin film of mucous where odors become dissolved. 2. **Olfactory Neurons:** Located in the mucous. The dendrites of olfactory neurons are enlarged and contain cilia. 3. **Dendrites:** Pick up odor, depolarize, and carry odor to axons in the olfactory bulb (cranial nerve I). 4. **Frontal and Temporal Lobes:** Process odor. graphic: An illustration of the human nose and olfactory system. graphic: A cross-section of the nasal cavity showing the olfactory bulb, nasal cavity, and tongue. ### **Pheromones** - Chemical messenges sent by another individual. - Ectohormones. - Cause a behavioral change in another animal. - Usually communicate information about the reproductive status of a potential mate. #### **Functions** - Signaling food. - Alarming other animals. - Deliating territory. - Bonding between mother and offspring. - Most studies have found it challenging to definitively prove the existence of pheromones in humans. - In this study of Preti (2005), it discusses the challenges of identifying human pheromones and the complexities surrounding their potential effects on human behavior, suggesting that while there are claims of pheromone-like substances, conclusive evidence remains elusive. ## 6. SOMATOSENSORY: Touching ### **Somatosensory** - Input of conscious perception of touch, pressure, pain, temperature, position, movement, and vibration. - Four distinct skin sensations: - Pressure. - Warmth. - Cold. - Pain. graphic: An illustration of two hands with fingers touching each other. ### **Sensory Receptors** #### **Rapid-Adapting** - Meissner's Corpuscle (maintaining grip) #### **Slowly-Adapting** - Merkel's Disc (shape and texture) #### **Large Receptive Fields** - Pacinian Corpuscle (use of tools) #### **Small Receptive Fields** - Ruffini's Ending (skin stretching) graphic: A table summarizing the different types of sensory receptors and their functions. graphic: An illustration of the different sensory receptors located on the skin. ### **Thermoception** - Temperature perception. ### **Nociception** - Sensory signal indicating potential harm and maybe pain. ### **Inflammatory Pain** - Signals some type of tissue damage. ### **Neuropathic Pain** - A nerve pain due to nervous system malfunctions or damage. ## Other Sensory Systems #### **Vestibular Input (Balance)** - Found in the inner ear. - Contributes to our sense of body position in space. #### **Proprioceptive Input (Movement)** - Found in the muscles, tendons, ligaments and joint receptors. - Helps us to feel grounded and know where we are and what we are doing. #### **Interoceptive Input (Internal)** - Hidden sense. - Gives us the ability to feel what is happening inside our body. graphic: An illustration showing a cross-section of the human head showing the inner ear, temporal bone, semicircular canals, vestibular apparatus, cochlea, auditory ossicles, eustachian tube, and external auditory canal. ## 2. Perception ### **Perception** - The process of using our senses to identify, organize, and interpret sensory information in order to understand the world around us. - The ability to see, hear, or become aware of something through the senses. - “The normal limits to human perception.” #### **Types of Perception** - Visual Perception - Auditory Perception - Tactile Perception - Olfactory Perception - Gustatory Perception ### Sensory Interaction - Refers to the way different senses, such as sight, sound, touch, taste, and smell, influence and interact with each other to shape our perception and experience of the world. - This concept is important in understanding how our brain processes information from various sensory inputs and how they can affect one another. #### **McGurk Effect** - A perceptual phenomenon that demonstrates the interaction between hearing and vision in speech perception. - It occurs when the auditory component of one sound is paired with the visual component of another, leading to a third, distinct perception of the sound. ### **Selective Attention** - The cognitive process of focusing on a specific piece of information or task while ignoring other irrelevant stimuli in the environment. - It allows us to prioritize important information and manage limited cognitive resources efficiently. ### **Sensory Adaptation** - The process of focusing on specific stimuli or information while ignoring other distractions in the environment. - This ability enables individuals to concentrate on what is most relevant at a given moment, filtering out irrelevant sensory data. ### **Perceptual Constancy** - Refers to the brain’s ability to recognize objects as being consistent and unchanged, even when sensory input about them varies. - This phenomenon ensures that we perceive the world as stable despite changes in lighting, distance, angle, or other environmental factors. ### **Illusions** - These are perceptual phenomena where our interpretation of sensory information does not match the physical reality. - They occur when the brain processes sensory input in ways that create a discrepancy between what is perceived and what is objectively true. #### **Types of Illusion** #### **Visual Illusions** - The most commonly studied illusions, these involve misinterpretations of visual stimuli. - **Müller-Lyer Illusion:** Two lines of the same length appear different due to the orientation of arrow-like ends. #### **Auditory Illusions** - These involve misperceptions of sound, often caused by context, timing, or spatial factors. - **Shepard Tone:** A series of tones that sound like a never-ending ascending or descending pitch. - **McGurk Effect:** A mismatch between lip movements and speech sounds creates a perceived third sound. graphic: An illustration showing two visual illusions and two auditory illusions, including: Müller-Lyer Illusion, Shepard Tone, Ames Room, and the McGurk Effect. #### **Tactile Illusions** - These are distortions in the sense of touch. - **The Rubber Hand Illusion:** Feeling ownership of a fake hand when it is stroked in sync with your hidden real hand. - **Phantom Limb Sensation:** Sensation perceived in a limb that is no longer present. #### **Olfactory & Gustatory Illusions** - Misperceptions in taste or smell often arise from interactions with other senses. - The flavor of food changes based on its smell, color, or even texture (e.g., clear soda might be perceived as flavorless). graphic: An illustration showing two tactile illusions and two olfactory and gustatory illusions, including: The Rubber Hand Illusion, Phantom Limbs Sensation, Olfactory, and Gustatory. #### **Cognitive Illusions** - These involve higher-level processes such as reasoning, expectations, or biases that lead to incorrect conclusions. - **Stroop Effect:** Difficulty naming the color of a word when the word itself represents a different color (e.g., the word “red” written in blue ink). graphic: An illustration showing the Stroop Effect. #### **Moon Illusion** - A phenomenon where the moon appears larger when it is near the horizon compared to when it is high in the sky, despite its actual size remaining constant. - This is one of the most famous perceptual illusions and has puzzled scientists and philosophers for centuries. graphic: An illustration of the moon illusion. ### **Factors Affecting Perception** 1. **Sensory Adaptation:** A reduction in sensitivity to a sensory stimulus after constant exposure to it. - **Sensory Deprivation or Perceptual Isolation:** The deliberate reduction or removal of stimuli from one or more of the senses. 2. **Selective Attention:** The act of focusing on a particular object for a while, simultaneously ignoring distractions and irrelevant information. - **Inattentional Blindness:** Failure to notice something that is completely visible because of a lack of attention. 3. **Motivation:** Change in stimulus detection as a function of current mental state. 4. **Beliefs, values, prejudices and expectations** 5. **Life/Cultural experiences** ### **Müller-Lyer Illusion** - In the Müller-Lyer illusion, lines appear to be different lengths although they are identical. graphic: An illustration of the Müller-Lyer illusion. ### **Gestalt Principles of Perception** - **Gestalt Psychology:** Field of psychology based on the idea that the whole is different from the sum of its parts. - The brain creates a perception that’s more than simply the sum of available sensory inputs. #### **Principles** - Figure-ground relationship - Proximity - Continuity - Closure - Similarity #### **Figure-Ground Relationship** - The idea that we tend to segment our visual world into figure and ground. - Figure: The focus of the visual field. - Ground: The background. - Our perception can vary depending on what we view as figure and what we view as ground. graphic: An illustration of the figure-ground relationship. #### **Gestalt Principle of Proximity** - The idea that things that are close to one another tend to be grouped together. graphic: An illustration showing the Gestalt principle of proximity. #### **Gestalt Principle of Similarity** - The idea that things that are alike tend to be grouped together. graphic: An illustration showing the Gestalt principle of similarity. #### **Gestalt Principle of Continuity** - The idea that we are more likely to perceive continuous, smooth flowing lines rather than jagged, broken lines. graphic: An illustration showing the Gestalt principle of continuity. #### **Gestalt Principle of Closure** - The idea that we organize our perceptions into complete objects rather than as a series of parts. graphic: An illustration showing the Gestalt principle of closure.