Perception & Sensation
1.6.A.1
Sensation - the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. Sensory systems (like vision, hearing, touch) transform physical stimuli (light, sound waves, pressure) into neural impulses that the brain can interpret. Sensation is the foundation for perception, which influences our behavior and cognitive functions. For instance, visual sensations enable us to navigate our environment, recognize faces, and interpret social cues.
Absolute Threshold - is the minimum intensity of a stimulus that one can detect at least 50% of the time. It represents the boundary between not perceiving and perceiving a stimulus. In a dark room, the absolute threshold for vision is the minimum amount of light needed for someone to detect a light source, such as a candle flame seen from 30 miles away on a clear, dark night.
1.6.A.2
Just-Noticeable Difference (Difference Threshold) - the smallest change in the intensity of a stimulus that one can detect. It varies depending on the initial intensity of the stimulus. When adjusting the volume on a radio, the JND is the smallest increase in volume that you can notice from the current setting.
Weber's Law - states that the JND for a stimulus is a constant proportion of the original stimulus intensity. It implies that the perception of change in a given stimulus is relative to the original intensity. If you are holding a 100g weight, adding 5g may be noticeable (JND), but if you are holding a 200g weight, you might need to add 10g to notice a difference. The JND increases with the intensity of the initial stimulus.
Sensory Adaptation - occurs when sensitivity to a constant stimulus decreases over time. This allows us to focus on changes in our environment without being overwhelmed by unchanging stimuli. Sensory adaptation helps conserve cognitive resources and keeps us from becoming desensitized to critical changes in our surroundings. When you enter a room with a strong odor, you may initially find it overwhelming, but after a few minutes, you no longer notice the smell because of sensory adaptation.
1.6.A.3
Sensory Interaction - refers to the principle that one sensory modality can influence another. Our senses do not operate in isolation but interact to create a coherent perceptual experience. Sensory interaction is essential in tasks requiring coordination of multiple senses, such as driving, where visual and auditory inputs must be integrated. When eating, the flavor of food is a combination of taste and smell. If you have a cold and your sense of smell is impaired, food may taste bland.
Synesthesia - is a condition where stimulation of one sensory pathway leads to automatic, involuntary experiences in a second sensory pathway. People with synesthesia might "see" sounds or "taste" colors. A person with synesthesia might hear music and simultaneously see colors in their mind, each musical note evoking a specific hue.
1.6.B.1
Cornea - is the eye's outermost layer, providing most of the eye's optical power by bending (refracting) incoming light. The cornea’s shape and clarity are crucial for sharp vision. Any irregularities can cause visual distortions.
Retina - a light-sensitive layer at the back of the eye containing photoreceptor cells (rods and cones) that convert light into neural signals.The retina plays a pivotal role in visual perception. The signals processed here are sent to the brain via the optic nerve, influencing how we perceive and interact with the world.
Blind Spot - is an area on the retina where the optic nerve exits the eye, lacking photoreceptors. Normally, the brain fills in the missing information, so we don't notice the blind spot during everyday vision.
Pupil - is the opening in the iris that allows light to enter the eye. Its size adjusts in response to light intensity, controlled by the iris muscles. The pupil's dilation and constriction help regulate the amount of light reaching the retina, affecting how well we see in different lighting conditions.
Iris - is the colored part of the eye surrounding the pupil. It contains muscles that adjust the pupil size. The iris' ability to control pupil size directly impacts visual clarity and the eye’s adaptation to varying light environments.
1.6.B.2
Lens - is a transparent structure behind the iris that focuses light onto the retina. It changes shape through accommodation to adjust focus for objects at different distances. Presbyopia, the loss of lens flexibility with age, impairs close-up vision, necessitating reading glasses.
Accommodation - refers to the lens changing shape to focus on objects at varying distances, facilitated by the ciliary muscles. This process is essential for maintaining a clear vision as we shift focus between near and far objects.
Nearsightedness (Myopia) - occurs when light is focused in front of the retina, making distant objects appear blurry. Individuals with myopia struggle with activities requiring clear distance vision, such as driving.
Farsightedness (Hyperopia) - occurs when light is focused behind the retina, making close objects appear blurry. People with hyperopia may experience eyestrain and headaches from attempting to focus on nearby objects.
1.6.B.3
Photoreceptors - (rods and cones) convert light into neural signals. Rods are sensitive to low light, while cones detect color and detail. The proper functioning of photoreceptors is fundamental to visual perception, affecting everything from night vision (rods) to color discrimination (cones).
Rods - are a type of photoreceptor cell in the retina of the eye that are highly sensitive to light, making them essential for vision in low-light conditions (scotopic vision). They do not detect color and more numerous in the periphery of the retina than their cones counterpart. They allow us to see in dim environments where cones are ineffective. The high sensitivity of rods to light makes them crucial for detecting movement and shapes in low-light conditions, contributing to our ability to navigate and react to our environment when lighting is poor.
Cones - are a type of photoreceptor cell in the retina responsible for color vision and visual acuity. Unlike rods, which function well in low light and provide black-and-white vision, cones are active at higher light levels (photopic vision). The human retina contains three types of cones, each sensitive to different wavelengths of light: short-wavelength (S-cones, blue), medium-wavelength (M-cones, green), and long-wavelength (L-cones, red). They are densely packed in the fovea, the central region of the retina, which provides the sharpest vision.
Transduction - is the process by which sensory stimuli are converted into neural signals that can be interpreted by the brain. In the context of sensation, transduction occurs when sensory receptors transform external stimuli (such as light, sound, touch, taste, or smell) into electrical impulses. This is a fundamental step in sensory perception, allowing the brain to process and respond to information from the environment.
Vision: Photoreceptors in the retina (rods and cones) transduce light into neural signals.
Hearing: Hair cells in the cochlea transduce sound vibrations into neural impulses.
Touch: Mechanoreceptors in the skin transduce mechanical pressure into neural signals.
Taste: Taste receptors on the tongue transduce chemical molecules into neural signals.
Smell: Olfactory receptors in the nose transduce chemical molecules into neural signals.
1.6.B.4
Trichromatic Theory - the retina contains three types of cones sensitive to red, green, and blue light, and all colors are perceived through the combined activation of these cones. This theory explains the basis of color vision and its variations among individuals. The trichromatic theory underlies technologies like digital screens, which use red, green, and blue pixels to create a full spectrum of colors.
Opponent Process Theory - color perception is controlled by opposing retinal processes (red-green, blue-yellow, and black-white). It explains phenomena such as afterimages, where staring at a color lead to seeing its opposite when looking away. After staring at a red image, one might see a green afterimage upon shifting gaze to a white surface.
1.6.B.4.i
Fovea - is a small central pit in the retina densely packed with cones, crucial for sharp central vision. It is essential for tasks requiring detailed vision, like reading and recognizing faces.
1.6.B.4.ii
Afterimages - occur when overstimulation of photoreceptors leads to continued visual perception after the stimulus is removed.
Ganglion Cells - in the retina receive visual information from photoreceptors via bipolar cells and transmit it to the brain through their axons, which form the optic nerve. These cells integrate and relay visual information, crucial for visual processing.
1.6.B.4.iii
Dichromatism - is a form of color blindness where one type of cone is missing or dysfunctional, leading to difficulty distinguishing certain colors. A person with red-green color blindness may struggle to distinguish traffic light colors.
Monochromatism - or total color blindness, occurs when two or all three cone types are nonfunctional, resulting in seeing only shades of gray.Individuals with monochromatism may find activities like choosing ripe fruits challenging due to the lack of color cues.
1.6.B.5
Prosopagnosia - or face blindness, is a neurological disorder impairing the ability to recognize faces. This condition affects social interactions and the ability to identify individuals, impacting relationships and social behavior. People with prosopagnosia often rely on non-facial cues like voice or clothing to recognize others.
Blindsight - is a condition where individuals with damage to the primary visual cortex can respond to visual stimuli without conscious awareness of seeing. Blindsight challenges our understanding of conscious visual perception, suggesting that some visual processing occurs outside conscious awareness. A person with blindsight might navigate obstacles in a room without being consciously aware of them.
1.6.C.1
Pinna - or auricle, is the visible part of the outer ear that collects sound waves and directs them into the ear canal. It helps to localize sound sources and funnel sound waves toward the eardrum.
Eardrum (Tympanic Membrane) - is a thin membrane that vibrates in response to sound waves. These vibrations are then transmitted to the bones of the middle ear.
Cochlea - is a spiral-shaped, fluid-filled structure in the inner ear that contains the organ of Corti, where sound vibrations are converted into neural signals by hair cells.
Bones of the Middle Ear ossicles (malleus, incus, and stapes) - amplify and transmit vibrations from the eardrum to the cochlea.
Auditory Nerve - also known as the cochlear nerve, carries neural signals from the cochlea to the auditory cortex in the brain, where sound is processed and interpreted.
Wavelength - refers to the distance between successive peaks of a sound wave. It determines the pitch of the sound, with shorter wavelengths corresponding to higher pitches and longer wavelengths corresponding to lower pitches. In music, different instruments produce notes with specific wavelengths, allowing us to identify a piano's high-pitched notes versus a bass guitar's low-pitched tones.
Amplitude - is the height of the sound wave and determines the loudness of the sound. Higher amplitudes produce louder sounds, while lower amplitudes produce softer sounds. A fire alarm's high amplitude ensures that it can be heard clearly over other sounds, prompting immediate attention and action in an emergency.
1.6.C.2
Place Theory - posits that different parts of the cochlea are activated by different frequencies of sound. High-frequency sounds stimulate the base of the cochlea, while low-frequency sounds stimulate the apex. An audiologist uses place theory principles to design hearing aids that amplify specific frequencies where a person's hearing is impaired.
Frequency Theory - suggests that the rate of nerve impulses traveling up the auditory nerve matches the frequency of the sound wave, allowing us to perceive its pitch. When tuning a musical instrument, a musician relies on their ability to perceive exact pitches, which involves frequency theory to match the instrument's sound to a reference tone.
Volley Theory - extends frequency theory by proposing that groups of auditory nerve fibers fire action potentials in rapid succession, combining their outputs to encode higher frequencies than any single neuron could.
1.6.C.3
Sound Localization - the process by which we determine the direction and distance of a sound source. It relies on binaural cues, such as interaural time differences (differences in the time a sound reaches each ear) and interaural level differences (differences in sound pressure level reaching each ear). In a busy street, sound localization allows us to detect the direction of an approaching car, enabling us to respond appropriately and avoid danger.
1.6.C.4
Conduction Deafness - also known as conductive hearing loss, occurs when there is a problem in the transmission of sound waves through the outer ear, tympanic membrane (eardrum), or middle ear (ossicles: malleus, incus, and stapes). This type of hearing loss is typically caused by blockages, infections, damage to the ear structures, or abnormalities.
Sensorineural Deafness - also known as sensorineural hearing loss, occurs due to damage to the inner ear (cochlea) or the auditory nerve pathways leading to the brain. This type of hearing loss is often permanent and can be caused by factors such as aging, exposure to loud noises, head trauma, infections, and genetic conditions. Age-related hearing loss typically affects higher frequencies first and is a common form of sensorineural hearing loss in older adults, impacting their ability to understand speech, especially in noisy environments.
1.6.D.1
Transduction of Olfactory Stimuli - refers to the process by which odorant molecules are detected by olfactory receptors in the nasal cavity and converted into neural signals that the brain can interpret as smells.
Pheromones - are chemical signals released by an individual that affect the behavior or physiology of other members of the same species. In humans, pheromones play a role in social communication and attraction.Some studies suggest that pheromones may influence human attraction, such as increasing the attractiveness of individuals wearing certain perfumes or colognes that mimic natural pheromones.
1.6.D.2
Gustation (Taste) - is the sense that detects chemicals in food and drink via taste receptors on the tongue. The primary tastes are sweet, salty, sour, bitter, and umami, with oleogustus (fat taste) being a proposed sixth taste.
1.6.D.3
Supertasters, Medium Tasters, and Nontasters are categories based on individual differences in taste sensitivity, particularly to bitter compounds. Supertasters have more taste buds and are highly sensitive to tastes, while nontasters have fewer taste buds and less sensitivity. Supertasters may find broccoli or kale overly bitter and unpleasant, while nontasters might enjoy these vegetables without issue, influencing their overall diet and nutrition.
1.6.D.4
Chemical Senses (Olfaction and Gustation) Interact - to create the perception of flavor. Smell contributes significantly to the taste experience, as the olfactory system detects volatile compounds released during chewing. When eating a strawberry, the combination of its sweet taste and its characteristic aroma creates the full flavor experience. A cold or nasal congestion that impairs the sense of smell can significantly dull the perception of flavor.
1.6.E.1
Skin Receptors - The skin contains various types of receptors that detect different sensory stimuli, including touch, pressure, temperature, and pain. These receptors include mechanoreceptors (touch and pressure), thermoreceptors (temperature), and nociceptors (pain).
Gate Control Theory - of pain proposes that there is a neural "gate" in the spinal cord that can open or close to modulate the transmission of pain signals to the brain. It suggests that non-painful input, such as rubbing or massage, can close the gates and reduce the perception of pain. Applying ice to an injured area can temporarily reduce pain by activating cold thermoreceptors, which can close the "gate" and decrease the transmission of pain signals to the brain.
1.6.F.1
Phantom Limb Sensation - occurs after the amputation of a limb, where individuals continue to experience sensations such as pain, itching, or movement in the absent limb. This phenomenon is thought to result from the brain's attempt to reorganize sensory input after losing input from the amputated limb. An amputee may feel as though their missing hand is clenched into a fist, despite the physical absence of the limb, illustrating how the brain continues to process sensory information related to the limb.
1.6.G.1
Vestibular Sense - is the sensory system responsible for detecting balance, spatial orientation, and movement of the head and body in relation to gravity. It is in the inner ear and consists of fluid-filled structures called semicircular canals and otolithic organs (utricle and saccule). Maintaining balance while walking on uneven terrain or riding a bike relies on the vestibular sense to detect changes in body position and adjust posture and movements accordingly.
Semicircular Canals - are three looped structures in the inner ear filled with fluid and lined with hair cells. They detect rotational movements of the head and help maintain balance. When you spin around and then stop, the semicircular canals detect the rotation and help your brain adjust, preventing you from feeling dizzy and falling.
1.6.G.2
Kinesthesis (Proprioception) - to the sense of the position and movement of body parts. It involves receptors located in muscles, tendons, and joints that provide feedback about the body's position in space and the effort being exerted during movement. Writing with a pen involves kinesthetic feedback from the muscles and joints of the hand and fingers, allowing for precise control of movement and pressure to produce legible handwriting.
2.1.A.1
Perception - is the process by which individuals organize, interpret, and make sense of sensory information from the environment. It involves not just the passive reception of stimuli but also the active interpretation of these stimuli based on previous experiences, expectations, and contextual cues.
External Sensory Information (Bottom-Up Processing) - refers to the raw data received by our sensory organs from the environment. This includes visual, auditory, tactile, olfactory, and gustatory stimuli. The brain processes this information to construct a coherent representation of the world. The sensory organs collect external stimuli and send this information to the brain for processing. The brain then integrates these signals to form perceptions that guide our actions and decisions. In a classroom setting, a student relies on visual information from the blackboard, auditory information from the teacher’s lecture, and tactile information from writing notes.
Internal Prior Expectations (Top-Down Processing) - are the preconceptions and knowledge that individuals bring to the perceptual process. These expectations are shaped by past experiences, cultural background, and personal beliefs. They influence how we interpret sensory information and can sometimes lead to perceptual biases or illusions. Prior expectations help the brain make sense of ambiguous or incomplete sensory information by filling in gaps based on previous experiences. When you hear a familiar song playing faintly in the background, your brain uses prior knowledge of the song to recognize it, even if the auditory signal is weak.
2.1.A.2
Schemas - are cognitive frameworks or mental structures that help individuals organize and interpret information. They are developed through experience and provide a way of understanding and predicting the world. Schemas guide attention, influence the way new information is perceived, and shape the retrieval of information from memory. Schemas play a crucial role in perception by enabling individuals to quickly process and categorize new information based on existing knowledge.
Perceptual Sets - are the tendencies to perceive or notice some aspects of the available sensory data and ignore others. They are influenced by expectations, experiences, emotions, and culture. Perceptual sets prime individuals to perceive information in a particular way, based on prior knowledge and current context. Perceptual sets affect how individuals interpret sensory information. They can facilitate quick and efficient processing by focusing attention on relevant aspects while filtering out irrelevant details.
2.1.A.3
Contexts - refer to the circumstances or surroundings in which perception occurs. They provide essential information that influences how individuals interpret sensory information and make sense of their environment. Contexts include physical surroundings, social settings, and temporal factors that shape perception.
Experiences - encompass individual encounters and interactions with the world over time. They include personal memories, learning, and past events that shape perceptions, beliefs, and expectations. Experiences contribute to the formation of schemas and perceptual sets that influence how individuals interpret new information.
Cultural Experiences - refer to the shared beliefs, values, norms, and practices of a particular cultural group. They influence perception by shaping expectations, interpretations, and responses to sensory information based on cultural context. Cultural expectations guide behavior and social interactions within the community.
2.1.A.4
Gestalt Psychology - is a theory of perception that emphasizes how humans perceive and organize visual information into meaningful wholes or gestalts rather than as isolated elements. It proposes that the whole ofperception is greater than the sum of its parts, highlighting the role of innate principles in organizing sensory stimuli.
2.1.A.5
Attention - refers to the cognitive process of selectively concentrating on specific aspects of the environment while ignoring others. It is crucial for perception because it determines which sensory information is processed and prioritized for further cognitive processing. Attention influences various cognitive processes, including perception, memory, learning, and decision-making. By focusing attention on relevant stimuli, individuals can effectively interpret and respond to their surroundings.
Closure - allows individuals to perceive objects or shapes even when some parts are missing or obscured. It facilitates rapid recognition and interpretation of visual information by reducing ambiguity and creating a sense of completeness.
Figure and Ground - is a gestalt principle that involves perceiving visual stimuli in terms of a figure (the object of focus) and its background (the surrounding context). It helps individuals distinguish between foreground elements and the background against which they are perceived.
Proximity - is a gestalt principle that refers to the tendency to perceive objects that are close together as belonging to a unified group. It influences how individualsgroup and organize visual stimuli based on their spatial proximity or closeness to each other.
Similarity - is a gestalt principle that involves grouping together objects or elements that are similar in shape, size, color, texture, or orientation. It facilitates the perception of patterns and relationships based on shared visual characteristics.
2.1.A.5.i
Selective Attention - is the cognitive process of focusing on a specific aspect of the environment while ignoring others. It allows individuals to prioritize relevant information and filter out distractions, enhancing perceptual efficiency and cognitive processing. In a crowded classroom, selective attention enables students to focus on the teacher's lecture while filtering out background noise, such as conversations or footsteps in the hallway.
The Cocktail Party Effect - is a phenomenon that demonstrates the ability to selectively attend to one auditory stimulus while filtering out other competing stimuli. It allows individuals to focus on a specific conversation or sound amidst a noisy or crowded environment. At a social gathering, individuals can engage in a conversation with one person while simultaneously ignoring background noise, such as music or other conversations.
2.1.A.5.ii
Change Blindness - is a phenomenon where individuals fail to detect changes in visual scenes, even when those changes are significant. It occurs when attention is not directed to the changing element or when the change is gradual or subtle, leading to the perception that the scene has remained unchanged. In a busy cityscape, pedestrians may not notice changes in billboard advertisements or storefront displays if their attention is directed toward navigating crowded sidewalks or avoiding obstacles.
2.1.B.1
Binocular Cues - are visual cues that require the use of both eyes to perceive depth or distance accurately. These cues provide information about the spatial relationships between objects in the environment by comparing the slightly different views seen by each eye.
Retinal Disparity - is the discrepancy between the images projected onto each retina due to the distance between the eyes. It is a binocular cue that helps determine the relative distance of objects. Greater retinal disparity indicates closer objects, while smaller disparity suggests greater distance.
Convergence - is a binocular cue that involves the inward movement of both eyes to maintain focus on nearby objects. It signals the brain about the proximity of objects based on the degree of muscular tension required to keep both eyes aligned. When reading a book held at arm's length, convergence adjusts to focus on the text. The greater inward movement of the eyes signals that the book is nearby, facilitating comfortable and clear vision for close-up tasks.
2.1.B.2
Monocular Depth Cues - are visual cues that require input from only one eye to perceive depth or distance in the environment. These cues provide essential information for organizing the perceptual world by enabling individuals to perceive three-dimensional space using visual information available to each eye separately.
Relative Clarity - or atmospheric perspective, is a monocular depth cue that involves the perception of depth based on the clarity or sharpness of visual stimuli. Objects that are closer appear sharper and more detailed, while distant objects appear hazy or blurred due to atmospheric conditions such as fog or smog.
Relative Size - is a monocular depth cue that involves perceiving depth based on the apparent size of objects in the visual field. Objects that appear larger are perceived as closer, while smaller objects are interpreted as farther away, assuming they are of similar actual size.
Texture Gradient - is a monocular depth cue that involves the perception of depth based on the gradual change in texture or detail of a surface as it recedes into the distance. Objects or surfaces with finer texture or more distinct details are perceived as closer, while those with less detail appear farther away.
Linear Perspective - is a monocular depth cue that involves the perception of depth based on the convergence of parallel lines that appear to converge at a vanishing point in the distance. It creates the illusion of depth and distance by simulating the way parallel lines appear to converge as they recede into the distance.
Interposition (Overlap) - is a monocular depth cue that involves perceiving depth based on the partial obstruction of one object by another. When one object partially covers or overlaps another, the partially obscured object is perceived as farther away, while the overlapping object is seen as closer.
2.1.B.3
Perceptual Constancies - are the tendency of perceptual systems to maintain stable perceptions of objects despite variations in sensory input. They allow humans to perceive objects as stable and unchanged despite changes in size, shape, color, or orientation. Perceptual constancies play a crucial role in organizing the perceptual world by ensuring that individuals recognize and interpret objects accurately across different conditions and perspectives.
• Size Constancy: When viewing an object at different distances, size constancy allows individuals to perceive the object as maintaining a consistent size. For example, a car viewed from afar appears smaller than when viewed up close, yet it is perceived as the same size due to size constancy.
• Shape Constancy: Shape constancy enables individuals to perceive objects as maintaining their shape regardless of viewing angle or perspective. For instance, a circular table viewed from an angle is still perceived as a circle, demonstrating shape constancy.
• Color Constancy: Color constancy allows individuals to perceive the color of objects as stable under different lighting conditions. For example, a red apple appears red under both daylight and artificial light, despite variations in the wavelengths of light.
2.1.B.4
Apparent Movement - refers to the perception of motion or movement in visual stimuli that are actually static or presented sequentially. It occurs when discrete images or objects are presented in succession with a brief temporal delay, creating the illusion of continuous motion.
• Phi Phenomenon: The phi phenomenon refers to the perception of motion when two or more adjacent lights blink on and off in succession. This creates the illusion of a single light moving back and forth between the two locations.
• Beta Movement: Beta movement occurs when a series of static images are presented in succession with spatial displacement. Despite no actual motion, viewers perceive continuous movement due to the rapid presentation of images.