Lecture 5: Sensation & Perception PDF

Lecture 5: Sensation & Perception: 1. Sensation vs. Perception: ○ Sensation is the process by which sensory receptors and the nervous system detect stimuli from the environment (light, sound, touch, etc.). ○ Perception is how the brain organizes and interpre...

Lecture 5: Sensation & Perception: 1. Sensation vs. Perception: ○ Sensation is the process by which sensory receptors and the nervous system detect stimuli from the environment (light, sound, touch, etc.). ○ Perception is how the brain organizes and interprets this sensory information to make it meaningful, allowing us to recognize objects, events, and patterns. ○ Example: Sensation occurs when light hits the retina in the eye, while perception happens when the brain interprets this light as an image or object​(Psych 100-F24-Lecture 5…). 2. Sensory Receptors & Transduction: ○ Sensory receptors are specialized neurons that detect external stimuli. ○ Sensory transduction is the process of converting physical stimuli (like light or sound) into chemical energy (neuronal signals). This is the first step in sensation. ○ Example: In vision, light waves are transduced into neural signals that the brain interprets as visual images​(Psych 100-F24-Lecture 5…). 3. The Visual System: ○ Light is a form of electromagnetic radiation, with wavelengths between 380 nm and 760 nm being visible to the human eye. ○ The human eye has several key parts: 1. Cornea: Transparent outer layer where light enters. 2. Iris: Muscular ring that controls the size of the pupil (the hole where light enters). 3. Lens: Focuses light onto the retina. 4. Retina: Contains the photoreceptors (rods and cones) responsible for detecting light. 5. Optic nerve: Transmits signals from the retina to the brain​(Psych 100-F24-Lecture 5…). Photoreceptors: Rods vs. Cones: ○ Cones: 1. Responsible for detailed, color vision and work best in daylight. 2. Concentrated in the fovea, the area of the retina with the highest visual acuity. ○ Rods: 1. More numerous than cones and responsible for vision in low-light conditions. 2. Located primarily in the peripheral parts of the retina and does not detect color. ○ Example: In dim light, we rely more on rods, which is why colors are harder to see at night​. Depth Perception: ○ Binocular depth cues: - Relies on the slightly different views from both eyes (retinal disparity) and the convergence of the eyes when focusing on objects up close. ○ Monocular depth cues: - Useful for objects at greater distances and include cues like relative size (closer objects appear larger) and linear perspective (parallel lines appear to converge as they get farther away). Example: The Ponzo illusion is a classic example of how linear perspective can trick our depth perception​(Psych 100-F24-Lecture 5…). Gestalt Principles of Perception:  ○ Gestalt psychology studies how we perceive whole objects rather than just a collection of parts. ○ Key principles: Closure: We fill in gaps to create a complete object. Similarity: Objects that are similar are grouped together. Proximity: Objects that are near each other are perceived as related. Good continuation: We perceive smooth, continuous lines rather than disjointed ones. Perceptual Constancies: ○ Size constancy: We perceive objects as the same size even if their image on the retina becomes smaller as they move away. ○ Shape constancy: We perceive objects as maintaining the same shape even when viewed from different angles. ○ Color constancy: Our brain adjusts for changes in lighting so that we perceive objects as maintaining their color​(Psych 100-F24-Lecture 5…). Lecture 5: Sensation & Perception (Additional Notes): Light as a Stimulus: ○ Light is part of the electromagnetic spectrum (380-760 nm). ○ Wavelength determines color (short = blue/violet, long = red). The Auditory System: ○ Sound waves are created by vibrating objects. ○ Frequency (Hz) determines pitch, amplitude (dB) determines loudness. ○ Structure of the ear: - Outer ear (Pinna): Collects sound waves. - Middle ear: Tympanic membrane (eardrum) & ossicles (malleus, incus, stapes). - Inner ear: Cochlea, where sound is transduced into neural signals by hair cells. Transduction of Sound: ○ Sound vibrations move the basilar membrane, shearing hair cells, which convert it to neural signals (auditory nerve). Somatosensory System: ○ Detects sensations: touch, pressure, vibration, pain, temperature. ○ Receptors: pressure-sensitive, thermoreceptors, nociceptors (pain). The Homunculus & Somatosensory Cortex: ○ Sensory input is mapped in the brain; body parts with more sensory input are represented larger (e.g., hands, lips). Perception & Psychophysics:  ○ Psychophysics: Study of stimulus-perception relationship. ○ Absolute threshold: Minimum stimulus intensity detectable 50% of the time. ○ Subliminal perception: Processing stimuli below conscious detection. The Gestalt School & Grouping Principles: ○ Gestalt psychology: Perception of whole objects, not just parts. ○ Grouping principles: Similarity, proximity, continuity, closure.