🥸Intro to Psychology Unit 5 – Sensation and Perception

Key Concepts and Definitions

• Sensation involves detecting physical energy from the environment and encoding it as neural signals
• Perception interprets sensory signals to create meaningful experiences of the world
• Transduction converts physical signals detected by receptor cells into neural impulses
• Sensory adaptation occurs when sensory receptors become less responsive to a stimulus over time
• Absolute threshold represents the minimum intensity of a stimulus required for conscious detection 50% of the time
• Difference threshold (just noticeable difference) signifies the minimum difference in stimuli required to detect a change 50% of the time
• Weber's law states that the just noticeable difference is a constant proportion of the original stimulus intensity
• Signal detection theory explains how decision criteria affect sensory judgments, considering both sensitivity and response bias

Sensory Systems Overview

• Sensory systems gather information from the environment, allowing organisms to respond effectively
• Sensory receptors are specialized cells or neurons that detect specific types of energy (light, sound, pressure, chemicals)
• Sensory information travels through afferent neurons to the central nervous system for processing
• The brain processes and integrates sensory information to create perceptual experiences
• Sensory thresholds determine the limits of conscious perception
  • Subliminal stimuli fall below the absolute threshold but may still influence behavior and emotions
• Sensory adaptation helps maintain sensitivity to changes in stimuli over time
• Multimodal perception involves the integration of information from multiple sensory modalities (vision, hearing, touch)

The Visual System

• Light enters the eye through the cornea, passes through the lens, and focuses on the retina
• The lens adjusts its shape to focus light from varying distances, a process called accommodation
• Photoreceptors in the retina convert light into neural signals
  • Rods are sensitive to low light levels and are responsible for peripheral and night vision
  • Cones are sensitive to color and are responsible for central, high-acuity, and daytime vision
• Bipolar cells and ganglion cells in the retina process and transmit visual information to the brain via the optic nerve
• The optic chiasm is where optic nerves from each eye partially cross, allowing for binocular vision
• Visual information is processed in the lateral geniculate nucleus of the thalamus before reaching the primary visual cortex
• The primary visual cortex (V1) processes basic visual features like edges, orientation, and motion
• Higher-order visual areas (V2, V4, MT) process more complex features like color, form, and motion integration

Auditory Perception

• Sound waves are captured by the outer ear and funneled through the auditory canal to the eardrum
• The eardrum vibrates, transmitting sound to the ossicles (malleus, incus, stapes) in the middle ear
• The ossicles amplify and transmit vibrations to the oval window of the cochlea in the inner ear
• The cochlea contains the basilar membrane, which vibrates in response to sound, stimulating hair cells
• Hair cells convert mechanical vibrations into neural signals, which are transmitted via the auditory nerve to the brain
• The auditory cortex processes pitch, loudness, and localization of sounds
• Binaural cues, such as interaural time and level differences, help localize sounds in space
• The auditory system can distinguish between different sound frequencies and detect pitch
• Auditory scene analysis allows the brain to separate and group sound sources in complex auditory environments

Other Senses: Touch, Taste, and Smell

• Touch receptors in the skin respond to pressure, vibration, temperature, and pain
  • Mechanoreceptors detect pressure and vibration
  • Thermoreceptors detect temperature changes
  • Nociceptors detect pain and tissue damage
• The somatosensory cortex processes tactile information, with different areas representing different body parts (somatotopic organization)
• Taste receptors (taste buds) on the tongue detect five basic tastes: sweet, salty, sour, bitter, and umami
• Smell receptors (olfactory receptors) in the nasal cavity detect odor molecules dissolved in mucus
• The olfactory bulb and olfactory cortex process smell information
• Taste and smell interact to create the perception of flavor
• The trigeminal nerve contributes to the perception of spiciness, coolness, and other chemesthetic sensations

Perceptual Processing

• Top-down processing involves the influence of prior knowledge, expectations, and context on perception
• Bottom-up processing involves the direct interpretation of sensory information without the influence of higher-level factors
• Gestalt principles describe how the brain organizes visual information into meaningful patterns
  • Proximity: elements close together are perceived as a group
  • Similarity: similar elements are perceived as a group
  • Continuity: elements arranged in a continuous pattern are perceived as a group
  • Closure: incomplete elements are perceived as complete or whole objects
• Perceptual constancy allows the brain to maintain a stable perception of objects despite changes in sensory input (size, shape, color)
• Depth perception relies on monocular cues (relative size, occlusion) and binocular cues (retinal disparity) to estimate distance
• Motion perception involves the detection of changes in position over time, processed by the MT (middle temporal) area of the visual cortex

Illusions and Perceptual Errors

• Illusions demonstrate the brain's active role in constructing perceptual experiences
• Optical illusions exploit the brain's assumptions and processing mechanisms to create false or misleading perceptions
  • The Müller-Lyer illusion shows how the brain uses context to judge line length
  • The Ebbinghaus illusion demonstrates how the brain uses relative size to judge object size
• Multistable percepts, like the Necker cube, show how the brain can alternate between different interpretations of the same sensory input
• The McGurk effect illustrates the influence of visual information on speech perception
• Perceptual errors can occur due to sensory limitations, ambiguous stimuli, or cognitive biases
• Inattentional blindness occurs when focusing on a task causes an individual to miss unexpected stimuli
• Change blindness is the failure to detect changes in a visual scene, especially when attention is diverted

Real-World Applications

• Understanding sensation and perception can improve product design, user experience, and ergonomics
  • Designing visual displays and interfaces that are easy to read and navigate
  • Creating auditory alarms and signals that are easily detectable and distinguishable
• Sensory substitution devices can help individuals with sensory impairments by translating information from one modality to another
  • Cochlear implants convert sound into electrical signals to restore hearing in deaf individuals
  • Tactile displays can convey visual information through touch for visually impaired individuals
• Virtual and augmented reality technologies rely on understanding sensory processing to create immersive experiences
• Studying perceptual illusions and errors can inform strategies for reducing accidents and improving safety
  • Designing road signs and markings that are resistant to perceptual distortions
  • Training pilots and drivers to recognize and overcome perceptual biases
• Art, music, and culinary arts exploit principles of sensation and perception to create aesthetic experiences and evoke emotions