Sensation and Perception

CHAPTER 4: SENSATION & PERCEPTION

Overview

  • This chapter discusses the distinct processes of sensation and perception, integral to understanding human interaction with the environment.

  • Sensation involves gathering information through the senses, while perception involves interpreting this information.

Reminders

  • Chapter 5 Learning Curves due: Sunday, Sept. 28th at 11:59 pm.

  • SONA Research Participation must be completed by December 5th.

SONA Research Participation (Detailed Guidelines)

  • Requirement: Earn six research participation credits through the SONA system.

  • Two methods to earn credits:

    1. Participate in research studies:

    • 30 minutes = 1 research participation credit.

    • In-person studies earn double credits.

    1. Write a research paper about a psychology study published in a journal:

    • 1 paper = 2 research credits.

    • Follow document requirements listed on the SONA tab of our D2L page.

CHAPTER OUTLINE

  • Sensation and Perception are Distinct Activities

  • Visual Pathways: Connections Between the Eye and the Brain

  • Visual Perception: Recognizing What We See

  • Hearing: More Than Meets the Ear

  • The Body Senses: More Than Skin Deep

  • The Chemical Senses: Adding Flavor

SENSATION AND PERCEPTION ARE DISTINCT ACTIVITIES

Making Sense of the World

  • Sensation: Defined as the simple stimulation of a sensory organ.

  • Perception: Defined as the organization, identification, and interpretation of a sensation to form a mental representation.

The Process of Sensation & Perception

  • Starts with Stimulus Energy (light, sound, smell, etc.).

  • Interaction with Sensory Receptors (eyes, ears, nose, etc.).

  • Leads to Neural Impulses that are processed in the brain (visual, auditory, olfactory areas).

Steps of Sensation

  1. Reception: Stimulation of sensory receptor cells by energy.

  2. Transduction: Conversion of physical signals from the environment into neural signals sent to the Central Nervous System.

  3. Transmission: Delivering neural information to the brain for processing.

Sensory Adaptation

  • Definition: The decline in sensitivity to prolonged stimulation over time as an organism adapts to constant conditions.

  • Example: If an external stimulus remains unchanged, the sensory system reduces its response to prevent neurotic behaviors.

PSYCHOPHYSICS & SIGNAL DETECTION

Psychophysics

  • Definition: Methods that systematically relate the physical characteristics of a stimulus to an observer’s perspective.

  • Absolute Threshold: The minimal intensity needed to detect a stimulus 50% of the time across various trials.

    • Examples:

      • Vision: A candle flame 30 miles away on a clear, dark night.

      • Hearing: A clock’s tick 20 feet away when all is quiet.

      • Touch: A fly’s wing falling on the cheek from 1 cm away.

      • Smell: A single drop of perfume in a volume equivalent to six rooms.

      • Taste: A teaspoon of sugar dissolved in two gallons of water.

Just Noticeable Difference (JND)

  • Definition: The minimal change in a stimulus that can barely be detected.

  • Weber’s Law: Denotes that the change in a stimulus that is just noticeable is a constant proportion relative to the initial stimulus's intensity.

Signal Detection Theory

  • Definition: Suggests that the response to a stimulus is influenced by both an individual's sensitivity to the stimulus amid background 'noise' and their decision criteria for detecting it.

  • Example: Waiting for an important phone call amidst distractions.

VISUAL PATHWAYS: CONNECTIONS BETWEEN THE EYE AND THE BRAIN

Sensing Light

  • Visible Light: Form of electromagnetic energy with a specific wavelength range that humans can see.

  • Wavelengths: Distance between peaks; determines hue/
    color.

  • Amplitude: Corresponds to brightness/intensity.

  • Purity: Refers to how narrowly a light source emits its wavelengths.

Anatomy of the Eye

  • Cornea: Clear, smooth tissue that bends light waves.

  • Pupil: Opening in the iris, adjusting based on light intensity.

  • Iris: Colored muscle that controls the pupil size and light intake.

  • Lens: Bends light to focus on the retina, controlled by eye muscles.

  • Accommodation: The process in which the lens changes shape based on the distance of objects to maintain a clear image on the retina.

Common Vision Problems

  • Nearsightedness (Myopia): When the eyeball is too long, images focus in front of the retina.

  • Farsightedness (Hyperopia): When the eyeball is too short, images focus behind the retina.

Light Transduction in the Retina

  • Photoreceptor Types:

    • Cones: Responsible for color vision under daylight conditions; allow fine detail focus.

    • Rods: Active in low light; facilitate night vision.

  • Fovea: Area of retina providing sharpest vision, lacks rods.

  • Blind Spot: Area in visual field with no photoreceptors due to the optic nerve exit.

THE BRAIN'S VISUAL PATHWAYS

Visual Pathways in the Brain

  • Information from the optic nerve reaches the lateral geniculate nucleus in the thalamus, then to the primary visual cortex (V1).

  • Ventral Stream: Processes “what” we see (identifying objects).

  • Dorsal Stream: Processes “where” objects are located and perception for action.

Color Vision

  • Color perception fundamentally relies on the absorption of wavelengths by three types of cones (long, medium, and short wavelengths).

  • White light is understood as equal representation of all visible wavelengths.

VISUAL PERCEPTION: RECOGNIZING WHAT WE SEE

Object Recognition

  • Parallel Processing: Brain's ability to manage multiple activities simultaneously.

  • Perceptual Constancy: Consistency in perception, despite changes in sensory signals.

Gestalt Principles of Perceptual Organization

  • Focus on features grouping to form whole objects:

    • Figure-Ground: Focusing on an object against a background.

    • Simplicity: Preference for the simplest interpretation of an object’s shape.

    • Closure: Tendency to fill in missing parts of a visual scene.

    • Continuity: Grouping edges or contours with the same orientation.

    • Similarity: Perception of objects with similar attributes as part of the same group.

    • Proximity: Objects near each other are perceived to belong together.

    • Common Fate: Moving elements are perceived as one single object.

Depth and Size Perception

  • Depth Perception: Ability to visualize objects in three dimensions from two-dimensional retina images.

  • Types of Cues:

    • Monocular Cues: Information about depth from one eye, including distance, size, and texture gradients.

    • Binocular Cues: Distance judgments requiring both eyes, including retinal disparity.

HEARING: MORE THAN MEETS THE EAR

Sensing Sound

  • Sound waves are fluctuations in air pressure perceived over time.

  • Physical dimensions of sound:

    • Amplitude: Measured in decibels (dB), correlating to loudness.

    • Frequency: Measured in Hertz (Hz), correlating to pitch.

    • Timbre: Combination of amplitude and frequency, resulting in sound quality.

Anatomy of the Ear

  • Three Distinct Parts:

    1. Outer Ear: Funnels sound waves to the middle ear.

    2. Middle Ear: Transmits vibrations via ossicles to the oval window.

    3. Inner Ear: Converts sound waves into neural impulses.

Sound Transduction in the Inner Ear

  • Cochlea: Fluid-filled structure where sound wave vibrations are transduced into neural impulses.

  • Basilar Membrane: Moves with vibrations, stimulating hair cells that convey signals to the auditory nerve.

Neural Impulse Pathway to the Brain

  1. Auditory nerve carries signals to the brainstem.

  2. Signals are routed through the thalamus to Area A1 in the primary auditory cortex of the temporal lobe.

Steps of Hearing

  1. Vibration creates sound waves.

  2. Sound waves captured by the pinnae.

  3. Waves funneled through the auditory canal.

  4. Waves cause the eardrum to vibrate.

  5. Ossicles transmit vibrations.

  6. Waves travel into cochlea.

  7. Hair cells inside the cochlea vibrate.

  8. Hair cells stimulate the auditory nerve.

  9. Brain decodes signals into recognized sounds.

PERCEPTUAL ORGANIZATION

Review of Vision and Hearing

Vision Sequence:

  1. Light enters through the cornea, bending light waves.

  2. Light flows through the pupil, which adjusts size via iris.

  3. Light reaches the lens, which shapes itself for focus on retina.

  4. Retina translates this data into images.

Hearing Sequence:

  1. Vibrations create waves.

  2. Sound waves travel to the ear.

  3. Waves hit and vibrate the eardrum.

  4. Ossicles transmit and amplify vibrations.

  5. Hair cells trigger the auditory nerve.

THE BODY SENSES: MORE THAN SKIN DEEP

Sensing Touch

  • Haptic Perception: Involves active exploration through touch, involving various receptors for different sensations such as pain, pressure, and texture.

  • Skin transmits information about temperature, pain, and spatial locations.

Pain Perception

  • Definition: Adaptive response signaling tissue damage or potential harm detected by free nerve endings.

  • Pain pathways:

    • A-delta fibers: Transmit sharp, instantaneous pain.

    • C fibers: Convey slower, dull pain.

Gate-Control Theory of Pain

  • Proposes that sensory signals may be muted by interneurons in the spinal cord, offering an explanation for how focus or activity can affect pain perception.

Proprioception and Balance

  • Proprioception: The awareness of body position in space.

  • Vestibular System: Comprises semicircular canals that assist in maintaining balance and sensing head movement.

CHEMICAL SENSES: ADDING FLAVOR

Olfactory System

  • Definition: Sense of smell operates via airborne molecules that trigger responses in olfactory receptor neurons, bypassing the thalamus before reaching the olfactory bulb.

  • Pheromones: Biochemical signals influencing behavior and emotion.

  • Role in memory: Olfaction significantly interacts with memory and taste, notably in aversions and food evaluation.

Gustation

  • Taste Mechanism: Involves five basic tastes detected by taste buds in the papillae of the tongue:

    • Sweet

    • Salty

    • Sour

    • Bitter

    • Umami (savory)

  • Flavor Perception: Results from the combination of taste, smell, and texture, emphasizing multisensory interactivity in food experience.