Ch. 4 Sensation Perception PP

Chapter 4: Sensation & Perception

Sensation & Perception: The Distinction

  • Sensation: Process by which sensory receptors and nervous system receive and represent stimulus energy (Bottom-Up Processing).

  • Perception: Selection, organization, and interpretation of sensory input, enables recognition of meaningful objects (Top-Down Processing).

Sensation: Principles

  • Absolute Threshold: Minimum stimulus intensity detected 50% of the time.

  • Just Noticeable Difference (JND): Smallest difference between two stimuli detectable 50% of the time.

    • Weber’s Law: JND proportionate to the size of the initial stimulus.

Absolute Threshold

  • Detection Percentages:

    • 100% of correct detections when stimuli detectable above absolute threshold.

    • 75% to 50% detection indicates subliminal stimuli.

  • Thresholds: Low, Medium, and High absolute thresholds correlate with stimulus intensity.

Psychophysics: Concepts & Issues

  • Signal-Detection Theory: Involves sensory and decision processes.

    • Observer responses:

      • "Yes, I see it" (Hit)

      • "No, I don’t see it" (Miss)

      • Signal absent:

        • "False alarm" (mistake)

        • "Correct rejection" (correct).

  • Sensory Adaptation: Decline in sensitivity to prolonged stimulation.

The Eye: Transduction

  • Eye Components:

    • Cornea: Outer layer, light entry point.

    • Pupil: Regulates light amount.

    • Iris: Colored muscle controlling pupil size.

    • Lens: Focuses light rays on retina (Accommodation: adjusts for distance).

    • Retina: Absorbs light and processes images.

    • Optic Nerve: Transfers visual information to brain.

Types of Vision Disorders

  • Nearsightedness: Distant objects appear blurry due to focus point falling in front of retina.

  • Farsightedness: Close objects appear blurry with focus point falling behind retina.

The Retina

  • Fovea: Center of retina for clearest vision.

  • Blind Spot/Optic Nerve: No visual receptors at this point.

  • Photoreceptor Cells:

    • Rods: Enable black and white/low light vision.

    • Cones: Enable color vision (adaptation from various light conditions).

Wavelength and Amplitude

  • Color Vision:

    • Short wavelength = high frequency (blues); long wavelength = low frequency (reds).

    • Amplitude: Determines brightness (high amplitude = bright colors).

  • Additive Color Mixing: Combining colored light (RGB).

  • Subtractive Color Mixing: Mixing pigments (CMY).

Theories of Color Vision

  • Trichromatic Theory: Photoreceptors have red, green, and blue cones.

    • Dichromatism: Two types of cones, primarily in males.

    • Monochromatism: One type of cone, shades of gray.

  • Opponent Process Theory: Three pairs of antagonistic colors.

    • Afterimage effect: image persists post-stimulus removal.

Visual Information Processing

  • Order of processing: Light → rods/cones → bipolar cells → ganglion cells → optic nerve → optic chiasm → thalamus → occipital lobe.

  • Blindsight: Condition where individuals cannot consciously see but can detect object position due to brain processing.

Feature Detectors

  • Feature Detectors: Neurons responding to specific features like lines and edges, essential for complex visual processing (e.g., face detection).

Auditory System

  • Sound Waves: Vibrations in air characterized by amplitude (loudness) and wavelength (pitch).

    • Frequency measured in Hz (cycles per second).

The Ear

  1. External Ear: Collects sound via Pinna, Auditory Canal, and Tympanic Membrane.

  2. Middle Ear: Contains ossicles (hammer, anvil, stirrup).

  3. Inner Ear: Cochlea converts sound vibrations to neural signals.

Theories of Pitch Perception

  • Place Theory: Different pitches correspond to vibrations at specific locations on the basilar membrane.

  • Frequency Theory: Pitch correlates with the vibration frequency of the entire membrane.

  • Volley Theory: Neurons alternate firing for high frequencies.

Sound Localization

  • Cues critical for locating sound: intensity and timing differences between ears.

  • Types of Deafness:

    • Conduction Deafness: Sound blockage in outer/middle ear.

    • Sensorineural Deafness: Damage to cochlear hair cells.

The Chemical Senses: Taste

  • Taste (Gustation): Involves soluble chemicals affecting taste buds; paths to the brain involve neural impulses.

  • Primary Tastes: Sweet, Sour, Bitter, Salty, Umami, Oleogustus.

  • Tasters: Super, Medium, Non-tasters classified by taste bud density.

The Chemical Senses: Smell

  • Smell (Olfaction): Detects airborne chemicals via olfactory receptors; follows a distinct pathway to the brain.

  • Pheromones: Chemicals triggering social or sexual responses.

Skin Sense: Touch

  • Types of stimuli: pain, pressure, temperature.

  • Pathway: Sensory receptors → spinal column → brainstem → thalamus → somatosensory cortex.

  • Pain Control: Gate Control Theory explains pain signal regulation.

Other Senses: Interaction

  • Sensory Interaction: Experience with one sense may influence another (e.g., taste and smell).

  • Synesthesia: Mixing of sensory experiences (e.g., hearing colors).

  • Kinesthesis: Awareness of body movement and position.

Transduction

  • Transduction: Conversion of sensory input to neural impulses for brain processing occurs in various senses (eye, ear, tongue, nose).

Perception

  • Reversible Figures: Ambiguous images with dual interpretations.

  • Subjectivity of Perception: Influenced by experiences and biases.

Selective Attention

  • Inattentional Blindness: Failure to notice changes when focused elsewhere.

  • Change Blindness: Noticing changes without focused attention.

  • Selective Attention: Focus on a particular stimulus while ignoring others.

Perceptual Set

  • Perceptual Sets: Readiness to perceive stimuli in a certain way based on experiences.

Gestalt Principles of Perception

  • Gestalt Psychology: Emphasizes the whole context of perception.

  • Principles:

    1. Figure-ground

    2. Proximity

    3. Similarity

    4. Closure

Perceptual Constancies

  • Constancies: Recognizing objects as constant despite changes in perspective or conditions (size, shape, brightness).

Depth & Distance

  • Binocular Cues: Depth perception via retinal disparity and convergence.

  • Monocular Cues: Use of a single eye for depth perception (e.g., motion parallax).

    • Pictorial Cues: Techniques depicting depth in images (linear perspective, texture gradient).

Depth Perception

  • Visual Cliff Studies: Suggest depth perception can be learned through experience.

Apparent Motion

  • Stroboscopic Motion: Illusion of motion from rapid image succession.

  • Phi Phenomenon: Perceived motion when lights flash in sequence.

Optical Illusions

  • Optical Illusions: Differences between visual interpretation and reality; famous examples include Ponzo and Müller-Lyer illusions.