5-1 Sensation vs. Perception

Sensation vs. Perception

- Sensation: The process by which sensory receptors in the sense organs respond to external stimuli, converting them into neural impulses for the brain to interpret.

- Perception: Involves organizing and interpreting these sensory signals into meaningful experiences. Sensation is passive and constant, while perception requires active interpretation.

Processing Types

- Bottom-up Processing: Analyzing small details to build a full perception; data-driven and often slower but more accurate.

- Top-Down Processing: Using prior knowledge and expectations to interpret sensory information; expectation-driven, as seen in phenomena like backmasking (hearing hidden messages in music based on cues).

Attention Mechanisms

- Selective Attention: Focusing on specific stimuli among the many we encounter, like the "Cocktail Party Effect," where we can tune into a single voice in a noisy environment.

- Inattentional Blindness: Missing visible objects due to attention being focused elsewhere.

- Change Blindness: Failing to notice changes in a visual environment, illustrated in visual tests.

Sensory Thresholds

- Absolute Threshold: The minimum stimulus required for detection (e.g., hearing a watch tick from 20 feet away in silence).

- Difference Threshold (Just Noticeable Difference): The smallest detectable difference between two stimuli, governed by Weber's Law (constant percentage difference).

- Sensory Adaptation: Reduced sensitivity due to prolonged exposure, allowing focus on novel changes in the environment.

- Synesthesia: A condition where stimulation of one sense involuntarily triggers another, like associating colors with sounds. Notable individuals with synesthesia include Kanye West, Pharrell Williams, and Billie Eilish.

- Signal Detection Theory: Predicts when weak stimuli will be detected, influenced by factors like expectations, motivation, and alertness. Often exemplified in scenarios requiring high vigilance (e.g., air traffic control).

Subliminal Stimulation and Priming

- Subliminal Stimulation: Perception of stimuli below conscious awareness; may influence sensation but has limited evidence for behavior influence.

- Priming: Activating associations in memory; although it is often subtle, it can shape responses to stimuli based on previous exposure.

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5-2 Visual System

Vision as a Dominant Sense

- Vision is the primary way people gather information about their environment, though it is sometimes easily misled by visual illusions.

Visual System and Transduction

- Transduction: The conversion of light (electromagnetic energy) into neural impulses. Light wavelength determines color (hue), and amplitude determines brightness.

Structure of the Eye

- Cornea: Protects the eye and allows light to enter.

- Pupil and Iris: The pupil regulates light intake, and the iris adjusts based on light and emotion.

- Lens: Focuses light onto the retina; lens shape changes for near or far objects.

- Retina: Contains receptors (rods and cones) that detect light and color. Rods are for black-and-white vision (peripheral and low-light), while cones detect color and detail (center vision).

Visual Processing Pathway

- Optic Nerve: Transfers visual information to the brain, creating a blind spot where it connects to the retina.

- Thalamus and Visual Cortex: Neural signals from the optic nerve are sent to the visual cortex in the occipital lobe for interpretation.

Color Vision Theories

- Trichromatic Theory: The retina has three types of cones (red, green, blue) that combine to produce all colors.

- Opponent-Process Theory: Post-receptor processing interprets colors in opposing pairs (red-green, yellow-blue, black-white), explaining phenomena like afterimages.

Color Vision Deficiencies

- Dichromatism: Seeing only two of the three primary colors.

- Monochromatism: Complete color blindness, seeing shades of only one color.

Parallel Processing and Feature Detection

- Parallel Processing: The brain processes aspects like color, motion, shape, and depth simultaneously.

- Feature Detection: Specialized cells respond to visual features (e.g., lines, angles), with specific clusters for facial recognition.

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5-3 Perceptual Organization

1. Gestalt Psychology: Studies how we naturally integrate pieces of information into meaningful wholes. Key principles include proximity, similarity, and closure in organizing visual information.

2. Figure-Ground: The ability to distinguish a figure from its background, allowing us to focus on specific objects while distinguishing them from their surroundings.

3. Depth Perception: Our ability to perceive the world in three dimensions and judge distances. This ability develops in infancy.

4. Depth Cues:

- Binocular Cues (require both eyes):

- Retinal Disparity: The difference in images between the two eyes.

- Convergence: The inward angle of the eyes focusing on a close object.

- Monocular Cues (one eye only): Include interposition, linear perspective, relative size, clarity, and texture gradient.

5. Perceptual Constancy: Perceiving objects as unchanging despite changes in lighting, distance, or angle. Types include size, lightness, and color constancy.

6. Perceptual Adaptation: The ability to adjust to altered visual fields, such as an upside-down or shifted view.

7. Perceptual Set: A mental predisposition influenced by expectations or prior knowledge, shaping how we perceive stimuli.

8. Context Effects: Immediate surroundings can alter how we perceive an object or situation.

Vocabulary

- Gestalt Psychology: The study of how we organize parts into wholes.

- Figure-Ground: Differentiating an object (figure) from its background (ground).

- Depth Perception: The ability to see the world in three dimensions.

- Binocular Cues: Depth cues that require two eyes.

- Monocular Cues: Depth cues available with one eye.

- Perceptual Constancy: Recognizing objects as constant despite changes in appearance.

- Perceptual Adaptation: Adjusting to distorted visual inputs.

- Perceptual Set: Readiness to perceive something in a particular way based on expectations.

- Context Effects: Changes in perception influenced by surrounding context.

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5-5 Skin Senses

1. Somesthetic (Touch) Senses: The skin, our largest organ, has receptors for pressure, temperature, and pain, which alert us to potential harm.

2. Pain Perception:

- Biological Influences: Nociceptors detect harmful stimuli, and Gate Control Theory explains that the spinal cord can block or allow pain signals.

- Psychological Influences: Distraction and memory can alter pain perception, with memories focusing on peak moments and the end.

- Socio-Cultural Influences: Pain perception increases when we observe others in pain.

- Pain Control Methods: Include biological (drugs, acupuncture) and psychological (placebos, relaxation).

3. Kinesthetic System: Provides awareness of body position and movement through proprioceptors in muscles and joints, helping with tasks requiring spatial awareness.

4. Vestibular System: Maintains balance via fluid movement in the inner ear; it can cause sensations like dizziness or motion sickness due to sensory mismatches.

5. Touch Sensitivity:

- Receptors detect pressure, temperature, and pain. Only pressure has specific receptors, while combinations of signals (e.g., warm + cold) create complex sensations.

Vocabulary

- Somesthetic Senses: Skin-based senses (touch, temperature, pain).

- Nociceptors: Pain receptors detecting harmful stimuli.

- Substance P: Neurotransmitter involved in pain signal transmission.

- Gate Control Theory: Theory that spinal cord “gates” control pain signal transmission.

- Proprioceptors: Sensory neurons for body position and movement.

- Vestibular System: System in the inner ear managing balance and spatial orientation.

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5-6 Chemical Senses

1. Chemical Senses:

- Taste (Gustatory System): Detects six primary tastes: sweet, salty, sour, bitter, umami (savory), and oleogustus (fat). Taste buds, located on papillae, renew every two weeks. Expectations influence taste perception, and "supertasters" experience tastes more intensely.

- Smell (Olfactory System): 5 million receptors detect about 10,000 smells. The olfactory bulb processes smell without the thalamus, connecting directly to the limbic system, which associates smell with emotions and memories.

2. Pheromones: Chemical signals that influence behavior or physiology within a species, affecting areas like mating and territoriality.

3. Sensory Interaction: Senses influence one another (e.g., smell enhances taste). The McGurk Effect illustrates how vision can alter auditory perception.

4. Kinesthetic System: Involves proprioceptors in muscles and joints that detect body position and movement.

5. Vestibular System: Balances and orients the body using fluid movement in the inner ear. Conflicts with visual cues can lead to motion sickness.

6. Anosmia: The absence of the sense of smell, which can reduce enjoyment of food and make it harder to detect hazards.

Vocabulary

- Gustatory System: The sensory system responsible for taste.

- Papillae: Small bumps on the tongue that contain taste buds.

- Olfactory Cilia: Receptor cells for smell in the nasal cavity.

- Olfactory Bulb: The brain region where smell information is processed.

- Pheromones: Chemical substances affecting the behavior or physiology of others in the species.

- Sensory Interaction: The principle that senses can influence each other.

- Kinesthetic Sense: Awareness of body movement and position.

- Proprioceptors: Sensory receptors that detect body position.

- Vestibular System: Maintains balance and spatial orientation.

- Anosmia: Loss of the sense of smell.