Key Concepts in Sensation, Perception, Consciousness, Sleep, Stress, and Personality

Study Guide - Smart Notes

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Sensation and Perception

Difference Threshold / Just Noticeable Difference (JND)

The difference threshold, also known as the just noticeable difference (JND), is the minimum amount of change in a stimulus that can be detected.

Definition: The smallest difference in stimulation that can be reliably detected by an observer.
Example: Detecting the difference in weight between two objects.

Absolute Threshold

The absolute threshold is the minimum intensity of a stimulus that can be detected at least 50% of the time.

Example: The faintest sound a person can hear.

Weber's Law

Weber's Law states that the JND is a constant proportion of the original stimulus intensity.

Formula: where is the change in intensity, is the original intensity, and is a constant.
Application: If you can detect a 1 lb increase in a 10 lb weight, you will need a 2 lb increase to detect a difference in a 20 lb weight.

Sensation

Sensation refers to the process by which sensory receptors and nervous system receive and represent stimulus energies from the environment.

Perception

Perception is the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

Subthreshold Stimuli

Subthreshold (Subliminal) stimuli are stimuli that are below the threshold of conscious awareness.

Example: A brief image flashed so quickly that it is not consciously perceived.

Adaptation

Sensory adaptation is the diminished sensitivity to a constant stimulus over time.

Example: Not noticing the feeling of clothes on your skin after wearing them for a while.

Habituation

Habituation is a decrease in response to a stimulus after repeated presentations.

Vision and Hearing

Wavelength (Vision): Determines color.
Pitch (Sound): Determined by the frequency of sound waves.
Amplitude: Determines brightness (vision) or loudness (sound).

Purity

Purity refers to the complexity of a light or sound wave, affecting the saturation of color or timbre of sound.

Theories of Hearing

Place Theory: Different frequencies stimulate different places on the basilar membrane.
Frequency Theory: The rate of nerve impulses matches the frequency of a tone.

Ear Anatomy

Eardrum: Vibrates in response to sound waves.
Taste Buds: Sensory organs for taste.
Papillae: Structures on the tongue containing taste buds.

Gustation

Gustation is the sense of taste, involving five primary tastes: sweet, sour, salty, bitter, and umami.

Olfactory System

Olfactory senses are responsible for the sense of smell.

Somesthetic Senses

Somesthetic senses include skin senses (touch, pressure, temperature, pain), kinesthetic sense (body position), and vestibular sense (balance).

Gate-Control Theory

Gate-control theory proposes that the spinal cord contains a neurological "gate" that blocks or allows pain signals to pass to the brain.

Monocular and Binocular Cues

Monocular cues: Depth cues available to either eye alone (e.g., size, linear perspective).
Binocular cues: Depth cues that require both eyes (e.g., retinal disparity).

Constancy

Size constancy: Perception that an object remains the same size despite changes in its distance.
Shape constancy: Perception that an object maintains its shape despite changes in viewing angle.
Brightness constancy: Perception that the brightness of an object remains the same under different lighting conditions.

Gestalt Principles of Perception

Gestalt principles describe how we organize sensory information into meaningful wholes.

Proximity: Objects close together are perceived as a group.
Similarity: Similar objects are grouped together.
Closure: We fill in gaps to create a complete object.

States of Consciousness

Waking: Normal alert awareness.
Altered: Includes sleep, hypnosis, meditation, and drug-induced states.

Circadian Cycle

The circadian cycle is the biological clock that regulates bodily rhythms on a 24-hour cycle.

Suprachiasmatic nucleus: Part of the brain that controls sleep-wake cycles.
Melatonin: Hormone that regulates sleep.

Adaptive Theory of Sleep

The adaptive theory of sleep suggests that sleep evolved to protect animals during periods of vulnerability.

Sleep Disorders

Sleepwalking: Walking during sleep, typically during deep sleep.
Insomnia: Difficulty falling or staying asleep.
Apnea: Breathing interruptions during sleep.

Stress and Personality

Stress vs. Stressor

Stressor: Any event or situation that causes stress.
Stress: The body's response to a stressor.

Mental vs. Physical Symptoms of Stress

Mental symptoms: Anxiety, irritability, difficulty concentrating.
Physical symptoms: Headaches, muscle tension, fatigue.

Types of Stress

Distress: Negative stress.
Eustress: Positive, motivating stress.
Catastrophe: Large-scale, unpredictable events causing stress.
Hassles: Everyday minor irritations.
Pressure: Demands to perform or conform.
Frustration: Blocked goals.

Aggression

Regression: Reverting to earlier behaviors.
Displaced aggression: Redirecting anger to a safer target.

Conflict Types

Approach-approach conflict: Choosing between two desirable options.
Approach-avoidance conflict: One option has both positive and negative aspects.
Double approach-avoidance conflict: Choosing between two options, each with positive and negative aspects.

Sympathetic and Parasympathetic Systems

Sympathetic system: Activates "fight or flight" response.
Parasympathetic system: Calms the body, conserving energy.

Stressful College Students Checklist

A tool to assess common stressors among college students (e.g., academic pressure, social challenges).

Personality Types

Type A personality: Competitive, impatient, aggressive.
Type B personality: Relaxed, patient, easy-going.
Hardy personality: Resilient, able to cope with stress.

Social Support System

Social support refers to the presence of others who provide emotional or practical help during stressful times.

Sensation: Vision

Microsaccades

Microsaccades are tiny, involuntary eye movements that help maintain visual stability.

Dark Adaptation vs. Light Adaptation

Dark adaptation: The process by which eyes become more sensitive to low light.
Light adaptation: The process by which eyes adjust to bright light.

Cones and Rods

Cones: Photoreceptors responsible for color vision and detail, active in bright light.
Rods: Photoreceptors responsible for vision in dim light.

Blind Spot

The blind spot is the area on the retina where the optic nerve exits; no photoreceptors are present.

Trichromatic Theory

Trichromatic theory proposes that color vision is based on three types of cones sensitive to red, green, and blue.

Opponent-Process Theory

Opponent-process theory suggests that color perception is controlled by the activity of two opponent systems: red-green, blue-yellow, and black-white.

Brightness, Color, and Colorblindness

Brightness: Perceived intensity of light.
Color: Determined by wavelength.
Colorblindness: More common in males due to X-linked inheritance.

Feature	Trichromatic Theory	Opponent-Process Theory
Basic Idea	Three types of cones (red, green, blue)	Color pairs (red-green, blue-yellow, black-white)
Explains	Color mixing, color blindness	Afterimages, color contrast

Additional info: Some definitions and examples have been expanded for clarity and completeness.