Psychology Sensation and Perception Overview

Naïve Realism

• The belief that our senses are perfect and flawlessly portray the world around us.

Sensation

• Vision, hearing, smell, taste, and somatosensory are our five primary senses.

Transduction

• Process of converting external energy or substances into electrical activity within the nervous system.
• Done through sensory receptors, specialized cells that perform transduction for specific sensory systems.

Sensory Adaptation

• Sensory receptors respond most strongly when a stimulus is first detected.
• Strength of response declines over time.

The Eye

• Composed of:
  • Cornea: Transparent outer layer that bends incoming light to focus it at the back of the eye.
  • Pupil:Circular hole allowing light into the eye.
  • Lens: Changes curvature to keep images in focus.
  • Ciliary Muscles: Smooth muscles that change lens thickness to focus on objects at varying distances.
  • Aqueous Humor: Transparent fluid supporting the cornea and lens.
  • Vitreous Humor: Transparent fluid supporting the eye's structure and retina.
  • Fovea: Central portion of the retina, responsible for visual acuity.
  • Blind Spot: The point where the optic nerve connects to the retina. Contains no rods or cones.
  • Retina: Membrane at the back of the eye responsible for converting light into neural signals.

Photoreceptors

• Found in the retina and respond to light.
• Two types:
  • Rods: Sensitive to light, long and narrow, located on the retina's periphery. Enable us to see shapes and forms. Contain "rhodopsin" photopigments.
  • Cones: Sensitive to detail, cone-shaped, located in the center of the retina. Enable color vision. Contain "iodopsin" photopigments.

Color Blindness

• Inability to see some or all colors, often due to missing or reduced cones.
• Usually caused by genetic abnormalities, but can also be a result of brain injury.
• More common in males than females.

Blindness

• A severe reduction or inability to see.
• Vision is 20/200 or worse on the Snellen eye chart.
• Can be caused by:
  • Cataracts: Clouding of the lens.
  • Glaucoma: Damage to the optic nerve.
• Those with blindness often compensate by relying on other senses, like touch and hearing.

Visual Agnosia

• A condition where an individual can see but cannot recognize or interpret visual information.
• Caused by damage to the parietal lobes.

Hearing

• Sound is vibrations (waves) that can travel through gases, liquids, and solids.
• We hear best when sounds travel through air.

Elements of Sound

• Frequency:
  • The number of cycles per unit of time a sound wave completes.
  • Measured in Hertz (Hz).
  • Humans hear sounds between 3 - 20,000 Hz.
• Amplitude:
  • The strength (height) of a sound wave.
  • Measured in decibels (dB).
• Timbre:
  • Complexity or quality of sound, making musical instruments, voices, etc., unique.
  • Allows us to distinguish sounds with the same pitch and loudness.
  • Determined by harmonic content and dynamic characteristics, like vibrato.

The Ear

• Composed of:
  • Outer Ear:
    • Pinna: Amplifies sound and funnels it toward the eardrum.
    • Tympanic membrane: Vibrates according to sound frequency, also known as the eardrum.
  • Middle Ear:
    • Ossicles: Three bones (malleus, incus, stapes) that transmit vibrations from the eardrum to the oval window.
  • Inner Ear:
    • Oval Window: Membrane receiving vibrations from the ossicles and sending them to the cochlea.
    • Cochlea: Spiral-shaped fluid-filled structure containing the basilar membrane, cochlear duct, and organ of Corti.
      • Basilar Membrane: Translates vibrations into neural activity.
      • Cochlear Duct: Endolymph-filled cavity within the cochlea. Sound vibrations create waves in this fluid, causing movement in hair cells and cilia.
      • Organ of Corti: Contains hair cells and cilia, translating waves in the cochlear duct into neural activity.
    • Hair cells: Attached to the basilar membrane. Movement causes movement in cilia.
    • Cilia: Short hair-like structures extending from hair cells. Their movement opens ion channels, releasing neurotransmitters that send signals to the brain.

Smell

• Also known as "olfactory."
• Humans can detect between 2,000-4,000 odours.
• Decreased sense of smell can be an early sign of Alzheimer's or Parkinson's disease.
• Women have a better sense of smell than men.

Taste

• Also known as "gustation."
• Humans have a limited range of taste perception.
• Five basic tastes: sweet, salty, sour, bitter, and umami.
• Taste preferences are largely culturally determined.
• Emotional disorders (e.g., anxiety, depression) can distort taste perception.
• Different parts of the tongue contain different types of papillae (taste buds) with varying distributions of receptors.

Somatosensory

• Our sense of touch, temperature, and pain.
• Distinguished by signal detection theory.

Absolute Threshold

• Minimum intensity of a stimulus needed to be detected by the nervous system 50% of the time.

Just Noticeable Difference (JND)

• The smallest change in stimulus intensity needed to be detected.
• Weber's Law states there is a constant proportional relationship between JND and the original stimulus intensity.

Signal Detection Theory

• Attempts to explain how stimuli are detected under different conditions.
• Two components:
  • Signal: The stimulus being perceived.
  • Noise: Anything that might distract from the stimulus.

Stages of Perception

• Sensation:
  • External stimuli trigger action potentials in sensory neurons, which travel to the brain.
• Perceptual organization:
  • Grouping sensory features into internal representations of external stimuli.
• Identification and recognition:
  • Assigning meaning to perceived sensations.

Laws of Perceptual Grouping

• Law of Proximity: Objects physically close together are perceived as a whole.
• Law of Similarity: We perceive similar objects as composing a whole more than dissimilar ones.
• Law of Continuity: We perceive objects as wholes even if parts are blocked.
• Law of Closure: Our brains fill in missing visual information when partial information is present.
• Law of Symmetry: We perceive symmetrical objects as wholes more often than asymmetrical ones.
• Law of Figure-Ground: We make a quick decision to focus on the object or "figure," largely ignoring the surrounding background.

Perceptual Organization

• Two types of processing:
  • Bottom-up processing: Constructing a whole from its individual parts.
  • Top-down processing: Processing driven by beliefs and expectations.

Perceptual Illusions

• Parallel processing: The ability to attend to multiple sense modalities at the same time.

Explore the fascinating concepts of sensation and perception in psychology. This quiz delves into naïve realism, sensory adaptation, and the anatomy of the eye, highlighting how we perceive the world around us. Test your knowledge on the processes that underlie our sensory experiences.