Psychology 201 Chapter 3 Scholar Slides Spring 2025 (1)

Chapter 3: Sensation and Perception

SENSATION (PP. 78-94)

PERCEPTION (PP. 106-113)

Chapter Outline

I. Introduction to Sensation and PerceptionII. PsychophysicsIII. VisionIV. HearingV. The Chemical SensesVI. TouchVII. PerceptionVIII. Illusions

I. Introduction to Sensation and Perception

A. Basic Terms

1. Stimulus: Any form of energy that can be detected by the senses.

B. Introduction to Sensation

2. Senses/Sense Organs:

   • Systems that convert information (energy) from the environment into neural activity.

   • Vision is the system (sense) and The Eye is the organ that translates light into neural signals.

3. Transduction:

   • The process of converting external stimuli into neural activity.

   • Occurs in receptor cells within sense organs.

4. Sensation:

   • The response of sense organs to external stimuli, which sends messages to the brain.

5. Perception:

   • The brain's interpretation of sensory input, giving meaning to the messages received.

II. Psychophysics

A. Thresholds

• The concept of threshold relates to the minimum stimulation required to detect a stimulus.

• Two key types of thresholds are:

  1. Absolute Threshold

  2. Difference Threshold

B. Absolute Threshold

• The minimum energy required to detect a stimulus 50% of the time.

• Sensitivity and response bias affect detection.

• Subliminal Stimulation: Stimuli that are below the absolute threshold and are not consciously detected.

• Supraliminal Stimulation: Stimuli that are consistently above absolute threshold and can be detected.

C. Difference Threshold

• The smallest difference in stimulus intensity that can be detected 50% of the time (JND - Just Noticeable Difference).

• Weber’s Law: The smallest detectable difference is a constant proportion of the stimulus intensity.

III. Vision

A. The Eye

1. Physical Stimulus for Vision: Light, which is a form of electromagnetic energy.

2. Physical Dimensions of Light Waves:

   • Amplitude (brightness)

   • Wavelength (color)

B. Anatomy of the Eye

1. Cornea: Transparent covering that bends light.

2. Aqueous Humor: Nourishes the eye and keeps the cornea moist.

3. Pupil: Adjustable opening that controls light entry.

4. Iris: Muscle that controls the pupil size.

5. Lens: Focuses visual images on the retina.

6. Ciliary Muscles: Change lens shape for focusing.

7. Vitreous Humor: Jelly-like substance that maintains eye shape.

8. Retina: Light-sensitive tissue where transduction occurs.

   • Contains photoreceptor cells: Rods (black-and-white vision) and Cones (color vision).

9. Fovea: Area with the highest density of cones, essential for sharp vision.

10. Blindspot: Area without receptor cells where the optic nerve exits the eye.

11. Optic Nerve: Transmits visual information to the brain.

C. Adaptation and Color Vision

1. Sensory Adaptation: Reduced response to constant stimulation.

2. Color Vision Theories: Including Trichromatic, Opponent Process, and Dual-Process Theories.

   • Trichromatic Theory: Cones sensitive to blue, green, and red.

   • Opponent-Process Theory: Color sensitivity organized in opposing pairs.

   • Dual-Process Theory: Combines both previous theories for color understanding.

3. Colorblindness: Variability in color perception, including Trichromats (normal), Dichromats (one color blind), and Monochromats (total color blind).

IV. Audition – Hearing

A. Physical Stimulus for Hearing

• Sound: Repetitive fluctuations in air pressure.

B. Anatomy of the Ear

1. Outer Ear: Pinna and auditory canal collect sound.

2. Middle Ear: Contains the tympanic membrane and ossicles which amplify sound.

3. Inner Ear: Houses the cochlea, vestibular structures, and auditory nerve.

C. Deafness

1. Conduction Deafness: Problems in the middle ear; treatable through surgery or hearing aids.

2. Nerve Deafness: Usually from hair cell damage; can be progressive with age or noise exposure.

V. The Chemical Senses - Smell and Taste

A. Olfactory Perception

• Smell: Processed through the nose, mouth, and throat; does not go through the thalamus.

B. Gustatory Perception

• Taste: Receptors are taste buds in the mouth; detect basic tastes: sweet, sour, bitter, salty, and umami.

VI. Touch

• Sensation of touch is elicited by physical pressure on the skin; receptors located in or below the skin.

VII. Perception

A. Principles of Organization

• Figure-Ground: Differentiating between figure and background.

• Grouping Principles: Similarity, proximity, closure, and continuity.

B. Perceptual Set

• Readiness to perceive stimuli influenced by expectations and experiences, may lead to functional fixedness.

C. Perceptual Constancies

• 1. Size Constancy

• 2. Shape Constancy

• 3. Brightness Constancy

D. Depth Perception

• Two types: binocular (requires both eyes) and monocular (requires one eye) cues.

E. Perception of Movement

• Identifying real vs. apparent motion; includes stroboscopic motion and autokinetic effects.

VIII. Perceptual Illusions

• Illusions are convincing yet incorrect perceptions; examples include the Ponzo, Ames Room, and Muller-Lyer illusions.