Chapter 4: Sensation and Perception Study Notes

Chapter 4: Sensation and Perception

Chapter Preview

  • Overview of Sensation and Perception

    • Basic Principles

    • Vision

    • Hearing

    • Other Senses

    • Health and Wellness

Basic Principles – How We Sense and Perceive the World

  • Sensation:

    • Definition: The process of receiving stimulus energies from the external environment and transforming them into neural energy.

  • Perception:

    • Definition: The process of organizing and interpreting sensory information so that it makes sense.

Sensation and Perception Unified Information Processing System

  • Bottom-Up Processing:

    • Initiated by sensory input.

    • Relies on the external world’s influence on perception.

  • Top-Down Processing:

    • Initiated by cognitive processing.

    • Influenced by the internal/mental world’s understanding of perception.

    • Takes into account expectations and prior knowledge.

Sensation

Sensory Receptors

  • Definition: Specialized cells that selectively detect and transmit sensory information to the brain.

  • Function: Cells send signals via distinct neural pathways.

Types of Sensation

  1. Photoreception (Vision):

    • Definition: Detection of light.

  2. Mechanoreception (Touch):

    • Definition: Detection of pressure, vibration, and movement.

  3. Chemoreception (Smell and Taste):

    • Definition: Detection of chemical stimuli.

Unique Sensory Phenomena

  • Synesthesia:

    • Definition: A condition where one sense induces an experience in another sense, such as “seeing” music or “tasting” color.

  • Phantom Limb Pain:

    • Description: Pain felt in a limb that has been amputated, highlighting the complex nature of sensation and perception.

Sensory Thresholds

1. Absolute Threshold

  • Definition: The minimum amount of energy an organism can detect 50 percent of the time.

2. Noise

  • Definition: Any stimulus that interferes with the perception of another stimulus.

3. Difference Thresholds

  • Definition: The amount of change in stimulation necessary for detection.

  • Just Noticeable Difference (JND):

    • Explanation: JND is larger at higher stimulus levels.

    • Low stimulus levels allow small changes to be detected.

    • High stimulus levels mean small changes are less noticeable.

4. Weber’s Law

  • Definition: To be perceived as different, two stimuli must differ by a constant proportion, rather than a constant amount.

Subliminal Perception

  • Definition: The influence of information below the level of conscious awareness.

  • Priming: Activating a particular concept or idea in memory so that it affects the person subconsciously.

Signal Detection Theory

1. Overview

  • Definition: A decision-making process regarding stimuli under uncertain conditions.

  • Detection: Depends on more than just the physical intensity of stimulus.

  • Factors Influencing Detection: Fatigue, expectations, and urgency.

  • Information Acquisition: Gathering relevant indicators for decision-making.

  • Criterion: Standards used to make a decision.

2. Possible Outcomes

  • Observer Response: “Yes, I see it”

    • If Signal Present: Hit (correct)

    • If Signal Absent: False Alarm (mistake)

  • Observer Response: “No, I don’t see it”

    • If Signal Present: Miss (mistake)

    • If Signal Absent: Correct Rejection (correct)

Stroop Effect

1. Demonstration

  • Task: As fast as possible, name each color of ink used to print rectangles (dual task).

  • Highlight: Cognitive interference when the color of the ink conflicts with the name of the color written on it.

Factors Affecting Perception

1. Attention

  • Definition: Focusing awareness on a narrowed aspect of the environment.

  • Selective Attention:

    • E.g., Cocktail Party Effect: The ability to focus on one conversation amidst a noisy environment.

    • Stroop Effect: A demonstration of failure of selection.

    • Attention drawn by novelty, size, color, movement, and emotional stimuli.

  • Emotion-induced Blindness: Difficulty focusing on stimuli when emotionally charged.

  • Inattentional Blindness: Failure to notice an unexpected stimulus in one’s visual field.

2. Perceptual Set

  • Definition: Predisposition or readiness to perceive something in a particular way.

  • Relation: Tied closely with top-down processing.

3. Sensory Adaptation

  • Definition: Change in responsiveness of sensory system based on the level of surrounding stimulation, such as adapting to darkness in a darkened room or bright light outside.

The Structure of the Eye

Retina and Photoreceptor Cells

  1. Rods:

    • Sensitivity: Sensitive to dim light but not color.

    • Function: Operate well in low illumination.

    • Quantity: Humans have approximately 120 million rods.

  2. Cones:

    • Sensitivity: Respond to color.

    • Function: Operate best under high illumination.

    • Quantity: Humans have approximately 6 million cones.

Color Vision

Trichromatic Theory

  • Description: Based on three types of receptors for colors: red, blue, and green cones.

  • Color Blindness: Occurs when one or more cone types are inoperative.

Afterimages

  • Experiment: Stare at a dot, then switch to a different colored background to observe the effect of afterimages on perception.

Opponent-Process Theory

  • Definition: Proposes that perception of color is controlled by the activity of opponent neurons responding to complementary color pairs (red-green, blue-yellow).

  • Mechanism: The brain utilizes both trichromatic and opponent-process methods to perceive color.

Visual Perception

Organizing Visual Signals

  • Dimensions of visual perception include:

    • Shape

    • Depth

    • Motion

    • Constancy

Gestalt Psychology

  • Concept: Perceptions are naturally organized in certain patterns.

  • Principle: The whole is different from the sum of its parts.

  • Gestalt Principles include:

    • Closure: The mind tends to fill gaps in visual information.

    • Proximity: Objects closer together are perceived as a group.

    • Similarity: Similar items are grouped together.

    • Continuity: Perceiving smooth, continuous patterns rather than discontinuous ones.

    • Figure-Ground: The ability to distinguish a figure from its background.

Depth Perception

  • Definition: The ability to see objects in three dimensions.

  • Mechanism: The brain converts two-dimensional retinal images to three-dimensional perceptions.

  • Binocular Cues: Depth cues using both eyes.

    • Examples: Disparity and convergence.

  • Monocular Cues: Depth cues requiring only one eye.

    • Examples: Familiar size, height in field of view, linear perspective, overlap, shading, texture gradient.

Motion Perception

  • Function: Humans have specialized motion detectors.

  • Concept: Apparent movement occurs when stationary objects appear to move, highlighting the complexity of visual processing.

Visual Constancy

  • Definition: The ability to perceive consistent color, size, and shape despite changes in sensory input.

Qualities of Sound

Physical Dimension

Perceptual Dimension

Form of Sound Waves


Amplitude (intensity)

Loudness

Frequency

Pitch

(Low/High)


Complex sounds

Timbre

Auditory Anatomy

  • Outer Ear: Pinna, Auditory canal.

  • Middle Ear: Hammer, Anvil, Stirrup, Eardrum.

  • Inner Ear: Cochlea, Semicircular canals.

  • Pathway of Auditory Information: Cochlea → auditory nerve → brain stem → temporal lobe (most information crosses to the opposite hemisphere).

Theories of Hearing

1. Place Theory of Pitch Perception

  • Explanation: The location of stimulation along the basilar membrane is crucial for pitch perception.

  • Limitation: This theory only explains the perception of high frequencies.

2. Frequency Theory of Pitch Perception

  • Explanation: Relies on the frequency of nerve firing to explain perception.

  • Limitations: Neuronal firing rates can only reach limited frequencies.

3. Volley Principle

  • Explanation: Clusters of cells can fire in alternating fashion, helping to exceed the limitations of individual neuronal firing rates.

Other Senses

Overview

  • Categories include:

    • Skin Senses (Touch, temperature, and pain).

    • Chemical Senses (Taste and smell).

    • Kinesthetic Senses (Movement, posture, and orientation).

    • Vestibular Senses (Balance and movement).

Skin (Cutaneous) Senses

  • Touch: Receptors transmit information through spinal cord to the thalamus and somatosensory cortex of the parietal lobe.

  • Temperature: Detected by thermoreceptors, capable of perceiving warm and cold stimuli, which can be interpreted as hot when both are perceived simultaneously.

Chemical Senses
Taste

  • Mechanism: Taste receptors (papillae) identify primary tastes: sweet, sour, bitter, salty, umami, and fat.

  • Influence: Culture significantly affects the experience of taste.

Smell (Olfactory Sense)

  • Mechanism: Involves olfactory epithelium and connects to the temporal lobe and limbic system; important for detecting food and odor tracking.

Kinesthetic and Vestibular Senses

  • Kinesthetic Senses: Involve perception related to movement, posture, and orientation, primarily through muscle fibers and joints.

  • Vestibular Senses: Responsible for balance and detecting head movements; utilizes the semicircular canals for feedback coordination.

Health and Wellness

Caring for Senses

  • Eyes:

    • Recommendations include eating a healthy diet, utilizing proper lighting for reading, wearing sunglasses, and scheduling regular vision screenings.

  • Hearing:

    • Recommendations include avoiding loud noise to protect auditory health.

Chapter Review

  • Topics to understand:

    • Describe sensation and perception.

    • Explain the structural components of the eye and how the brain processes visual information.

    • Identify structural parts and functions of the ear and how sound is detected.

    • Understand how skin, chemical, kinesthetic, and vestibular senses function.

    • Identify everyday practices for protecting vision and hearing.