Introductory Psychology Study Notes

INTRODUCTORY PSYCHOLOGY (PSYC-1100 YAO – WEEK 07)

HISTORICAL PERSPECTIVE: PSYCHOPHYSICS

  • Subjective experiences of the world are based on physical phenomena.

  • Early psychologists investigated how physical stimuli translate into psychological experiences, termed psychophysics.

  • Psychophysics: The study of how physical stimuli (e.g., light) are translated into psychological experiences.

GUSTAV FECHNER (1801-1887)

Background

  • Fechner: German physicist.

  • Focused on:

    • Strength of stimuli.

    • Detection and differentiation of environmental information.

Key Concepts

  • Stimulus: Any detectable input from the environment.

Detection Thresholds

  • Fechner's research emphasized the minimum intensity required to detect stimuli, called the Threshold for detection.

    • Example: Determining the dimness level of light that becomes undetectable.

  • Threshold: A dividing point between energy levels that do and do not have a detectable effect.

Just Noticeable Differences (JND)

  • Investigated the minimum difference between two stimuli required for detection, termed Just Noticeable Differences (JND).

  • Just Noticeable Difference: The smallest difference in the amount of stimulation that a specific sense can detect.

    • Example: The incremental dimness in light required to perceive it as different from a brighter light.

SENSATION VS. PERCEPTION

  • The nervous system encodes environmental information via neurons and sensory receptors (e.g., light detection by eye cells).

  • Transformation of sensory information into mental representation occurs in two main processes: sensation and perception.

SENSATION

  • Detects information from the environment through our sensory organs.

  • Sensation: The stimulation of sensory organs.

  • Example: Detection of light when it hits the retina.

  • More than six senses exist (e.g., proprioception).

Sensory Receptors

  • Sensory receptors convert environmental stimuli into electrical signals (action potentials).

  • Sensory Neurons: Nerve cells transmit sensory information from the body to the brain and spinal cord.

  • Primary receptors can directly convert stimulus to electrical signals.

    • Primary Sensory Receptors: Neurons that conduct electrical impulses to the central nervous system (CNS).

    • Example: Touch receptors detecting pressure.

  • Many receptors rely on secondary receptors: non-neuronal cells that communicate stimuli to secondary sensory neurons.

    • Example: Hair cells in hearing.

SENSATION OVERVIEW

  • Sensation is the process where sensory cells convert stimuli into action potentials transmitted to the brain via sensory neurons.

PERCEPTION

  • Perception: The process of selecting, organizing, and interpreting sensory input to create conscious experience.

  • Mental representations formed from sensory experiences are called percepts.

    • Example: Visualizing an object seen previously.

  • Perception occurs in the brain after sensation has taken place and aids in recognizing objects and understanding context.

    • Sensation happens in the body; perception is a brain activity.

SIGNAL DETECTION THEORY

  • Examines detection of stimuli beyond mere intensity and incorporates decision-making processes influenced by context and psychological factors.

  • The Cocktail Party Effect: Ability to hear personal cues (e.g., hearing one's name) amidst noise, illustrating shifting detection thresholds.

  • Signal Detection Theory: Suggests that stimulus detection involves both decision and sensory processes, influenced by multiple factors.

SENSORY ADAPTATION

  • The sensitivity of sensory systems diminishes with continuous stimulation, termed sensory adaptation.

    • Sensory Adaptation: A gradual decline in sensitivity due to prolonged stimulation.

    • Example: Difficulty seeing in the dark after prolonged exposure to bright light.

VISION

THE RETINA

  • Light passes through the cornea and lens, focusing on the retina containing light-sensitive cells (rods and cones).

  • Retina: Layer of photoreceptor cells in the eye capturing light and transmitting visual signals.

    • Cells convert light to electrical signals sent to the brain.

RODS & CONES

  • Rods: Responsible for night and peripheral vision.

  • Cones: Responsible for daylight and color vision.

BLIND SPOT

  • The optic nerve exits the eye at a location lacking photoreceptor cells, creating a blind spot where no image detection occurs.

VISION IN THE BRAIN

  • Visual fields are processed contralaterally (opposite hemispheres).

    • Contralateral: Projected to opposite sides; Ipsilateral: Same side.

  • The optic chiasm is the crossing point for visual information.

  • Visual processing begins in the primary visual cortex (V1) located in the occipital lobe.

HUBEL & WIESEL (1962): FEATURE DETECTORS

  • Discovered that certain neurons in the brain respond to specific visual features, like angles and line width.

  • Feature Detectors: Neurons that respond selectively to particular visual elements.

  • This work earned them a Nobel Prize in 1981.

FEATURE ANALYSIS

  • The process by which visual features are detected and assembled into complex forms, referred to as Feature Analysis.

AMBIGUOUS FORMS

  • Perception can lead to misinterpretation; visual illusions arise from the absence of direct correspondence between sensation and perception, influenced by memory and expectation.

    • Reversible figures are examples of images with two compatible interpretations.

"WHAT" & "WHERE" PATHWAYS

  • Different pathways process visual information:

    • Dorsal Stream: Responsible for where objects are (location).

    • Ventral Stream: Responsible for what objects are (identification).

  • Pathways are spatially organized in the brain's structure, aiding object identification.

THEORIES OF COLOR

TRICHROMATIC THEORY

  • Trichromatic Theory of Color: Proposes color perception relies on three types of cone receptors (red, green, blue) in the retina.

    • This theory explains color blindness, where individuals may be deficient in distinguishing particular colors.

OPPONENT PROCESS THEORY

  • Opponent Process Theory: Explains color perception through opposing pairs of color receptors, causing perception of opposing colors in after-images due to sensory adaptation.

COLOR VISION INTEGRATION

  • Current understanding suggests partial correctness of both theories, integrating elements of each in explaining how color is perceived in the brain.

VISUAL ILLUSIONS

DEFINITION

  • Visual illusions arise from discrepancies between the sensed stimulus and its physical properties, affected by assumptions and prior experiences.

  • Visual Illusions: Errors in perception caused by common visual cues and contextual influences.

CONTEXTUAL INFLUENCES

  • Perception is affected by contextual surroundings, leading to assumptions about size and shape.

ILLUSORY MOTION

  • Occurs when stationary objects appear to move due to conflicting visual cues interpreted by the brain.

NEGATIVE SPACE & LIGHT FROM ABOVE

  • Negative Space Illusions: Occur when the brain fills in missing information, causing confusion between main objects and surrounding space.

  • Light from Above Prior: A perceptual bias where ambiguous lighting is typically interpreted as coming from above, based on past learning.

SENSORY INTEGRATION, AUDITION (HEARING), AND BALANCE

SENSORY INTEGRATION

  • Different sensory systems are interrelated, influencing perception across modalities (e.g., visual cues affecting auditory perception).

AUDITORY ILLUSIONS

  • Expectations shaped by visual stimuli can lead to auditory illusions when sensory modalities do not match.

    • McGurk Effect: Shows discrepancies between heard and seen sounds affect perception.

    • Shepherd Tone: Creates an endless ascending or descending auditory illusion.

HEARING (AUDITION)

  • Sound vibrations travel through the outer ear, using three ossicles to reach the cochlea.

    • Ossicles: Malleus, Incus, Stapes—the three small bones transmitting sound vibrations to the inner ear.

HAIR CELLS AND VESTIBULAR SYSTEM

  • Hair cells detect sound vibrations and convert them into electrical signals sent to the brain.

  • The Vestibular System maintains balance and spatial orientation, containing hair cells for detecting head movement.

HEARING & THE BRAIN

  • Auditory information processed in the primary auditory cortex (A1), organized tonotopically for sound frequency processing.