PYSC Chapter 4-Perception

Chapter 4: Sensation and Perception

Introduction

  • Sensation and perception are vital functions of the brain and sensory organs.

What are Sensation and Perception?

  • Sensation: Detection of physical energy by our sense organs.

  • Perception: The brain’s interpretation of these raw sensory inputs.

Transduction & Psychophysics

  • The nervous system converts external stimulus into electrical signals within neurons.

  • Psychophysics: Study of how we perceive sensory stimuli based on physical characteristics.

  • Gustav Fechner (1860): Established foundational principles in psychophysics.

Absolute Threshold, JND & Weber's Law

  • Absolute Threshold: The minimum level of stimulus intensity detected 50% of the time.

  • Just Noticeable Difference (JND): The smallest change in intensity of a stimulus detectable.

  • Weber’s Law: The JND is a constant proportion of the original stimulus intensity.

Signal Detection Theory

  • Hit: Detected stimulus that was present.

  • Miss: Failed to detect a stimulus that was present.

  • False Alarm: Indicated a stimulus was present when it was not.

  • Correct Rejection: Indicated no stimulus when none was present.

The Role of Attention

  • Attention focuses on certain stimuli, possibly excluding others.

  • Selective Attention: Focusing consciously on certain stimuli.

  • Inattentional Blindness: Failing to perceive stimuli when focused elsewhere.

The Visual System

  • Wavelength: Influences color perception. Different ranges impact how we experience light.

    • Visible light range: Approximately 400 nm to 700 nm.

The Eye

  • Light enters through the pupil and is focused by the cornea and lens onto the retina.

  • Accommodation: Lens changes shape to focus on objects at various distances.

The Retina

  • The retina processes images, absorbs light, and sends information to the brain.

  • Contains the fovea responsible for sharp visual acuity.

Rods and Cones

  • Cones: Facilitate daytime and color vision.

  • Rods: Assist in low-light (night) and peripheral vision.

Perceiving Shape and Contour

  • Research by Hubel & Wiesel (1960s) revealed feature detection in response to specific patterns and orientations.

  • Distinctions between simple and complex feature detector cells.

Perceiving Color

  • Trichromatic Theory: Color perception based on three receptors (red, green, blue).

  • Opponent-Process Theory: Color perception influenced by opposing responses (e.g., yellow vs. blue, red vs. green).

The Auditory System

  • Sound waves are molecular vibrations traveling through a medium.

  • Characteristics include amplitude, wavelength, and purity.

Structure of the Ear

  • Outer, middle, and inner ear structures facilitate sound processing:

    • Parts include pinna, eardrum, cochlea, auditory nerve.

Perceiving Pitch

  • Place Theory: Pitch perception tied to different locations on the basilar membrane.

  • Frequency Theory: Pitch perception corresponds to the frequency of membrane vibration.

Taste and Smell

  • Taste: Involves receptors for sweet, sour, salty, bitter, and umami.

  • Smell (Olfaction): Detection through olfactory receptors including olfactory bulb.

Taste and Smell Perception

  • Integration occurs in multiple brain regions:

    • Orbitofrontal cortex, olfactory bulb, somatosensory cortex, gustatory cortex.

Body Senses - Touch, Position, & Balance

  • Body senses include touch, proprioception, and the vestibular system for balance.

    • Sensitive to pressure, temperature, and pain through various receptors.

Pain Perception

  • Pain can result from various stimuli (heat, chemical, pressure).

  • Signals transmitted via:

    • Fast Pathway (A-delta pathway)

    • Slow Pathway (C fibre pathway)

Proprioception

  • Monitors body position to enable efficient movement.

  • Proprioceptors sense stretch and force in muscles.

  • The vestibular system assists with spatial orientation and gravity response.

Perception: Parallel Processing

  • Ability to process multiple sensory modalities at once.

  • Bottom-up processing: Constructing perception from sensory input.

  • Top-down processing: Influence of beliefs and experiences on perception.

Perceptual Constancy

  • The consistent perception of stimuli across varying conditions:

    • Size Constancy

    • Shape Constancy

    • Color Constancy

Gestalt Principles

  • Perception governed by principles such as:

    • Proximity

    • Similarity

    • Closure

    • Continuity

    • Symmetry

    • Figure-ground relationships.

Face Perception

  • Innate ability to recognize faces, evidenced by infants imitating facial gestures early.

Depth Cues

  • Monocular Depth Cues: Visual information that can be perceived with one eye.

  • Binocular Depth Cues: Require both eyes for perception, such as retinal disparity and converging focus.

Locating Sounds

  • Auditory localization aided by ear placement and cues from sound intensity and timing.

Conclusion

  • Understanding sensation and perception involves examining multiple systems and processes, allowing us to accurately perceive and interpret the world around us.