IP3__Sensation___Perception

IP3: Sensation & Perception Overview

• Date: Mon. Jan. 23, 2023

• Main Concepts:

  • Perception: Brain's interpretation of sensory input.

  • Sensation: Detection of environmental stimuli.

  • Despite similar sensations, perceptions differ among individuals.

  • Sensation vs. Perception: They blend together; the nervous system processes sensory information in real-time.

Understanding Sensation

Sensation Processing

• Raw Data Processing:

  • Process: Sensory receptors (eyes, ears, etc.) receive and transmit information.

  • Key Functions:

    1. Transduction: Conversion of sensory stimuli into neural impulses.

       • Brain interprets neural impulses, not raw stimuli (light/sound).

    2. Sensory Reduction: Filtering and analyzing incoming sensations.

       • Prevents overstimulation of the brain.

    3. Coding: Neural impulses reach different brain parts based on their nature.

       • Visual info processed in occipital lobe, auditory in temporal lobe.

Measurement Issues in Sensation

Psychophysics

• Definition: Relationship between physical stimuli and psychological experience.

• Detection:

  • Absolute Threshold (50%): Minimum stimulus intensity detectable.

  • Subliminal Stimuli: Below the threshold of conscious perception.

Discrimination

• Difference Threshold (Just Noticeable Difference): Smallest difference detected between two stimuli.

  • Example: Noticing slight changes in sound or light intensity.

Sensory Adaptation

• Concept: Diminished sensitivity to constant stimulation.

• Examples:

  • Smokers become desensitized to smoke odor.

  • Clothing sensations diminish over time due to constant exposure.

• Exceptions: Eyes and intense pain stimuli remain alert.

Vision: Sensation

Electromagnetic Spectrum

• Definition: Light as electromagnetic energy in waves.

• Visible Spectrum:

  • Wavelengths from 400 nm (violet) to 700 nm (red).

  • Frequency relates to color perception: High frequency = violet; Low frequency = red.

• Amplitude: Height of waves correlates to brightness; higher amplitude = brighter color.

The Eye

Structure and Function

• Positions of Eyes:

  • Predators: Forward-facing for depth perception.

  • Prey: Side-facing for wider field of vision.

• Parts of the Human Eye:

  • Pupil: Adjustable opening for light.

  • Iris: Controls pupil size.

  • Cornea: Focuses entering light.

  • Lens: Fine-tunes focus; changes shape based on distance.

  • Retina: Contains photoreceptors.

  • Fovea: Site of highest visual acuity.

  • Optic Nerve: Transmits visual input to the brain; blind spot with no receptors.

Retinal Image Processing

• Analogy: Eye functions like a camera (lens, focus, processing).

• Common Eye Issues:

  • Myopia (Nearsightedness): Focuses before the retina.

  • Presbyopia (Farsightedness): Focuses behind the retina.

Photoreceptors

• Types:

  1. Cones: Responsible for color and detail; most active in bright light (6 million per eye).

     • Sensitive to blue, green, red wavelengths.

  2. Rods: Responsible for vision in low light; more abundant (120 million per eye).

Perception in Vision

Selection

• Selective Attention: Focusing on relevant stimuli, filtering others (e.g., cocktail party effect).

• Feature Detectors: Specific neurons responsive to certain visual stimuli (like movement or faces).

• Habituation: Reduced response due to repeated stimuli.

Perceptual Organization

• Parallel Processing: Brain segments the visual scene into multiple components (form, color, depth).

• Gestalt Principles: Wholeness perception; the whole is more than the sum of parts.

  • Common principles include Proximity, Similarity, Continuity.

Depth Perception

Cues

• Monocular Cues (one eye needed):

  • Relative Size: Smaller items appear further away.

  • Interposition: Overlapping objects indicate distance.

• Binocular Cues (both eyes needed):

  • Retinal Disparity: Different images from each eye converge into perception.

  • Convergence: Eyes angle inward for close objects.

Perceptual Constancies

• Definition: Stable perception across varying sensory inputs.

  • Size, Shape, Colour Constancy: Object perception remains constant despite changes in distance, angle, or lighting.

Non-Visual Senses

Hearing

• Sound Waves: Interactions with ear structures.

• Frequency: Determines pitch; higher peaks = higher pitch.

• Amplitude: Tall peaks represent loudness.

Ear Anatomy

• Sections: Outer, Middle (Ossicles), Inner (Cochlea).

  • Cochlea: Contains basilar membrane that converts sound waves to nerve impulses.

Sound Processing

• Steps:

  1. Sound channels through outer ear to eardrum.

  2. Eardrum vibrations stimulate ossicles, amplifying sound.

  3. Cochlea fluid movement triggers hairs, converting stimuli to signals.

Pitch Perception Theories

• Place Theory: Different frequencies activate specific cochlear areas.

• Frequency Theory: Matching firing rates of auditory nerve to sound frequency.

• Volley Principle: Collaborative firing of neurons for higher frequencies.

Hearing Loss Types

• Conductive: Damage to outer/middle ear affecting sound transfer.

• Sensorineural: Damage to inner ear or auditory nerve.

Body Position & Movement Senses

• Kinesthesia: Awareness of body part positions via sensory feedback.

• Vestibular Sense: Balance and spatial orientation from inner ear signals.

Interactions Between Senses

• Sensory Interaction: One sense influences another (e.g., McGurk Effect).

• Embodied Cognition: Physical sensations affect cognitive processes and judgments.