PSY-402-16-30_compressed

Visual System

Overview of Visual Processing

• Visual processing begins as signals emerge from the back of the eye via the optic nerve, transmitting information toward the brain.

• Key components shaping vision include:

  • Cornea and Lens: Focus light onto the retina.

  • Retina: Contains receptors (rods and cones) and neurons that initiate visual processing.

Accommodation

• Accommodation refers to the lens changing its shape to focus on objects at varying distances unconsciously.

• Demonstration of accommodation:

  • Holding a pencil at arm's length while focusing on a distant object.

  • The pencil appears blurred when not the focus, and clarity diminishes when brought too close.

  • Introduces concepts of the near point and presbyopia, with older adults having increased near points due to lens hardening and weaker ciliary muscles.

Transforming Light into Electricity

• The process of transduction involves transforming light into electrical signals by rod and cone receptors.

• Rods vs. Cones:

  • Rods: More sensitive to light, involved in night vision.

  • Cones: Responsible for color vision and detail.

• Diagram Explanation: Rod receptors contain visual pigment molecules vital for light detection, where absorption of photons triggers electrical signal generation.

Rods and Cones Structure

• Rods and cones vary in distribution across the retina:

  • Fovea: Contains only cones, focused on direct vision.

  • Peripheral Retina: Includes both rods and cones; more rods than cones overall.

Blind Spot

• The optic nerve's exit point creates a blind spot due to no receptors present.

• Activity demonstration illustrating how the brain fills the gap in visual perception.

Pathways from Retina to Brain

• Most retinal signals are processed through the lateral geniculate nucleus (LGN) in the thalamus, then to the primary visual area in the occipital lobe (striate cortex).

• From the striate cortex, two pathways arise:

  • Ventral Pathway (What): Identifies objects.

  • Dorsal Pathway (Where): Determines object location.

Lateral Geniculate Nucleus (LGN)

• The LGN is organized into layers, each receiving input from one eye, with specific layers for ipsilateral (same side) and contralateral (opposite side) inputs.

Streams of Visual Processing

Ungerleider and Mishkin's Findings

• Research conducted in the 1980s highlighted two distinct visual streams:

  • What Pathway: Associated with object identification (ventral stream).

  • Where/How Pathway: Associated with spatial awareness and action guidance (dorsal stream).

Behavioral Studies with Monkeys

• Ablation studies demonstrated that damaging specific brain areas affected object vs. spatial processing capabilities in monkeys.

Perceptual Organization

Gestalt Principles

• Gestalt psychology emphasizes that the whole is different from the sum of its parts, highlighting principles like:

  • Law of Pragnanz: Simplicity and organization in perception.

  • Law of Similarity: Similar items are grouped together.

  • Law of Proximity: Items close together are perceived as a group.

Visual Illusions

• Demonstrates how perceptual processes can be misled leading to incorrect visual interpretations, often employed in psychological studies to understand cognitive processes.

Perception of Scenes

Gist Perception

• The human visual system can rapidly interpret the overall meaning of a scene (the gist), integrating contextual cues to perceive objects effectively.

Factors Influencing Scene Gist

• Naturalness, openness, roughness, expansion, and color greatly contribute to how a scene is interpreted at a glance.

Depth and Size Perception

Cue Approach to Depth Perception

• Depth cues are divided into:

  • Oculomotor: Relying on eye movements such as convergence and accommodation.

  • Binocular: Relying on binocular disparity for depth judgment.

  • Monocular: Which can be depicted via pictorial cues such as linear perspective.

Learning: Classical Conditioning

Basics of Learning

• Learning is an experience-based process resulting in a consistent change in behavior potential.

• Examples of applications include responses in children during reinforcement and consequences in classical conditioning (e.g., Pavlov's dog).

Classical Conditioning Processes

• Neutral Stimulus (CS) paired with an Unconditioned Stimulus (UCS) leads to a Conditioned Response (CR) through repeated associations.

• Extinction occurs when the CS is presented without the UCS, leading to a decrease in the strength of the CR.

Applications in Behavior Management

• Classical conditioning principles are utilized across various domains, from treatment of phobias to marketing strategies.

Reinforcement in Operant Conditioning

Mechanisms of Operant Conditioning

• Learning that occurs via consequences of previous actions, aimed at increasing or decreasing behavior through reinforcement contingencies.

• Operant conditioning demonstrated through real-world examples, emphasizing the importance of rewards and punishments.

Reinforcement Types and Schedules

• Positive and negative reinforcement involve the addition or removal of stimuli to influence behavior, while various schedules define when and how often reinforcement is given to shape learning behavior.