2nd_Lecture__Perception_in_Cognitive_Psychology

Perception in Cognitive Psychology

1. From Sensation to Perception

• Sensation vs. Perception:

  • Sensation: Raw input from the senses.

  • Perception: Organized interpretation of sensory inputs.

• Perceptual Illusions:

  • Our sensations do not always match our perceptions (e.g., optical illusions).

• Visual System Process:

  • Pathway: Cornea → Pupil → Retina → Optic Nerve → Brain.

  • Two Processing Streams:

    • Dorsal Pathway (Parietal Lobe): Responsible for location and motion.

    • Ventral Pathway (Temporal Lobe): Focuses on object identification.

2. Approaches to Perception

• Bottom-Up Processing (Data-driven):

  • Perception starts with raw stimuli.

  • Direct Perception (Gibson):

    • Perception solely based on sensory input.

  • Template Theories:

    • Comparison of stimuli with stored patterns (e.g., barcode scanners).

  • Feature-Matching Theories:

    • Recognition through distinct features (Selfridge’s Pandemonium Model).

  • Recognition-by-Components (Biederman):

    • Objects broken into 3D geons for recognition.

• Top-Down Processing (Concept-driven):

  • Perception influenced by expectations, prior knowledge, and context.

  • Constructive Perception:

    • Perception built through sensory and cognitive processes.

  • Context Effects:

    • Surroundings influence perception.

  • Superiority Effects:

    • Recognition is easier in certain contexts.

• Synthesis of Theories:

  • Bottom-up and top-down processes work together to form perception.

3. Perception of Objects & Forms

• Representation Views:

  • Viewer-Centered:

    • Objects stored based on personal viewpoint.

  • Object-Centered:

    • Objects stored in a stable form, independent of perspective.

  • Landmark-Centered:

    • Objects identified relative to known landmarks.

• Gestalt Laws of Perception (Grouping Visual Information):

  • Law of Prägnanz: Simplicity prevails.

  • Proximity: Close objects are grouped.

  • Similarity: Similar objects are grouped together.

  • Continuity: Smooth, continuous patterns are perceived.

  • Closure: Filling in missing gaps to perceive whole forms.

  • Symmetry: Preference for balanced, symmetrical images.

  • Figure-Ground Perception: Distinguishing objects from backgrounds.

• Face Recognition:

  • Utilizes feature analysis (identifying parts) and configuration system (holistic features).

  • Fusiform Gyrus: Key region for face recognition.

4. Environmental Influences on Perception

• Perceptual Constancy:

  • Perception remains stable despite sensory changes.

  • Size Constancy: Objects maintain size regardless of distance.

  • Shape Constancy: Objects maintain shape despite changes in angle.

• Depth Perception:

  • Monocular Cues (2D, one eye):

    • Involves relative size, texture, and shadowing.

  • Binocular Cues (3D, two eyes):

    • Stereopsis provides depth perception from two images.

5. Deficits in Perception

• Agnosia ("What" Deficit):

  • Inability to recognize objects despite normal vision.

  • Causes: Damage to temporal & occipital lobes.

  • Simultagnosia: Inability to focus on multiple objects.

• Ataxia ("How" Deficit):

  • Difficulty guiding movements using vision.

  • Causes: Damage to parietal lobe.

  • Effect: Trouble reaching for objects.

• Color Perception Deficits:

  • Achromacy: Complete lack of color vision.

  • Dichromacy: Partial color blindness.

    • Protanopia: Red-green deficit.

    • Deuteranopia: Green weakness.

    • Tritanopia: Blue-yellow confusion.