Lecture Notes: Understanding Brain Perceptions and Illusions

1. Blind Sight

• Example: Patient Tienne, blind due to strokes, can catch balls and dodge obstacles.
  • His brain processes visual info without conscious awareness.
  • Demonstrates subconscious brain activity similar to an unseen security guard.
• Implications: Your brain processes visual information and makes decisions before conscious awareness.

2. Filling in Visual Blanks

• Concept: Brain guesses visual details from limited info and past experiences.
  • Example: Not seeing your nose unless prompted.
• Brain's Role: Acts like a photo editor, removing and adding details to create coherent images.
• Phenomenon: Misleading brain guesses, such as seeing faces in crowds.

3. Choice Blindness

• Study: Participants switched photos or jams unknowingly and justified choices they didn't make.
• Brain's Role: Acts like a lawyer, rationalizing decisions with made-up evidence.
• Implications: Occurs with food and political beliefs, demonstrating brain's narrative creation.

4. Change Blindness

• Experiment: People don’t notice when a person changes during a conversation.
• Brain's Role: Takes snapshots and fills gaps with assumptions.
• Everyday Occurrence: Misremembering details, influenced by story focus rather than visual accuracy.

5. Pareidolia

• Concept: Seeing faces in non-face objects like clouds or outlets.
• Evolutionary Aspect: Quick recognition of faces was crucial for early humans.
• Modern Effect: Overactive face recognition, like seeing the 'face on Mars'.

6. McGurk Effect

• Discovery: Mismatch of visual and auditory info creates a third perceived sound.
• Real-life Examples: Occurs during TV viewing or noisy environments.
• Challenge: Even when aware, the brain continues to create false perceptions.

7. Motion-Induced Blindness

• Phenomenon: Brain erases visible items, like a star, when overwhelmed with movement.
• Daily Impact: Overlooked objects in busy environments due to brain’s filtering.

8. Motion Aftereffect

• Example: Staring at motion (e.g., waterfall) leads to false motion perception when looking away.
• Brain's Role: Motion-detecting cells get tired, mislead perception.

9. False Memories

• Concept: Brain constructs and sometimes fabricates memories.
• Experiments: Planting false memories, leading to detailed but fake recollections.
• Implications: Challenges reliability of eyewitness testimony and personal memory.

Conclusion: The brain's role in perception is complex, often misleading, and not entirely reliable. Understanding these phenomena can provide insight into human cognition and psychology.

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