6.1

Introduction

• Doctor Flux introduces the topic of sensation and perception, the sixth module in general psychology.

• Reminder of previous session covering the brain's inner workings through lesion studies, split brain research, and brain imaging.

• Emphasis on the importance of sensation (raw data) vs perception (brain's interpretation).

Key Concepts

• Sensation vs. Perception:

  • Sensation: Process of detecting environmental information (e.g., light, sound, pressure).

  • Perception: Interpretation of sensory information (e.g., recognizing a friend's face).

• Example:

  • Vision: Light forms an upside down image on the retina (sensation); the brain flips this image right side up (perception).

  • Hearing: Sound waves as vibrations (sensation) vs recognizing music or speech (perception).

Refresher Questions

• Reflexes controlled by the spinal cord.

• Patient case (H.M.) demonstrates hippocampus's role in memory formation, causing anterograde amnesia.

Model Building of Reality

• Brain as a 'model making machine' – builds models of reality from sensory data, but these models are not perfect.

• Quote: "All models are wrong, but some are useful" – highlights the brain's interpretation of reality based on limited information.

Bottom-Up vs Top-Down Processing

• Bottom-Up Processing:

  • Begins with raw sensory data, building a perception from the ground up (data-driven).

  • Example: Encountering a new object and noting its features to identify it.

• Top-Down Processing:

  • Uses prior knowledge and experiences to interpret sensory data.

  • Example: Completing sentences or identifying objects in ambiguous visual stimuli.

Cognitive Gaps and Errors

• The brain makes assumptions and fills gaps which can lead to misperceptions (e.g., hearing someone’s name when it’s not said).

• Perceptual errors remind us that perception isn’t direct reality; it’s a best guess by the brain.

Perceptual Illusions

• Illusions reveal limits of sensory processing; how assumptions may misfire. Examples include the famous dress color debate, blind spots filled in by the brain, and various optical illusions.

• Checker Shadow Illusion: Same colors perceived differently due to shadow context.

• Ames Room: Distorts perception of size in a manipulated space.

• Afterimages: Ghost images created by fatigued photoreceptors in contrasting colors.

Gestalt Principles

• Gestalt psychology posits that the whole is greater than the sum of its parts.

• These principles help organize sensory input into a meaningful experience.

• Key Principles:

  • Figure-Ground Organization: Differentiating the main object from the background.

  • Proximity: Objects close together tend to be grouped mentally.

  • Similarity: Similar items are perceived as part of a group.

  • Continuity: Preference for smooth, continuous patterns over disconnected lines.

  • Closure: Filling in gaps to create a complete perceptual experience.

Conclusion and Review

• Summary of how sensation translates to perception through bottom-up and top-down processing.

• Understanding of perceptual illusions and the role of Gestalt principles in creating coherent experiences.

• Final thoughts on the fallibility of perception and the utility of the brain's models in navigating the world.

• Review session questions reiterate key concepts (perception as interpretation, bottom-up vs top-down).