CH. 3 CP

Introduction

  • Perception: Experiences resulting from stimulation of the senses.

Key Questions

  • Why can two people experience different perceptions in response to the same stimulus?

  • How does perception depend on a person's knowledge about characteristics of the environment?

  • How does the brain become tuned to respond best to things likely to appear in the environment?

  • What is the connection between perception and action?

Crystal's Beach Experience

  • Crystal's run along the beach illustrates how perception can change based on added information and involve reasoning or problem solving.

  • Initial Perception: Mistakenly sees an umbrella as driftwood in misty conditions.

  • Correction of Perception: Realizes it is an umbrella upon closer inspection.

Nature of Perception

  • Perception is not automatic; it involves complex processes.

  • Example of coiled rope: Assumed to be continuous based on past experience.

  • Perception is linked with action—Crystal’s running and later grasping her coffee cup demonstrates coordination between seeing and physical interaction.

Characteristics of Perception

  • Dynamic Process: Rapid adjustments based on knowledge and sensory input.

  • Reasoning Involvement: Sometimes mimics reasoning or problem solving.

  • Interaction with Action: Essential for tasks such as grasping objects, which involve continuous spatial awareness.

Understanding Scene Perception

  • Example: Roger viewing Pittsburgh from PNC Park demonstrates the ability to interpret various buildings and objects in a scene.

  • Perceptual Puzzles: Humans can interpret complex visual scenes instinctively, while computers struggle to achieve the same understanding.

Computer vs. Human Perception

  • Computers have historically struggled with visual perception despite advancements.

  • Early systems required excessive processing time versus rapid human interpretation.

  • Challenges for Computer Vision:

    • Ambiguous stimulus on receptors (inverse projection problem).

    • Objects potentially hidden or blurred.

    • Objects appearing different from alternate viewpoints.

    • High-level contextual information needed for scene understanding.

Mechanisms of Perception

  • Bottom-Up Processing: Starts with stimulation of the receptors leading to image transmission to the brain.

  • Top-Down Processing: Involves existing knowledge impacting perception, aiding recognition and meaning-making in context.

  • Examples:

    • Blobs perceived differently in varying contexts based on prior knowledge.

    • Rapid object identification in scenes, informed by statistical learning acquired over time.

Approaches to Object Perception

Helmholtz's Theory

  • Unconscious Inference: Perceptions are based on past experiences (likelihood principle).

Gestalt Principles

  • Emphasize innate organizing principles over learned experiences.

  • Illustrate principles such as good continuation and simplicity in perception.

Regularities in the Environment

  • Physical Regularities: Frequent features in human-made and natural environments influence perception.

  • Semantic Regularities: Relate to the inferred meanings and typical functionalities within scenes.

Bayesian Inference

  • Combines prior probabilities with likelihood based on new evidence to enhance perceptual conclusions.

Neural Basis of Perception

  • Experience-Dependent Plasticity: Neurons adapt to respond to common environmental characteristics.

  • Neuroscientific Evidence: Specialized neurons respond primarily to environmental regularities, established through evolutionary adaptation.

Action and Perception Interaction

  • Movement as a Tool for Perception: Movement allows for enhanced understanding through revealing hidden aspects of objects.

  • Coordination in Actions: Everyday actions, such as reaching for a coffee cup, require dynamic integration of perception and action, facilitated by separate but coordinated neural pathways.

What and Where Streams

  • Perception Pathway (What): Identifies objects.

  • Action Pathway (Where): Facilitates spatial location for interactions.

Mirror Neurons

  • Mirror neurons fire during both action execution and observation, linking perception and action more closely.

  • They may offer insights into the intentions behind observed actions, guiding social interactions and understanding.

Conclusion

  • Perception is complex, integrating sensory input, prior knowledge, and action capabilities into a coherent interaction with the environment.