Understanding Perception Concepts

Perception: Key Concepts

• Perception is the sensory experience resulting from stimulation of the senses.
• Perceptions can change based on additional information.
• Perception is a process similar to reasoning and problem-solving and is closely tied to action.
• Perception may be unique to humans.

The Difficulty of Artificial Perception

• The inverse projection problem refers to determining the object responsible for an image on the retina. It starts with the image and works backwards.
• Hidden or blurred objects can still be identified by humans.
• Viewpoint invariance allows us to recognize objects from different perspectives.
• Scenes contain high-level information contributing to their complexity.

Information in Human Perception

• Perception uses environmental energy stimulating receptors and the observer's knowledge and expectations.

Approaches to Understanding Perception

• Direct perception theories (bottom-up): Perception arises directly from stimuli in the environment. Parts are identified and combined for recognition.
• Constructive perception theories (top-down): People actively construct perceptions using expectations and prior knowledge.

Complexity of Perception: Bottom-up and Top-down Processing

• Bottom-up processing: Perception begins with the senses, processing raw sensory data.
• Top-down processing: Perception begins with the brain, utilizing knowledge, experience, and expectations.

Hearing Words in Sentences and Top-down Processing

• Top-down processing influences word perception based on experience with the language.
• Speech Segmentation: The ability to differentiate word boundaries.
• Transitional probabilities: Knowing which sounds likely follow each other within words.
• Statistical learning: Learning characteristic and probabilities of different sounds in a language.
• Likelihood principle: We perceive the world according to the most probable interpretation based on past experience.

Multiple Choice Questions

• Viewpoint _____: Invariance (recognizing the same object from different perspectives).
• Sequence of steps in visual processing: Bottom-up (stimulus to electrical signals to neural processing).

Apparent Motion

• Apparent motion occurs when flashing lights are perceived as moving, with our brains adding movement.

Gestalt Principles of Perceptual Organization

• Principle of good continuation: Lines are perceived as following the smoothest path.
• Law of Prägnanz (simplicity/good figure): Stimulus patterns are perceived in the simplest form possible.
• Principle of similarity: Similar objects tend to be grouped together.

Regularities in the Environment: Physical

• Oblique effect: We perceive verticals and horizontals more easily than other orientations, because they are common in the environment.
• Light-from-above heuristic: We typically assume light comes from above, influencing our perception of shadows and depth.

Regularities in the Environment: Semantic

• Semantic regularities: Characteristics related to the functions within scenes (i.e., a jewelry case likely contains jewelry, not pizza).
• Scene schema: Our knowledge of what a scene typically contains.

Bayesian Inference

• Bayesian inference: Probability estimates of outcomes are influenced by prior knowledge and the likelihood of that outcome occurring.

Comparing Conceptions of Object Perception

• Top-down processing depends on unconscious inference, environmental regularities, and Bayesian inference.
• Bottom-up processing depends on Gestalt principles.

Neurons, Knowledge, and the Environment

• Neurons respond optimally to common environmental stimuli.
• Experience-dependent plasticity: Neurons adapt to be optimal for the environment (e.g. horizontal and vertical orientations).

Movement and Perception

• Movement significantly improves perception compared to remaining static.

Perception and Action

• Perception and action are constantly coordinated in the brain.

Olympic Rings Example

• The Gestalt principle of simplicity helps in correctly perceiving the five interlocking circles.

Gauthier's Greeble Experiment

• The results of Gauthier's experiments illustrate experience-dependent plasticity, where training influences how neurons fire to different objects.

Perception and Action (What and Where Pathways)

• What pathway (ventral pathway): Identifies the identity of an object (temporal lobe).
• Where pathway (dorsal pathway): Determines the location of an object (parietal lobe). Also called the "how pathway."

Patient DF (Apperceptive Agnosia)

• Patient DF's case involved deficits in object perception and action.

Mirror Neurons

• Mirror neurons fire when observing an action being performed. The mirror neuron system in the brain responds strongly to intent to perform the same action.

Course Information (Test 1)

• 90-minute test
• Starts at 9:30 am
• 30 multiple choice questions
• 3 short answer questions
• Study iClickers for MC questions
• Study material discussed across multiple lectures for SA questions