Perception
Likelihood principle
we perceive the world in the way that is "most likely" based on our past experiences
Law of good figure (simplicity or prägnanz)
Every stimulus pattern is seen so the resulting structure is as simple as possible
Law of good continuation
Lines tend to be seen as following the smoothest path
Law of similarity
Similar things appear grouped together
Neurons and the Environment
Some neurons respond best to things that occur regularly in the environment Neurons becomes tuned to respond best to what we commonly experience - Horizontals and verticals - Experience-dependent plasticity
Law of familiarity
Things are more likely to form groups if the groups appear familiar or meaningful
Law of common fate
Things moving in the same direction appear to be grouped together
Law of proximity
Things near each other appear grouped together
Perception and Action: What and Where
What stream: identifying an object Where stream: identifying the object's location
Occlusion heuristic
When object is partially covered by a smaller occluding object, the larger one is seen as continuing behind the smaller occluder
Sensation
absorbing raw energy (e.g., light waves, sound waves) through our sensory organs
Perceived size is a function of
both bottom-up and top-down processing
Attention
concentration of mental energy to process incoming information
Transduction
conversion of this energy to neural signals
Gestalt laws
often provide accurate information about properties of the environment - Reflect experience - Used unconsciously - Occasionally misleading are heuristics
Top-down processing
the perceived distance of the object the size of the object relative to other objects in the environment
Bottom-up processing
the size of the image on the retina
Geons
three-dimensional volumes
One function of the mirror neurons might be
to help understand another person's actions and react appropriately to them (Rizzolatti & Arbib, 1998; Rizzolatti et al., 2000, 2006)
Perception
selecting, organizing, and interpreting these signals
Heuristic
"rule of thumb" - Provides best-guess solution to a problem - Fast - Often correct
Perceptual Organization
- "Old" view - "New view
The Complexity of Perception
- Bottom-up processing - Top-down processing
Direct perception theories
- Bottom-up processing - Perception comes from stimuli in the environment - Parts are identified and put together, and then recognition occurs
Approaches to Understand Perception
- Direct perception theories - Constructive perception theories
Overview: Sensation and Perception
- Energy contains information about the world (usually incomplete, full of noise, and distorted) - Accessory structure modifies energy - Receptor transduces energy into a neural response - Sensory nerve transmits the coded activity to the central nervous system - Thalamus processes and relays the neural response - Relayed to specialized areas of the cortex - Perception of the world is created
"New" View
- Gestalt psychologists - The mind groups patterns according to laws of perceptual organization
Gestalt Laws of Perceptual Organization
- Law of good continuation - Law of good figure (simplicity or prägnanz) - Law of similarity - Law of familiarity - Law of proximity - Law of common fate
Light-from-above heuristic
- Light comes from above - Is usually the case in the environment - We perceive shadows as specific information about depth and distance
Other Perceptual Heuristics
- Light-from-above heuristic - Occlusion heuristic
Mirror Neurons
- Neurons that respond the same way when actually performing an act and when observing someone else perform the act - Located in the premotor cortex
Single dissociation
- One function is lost, another remains Example: Monkey A has damage to temporal lobe. This monkey is no longer able to identify objects (what) but can still identify locations (where) - Therefore, what and where rely on different mechanisms, although they may not operate totally independent of one another
Top-down processing
- Perception may start with the brain - Person's knowledge, experience, expectations
Bottom-up processing
- Perception may start with the senses - Incoming raw data - Energy registering on receptors
Double dissociation
- Requires two individuals with different damage and opposite deficits Example: Monkey A with temporal lobe damage has intact where but impaired what; Monkey B with parietal lobe damage has intact what but impaired where - Therefore, what and where streams must have different mechanisms AND operate independently of one another
Perception is...
- The process of recognizing, organizing, and interpreting information from senses - Not an exact copy of "the world" - Based on our past experience and expectations
Constructive perception theories
- Top-down processing - People actively construct perceptions using information based on expectations
Helmholtz's Theory Of Unconscious Inference (~1860)
- Top-down theory - Some of our perceptions are the result of unconscious assumptions we make about the environment - We use our knowledge to inform our perceptions - We infer much of what we know about the world
Recognition-by-components theory (RBC)
- We perceive objects by perceiving elementary features - Objects are recognized when enough information is available to identify object's geons
Top-down Processing (Constructive Perspective)
- involves making inferences based on context, guessing from experience, and basing one perception on another - Occurs quickly, automatically
Algorithm
- procedure guaranteed to solve a problem - Slow - Definite result
"Old View
- structuralism - Perception involves adding up sensations
Geons: Distinct
36 different geons have been identified
Perception and Action: Using Dissociation Logic
If you are trying to understand a complex system, you can logically deduce conclusions from "malfunctions" Damage to different areas of the brain cause very different deficits - We can conclude that a specific area is necessary for a specific function Brain Ablation method allows scientists to damage specific areas of otherwise normal brains (usually in monkeys or cats) - Controlled damage allows for clear conclusions to be drawn
Bottom-up Processing: Behavioral
Recognition-by-components theory (RBC)
Geons: Discriminability
geons can be distinguished from other geons from almost all viewpoints
Geons: Resistance to visual noise
geons can be perceived in "noisy" conditions