Week 5: Perceiving objects part 1 Flashcards
Gestalt psychology
- a school of psychology concerned with how perceptual organisation is achieved
Feature detection
A theoretical approach, most commonly in pattern recognition, in which stimuli/ patterns are identified by breaking them up into their constituent features.
Perceptual constancy
tendency of humans to see familiar objects as having standard shape, size and/or colour, regardless of changes in the angle, pov, distance or lighting.
Agnosia
a deficit in the ability to name objects that arises from brain damage
Holistic processing
Involves the integration of info from an entire object
Propoagnosia
(face blindness) Individuals experience poor face recognition, but good object recognition
Detecting features: bottom-up processing
stimulus driven, very simplistic
- Based on bottom-up processing, we can see 3 pie-like circles and pink V-shapes
Feature detecting: Top-down processing
Concept-driven
(e.g. if can’t see whole object, rely on interpretation, past experience, prior knowledge more complex)
- Based on top-down processing, our existing knowledge allows us to see a triangle in the middle
Gestalt psychology
(derived from German word meaning ‘form’ or ‘appearance’)
* Concerned with how perceptual organisation is achieved * Describe how we separate and link (or parse) into individual objects
Parse
how we separate/ link different objects
Guiding principles of prägnanz: meaning
when people are presented with complex shapes or a set of ambiguous elements, their brains choose to interpret them in the easiest manner possible
Guiding principles: Similarity principle
Group together objects that resemble each other
Guiding principles: proximity principle
The closer objects are to each other, the more likely we are to group them together perceptually
Guiding principles: Good continuation
Prefer to organise objects where contours continue smoothly
(brain would prefer to see it at one whole object, rather than 2 separate ones)
Guiding principles: closure
Bias toward perceiving closed objects rather than incomplete ones
Guiding principles: Simplicity
Interpret an object in the simplest way possible
Guiding principles: Figure-ground segregation
Separating an object from its background
relies on past experience/learning - not innate!
Gestalt psychology: strengths
- Focuses on fundamental issues
- Principles applicable to complex images
- Simplicity is key!
Weaknesses
- Deemphasised the importance of past experience
- Provide descriptions (not explanations) of perceptual phenomena
- Principles of perceptual organisation based on 2D drawings (applicable to real life?)
Feature detection theories
A simple pattern, fragment or component
– Appears in combination with other features across a variety of stimuli
Visual search
Pps Indicate as quickly as you can whether a particular target is present (an odd one out) (Treisman, 1986)
Takes longer when searching for a combination of features
Feature Nets
– bottom-up - Piece together features of the stimuli - from features, to letters to the word
- Top-down - When pps primed with images of animals, they’re more likely to choose an animal word
Geometric ions
All objects reduced to geometric ions/ shapes (“geons”)
Recognition-by-components (RBC) theory… components = geons
Recognition-by-components (RBC)
- Perceiving components is the first major step in object recognition
- Object recognition is a joint effort between two processes:
- One responsible for features and components
- Another for overall shape and global patterns
- Object recognition is a joint effort between two processes:
Evidence for RBC
- If a pattern is degraded (parts missing), it matters where it is degraded
- Non-recoverable objects
– Vertices (point where two lines meet) missing
– Cannot or take longer to recognise object - Recoverable objects
– Segments of smooth, continuous edges missing
– Easy to fill-in missing parts and recognise object
Biederman (1987)
- Non-recoverable objects
Weaknesses
- Tied to bottom-up processing
- Some evidence contradicts the “features-first” aspect of the model
– Whole object can be perceived rapidly and automatically - Embodied cognition
– Perception of objects influenced by our expectation of how we will
interact with those objects
Summary so far
- Object perception is complex
– Detect different features (bottom-up)
– Interpret features (top-down)- Gestalt Psychology – prägnanz
– Similarity; proximity; good continuation; closure; simplicity; figure-ground segregation - Theories of object perception
– Feature nets
– Recognition-by-components (geons)
- Gestalt Psychology – prägnanz
