1. Cognitive Processes PSY 334 Chapter 2 – Perception

2. Concerns about Cognitive Models  Relevance – do lab-task processes operate in the same manner in real life?  Sufficiency – can simple theories explain complex processes? Cognitive architectures  Necessity – does the mind actually work as described by specific theories? Cognitive neuroscience

3. Other Approaches to Cognitive Psychology  Connectionism (neural net models) – can higher level functions be accomplished by connected neurons? Parallel distributed processing (PDP) -- Rumelhart & McClelland  Situated cognition – the ecological approach Gibson’s affordances Do we explain cognition in terms of the external world or internal mind?

4. Cognitive Neuroscience  Pages 16-31 review basic concepts about the brain. If you have not taken PSY 210 and find this material confusing, come see me.  New methods permit study of normal human functioning in more complex tasks: EEG Imaging techniques – PET & fMRI

5. Visual Perception  Distal stimulus -- tree  Proximal stimulus – image of tree on retina  Percept – interpretation of proximal stimulus as a tree Size and color constancy

6. Information Coding  On-off cells in LGN feed into edge and bar detectors in the visual cortex.  Edge detectors – respond positively to light on one side of a line, negatively on the other side of the line.  Bar detectors – responds maximally to a bar of light covering its center.

7. Marr  Depth cues (texture gradient, stereopsis) – where are edges in space?  How are visual cues combined to form an image with depth? 2-1/2 D sketch – identifies where visual features are in relation to observer. 3-D model – refers to the representation of the objects in a scene.

8. Pattern Recognition  Classification and recognition occurs through processes of pattern recognition.  Bottom-up processes – feature detection  Top-down processes -- conceptually driven processing

9. Object Recognition  Two stages: Early phase – shapes and objects are extracted from background. Later phase – shapes and objects are categorized, recognized, named.

10. Disruptions of Perception  Visual agnosias – impairment of ability to recognize objects. Demonstrate that shape extraction and shape recognition are separate processes.  Apperceptive agnosia (lateral) – problems with early processing (shape extraction).  Associative agnosia (bilateral) – problems with later processing (recognition).  Prosopagnosia – visual agnosia for faces.

11. Gestalt Priniciples  Wertheimer, Koffka, Kohler.  Form perception – segregation of a display into objects and background.  Principles of perceptual organization allow us to see “wholes” (gestalts) formed of parts. We do not recognize objects by identifying individual features.

12. Five Principles  Proximity  Similarity  Good continuation  Closure  Common fate Elements that move together group together.  These will be on the midterm.

13. Examples Gestalt principles of organization Reversible figures Stuart Anstis demos: http://psy.ucsd.edu/~sanstis/SACamov.html http://psy.ucsd.edu/~sanstis/motion.html

14. Law of Pragnanz  Of all the possible interpretations, we will select the one that yields the simplest or most stable form.  Simple, symmetrical forms are seen more easily.  In compound letters, the larger figure dominates the smaller ones.