Cognitive Processes PSY 334

1. Cognitive ProcessesPSY 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.