Cognitive Processes PSY 334

1. Cognitive ProcessesPSY 334 Chapter 4 – Perception-Based Knowledge Representation April 21, 2003

2. Dual-Code Theory • The mind operates upon internal representations of knowledge. • How is visual information (imagery) represented in memory? • Paivio’s Dual-Code Theory – memory is better if we encode information visually and verbally. • Separate representations are maintained for verbal and visual information.

3. Evidence for Dual Codes • Santa compared linear and spatial arrays of: • Three geometric objects • Three names of geometric objects • Subjects were asked whether the arrays contained the same objects or names. • Subjects were faster when shapes were in the same spatial arrangement but faster when words were linear.

4. Evidence From Brain Imaging • Subjects were asked to mentally rehearse: • A word jingle • Navigating their neighborhood • Increased blood flow occurred in different areas of the brain, depending upon the task. • The same brain areas were active as when actually speaking or seeing.

5. No Homunculus • Homunculus -- the idea that there are “pictures in the head” implies someone to look at those pictures. • Both images and percepts are represented topographically in the brain, but there is no homunculus to view them. • Kosslyn -- the same processes are used to view mental images and external percepts.

6. Mental Rotation • Shepard – two-dimensional and three-dimensional mental images are rotated in the same way as actual objects. • The more an object is rotated, the longer it takes to respond in a same/different task. • Georgopoulos et al. – measured neurons firing in monkey brains when moving a handle. • Intermediate cells fire showing rotation.

7. Image Scanning • Brooks – subjects scanned imagined diagrams (like letter F) and noted outside corners, or sentences noting nouns. • Respond by saying “yes” or “no” • Tap left hand for “yes,” right hand for “no” • Point to Y or N on a sheet • Scanning a sheet for Y’s & N’s conflicted with scanning the mental image. • Conflict is spatial not visual.

8. Comparing Visual Quantities • Time to make a judgment decreases as the difference in size between objects increases. • The smaller the difference the longer it takes to make a judgment. • Which is larger: • moose or roach, wolf or lion? • The same pattern emerges when asked to judge actual differences, line lengths.