1. Cognitive - perception.ppt © 2001 Laura Snodgrass, Ph.D.1 Perception The final image we are consciously aware of is a “constructed” representation of the outside world Retinal Image Theory –assumes that we “see” the image projected onto our retinas –However, perception does NOT match the retinal image –3 components distal stimulus; proximal stimulus; representation

2. Cognitive - perception.ppt © 2001 Laura Snodgrass, Ph.D.2 Retinal Image Theory Evidence that we DO NOT “see” our retinal image: –blind spot –no color in periphery –double images –no depth –constancies –ambiguous figures

3. Cognitive - perception.ppt © 2001 Laura Snodgrass, Ph.D.3 The Basic Units of Pattern Perception What is stored in LTM –distinctive features –structural models –prototypes (template) –recognition by components Factors that influence the size and nature of what can be a unit

4. Cognitive - perception.ppt © 2001 Laura Snodgrass, Ph.D.4 Local versus Global Elements Which is processed first or faster, the small local elements or the large global elements? Where are the boundaries between local and global

5. Cognitive - perception.ppt © 2001 Laura Snodgrass, Ph.D.5 Integral vs. Separable Features Separable features are easy to mentally take apart –e.g. Shape and color. Integral features combine to form a new unit in which it is hard to see the parts –hue and brightness ; red and white make pink

6. Cognitive - perception.ppt © 2001 Laura Snodgrass, Ph.D.6 Emergent Features Sometimes when integral features combine they produce an “emergent feature”, a quality of the whole that is not there in the individual features

7. Cognitive - perception.ppt © 2001 Laura Snodgrass, Ph.D.7 Direction of Processing Do the encoded features determine the representation (bottom-up)? OR Does the representation determine what gets encoded (top-down)?

8. Cognitive - perception.ppt © 2001 Laura Snodgrass, Ph.D.8 Direction of Processing Bottom-up –automatic, fast, rigid –e.g. template and distinctive feature models Top-down –slower, flexible, influenced by experience and expectations (set, schemas) –e.g. ambiguous figures, scene perception –context effects