1. Modified View of all this… Magnitude Estimation Steven’s Law: Power Function Cross Modality Match

9. Visual system characteristics Retina: 120 million rods & 6 mill. Cones Retinal distribution meaningful

11. System operating characteristics Color Sharpness or acuity: 1 sec. line (1 inch at 3.5 miles) Sensitivity (range (candle at 10 mi. to noon sun 10,000,000,000,000:1) Differential course of adaptation

12. Duplex Theory of Vision Two systems: –Rod based Sensitive Low acuity Monochromatic –Cone based High threshold High acuity Color

13. Adaptation Overall range of light 10 13 : 1 Adaptation range of eye 10 5 : 1

16. We’re not from Missouri! Color Vision ( Perceptual constancies/neural interactions) Feature Detection--the analysis of visual input –Limulus –Cats –Humans Top-down perceptual processes and their interactions with bottom-up

17. Active processing Sentence Necker Cube Gestalt principles

28. Feature Detection: the analysis of visual input Bottom-up perceptual processes (lateral inhibition) –Limulus (Hartline & Ratliff) –Frogs (Matarana, Lettvin, McCullough & Pitts) –Cats (Kuffler, Hubel & Weisal) –Humans Top-down perceptual processes and their interactions with bottom-up

46. Top-down processes: Some examples and a mechanism

50. Word Superiority Effect & its Mechanism

53. Conclusion Perception is an active process that tries to extract a more or less coherent iinterpretation of the world from the barrage of stimuli impacting us. It focuses on change (temporal or spatial). In order to quickly extract info from the deluge, it must distort the world to attempt to see it for what it is!!

54. Attention System interrupt attracted by alternative stimuli (dog in street) Conscious reallocation device Attention as limited resource Attention as bottleneck –Cocktail party effect : Colin Cherry –Filter theory: Donald Broadbent –Attenuation theory: Anne Triesman –Late selection theory: Donald MacKay (pennies) –Spotlight model: Michael Posner