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3. Perception and Cognition • We have elaborate perceptual mechanisms to provide information to our brains to guide current or future behavior

4. Perception and Cognition • We have elaborate perceptual mechanisms to provide information to our brains to guide current or future behavior • Notice there’s no mention of consciousness

5. Perception and Cognition • We have elaborate perceptual mechanisms to provide information to our brains to guide current or future behavior • Notice there’s no mention of consciousness • Lot’s of information gets processed and used by your brain without you noticing

6. Perception and Cognition • We have elaborate perceptual mechanisms to provide information to our brains to guide current or future behavior • Notice there’s no mention of consciousness • Lot’s of information gets processed and used by your brain without you noticing • Consider an example

7. Blindsight and the Dorsal Stream • Lesions (usually due to stroke) in primary visual cortex cause a region of blindness called a scotoma • Identified using perimetry X

8. Blindsight and the Dorsal Stream • Patients with lesions to primary visual cortex occasionally retain some visual abilities: • better than chance performance on forced-choice discrimination tasks • spatial navigation and coordination (i.e. avoid obstacles, interact with environment)

9. Blindsight and the Dorsal Stream • Patients with lesions to primary visual cortex occasionally retain some visual abilities: • better than chance performance on forced-choice discrimination tasks • spatial navigation and coordination (i.e. avoid obstacles, interact with environment) • Thought to be because of other “backdoor” pathways that send signals to the Dorsal Stream, A.K.A the “Where and How Pathway”

10. “WHERE” “WHAT” Blindsight and the Dorsal Stream • The Dorsal Stream is thought to mediate much spatial processing and interaction with the environment

11. Blindsight and the Dorsal Stream • The Dorsal Stream is thought to mediate much spatial processing and interaction with the environment • But the neural activity in these structures does not (is not alone sufficient to) enter into consciousness

12. The Hard Problem Returns • MYSTERY: what is special about neural activity that leads to awareness ? NOBODY KNOWS !

13. Attention and Consciousness • Sensory information must be attended for it to be entered into awareness • This involves a subtle interaction between perception and memory… • Put another way: sensory information must be attended to be encoded into memory

14. Object Substitution Masking • Masking occurs when one stimulus impairs perception of a nearby stimulus • In special cases the stimuli don’t have to overlap in space or time!? • Object Substitution masking occurs when attention cannot select a target object before it vanishes …AND… • A mask is visible at the target location after the target has vanished

15. Object Substitution Masking • Masking highlights the complex and subtle interaction between perception, attention, memory and awareness: Shapes enter visual system Mask cues attention to the target location Conscious system tries to recover shape that had been there

16. Object Substitution Masking • Maybe we should learn more about memory…

17. MEMORY

18. Overview of Memory • Atkinson-Shiffrin Model RETRIEVAL ATTENTION Sensory Memory Short-Term Memory Long-Term Memory Sensory Signals REHEARSAL

19. “Types” of Memory • Sensory Memory • brief ( < 1 second) • preattentive / parallel processing (very large capacity)

20. Sensory Memory

21. Capacity • Describe a simple experiment that could measure the capacity of “memory”

22. Capacity • Describe a simple experiment that could measure the capacity of “memory” • Briefly present some letters or digits and then ask the subject to report them • Called “whole report”

23. Capacity +

24. Capacity F S F E G S A U T O C G +

25. Capacity “Recall as many letters as you can”

26. Capacity • George Sperling - Systematic investigation of memory capacity • Result: subjects accurately recall 3 or 4 items • What can you conclude from this result? • Maybe subjects can only hold 3 or 4 items?

27. Capacity • Could it be that subjects had encoded all the lettersbut failed to retrieve the information?

28. Capacity • For example: What if they forgot the information before they could report it? • You would get the same result! • How could you modify the experiment to measure the instantaneous capacity, before any forgetting can occur?

29. Capacity • Partial Report - briefly present letters or digits and ask subject to report only some of them “Report the letters in the row indicated by the arrow”

30. Capacity +

31. Capacity U E S B O D W A I B V S +

32. Capacity +

33. Capacity +

34. Capacity Which Letters?

35. Capacity • Partial Report • Result: subjects can recall any 3 or 4 letters that are indicated by the arrow !

36. Capacity • Partial Report • Result: subjects can recall any 3 or 4 letters that are indicated by the arrow ! • What does this mean about the capacity of memory?

37. Capacity • There is some part of the perception system that stores huge amounts of information… • in fact, if only a single letter is probed, instantaneous capacity is seen to be unlimited

38. Duration • There is some part of the perception system that stores huge amounts of information… • But for how long? How would you design an experiment to measure the duration of this high-capacity memory system?

39. Duration • There is some part of the perception system that stores huge amounts of information… • But for how long? How would you design an experiment to measure the duration of this high-capacity memory system? • Vary the onset of the probe

40. Duration • Partial Report 10 # of letters potentially recalled 4 0 0 ms 500 ms never Probe Delay

41. Duration • Partial Report 10 # of letters potentially recalled 4 0 0 ms 500 ms never Delay Interpretation: Information dwells in a brief storage “buffer” duration of storage lasts about 1/2 of one second

42. Iconic Memory • a brief storage of “raw data” in the visual system

43. Echoic Memory • Auditory information is stored in a similar sensory “buffer” • Echoic memory seems to last for several seconds

44. Properties of Sensory Memory • Brief (iconic ~500ms; echoic ~2 seconds)

45. Properties of Sensory Memory • Brief (iconic ~500ms; echoic ~2 seconds) • Virtually unlimited capacity

46. Properties of Sensory Memory • Brief (iconic ~500ms; echoic ~2 seconds) • Virtually unlimited capacity • pre-attentive