Opportunities for extra credit: Keep checking at:

March 22 More about conscious perception Overview of Memory March 24 Sensory Memory March 29 Short-Term/Working Memory (Brooks expt. 1) March 31 Long-Term Memory April 5 NO CLASS April 7 Long-Term Memory and False Memories (Loftus) April 12 Consciousness and “Perception without Awareness” Subliminal Messages (Vokey and Read) April 14 Memes (Dawkins) Upcoming

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

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

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

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

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

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)

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”

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

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

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

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

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

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

Object Substitution Masking Maybe we should learn more about memory…

MEMORY

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

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

Sensory Memory

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

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”

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Capacity “Recall as many letters as you can”

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?

Capacity Could it be that subjects had encoded all the letters but failed to retrieve the information?

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?

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”

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Which Letters?

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

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?

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

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?

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

Duration Partial Report Probe Delay # of letters potentially recalled 500 ms0 msnever

Duration Partial Report Delay # of letters potentially recalled Interpretation: 1.Information dwells in a brief storage “buffer” 2.duration of storage lasts about 1/2 of one second 500 ms0 msnever

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

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

Properties of Sensory Memory 1.Brief (iconic ~500ms; echoic ~2 seconds)

Properties of Sensory Memory 1.Brief (iconic ~500ms; echoic ~2 seconds) 2.Virtually unlimited capacity

Properties of Sensory Memory 1.Brief (iconic ~500ms; echoic ~2 seconds) 2.Virtually unlimited capacity 3.pre-attentive