Consciousness: An Introduction by Susan Blackmore Section 2: The World presented by Haley Mack & Scott Mackenzie

Let’s Start at the End  Hopefully the next slide won’t spoil the presentation. Think about the answers we provide and how the theories and data that follow them either support or detract from their plausibility.  People usually think of attention in relation to vision (and a lot of studies focus on it), but remember that it can apply to any kind of sensory stimulation.

What is Attention’s Goal?  Truthful perception of the world is neither required nor necessarily attempted  Conscious experiences focus on gathering information quickly  Details are filled-in to give a sense of continuity to our perceptions  This is the point of attention in general, i.e., to concentrate on what is important

Chapter 4: Attention & Timing  Attention vs. Consciousness  Directing Attention  Libet’s Half-second Delay From

William James ( )  Does consciousness cause awareness?  Does awareness cause consciousness?  Do they affect each other at all?  “It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought.” (1890)

Free Will  James: “My experience is what I agree to attend to”  Firmly believed we have the ability to control our consciousness through free will  Is it possible we simply think we have control over our experiences?  We assume a choice was made because attention shifted, not because we made it

Filtering Attention  Dichotic listening experiments  Attention will switch between ears to follow a message without subject noticing  Broadbent’s theory  Subconscious filters parallel processing streams to produce focused serial outputs  Subtler models claim attention may simply allocate more resources; not a spotlight  Attention so complicated, it may not even exist (Pashler, 1998)

Effect and Cause Theories  James: is attention decided “by other brain-cells, or by some spiritual force”?  Effect Theory: brain cells guide brain cells  Cause Theory: “force” guides brain cells  Similar to the difference between physicalism and dualism  Couldn’t defend either side well, so he chose cause theory due to personal bias

How Sure Are You?  “I heard the door open and so I turned around to see who it was.”  Did you consciously perceive the door opening and then choose to turn?  Or, did you turn for some other reason and assume it was because the door opened?

Directing Attention  Visual saccades can be voluntary, but usually we aren’t aware of them  Smooth pursuit is never voluntary even though we are tracking the object!  The target it kept on the fovea automatically  Lots of other involuntary body movements occur, like rotating the head or torso

Selective Attention  Covert attention scanning (Helmholtz)  Look directly at one place but pay attention to someplace else  Premotor theory (Rizzolati et al)  Giving attention to a certain spatial location involves neurons that guide actions toward it  Example: if attending to a location on your right, neurons are activated that would used to turn to the right and do something

Pop-outs  Usually do a serial search to find one stimulus among many other similar ones  Takes a long time to evaluate each in turn  Sometimes the slight difference is a key characteristic, so it is immediately obvious From

Libet’s Half-second Delay  Electrically stimulated patients’ somatosensory cortices during surgery  Minimum level of stimulation necessary  At this intensity, ½ second of continuous stimulation before any perception  Shorter stimulation requires greater intensity

What Happens to the Lag?  Reaction times can be 200 ms, recognition can take ms, but Libet’s delay is 500 ms…  Our body responds before we are conscious of why it is responding  Subjective referral: after neuronal adequacy is reached, the event is referred back to the point at which it occurred

Libet’s Conclusions  Consciousness requires neuronal adequacy to occur  Backward referral challenges materialism and the idea that consciousness equals certain brain activity  Believes data supports dualism  When a noise is heard, it is processed unconsciously very quickly  We become conscious of it only after turning  Can still make some decisions consciously

Test Libet’s Delay Yourself!  Cutaneous Rabbit: tap a pointed object (quickly and evenly) five times on another person’s wrist, three times at the elbow, and twice on the upper arm  The taps should feel spread out along the entire arm instead of in only three spots  This phenomenon should occur BEFORE all the taps have been completed

The Phi Phenomenon  Same principle as the cutaneous rabbit  Two lights in different positions are flashed one after the other  Creates illusion of movement  If the lights are different colors, the color seems to change as the light moves  Notice that this means the first light appears to have an in-between hue before the actual change to the second light

Chapter 5: Theater of the Mind  Cartesian Dualism  Global Workspace Theory  Consciousness without a Theater ©2005 Dan L. Henderson

Thinking about Experience  John Cage: “Writing about music is like dancing about architecture.”  Closed eye exercise…  An journey to the ‘theater of the mind’

The Cartesian Theater  Hume: “The mind is a kind of theatre, where several perceptions successively make their appearance” (1739)  What is on stage is in consciousness  Does it feel like you just sit in your head and watch the world outside?  Is imagining like playing a fictional film instead of the real world?

Cartesian Materialism  Daniel Dennett rejects the Cartesian theater and Cartesian materialism  Claims most materialists still believe in something like the CT  CM is what he calls the implied belief in CT despite materialists’ rejection of dualism  Any notion that there is a place where “consciousness happens” suggests the belief in Cartesian dualism

Locating Consciousness  Many areas of the brain are correlated with certain kinds of processing  Stimuli enter the brain through the senses, the brain processes it, & behavior results  Consciousness does not appear in a place  Consciousness does not appear at a time  Dennett says we cannot ask these questions without believing in the CT

Mental Screen  Roger Shepard’s 1971 experiment: the time to rotate a block in the mind is proportional to the degree of rotation  Suggests we recreate the world in our head, just like the idea of a Cartesian theater  Not proof of conscious imagining; we rotate objects every day without noticing  Same part of brain active whether imagining or consciously viewing

Examples of different degrees of mental rotation. Try to figure out which sets are of the same block and which are not. Notice how relatively little time is necessary for (A) while a lot more is needed for greater rotations present in (B) and (C). From

Global Workspace Theory  Barrs, 1988: continues with the theater metaphor with a bright spot on stage  Unconscious contextual systems process information in the shadows to affect the events that occur in the bright spot  Each part of the “theater” is a different aspect of consciousness  Senses and ideas are “actors”  Memories, interpretations, and automatisms are the “audience”

Consciousness w/out Theater  Libet’s theory of neuronal adequacy  Most events do not reach the level necessary for conscious experience  Crick’s “astonishing hypothesis”  One’s sense of self is merely the result of interactions between neurons and molecules  Stimuli are consciously perceived if cells fire in synchrony to create reverberatory circuits

Multiple Drafts  Dennett proposes that everything in the brain is under constant revision  Perceptions and ideas are always present as multiple drafts at various stages  There is no point in asking which are conscious because this implies the CT exists  The sense of a narrative stream arises only when a question is presented and answered  Drafts can affect behavior in this way and leave traces in memory, but there is no actual experience that occurs

Chapter 6: The Grand Illusion  Filling in Gaps  Change Blindness  Inattentional Blindness From

What do we really see?  Illusions are things that are not what they appear to be  Most people believe that “seeing”  (1) is a conscious stream of moving images  (2) represents the world  Why do only parts of our visual experience become conscious?  Why should any of what we see be an authentic representation?

Filling-in the Gaps  When part of an object is obscured, we infer the missing information  Visual stimuli are pixilated spatially and temporally but our perception is not  Rods and cones are individual cells  Cells’ responses to changing stimuli take time  Blind spot is a significant gap, but we never see a black hole

Implication for the CT  Imagine a room full of identical pictures repeated over and over  The visual perception is that all are in focus, even though that is impossible  Dennett: there is no photocopy effect; the brain just guesses after the first few  If one picture is different, a brief glance is not long enough to notice it

Even More Filling-in  V.S. Ramachandran’s subject Josh has a very large blind spot (scotoma)  Presented with vertical lines above and below, he could actually see the gap close  Offset lines took ~5 s to line up and close  A row of numbers was filled in with numbers that couldn’t be read  Twinkling black dots on a red background: each feature was filled-in individually

Change Blindness  People often don’t notice minor changes between two pictures  This is especially true if you don’t see them at the same time  A subject scanning text will not notice changes outside his focus that are very obvious to others (Grimes, 1996)  Differences in alternating images are found more quickly if the change is in an area of interest (Rensink et al, 1997)

Examples of Rensink’s Films Java Applet Versions (can change settings) Downloadable QuickTime Versions

Inattentional Blindness  Subjects told to attend to one area will actively inhibit attention elsewhere  Focus and attention are not the same!  If the fovea is centered on a fixation point, attention can still be directed to the side  Will not notice a stimulus at the fixation point, even though the eye is directed right at it

Gorillas in our Midst  Subject watched teams dressed in black and white throw a ball in a film (Simons and Chabris, 1999)  Told to pay attention to white team’s passes  50% had no memory of seeing a person in a black gorilla suit walk around

Vision Theories  Simons & Levin: from each fixation we get a gist, which we compare to later gists  If the gists are similar, we don’t notice any changes in the details  Rensink: low-level processing creates a “coherence field” for each object  “Virtual representation” creates a rich experience without utilizing all information  O’Regan: no need to store everything because the brain can call on the world as a kind of external memory

What is Vision’s Goal?  Truthful perception of the world is neither required nor necessarily attempted  Conscious experiences focus on gathering information quickly  Details are filled-in to give a sense of continuity to our perceptions  This is the point of attention in general, i.e., to concentrate on what is important