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PERCEPTION AND CONSCIOUSNESS: BASICS OF INFORMATION INTAKE
Basic Issues in Perception
Sensation vs. Perception
●Sensation: − Early processing− Physiological (neuronal)
●Perception: −Later processing−Psychological (interpretive)
THE FIELD OF COGNITIVE PSYCHOLOGY
IS FILLED WITH FASCINATING SCIENTIFIC
FINDINGS OF INTERESTING PHENOMENA
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THE FIELD OF COGNITIVE PSYCHOLOGY
IS FILLED WITH FASCINATING SCIENTIFIC
FINDINGS OF INTERESTING PHENOMENA
Bottom-up and top-down processing
● Bottom-up processes (aka: data-driven)− Based on information from the stimulus
● Top-down processes (aka: conceptually-driven)− Based on knowledge, expectations, context
» Perception: Constructed or Directly Experienced?
● Constructive View− Emphasizes the role of top-down processing in
arriving at a percept
● Direct View− Emphasizes the role of bottom-up processing in
arriving at a percept
The Basic Tasks of Visual Perception
● Pre-attentive Processing− Before attention is directed at a stimulus array− Organization of an incoming stimulus array into
discrete elements
● Post-attentive Processing − After attention is directed at a stimulus array− Identification of these elements for further processing
and categorization
Perceptual Organizational Processes
» Grouping and Region Segmentation● Grouping Principles− Similarity
− Proximity
− Good Continuation
− Closure
− Common Fate
− Element Connectedness
− Common Region
Palmer and Beck (2007)
Repetition discrimination task: “is repeated element a circle or a square”
RT was measured
Stimuli
Results Within was faster than between
Within
Between
» Figure-Ground● Tendency to segment a visual scene as a figure
superimposed on a background
● Figures relative to ground:− Are bigger− Contain more symmetrical features− Are meaningful− Are surrounded by other elements in the visual scene− Are lower in the visual field− Display convexity
» Global Precedence
● Aspects of the environment that are processed first and automatically − The whole or the parts?
Navon (1977)
Presented big letters made up of small objects
Different stimulus types:
Big letter made up of small letters♦ Consistent ♦ Conflicting
Big letter made up of neutral stimuli♦ Control Condition
Subjects were given either
“Local-directed” instructions: identify small object “Global-directed” instructions: identify large object
RT to identify directed letter was measured
Predictions
RT to detect directed letter compared to neutral
If local is a primitive
Global directed condition♦ Consistent
No difference in RT
♦ Conflicting
Slower RT
Local directed condition♦ Consistent
No difference in RT
♦ Conflicting
No difference in RT
If global is a primitive
Global directed condition♦ Consistent
No difference in RT
♦ Conflicting
No difference in RT
Local directed condition♦ Consistent
No difference in RT
♦ Conflicting
Slower RT
Local is a primitiveGlobal is a primitive
Global directed condition
Consistent♦ No difference in RT♦ No difference in RT
Conflicting♦ Slower RT♦ No difference in RT
Local directed condition
Consistent ♦ No difference in RT♦ No difference in RT
Conflicting♦ No difference in RT♦ Slower RT
Results
Overall, global letters were reported more quickly (a main effect)
Big letters not affected by identity of small letters (same as neutral), but small letters were affected by identity of big letter (Interaction)
Global Precedence Effect–global perceived before local
● Is global precedence universal?
Ebbinghaus illusion
Davidoff, Fonteneau, and Fagot (2008)
Tested Himba and UK participants
Stimuli
Task Indicate which comparison stimulus “is most like the
target?”
Comparison stimuli
Predictions
Global Precedence♦ Choose left stimulus
Local Precedence♦ Choose right stimulus
Results UK participants: global precedence (86% chose left) Himba participants: local precedence (77% chose right)
Multisensory Interaction and Integration
Synesthesia
Strong synesthesia (rare)− Input to one sensory modality produces a perceptual
experience in that modality and another one
− Tend to be:◘ Unidirectional ◘ Consistent
If synesthesia is due to: Sensory processing:
♦ Will see purple Synesthetic experience caused by sensation of
a /b/
Perceptual processing♦ Will see pink
Synesthetic experience caused by blended perception of a /d/
Results Saw pink Strong synesthesia is the result of later
(perceptual) processing
Comparing the Senses
» Vision and Audition● Ventriloquist effect
− “Sound” perceived as coming from visual display
» Vision and chemical senses
Morrot, Duchet, and Dubourdieu (2001) Stimuli
White wine colored red
Participants Wine experts
Task Describe the smell of the wine
Results Smell illusion: described smell with words used to
describe the smell of red wine (e.g., clove, cherry)
» Vision and Touch● Rubber hand illusion
Pavani, Spence, and Driver (2000)
MethodologyHeld cubes vibrated on top and bottomSeen cubes lit up on top and bottomLight and vibration matched or mismatched Seen hands were aligned or misaligned with own hands
Task: identify the source of vibration (top or bottom)
RT was recorded
Results
Cue-Position MatchCue-Position Mismatch
Ehrsson, Rosen, Stockselius, Ragno, Kohler, and Lundborg (2008) Participants: upper-limb amputees Rubber glove holding cube with LED on top and bottom Vibration to top or bottom of stump LED and vibration were simultaneous and consistent Results Participants felt vibration in phantom hand
♦ Resulted in feeling of ownership of the “hand”
Perception and Action
Perception evolved to:− maximize survival− defend us from having to think
» Affordances● Actions offered by an object
Ishak, Adolph, and Linn (2008)
Apparatus Candy at the end of a long flat stick
Aperture
Good aperture perception (knew when aperture was big enough to retrieve candy): Motor decision function should be highest at aperture
threshold and drop precipitously below it
Results
Motor decision function
Aperture Threshold
» Embodied perception
Proffitt, Bhalla, Gossweiler, Midgett (1995)
Task: Estimate slant of two hills (both 5º) Before rigorous run After rigorous run (fatigue)
3 conditions Verbal
Visual
Haptic
Results
Witt, Linkenauger, Backdash, Augustyn, Cook, and Proffit (2009)
Participants did or did not suffer with minor, but chronic, pain of back and/or lower extremities
Task: estimate distance from various traffic cones
Results Chronic pain sufferers judged distances to be longer
than those not suffering from chronic pain
Visual perception evolved: − to maximize survival (efficient “expenditure of energy”)− to avoid having to think
● Positive Complement
Witt, Linkenauger, Backdash, and Proffitt (2008) Participants putted into a practice putting hole
Difficult: just over 7 feet Easy: just under 1½ feet
Task: estimated size of hole
Results Estimates of hole size were larger after easy than
difficult putts
Another study found a negative correlation between estimate hole size and golfing score
Consciousness
Varieties of consciousness● Access consciousness
− What the cognitive system is actually doing
● Phenomenal consciousness− Knowledge of what our cognitive system is doing
● Monitoring consciousness− Ability to reflect on one’s cognitive processing
● Self-consciousness− General knowledge of self
● Most cognitive processes occur outside of phenomenal consciousness making self-report highly suspect
− Signal detection theory
◘ Perceptual experiences are the joint product of: Sensitivity of the particular sensory system Response bias (willingness to report the
perception)
Dissociations in consciousness
» Authorship Processing● Set of processes that leads actions to be attributed
to the entities that caused them
Illusion of conscious control− Results from close proximity between relevant thought and
action
Wegner, Sparrow, and Winerman (2004)
Methodology Confederate in back is giving
commands Passive participant Looking in mirror Hears commands Does not hear commands
mirrorconfederateparticipant
Dependent variable “Rate degree to which you feel you are consciously willing
the arm movement”
Results Higher rating when heard command than when did not
hear command♦ Phenomenal consciousness in the absence of access
consciousness
Metcalfe and Greene (2007) Investigated metacognition of one’s sense of agency
Participants played video game in which X’s and O’s moved downward on the computer screen
Task: use mouse to move cursor to touch the X’s, but avoid the O’s Received 1 point for each X they touched At random times, game stopped and participants were
asked to rate the degree to which they had been in control of the cursor (judgment of agency)
Three independent variables: Speed at which X’s and O’s moved down the screen
♦ Fast♦ Slow
Fidelity of mouse cursor relationship (turbulence)♦ No turbulence: perfect correlation between mouse
movement and cursor movement♦ Turbulence: loose correspondence between mouse
movement and cursor movement
How close the cursor had to be to the X to receive credit for touching it
♦ Magic: within 10 pixels to receive credit♦ No magic: must touch it to receive credit
Two dependent variables: Hit rate: proportion of X’s that were touched Judgments of Agency (JoA) ratings: How in control was
I?
Predictions Hit rates should show similar patterns as JoA ratings if
performance is basis for JoA ratings They were responsible for the hit rates
If similar patterns are not obtained, something other than performance is the basis for the JoA ratings
♦ They were not responsible for the hit rates
Results
Speed♦ Hit rates were greater in slow than fast, but JoA ratings
were the same Participants were metacognitively aware that their
performance was due to the speed with which the X’s and O’s were falling
Turbulence♦ Hit rates were almost identical in turbulence and no
turbulence conditions, but JoA ratings were greater in no turbulence than turbulence condition
Participants were metacognitively aware that they had little control over their performance in the turbulence condition
Magic♦ Hit rates and JoA ratings were greater in the magic
than no magic conditions, but the difference was greater for hit rates than JoA ratings
Participants were metacognitively aware that they had less control over their performance in the magic condition
Conclusion There is good metacognitive awareness of one’s sense
of agency Wegner et al. study is most likely the exception, rather
than the rule
» Blindsight● Access consciousness in the absence of phenomenal
consciousness
● D.B. was completely blind in left visual field− Unable to identify objects (no phenomenal
consciousness)− Possessed knowledge of those objects, such as
location (access consciousness)
● Two distinct neurologic systems underlying vision
− What system◘ Located primarily in visual cortex◘ Relatively late in visual processing◘ Responsible for identifying, recognizing, and
becoming aware of visual stimuli
− Where system◘ Located primarily in subcortical structures◘ Relatively early in visual processing◘ Responsible for detection and localization
Systems are dissociated in blindsight
Subliminal Perception Can semantic (meaning-based) processing occur
outside of phenomenal consciousness
Pepper
Pepper
Pepper
Pepper
Binocular suppression paradigm
Visible and consciously perceived
Increased in brightnessuntil visible
Results Initially invisible target emerged from suppression sooner
when prime was related than when it was unrelated
» The effects of subliminal primes
Questions of definition and method
● Do subliminally presented stimuli influence behavior
− Depends◘ What does “subliminal” mean?◘ What does “influence” mean?
Marcel (1983)
Task: identify color of presented patch
Patch preceded by a word (prime) that was:♦ Neutral (table)♦ Matched (blue)
Priming: RT for match should be faster than neutral
Results Priming occurred in both conditions, but it was larger in
supraliminal than subliminal
But was subliminal truly subliminal?
Cheesman and Merikle (1984)
Subjective vs. objective thresholds
3 conditions
Subjective (pretest: 50% identification of color patch)
Objective (pretest: 25% in forced choice selection of color patch)
Supraliminal
Awareness (Supraliminal)
Subjective Threshold
Subject says
“I don’t see it” BUT
can guess what it is
Objective Threshold
Subject says
“I don’t see it” AND
can’t guess what it is
Predictions
Objective threshold
♦ If subliminal perception exists Priming should be obtained in objective
threshold condition
♦ If subliminal perception does not exist Priming should not be obtained in objective
threshold
Results
What is meant by influence behavior?
Cognitive psychologists find effects of subliminal perception to be on the order of 1/20th of a second increase in RT
Social psychologists claim that subliminal perception increases the activation of a concept, which is unlikely to have any long range effects on behavior
− Consistent with this view, priming a concept relevant to a current goal or motive can lead to subliminal priming effects
Karremans, Goelz, Johr, Neumann, Ecker, and Doerr (2009) − Subliminally presented drink brand names influenced
preference for that brand, but only for those who were thirsty
Bermeitinger, Goelz, Johr, Neumann, Ecker and Doerr (2009)
− Consumption of a particular brand of dextrose (sugar) pills was influenced by subliminally presented logos, but only for those who were tired
● Lowery, Hardin, Eisenberger, and Sinclair (2007 ) − Students primed with a word related to intelligence did
better on a midterm exam that occurred days later
Top-down processing
Greenwald, Spangenberg, Pratkanis, and Eskenazi (1991)
Participants took tests to assess their memory and self-esteem
Given subliminal messages embedded in taped nature sounds, classical music, or popular music Tapes were labeled as memory improvement or self-
esteem improvement Label was unrelated to content of subliminal message♦ Listened to tapes each day for one month
● Most are skeptical of the effectiveness of subliminal perception.
However…
● Dijksterhuis, Aarts, and Smith (2005) suggest there are good reasons to continue research− There may be potential benefits (e.g., studies by social
psychologists)− Understanding them and informing the public about how
they work would be one effective tool for preventing misuse and abuse
− Abandonment would be an overreaction to fallacious and preposterous claims made by shoddy researchers
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