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