PSYC 1020PSYC 1020

Sensing and Perceiving ISensing and Perceiving I

Sense ModalitiesSense Modalities

PsychophysicsPsychophysics

Light, Eye & BrainLight, Eye & Brain

Internet : http: // www.psy.uq.edu.auInternet : http: // www.psy.uq.edu.au

Dr. Jack Broerse Dr. Jack Broerse

Visual elaborationVisual elaboration

Visual sensationVisual sensation(visual cortex)(visual cortex)

Skin sensationSkin sensation

Auditory Auditory sensationsensation

MovementMovement

Conscious elaboration& thought

Perceptual Perceptual judgementjudgement

Body sensationBody sensation(cerebellum)(cerebellum)

Sensing States & Events:Sensing States & Events:External versus InternalExternal versus Internal

External States & EventsExternal States & Events

SweetSalty

SourBitter

Taste & SmellTaste & Smell

Skin SensesSkin SensesTouch, Temperature,Pressure, Pain

VisionVision

AuditionAudition

Hue, Brightness,Saturation (Density)

Volume, Frequency,Tonal Quality (Density)

FloweryFruity

Spicy

BurnedPutrid

Resinous

??

Extrasensory Perception:Extrasensory Perception:Phenomena in Science or Pseudoscience? Phenomena in Science or Pseudoscience?

!

Extrasensory Perception:Extrasensory Perception:Charles Darwin’s ScepticismCharles Darwin’s Scepticism

Thought Transference (1870s)Thought Transference (1870s)

For:For:Alfred Russel Wallace Alfred Russel Wallace

Against:Against:Charles DarwinCharles DarwinThomas H. HuxleyThomas H. Huxley

(see Scientific American,(see Scientific American,October, 1996).October, 1996).

Internal States & EventsInternal States & Events

Proprioception & KinaesthesisProprioception & Kinaesthesis

Sensations of body/limb/muscleSensations of body/limb/muscle position & movementposition & movement

InteroceptionInteroception

Vague sensations of internal organs &Vague sensations of internal organs &deep paindeep pain

Psychophysics & MeasurementPsychophysics & MeasurementStimulus to Conscious ExperienceStimulus to Conscious Experience

Psychophysical Relationship Psychophysical Relationship

Classical PsychophysicsClassical PsychophysicsAbsolute ThresholdsAbsolute ThresholdsS

enso

ryS

enso

ry M

odal

ity

Mod

alit

y

Detection Threshold (Limen) Detection Threshold (Limen)

Vision A candle flame at 60 km on clear dark night

Hearing A watch ticking at 6 m in quiet conditions

Touch Wing of a bee falling on your cheek from 1cm

Smell One eye drop of perfume in 3-room appartment

Taste One teaspoon sugar in 10 litres water

Difference ThresholdsDifference ThresholdsJust Noticeable Differences (JND)Just Noticeable Differences (JND)

L L

LL11

LL22 + + L L

LL2 2

LL1 1 + + L L wherewhere

WEBER’s LAW WEBER’s LAW LL

LLConstant Constant

Discriminations: Same vs DifferentDiscriminations: Same vs Different

Thresholds & DecisionsThresholds & DecisionsSignal Detection Theory (SDT)Signal Detection Theory (SDT)

Stimulus RealityStimulus Reality

Res

pons

e/D

ecis

ion

Res

pons

e/D

ecis

ion Same/PresentSame/Present Diff/AbsentDiff/Absent

Same/PresentSame/Present

Diff/AbsentDiff/Absent

HITHITFALSEFALSEALARMALARM

MISSMISS CORRECTCORRECTREJECTIONREJECTION

Hits – False AlarmsHits – False AlarmsSensitivitySensitivity Decision CriterionDecision Criterionvsvs

Key WordsKey Words

Subliminal Perception?Subliminal Perception?A case study for SDTA case study for SDT

Perceptual DefencePerceptual DefenceMotivationMotivation Mental SetMental Set

Key WordsKey Words

Subliminal Perception?Subliminal Perception?A case study for SDTA case study for SDT

Perceptual DefencePerceptual DefenceMotivationMotivation Mental SetMental Set

Key WordsKey Words

The Stimulus for VisionThe Stimulus for VisionElectromagnetic RadiationElectromagnetic Radiation

Frequency= 1/Frequency= 1/

Wavelength (Wavelength ())

Am

plit

ude

Am

plit

ude

Visible Visible LightLight Spectrum 400 – 700 nanometres (10 Spectrum 400 – 700 nanometres (10 -9-9m) m)

= 10 = 10 1515 mm

= 10 = 10 77mm –10 –10 1313mm

The EyeThe EyeAnatomy & Physiology Anatomy & Physiology

Retina (photosensitive rods & cones)

Fovea (central vision)

Lens

CorneaBlind Spot

Pupil

IrisOptic Nerve

++

Approx. 9 cm at normal viewing distance

Retinal Rods and ConesRetinal Rods and ConesSensitivity & Dark AdaptationSensitivity & Dark Adaptation

Log

. Rel

ativ

e Se

nsit

ivit

yL

og. R

elat

ive

Sens

itiv

ity

Log

. T

hres

hold

L

og.

Thr

esho

ld

Wavelength (nm) Wavelength (nm) Minutes in Dark Minutes in Dark

1.01.0

2.02.0

4.04.0

3.03.0

5.05.0

6.06.0

7.07.0

1.01.0

2.02.0

4.04.0

3.03.0

5.05.0

6.06.0

400400 500500 600600 700700

RodsRods

ConesCones

300 x300 x

1010 2020 3030 4040 5050

ConesCones

RodsRods

Visual Cortex

Brodmann Areas 17, 18, 19

Corpus Callosum Thalamus

Cerebellum

Retina to BrainRetina to BrainCentral Visual Pathway Central Visual Pathway

Basic Visual Functions:Basic Visual Functions:Everyday Tests of Visual AcuityEveryday Tests of Visual Acuity

ERKFVMWXL

Snellen ChartSnellen Chart

Landolt ‘C’Landolt ‘C’

BNE

C

Enmetropic (normal acuity)Enmetropic (normal acuity)

Myopic (nearsightedness)Myopic (nearsightedness)

Hyperopic (farsightedness)Hyperopic (farsightedness)

Astigmatic (Blurring in some axis)Astigmatic (Blurring in some axis)

Presbyopic (Accomodation problems)Presbyopic (Accomodation problems)

Optical Disorders:Optical Disorders:Focussing the imageFocussing the image