Sensory Physiology

Stimulus

(Physics)

(A)

Receptor

(Anatomy,Physiology )

(B)

Central Nervous System(Anatomy,Physiology)

(C)

Psycho- logical Response(Psychology)

(D)

Psychophysics

Sense modality Detection threshold

Light A candle flame seen at 30 miles ona dark clear night (ca. 10 quanta).

Sound The tick of a watch under quietconditions at twenty feet (ca.0.0002 dynes/cm).

Taste One teaspoon of sugar in 2 gallonsof water.

Smell One drop of perfume diffused intothe entire volume of a 3 roomapartment.

Touch The wing of a bee falling on yourcheek from a distance of 1 cm.

Absolute Thresholds of MajorSenses

Weber Fractions

Weber fraction Sensory Modality (Δ1/1)

( , )Vision brightness white light .08 ( , )Audition loudness noise .05 ( )Touch vibration at fingertip .04 ( )Kinesthesis lifted weights .02 ( )Taste table salt .08 ( )Smell butyl alcohol .07

REPRESENTATIVE VALUES FOR THE WEBER FRACTION FOR THE DIFFERENT SENSES

: 1971, , 1977.SOURCE Teghtsoonian and Caln

Decibel Scale Of Sound Energy

FECHNER’S LAW: = Klog I

STEVEN’S LAW: = K(i)n

Electromagnetic Spectrum

Color

Cone

Color Circle

Cross Section Of The Eye

Retinal Cells

Cross Section Of Retina

Path of

Light to

Rods &

Cones

THEORETICAL THRESHOLD FUNCTION

THRESHOLD FOR ONE QUANTUM

Stimuli for “Subliminal” Threshold ExperimentWord Freq. Value* Word Freq. Value*lotus 10 kotex 1**capon 10 mixer 1raped 13 terse 4lathe 11 penis 1**belly 47 hilly 10noted 45 knack 13clear 1 filth 4whore 4 clove 4tiara 4 bitch 4

Av. Taboo 10.6Av. Neutral 10.3

*frequency of occurrence in 4 1/2 million words according to the Thorndike-Lorge semantic count.

**estimated frequency

Payoff Matrices

Signal Signal

On Off On OffResponse: Yes +1c -10cYes +25c -

1cNo -1c +1c No -1c +1c

Frequency Of Signals In Detection Experiment

Presentation Presentationrate of .9 rate of .2

Signal Signal

On Off On OffResponse Yes .97 .62 Yes .28 .04

No .03 .38 No .72 .96

Rate of Hits and False Alarms as a Function of

the Relative Frequency of Trials on Which Signal was Presented.

% of trials on which signal is present

% hits % false alarms

90 96 80

50 72 40

10 39 5

ROC Curves

Day

Vision (cones)

Night

Vision (rods)

Rod Cone Sensitivity Functions

Dark Adaptation

Effect of Vitamin A Loss on Dark Adaptation Threshold

ACUITY

CHART

Measuring

Visual

Acuity

Effect of Illumination on Visual Acuity

Distributions Of Rods And Cones

Camera Vs. Eye

Duplicity Theory

Cones: Rods:

Number: >7 x 106 >125 x 106 Connections with ganglion cells: 1:1

1: many

Wavelength of greatest sensitivity: 555 nm 505 nm

Color vision: yes no

Dark adaptation: ~7 min ~40 min

Spatial resolution: high low

Temporal resolution: fast slow

Stabilized

Image

Comparison Of Eye And CameraEYE CAMERA

Stability of image Constantly oscillating

Steady

Shutter opened Continuous during waking hours

Discrete (shutter is typically closed)

Image quality Poor Sharp

Sensitivity Dynamic range 1,000,000 : 1

Specific to type of film

Black/White or Color

Both Specific to type of film

Refinement of image after exposure

Yes No

Adaptation Yes No

Temporal contrast Yes No

Simultaneous Yes No

Stimulus

Luminance Profile

Mach Bands - Edge Enhancement Illusion

Mach Bands

Lateral Inhibition

Interactions between excitatory & inhibitory cells How the retina enhances edges.

No Lateral Inhibition

Lateral Inhibition

Hit Miss

False CorrectAlarm Negative

Respond Responds "yes" "no"

Stimulus present

Stimulus absent

THE FOUR POSSIBLE OUTCOMES OFTHE DETECTION EXPERIMENT

A PAYOFF FUNCTION FOR ASIGNAL DETECTION EXPERIMENT

RESPONSE

YES NO

ON

OFF

$0.25 $0.05

$0.01$0.05

Rate of Hits and False Alarms as a Function of the Relative Frequency of Trials on

Which Signal was Presented.

% of Trials on Which %Hits: % False AlarmsSignal is present:

90 96 8050 72 4010 39 5

No

Lateral

Inhibition

Fovea