Sensation vs. PerceptionSensation vs. PerceptionSensation:Sensation: a process by which a process by which

our sensory receptors and nervous our sensory receptors and nervous system receive and represent system receive and represent stimulus energystimulus energy

Sensation is the raw data our brain Sensation is the raw data our brain takes in from the environment.takes in from the environment.

Sensation vs. PerceptionSensation vs. PerceptionPerception:Perception: a process of organizing and a process of organizing and

interpreting sensory information, interpreting sensory information, enabling us to recognize meaningful enabling us to recognize meaningful objects and events.objects and events.

Perception “makes sense” of sensation.Perception “makes sense” of sensation.Both involve one continuous process and Both involve one continuous process and

perceptual failure may occur at any level perceptual failure may occur at any level whether at the sensory level or the whether at the sensory level or the perceptual interpretation level. perceptual interpretation level.

Example:Example: ProsopagnosiaProsopagnosia

Bottom Up vs. Top Down Bottom Up vs. Top Down ProcessingProcessing

Bottom Up Processing:Bottom Up Processing: analysis that begins analysis that begins with the sense receptors and works up to the with the sense receptors and works up to the brain’s integration of sensory information.brain’s integration of sensory information.

Involves making sense of raw sensation.Involves making sense of raw sensation. Top Down Processing:Top Down Processing: Information Information

processing guided by higher-level mental processing guided by higher-level mental processesprocesses

As when we construct perceptions drawing on As when we construct perceptions drawing on our experience and expectations.our experience and expectations.

Our expectations and experiences shape how Our expectations and experiences shape how we perceive information.we perceive information.

ProsopagnosiaProsopagnosia

Is a condition…Is a condition…

Bottom Up vs. Top DownBottom Up vs. Top Down

Bottom Up Vs. Top DownBottom Up Vs. Top Down

What do you see?What do you see?

Bottom Up vs. Top DownBottom Up vs. Top Down

OLD WITCH IN PICTUREOLD WITCH IN PICTURE

PsychophysicsPsychophysicsPsychophysics:Psychophysics: study of study of

the relationship between the relationship between physical characteristics of physical characteristics of stimuli and our stimuli and our psychological experience of psychological experience of themthemLightLight- brightness- brightnessSoundSound- volume- volumePressurePressure- weight- weightTasteTaste- sweetness- sweetness

Sensation: ThresholdsSensation: ThresholdsAbsolute Absolute

Threshold:Threshold: minimum minimum stimulation needed stimulation needed to detect a to detect a particular stimulus.particular stimulus.

Usually defined as Usually defined as the stimulus the stimulus needed for needed for detection 50% of detection 50% of the time.the time.

““Subliminal Messages”Subliminal Messages” What does the research say?What does the research say?

http://jeffmilner.com/backmasking.htm

http://www.nlpweekly.com/?p=527

HomeworkHomework

Sensation: ThresholdsSensation: Thresholds Difference Threshold or (JND-Just Difference Threshold or (JND-Just

Noticeable Difference):Noticeable Difference): the minimum the minimum difference that a person can detect difference that a person can detect between two stimuli. What does it take between two stimuli. What does it take to tell two similar stimuli apart?to tell two similar stimuli apart?

Weber’s Law:Weber’s Law: to perceive a difference to perceive a difference between two stimuli, they must differ by between two stimuli, they must differ by a constant proportiona constant proportionlight intensity- 8%light intensity- 8%weight- 2%weight- 2%tone frequency- 0.3%tone frequency- 0.3%

Sensation: ThresholdsSensation: ThresholdsSignal Detection Theory:Signal Detection Theory: predicts predicts

how and when we detect the how and when we detect the presence of a faint stimulus (signal) presence of a faint stimulus (signal) amid background stimulation (noise)amid background stimulation (noise)

Assumes that there is no single Assumes that there is no single absolute thresholdabsolute threshold

What might a person’s detection What might a person’s detection of a stimulus depend on?of a stimulus depend on?

Sensory AdaptationSensory AdaptationSensory Adaptation:Sensory Adaptation: diminished diminished

sensitivity with constant stimulation.sensitivity with constant stimulation.

OceanOceanBad SmellBad SmellAds- cut in, zoom, fade outAds- cut in, zoom, fade out

Sensory Adaptation and Sensory Adaptation and VisionVision

The Science of Energy and The Science of Energy and SensationSensation

TransductionTransduction- conversion of one form - conversion of one form of energy to another.of energy to another.

WavelengthWavelength- the distance from the - the distance from the peak of one wave to the peak of the next.peak of one wave to the peak of the next.

HueHue- dimension of color determined by - dimension of color determined by wavelength of light…color is matter of wavelength of light…color is matter of how far wavelengths are apart.how far wavelengths are apart.

IntensityIntensity- amount of energy in a wave - amount of energy in a wave determined by amplitude.determined by amplitude.brightnessbrightnessloudnessloudness

Human Vision Represents Narrow Human Vision Represents Narrow Part of All Electromagnetic EnergyPart of All Electromagnetic Energy

ROY G. BIV: Starts from longer to shorter wavelengths. R=longest; V=shortest

Vision: Physical Property of Vision: Physical Property of WavesWaves

Short wavelength=high frequency(bluish colors, high-pitched sounds)

Long wavelength=low frequency(reddish colors, low-pitched sounds)

Great amplitude(bright colors, loud sounds)

Small amplitude(dull colors, soft sounds)

Biology of Vision Step One: Biology of Vision Step One: Light Enters the EyeLight Enters the Eye

1.) Light enters the eye through the 1.) Light enters the eye through the cornea:cornea: (transparent protector) and (transparent protector) and the light passes through the the light passes through the pupil:pupil: (small opening/hole). The size of the (small opening/hole). The size of the opening (pupil) is regulated by the opening (pupil) is regulated by the iris:iris: the colored portion of your eye the colored portion of your eye that is a muscular tissue which that is a muscular tissue which widens or constricts the pupil causing widens or constricts the pupil causing either more or less light to get in.either more or less light to get in.

Biology of Vision Step Two: Biology of Vision Step Two: An Image is ProducedAn Image is Produced

2.) Behind the pupil, the 2.) Behind the pupil, the lenslens, a transparent , a transparent structure, changes its structure, changes its curvature in a process curvature in a process called called accomodation,accomodation, and focuses the light and focuses the light rays into an image on rays into an image on the light-sensitive back the light-sensitive back surface called the surface called the retina:retina: where image is where image is focuses. focuses.

Biology of Vision Step Three: Biology of Vision Step Three: Chemical Reactions and SightChemical Reactions and Sight3.) Image coming through activates 3.) Image coming through activates

photoreceptors in the retina called photoreceptors in the retina called rods and rods and cones.cones. As rods and cones set off chemical As rods and cones set off chemical reactions they form a synapse with reactions they form a synapse with bipolar bipolar cells cells which forms a synapse with which forms a synapse with ganglion ganglion cellscells which fire action potentials along the which fire action potentials along the optic nerve:optic nerve: that carries this information to that carries this information to be processed by the be processed by the ThalamusThalamus: (sensory : (sensory switchboard)switchboard) that sends information to the that sends information to the visual cortexvisual cortex which resides in the which resides in the occipital occipital lobe.lobe. The brain then constructs what you The brain then constructs what you are seeing and turns image right side up.are seeing and turns image right side up.

Parts of RetinaParts of RetinaBlind Spot:Blind Spot: part of retina where optic nerve part of retina where optic nerve

leaves the eye…no receptor cells are there. leaves the eye…no receptor cells are there. Brain fills information in with info from other Brain fills information in with info from other eye.eye.

Fovea:Fovea: central focal point of the retina, central focal point of the retina, where cones cluster.where cones cluster.

Cones:Cones: located near center of retina (fovea) located near center of retina (fovea)fine detail and color visionfine detail and color visiondaylight or well-lit conditions daylight or well-lit conditions

Rods:Rods: located near peripheral retina located near peripheral retina detect black, white and graydetect black, white and graytwilight or low lighttwilight or low light

Rods & ConesRods & ConesReceptors in the Human Eye

Cones Rods

Number

Location in retina

Sensitivity in dim light

Color sensitive? Yes

Low

Center

6 million

No

High

Periphery

120 million

Errors In VisionErrors In Vision

Acuity:Acuity: the sharpness of vision the sharpness of visionNearsightedness:Nearsightedness:

nearby objects seen more clearlynearby objects seen more clearlylens focuses image of distant lens focuses image of distant

objects in front of retinaobjects in front of retinaFarsightedness:Farsightedness:

faraway objects seen more clearlyfaraway objects seen more clearlylens focuses near objects behind lens focuses near objects behind

retinaretina

Errors in VisionErrors in Vision

NormalNormal NearsightedNearsighted Farsighted Farsighted Vision Vision Vision Vision VisionVision

Visual Involves Parallel Visual Involves Parallel ProcessingProcessing

Parallel vs. Serial:Parallel vs. Serial: parallel means parallel means simultaneous while serial means step by simultaneous while serial means step by step. Our brains process are often parallel step. Our brains process are often parallel processes while computers work serially. processes while computers work serially.

Parallel Processing:Parallel Processing: simultaneous simultaneous processing of several dimensions through processing of several dimensions through multiple pathways. Different part of brain multiple pathways. Different part of brain for:for:colorcolormotionmotionformformdepthdepth

Parallel ProcessingParallel Processing

Feature Detectors:Feature Detectors: neurons in neurons in the visual cortex respond to the visual cortex respond to specific featuresspecific featuresshapeshapeangleanglemovementmovement

How The Brain PerceivesHow The Brain Perceives

Visual Information Visual Information ProcessingProcessing

Trichromatic (three color) Trichromatic (three color) TheoryTheoryYoung and HelmholtzYoung and Helmholtzthree different retinal color three different retinal color

receptorsreceptorsredredgreengreenblueblue

Color Deficient Color Deficient SyndromeSyndrome

People who suffer red-green blindness have trouble perceiving the number within the design

Visual Information Visual Information ProcessingProcessing

Opponent-Process TheoryOpponent-Process Theory- opposing - opposing retinal processes enable color vision. retinal processes enable color vision. Example: Jesus On Title Slide.Example: Jesus On Title Slide.

““ON”ON” “OFF”“OFF”redred greengreengreen green redred blue blue yellowyellow yellowyellow blueblue black black whitewhitewhite white blackblack

Stare At This for 30 Seconds Stare At This for 30 Seconds Then Look At A White SurfaceThen Look At A White Surface