Sensation and PerceptionSensation and Perception

SensationSensation

• Process by which body gathers Process by which body gathers information about environmentinformation about environment

• Connects us to the worldConnects us to the world

• Sensation generally occurs in the sense Sensation generally occurs in the sense organs organs

– – vision (detects light waves)vision (detects light waves)

– – audition (sense of hearing)audition (sense of hearing)

– – olifaction (sense of smell)olifaction (sense of smell)

– – gustation (sense of taste)gustation (sense of taste)

– – cutaneous (sense of touch)cutaneous (sense of touch)

PerceptionPerception

• Process by which the brain organizes and Process by which the brain organizes and interprets sensory information (“sensation interprets sensory information (“sensation PLUS perception”)PLUS perception”)

• Perception occurs in the brainPerception occurs in the brain

• 3 basic principles3 basic principleso adaptiveadaptiveo activeactiveo no one-on-one correspondence between no one-on-one correspondence between

physical and psychological realityphysical and psychological reality

PerceptionPerception

• Top-down processingTop-down processingo ““Conceptually-driven processing”Conceptually-driven processing”o Take information already existing in the Take information already existing in the

mind to interpret environmentmind to interpret environment

• Bottom-up processingBottom-up processingo ““Data-driven processing”Data-driven processing”o Take stimuli from the environment and Take stimuli from the environment and

make attempts to determine its meaningmake attempts to determine its meaning

SensationSensation

• Sensory receptors – Sensory receptors – Eyes, ears, nose, etc. detect Eyes, ears, nose, etc. detect physical energy physical energy (light/sound/smell) (light/sound/smell)

• Transduction – Transduction – Translates physical energy into Translates physical energy into neural signalsneural signals

• Absolute threshold – Absolute threshold – Each system’s minimal amount Each system’s minimal amount of energy of energy required to activate it required to activate it

• Difference threshold – Difference threshold – Each system’s minimal Each system’s minimal amount of energy amount of energy required to required to detect change from one level detect change from one level of of stimulus to anotherstimulus to another

– – Just-noticeable difference Just-noticeable difference (Weber’s Law)(Weber’s Law)

• In this experiment, say the color of the In this experiment, say the color of the word (not what the word says)word (not what the word says)

• Example: For the word Example: For the word REDRED you should say you should say “Red”. For the word “Red”. For the word REDRED you should say you should say “Yellow““Yellow“

• As soon as the words appear on your As soon as the words appear on your screen, read the list as fast as you canscreen, read the list as fast as you can

Stroop EffectStroop Effect

Stroop EffectStroop Effect

• In this experiment, look at a picture of an In this experiment, look at a picture of an animal and say the animal and say the namename of the animal. Do of the animal. Do NOT read the word placed on the picture. NOT read the word placed on the picture.

• For example: You should say "Cow" For example: You should say "Cow" because the animal in the picture is a cow.because the animal in the picture is a cow.

• You should sat “Cat” because the animal in You should sat “Cat” because the animal in the picture is a cat. the picture is a cat.

VisionVision

• Allows for the detection of movement, Allows for the detection of movement, light, depth perceptionlight, depth perception

• Transduction –Transduction – impulses from optic nerve impulses from optic nerve carry visual carry visual information from retina to optic chiasm; information from retina to optic chiasm;

neural messages then neural messages then travel to thalamus travel to thalamus and and into the visual cortexinto the visual cortex

VisionVision

• Motion perceptionMotion perception o Rods in retina sensitive to motion Rods in retina sensitive to motion

activate neurons in the visual cortex activate neurons in the visual cortex

o 2 systems for processing movement 2 systems for processing movement - Eye stationary as object movesEye stationary as object moves- Eye moves to maintain object at same Eye moves to maintain object at same

place on the retinaplace on the retina

VisionVision• Photoreceptors Photoreceptors

o Cones Cones - Highest concentration in the fovea- Highest concentration in the fovea- Require light to be activated- Require light to be activated- Less numerous (7+ million)- Less numerous (7+ million)- Color vision/trichromatic theory - Color vision/trichromatic theory

(“photopic vision”)(“photopic vision”)- High visual acuity- High visual acuity- Low sensitivity - Low sensitivity

o Rods Rods - Highest concentration in the retinaHighest concentration in the retina- More numerous (120+ million)More numerous (120+ million)- Night vision (“scoptic vision”)Night vision (“scoptic vision”)- Low visual acuityLow visual acuity- High sensitivity (esp. motion detection) High sensitivity (esp. motion detection)

VisionVision

• Color blindnessColor blindness• Inability to distinguish colorsInability to distinguish colors

• ““Disease” is linked to the X Disease” is linked to the X chromosome, thus males more likely chromosome, thus males more likely than females to be color blindthan females to be color blind

• Most common condition is red-green Most common condition is red-green color blindness (difficulty color blindness (difficulty distinguishing red and green)distinguishing red and green)

HearingHearing

• TransductionTransductiono Outer ear collects physical stimuli (sound Outer ear collects physical stimuli (sound

waves)waves)

o Middle ear converts waves of air pressure Middle ear converts waves of air pressure into movementsinto movements

o Inner ear carries movements via waves of Inner ear carries movements via waves of fluid (in ear drum) that generate neural fluid (in ear drum) that generate neural signals signals

o Signals sent to thalamus then to temporal Signals sent to thalamus then to temporal lobelobe

HearingHearing

• Volume Volume – – “loudness” determined by the height “loudness” determined by the height of sound of sound wave (amplitude) wave (amplitude)

• PitchPitch – – refers to the frequency of the sound refers to the frequency of the sound wave wave (low B flat/high C (low B flat/high C tone)tone)

TouchTouch

• Protects body from injury, helps identify Protects body from injury, helps identify objects, maintain body temperatureobjects, maintain body temperature

• 4 basic skin sensors (heat, cold, pain, 4 basic skin sensors (heat, cold, pain, pressure)pressure)

• Touch sensations differ throughout the bodyTouch sensations differ throughout the body

• TransductionTransductiono Sensory neurons in skin send impulses to spinal Sensory neurons in skin send impulses to spinal

cord or communicate with interneurons (that in cord or communicate with interneurons (that in turn stimulate motor neurons)turn stimulate motor neurons)

TasteTaste

• Refers to four basic tastes (sweet, sour, Refers to four basic tastes (sweet, sour, salty, bitter) and protects us from salty, bitter) and protects us from injecting toxic substances injecting toxic substances

• TransductionTransductiono Occurs in the taste budsOccurs in the taste buds

o Physical stimulus (soluble chemicals) Physical stimulus (soluble chemicals) activate taste receptor neurons which carry activate taste receptor neurons which carry information to thalamus and primary cortex information to thalamus and primary cortex to help identify tasteto help identify taste

SmellSmell

• Detect danger (e.g., smoke, spoiled Detect danger (e.g., smoke, spoiled food) and/or recognize familiar odorsfood) and/or recognize familiar odors

• TransductionTransductiono Physical stimulus (air molecules) enter Physical stimulus (air molecules) enter

nasal cavity through nosenasal cavity through nose

o Receptors in olfactory epithelium pass Receptors in olfactory epithelium pass information through the olfactory bulb to information through the olfactory bulb to the primary cortex, which then connects the primary cortex, which then connects with thalamus and amygdalawith thalamus and amygdala