Sensation vs. PerceptionSensation vs. Perception

• sensation:sensation: the experience of sensory the experience of sensory perceptionperception

• perception:perception: the process of creating the process of creating meaningful patterns from raw sensory meaningful patterns from raw sensory informationinformation

Sensory ThresholdsSensory Thresholds• absolute threshold: minimum stimulation

needed to detect a particular stimulus 50% of the time

• difference threshold (jnd): minimum difference between two stimuli that one can detect 50% of the time

—increases with magnitude of stimulus

Weber’s LawWeber’s Law

• The principle that the jnd for any given The principle that the jnd for any given sense is a constant fraction or proportion of sense is a constant fraction or proportion of the stimulation being judged.the stimulation being judged.

Approximate Absolute ThresholdsApproximate Absolute Thresholds

• Vision:Vision: a candle flame seen from 30 miles a candle flame seen from 30 miles on a clear, dark nighton a clear, dark night

• Hearing:Hearing: the tick of a watch from 20 feet the tick of a watch from 20 feet in very quiet conditionsin very quiet conditions

• Smell:Smell: 1 drop of perfume diffused 1 drop of perfume diffused throughout a three-room apartmentthroughout a three-room apartment

Approximate Absolute ThresholdsApproximate Absolute Thresholds

• Taste:Taste: .0356 ounce of table salt in 529 .0356 ounce of table salt in 529 quarts of waterquarts of water

• Touch:Touch: a bee wing falling on your cheek a bee wing falling on your cheek from a height of 1 centimeterfrom a height of 1 centimeter

Subliminal PerceptionSubliminal Perception

• definition: definition: below threshold below threshold

• We can process some information from We can process some information from stimuli too weak to recognize.stimuli too weak to recognize.

• effect of subliminal stimulationeffect of subliminal stimulation:: a subtle, a subtle, fleeting effect on thinkingfleeting effect on thinking

Does subliminal advertising work?Does subliminal advertising work?

• No. The goal of using subliminal No. The goal of using subliminal advertising is to increase the likelihood that advertising is to increase the likelihood that you will buy a particular product.you will buy a particular product.

• Research has repeatedly demonstrated that Research has repeatedly demonstrated that subliminal advertising cannot change an subliminal advertising cannot change an individual’s behavior.individual’s behavior.

Stimulus for VisionStimulus for Vision

wavelengthwavelength

amplitudeamplitude

The visible spectrum consists of:The visible spectrum consists of:

Cross Section of the EyeCross Section of the Eye

Rods ConesRods Cones

Receptors:Receptors: rods and cones rods and cones

• 120 million120 million

• peripheryperiphery

• sensitivitysensitivity

• night visionnight vision

• 8 million8 million

• centralcentral

• acuityacuity

• color visioncolor vision

Anatomical Pathway in the RetinaAnatomical Pathway in the Retina

Path to Occipital LobePath to Occipital Lobe

Path from Eye to Visual Cortex

light

photo-receptors

bipolar cells

ganglion cells

LGNvisual cortex