Sensation vs. Perception Sensation: a process by which our sensory receptors and nervous system receive and represent stimulus energy Sensation: a process by which our sensory receptors and nervous system receive and represent stimulus energy Sensation is the raw data our brain takes in from the environment. Sensation is the raw data our brain takes in from the environment.

Sensation vs. Perception Perception: a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. Perception: a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. Perception “makes sense” of sensation. Perception “makes sense” of sensation. Both involve one continuous process and perceptual failure may occur at any level whether at the sensory level or the perceptual interpretation level. Both involve one continuous process and perceptual failure may occur at any level whether at the sensory level or the perceptual interpretation level. Example: Prosopagnosia Example: Prosopagnosia

Bottom Up vs. Top Down Processing Bottom Up Processing: analysis that begins with the sense receptors and works up to the brain’s integration of sensory information. Bottom Up Processing: analysis that begins with the sense receptors and works up to the brain’s integration of sensory information. Involves making sense of raw sensation. Involves making sense of raw sensation. Top Down Processing: Information processing guided by higher-level mental processes Top Down Processing: Information processing guided by higher-level mental processes As when we construct perceptions drawing on our experience and expectations. As when we construct perceptions drawing on our experience and expectations. Our expectations and experiences shape how we perceive information. Our expectations and experiences shape how we perceive information.

Prosopagnosia Is a condition… Is a condition…

Bottom Up vs. Top Down

Bottom Up Vs. Top Down What do you see? What do you see?

Bottom Up vs. Top Down OLD WITCH IN PICTURE

Psychophysics Psychophysics: study of the relationship between physical characteristics of stimuli and our psychological experience of them Psychophysics: study of the relationship between physical characteristics of stimuli and our psychological experience of them Light- brightness Light- brightness Sound- volume Sound- volume Pressure- weight Pressure- weight Taste- sweetness Taste- sweetness

Sensation: Thresholds Absolute Threshold: minimum stimulation needed to detect a particular stimulus. Absolute Threshold: minimum stimulation needed to detect a particular stimulus. Usually defined as the stimulus needed for detection 50% of the time. Usually defined as the stimulus needed for detection 50% of the time.

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

Sensation: Thresholds Difference Threshold or (JND-Just Noticeable Difference): the minimum difference that a person can detect between two stimuli. What does it take to tell two similar stimuli apart? Difference Threshold or (JND-Just Noticeable Difference): the minimum difference that a person can detect between two stimuli. What does it take to tell two similar stimuli apart? Weber’s Law: to perceive a difference between two stimuli, they must differ by a constant proportion Weber’s Law: to perceive a difference between two stimuli, they must differ by a constant proportion light intensity- 8% light intensity- 8% weight- 2% weight- 2% tone frequency- 0.3% tone frequency- 0.3%

Sensation: Thresholds Signal Detection Theory: predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) Signal Detection Theory: predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) Assumes that there is no single absolute threshold Assumes that there is no single absolute threshold What might a person’s detection of a stimulus depend on? What might a person’s detection of a stimulus depend on?

Sensory Adaptation Sensory Adaptation: diminished sensitivity with constant stimulation. Sensory Adaptation: diminished sensitivity with constant stimulation. Ocean Ocean Bad Smell Bad Smell Ads- cut in, zoom, fade out Ads- cut in, zoom, fade out

Sensory Adaptation and Vision

The Science of Energy and Sensation Transduction- conversion of one form of energy to another. Transduction- conversion of one form of energy to another. Wavelength- the distance from the peak of one wave to the peak of the next. Wavelength- the distance from the peak of one wave to the peak of the next. Hue- dimension of color determined by wavelength of light…color is matter of how far wavelengths are apart. Hue- dimension of color determined by wavelength of light…color is matter of how far wavelengths are apart. Intensity- amount of energy in a wave determined by amplitude. Intensity- amount of energy in a wave determined by amplitude. brightness brightness loudness loudness

Human Vision Represents Narrow Part of All Electromagnetic Energy ROY G. BIV: Starts from longer to shorter wavelengths. R=longest; V=shortest

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

Biology of Vision Step Two: An Image is Produced 2.) Behind the pupil, the lens, a transparent structure, changes its curvature in a process called accomodation, and focuses the light rays into an image on the light- sensitive back surface called the retina: where image is focuses.

Biology of Vision Step Three: Chemical Reactions and Sight 3.) Image coming through activates photoreceptors in the retina called rods and cones. As rods and cones set off chemical reactions they form a synapse with bipolar cells which forms a synapse with ganglion cells which fire action potentials along the optic nerve: that carries this information to be processed by the Thalamus: (sensory switchboard) that sends information to the visual cortex which resides in the occipital lobe. The brain then constructs what you are seeing and turns image right side up.

Parts of Retina Blind Spot: part of retina where optic nerve leaves the eye…no receptor cells are there. Brain fills information in with info from other eye. Blind Spot: part of retina where optic nerve leaves the eye…no receptor cells are there. Brain fills information in with info from other eye. Fovea: central focal point of the retina, where cones cluster. Fovea: central focal point of the retina, where cones cluster. Cones: located near center of retina (fovea) Cones: located near center of retina (fovea) fine detail and color vision fine detail and color vision daylight or well-lit conditions daylight or well-lit conditions Rods: located near peripheral retina Rods: located near peripheral retina detect black, white and gray detect black, white and gray twilight or low light twilight or low light

Rods & Cones Receptors in the Human Eye ConesRods Number Location in retina Sensitivity in dim light Color sensitive?Yes Low Center 6 million No High Periphery 120 million

Errors In Vision Acuity: the sharpness of vision Acuity: the sharpness of vision Nearsightedness: Nearsightedness: nearby objects seen more clearly nearby objects seen more clearly lens focuses image of distant objects in front of retina lens focuses image of distant objects in front of retina Farsightedness: Farsightedness: faraway objects seen more clearly faraway objects seen more clearly lens focuses near objects behind retina lens focuses near objects behind retina

Errors in Vision Normal Nearsighted Farsighted Vision VisionVision Normal Nearsighted Farsighted Vision VisionVision

Visual Involves Parallel Processing Parallel vs. Serial: parallel means simultaneous while serial means step by step. Our brains process are often parallel processes while computers work serially. Parallel vs. Serial: parallel means simultaneous while serial means step by step. Our brains process are often parallel processes while computers work serially. Parallel Processing: simultaneous processing of several dimensions through multiple pathways. Different part of brain for: Parallel Processing: simultaneous processing of several dimensions through multiple pathways. Different part of brain for: color color motion motion form form depth depth

Parallel Processing Feature Detectors: neurons in the visual cortex respond to specific features Feature Detectors: neurons in the visual cortex respond to specific features shape shape angle angle movement movement

How The Brain Perceives

Visual Information Processing Trichromatic (three color) Theory Trichromatic (three color) Theory Young and Helmholtz Young and Helmholtz three different retinal color receptors three different retinal color receptors red red green green blue blue

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

Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision. Example: Jesus On Title Slide. “ON”“OFF” red green green red blue yellow yellow blue black white white black

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