VisionRods- The light-sensitive receptors in the retina that enable vision in black, white, and shades of grey in dim light- Mostly in the periphery; vision is not very sharpCones- The receptor cells in the retina that enable vision in color and fine details in adequate light, but that do not function well in dim light- Mostly in the foveaFovea- A small area at the center of the retina- Point of central focus- Densely packed cones, but no rodso Provided clearest, sharpest visionOpponent-process theory- Also suggests that there are three types of cells, but that each type has a pair of receptors working in opposition- Each type of receptor pair is sensitive to a given pair of colors: red/green yellow/blue- When one member of the pair is activated, the other member in inhibited. No simultaneous transmission.o No reddish greens Theories of Color VisionTrichromatic Theory- The theory of color vision suggesting that there are three types of cones (which are maximally sensitive to red, green, or blue), and that varying levels of activity in these receptors can produce all of the colors you see.PerceptionSensory information is fragmented- Occlusions in visual fieldo Retinal structureso Blind spoto Environmental occlusions or omissions - Blurriness outside the foveaPerception fills in the gaps - Creating a meaningful whole from fragmentary parts- Facilitating rapid understanding with minimal effort- Uses expectations from context and previous experience Bottom-up processing- Analyzing the components of the sensory information- Feature analysiso Identifying the various components that the sensory information comprises Eg. Scanning the visual information for horizontal lines, verticallines, evidence of motion, gradients, curves, and so on by specialized areas of the visual cortex Specialized analysis of facial features Pareidolia- ability to see faces in non human thing*Top-down processing- Making meaning of sensory information by fitting it to what you already knowo Expectations, past experiences, motivationso Imposing ordero Works in tandem with bottom-up Gestalt rules of organization- The whole is greater than the sum of its parts- Top-down processing helps is understand sensory information more efficientlyo Need to quickly make sense of a lot of information, not get overwhelmed- Sometimes can lead us astrayo PerceivingInfluence of context- Demonstration Consciousness - Consciousnesso A persons momentary awareness of experiencing sensations, thoughts, and feelingso Analogous to watching a theater production- Altered states of consciousnesso States that differ from normal working consciousness Sleep- Biological need- Deprivationo Reduces functioning Impaired attention/alertness Impaired concentration/problem solving Irritability and discomfort Trembling hands, drooping eyelids, staring, pain sensitivity,  Hallucinogens Microsleeps(few seconds of falling asleep)o Becomes almost unbearable after about three dayso Record is 11 dayso No long-term effects- Normal range is 5-11 hours, median is 8 hourso Sleep deficits(not sleeping enough) produce similar problems as deprivation(not sleeping at all) May be cumulative- Sleep is not a period of brain dormancyo Electroencephalogram(EEG) Electrical activity in the brain(brainwaves)- Four distinct sleep stagesStages of Sleep- Stage 1o Transition between sleep and wakefulnesso Alpha waves Rapid, low voltage waveso Possible vivid imageryo Hypnic jerks- Stage 2o Theta waves Slower and more regular wave patterns  Sleep spindleso Less easily aroused- Stage 3o Delta waves Slower wave patterns with higher peakso More difficult to arouse- Stage 4o Delta waves Even more slow and regularo Least responsive to environmental stimuli Most difficult to arouseo Occurs during earlier cycleso Somnambulism (sleep walking)- REM Sleepo About 90 minutes per night Increases with exertion or stresso Shallow stage, but difficult to arouseo Rapid eye movements  As if watching an evento Skeletal muscle paralysiso Period of dreamingo Deprivation of REM sleep produces REM rebound Chronic REM deprivation produces symptoms similar to sleep deprivation Dream function: Four main theories- Freudian wish fulfillmento Dreams represent unconsciousness wishes that the dreamer wants to fulfill Manifest content: the story line of the dream Latent content: the unconscious wish it representso Dreams contain universal symbolso Criticisms - Dreams for Survivalo Dreams represent the reprocessing of important information from daily lifeo Possibly an artifact form a time when people has limited brainpower o Dreams are inherently meaningfulo Criticisms - Reverse learning theoryo Dreams have no meaning at all o Mental housekeeping Flushing away unnecessary information accumulated throughout the dayo Un-learning of material that serves no purpose and could end up being confusing Searching for meaning in the dream content is therefore pointlesso Criticisms- Activation-synthesis theoryo Brian produces random electrical energy during sleepo Electrical energy randomly stimulates mental contento The brain excels at making meaning out of ambiguous or fragmentary stimuli  Present or recent fears, emotions, concerns, or experiences may guide the brain’s interpretation What starts out as random ends in something meaningful- Echo’s of FreudAttention- Attentiono A state of focused awareness on a subset of the available perceptual informationo “Focused consciousness”o Much of the available perceptual information in the environment never enters your awareness- Selective attentiono Choosing the stimuli in the environment that will enter awareness Goal-directed selection- Purposeful attention Stimulus-driven attention- Stimulus captures attentiono Unusual features: brightness, size, color, loudnesso Repetitiono Noveltyo ChangeAttentional Failures- Inattentional blindnesso Failing to see an obvious visual stimulus when your attention is narrowly focused- Change blindnesso Failure to notice changes in the visual field Distractions, multiple simultaneous changes, gradual changeso Internal representation of the visual world is not as precise as you might think Learning - Relatively permanent change in behavior brought about by experience- One of the most basic topics of psychology- In a sense, almost everything we do in influenced by what we have learned.Basic Vocabulary- Stimuluso Physical aspect of the environment