Chapter 6: Sensation and PerceptionYou may be able to see (sense) but not recognize (perceive) facesProsopagnosia- face blindnessPerception- the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and eventsThanks to an area underside of your brain’s right hemisphere, you can recognize a human faceSensation- the process by which our sensory receptors and nervous system receive + represent stimulus energies from our environmentBottom-up processing- analysis that begins with the sensory receptors and works up to the brain’s integration of sensory informationTop-down processing- information processing guided by higher-level mental processes, as we can construct perceptions drawing on our experience and expectationsNature’s sensory gifts suit each recipient’s needsPsychophysics- the study of relationships between physical characteristics of stimuli, such as their intensity, and our psychological experience to themAbsolute threshold- the minimum stimulation needed to detect a particular stimulus 50% of the timeThreshold- the point that must be exceeded to begin producing a given effectSensitivity to high-pitched sounds declines with normal agingSignal detection theory- a theory predicting how and when we detect particular stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends party on a person’s experience, expectations, motivation, and level of fatigueSignal detection can save life-or-death consequencesSubliminal (below threshold)- below one’s absolute threshold for conscious awarenessWe can sense stimuli below our absolute thresholdAbsolute threshold is merely a point at which detect stimuli HALF THE TIMEAlthough subliminally presented stimuli can subtly influence people experiments discount attempts at subliminal advertising + self improvementPriming- the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, and responseWakening of associationsMuch of our information processing occurs automatically, out of sight, off the radar screen of conscious mindSometimes we feel what we do not know and cannot describeTo function effectively we need absolute thresholds low enough to allow us to detect important sights, sounds, textures, tastes, and smellsDifference threshold- the minimum difference between two stimuli required for detection 50% of the time. We experience difference threshold as a just noticeable difference (jnd)Weber’s law- the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)For the average person to perceive their differences, 2 lights must differ in intensity by 8%, two objects must differ in weight by 2%, and two tones must fifer in frequency by only 0.3%Sensory adaptation- diminished sensitivity as a consequence of constant stimulationReduces our sensitivity but allows us to freely focus on informative changes in our environment without being distracted by the constant chatter of uninformative backgroundAfter constant exposure to a stimulus, our nerve cells fire less frequentlySensory adaptation: now you see it, now you don’tWe perceive not exactly as it is, but as it is useful for us to perceive itChanging stimulation helps explain televisions attention- grabbing powerAll our senses receive sensory information, and deliver that information to the brainTransduction- conversion of one form of energy into another, such as sights, sounds + smells, into neural impulses the brain can interpret (transformation)What strikes our eye is not the color but pulses of electromagnetic energy that our visual system perceives as colorsWhat we see as visible light is a thin slice of the electromagnetic spectrumOther organisms are sensitive to differing portions of the spectrumROY G. BIV (pg. 236) : electromagnetic spectrumRed- 700nmViolet- 400 nmCharacteristics of lightWavelength- the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from short blips of cosmic rays to the long pulses of radio transmissionHue- the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forthIntensity- the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the waves amplitudeshort wavelength-high frequency-high pitch-bluish colorslong wavelength- low frequency- low pitch- reddish colorsgreat amplitude- bright colorssmall amplitude- dull colorsThe EyeHow doe eye transform light energy into neural messages?light enters through the corneacornea- protects the eye + bends light to provide focusthe light then passes through the pupil which is surrounded by the irispupil- the adjustable opening in the center of the eye through which the light entersiris- a ring of muscle tissue that forms the colored portion of the eye around the pupil and controld the size of the pupil openingdilates/constricts in response to light intensity + inner emotionsso distinctive, that it can signal your identitybehind the pupil is the lens that focuses incoming light rays into an image on the retinalens- the transparent structure behind the pupil that changes shape to help focus images on the retinaretina- the light-sensitive inner surface of the ye, containing the receptor rods + cones plus layers of neurons that begin the processing of visual informationdoes not see a whole image. Rather, its millions of receptors cells convert particles of light energy into neural impulses and forward those to the brain. There, the impulses are reassembled into a perceived, upright seeing image.accommodation- the process by which the eye’s lens changes shape to focus near or far objects on the retinaThe RetinaRods- retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don’t respondCones- retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail + give rise to color sensationOptic nerve- the nerve that carries impulses from the eye to the brainBlind spot- the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located thereYour brain fills in the holeFovea- the central focal point of the retina,