PSYCH 100 1st Edition Lecture 7Sensation and Perception PART 1- Sensation: the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment - Perception: the process of organizing and interpreting sensory information- Bottom-up processing - Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind - Top-down processing- Info processing guided by higher level mental processes as we construct perceptions, drawing on our experience and expectations- Psychophysics - A study of the relationship between physical characteristic of stimuli and our psychological experience with them Ex: light to brightness, sound to volume, pressure to weight, sugar to sweet- Thresholds- Absolute Threshold: minimum stimulation needed to detect a particular stimulus 50% of the time - Subliminal threshold: when stimuli are below ones absolute thresholdfor conscious awareness- Sensory adaptation- Diminished sensitivity as a consequence of constant stimulation- Parts of the eye- Cornea: transparent tissue where the light enters the eye- Iris: muscle that expands and contracts to change the size of the opening (pupil) for light- Lens: focuses the light rays on the retina- Retina: contains sensory receptors that process visual info and sends it to the brain The Lens- Transparent structure behind the pupil that changes shape to focus images on the retina- Accommodation(how it changes shape): the process by which the lens changes shape to help focus near or far objects on the retina The Retina- The light-sensitive inner surface of the eye, containing receptor rods and cones in addition to layers of other neurons (bipolar, ganglion cells) that process visual infoo Rods only let us see in black, white, grey and helpus see at night (120 million in each eye)o Cones are in the center and are activated in bright light, help us see fine details, and help with color (500 million in each eye)- Photo receptors/Bipolar and Ganglion Cellso Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells  Optic nerve, Blind spot, and Fovea- Optic nerve o Carries neural impulse from the eye to the brain, creating a blind spot- Foveao Central point- Visual info processingo Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects tothe visual cortex- The stimulus input: light energy- We perceive color from energy- Animals may see things differently than humans- The Wavelength (Hue)- Hugh (color): is the dimension of color determined by the wavelength of the light- Wavelength: is the distance from the peak of one wave to the peak of the next Short wavelength= high frequency (bluish colors, high-pitched sounds) Long wavelength= low frequency (reddish colors, low-pitched sounds)- Intensity (Brightness)- Intensity: is the amount of energy in a wave determined by the amplitude (height) of the wave (related to perceived brightness) Great amplitude= bright colors, loud sounds Small amplitude= dull colors, soft sounds- Parallel processing- The processing of many aspects of a stimulus simultaneously - Color Vision- Young-Helmholtz Trichromatic (three color) Theory- Edward Hering Opponent-Process Theory- Current theory is that color processing occurs in two stages- Color blindness- Genetic disorder in which people are blind to green or red colors Normally lacking green or red sensitivities, sometimes both (certain cones) More prone for males than femalesSensation and Perception the Other Senses - The other senseso Hearing, touch, pain, taste, smell, body position/movement- Hearingo The stimulus input: sound waves Sound waves are compressing and expanding air molecules- The Earo Outer ear: Collects and sends sounds to the eardrumo Middle ear: chamber between eardrum and cochlea that concentrate the vibrations of the eardrum on the cochlea’s oval windowo Inner ear: innermost part of the ear containing the cochlea, semicircular canals, and vestibular sacs Cochlea: coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to auditory signals- Vibrations to the cochlea causes the cochlea membrane to vibrateo The fluid then moves and bends the hairs inside, and then triggers cells to fireo Those cells then form the auditory nerve- Toucho The sense of touch is a mix of four distinct skin senses-pressure, warmth, cold, and pain- Skin senseso Only pressure has identifiable receptorso Other skin sensations are variations of pressure, warmth, cold, and pain- Paino Tells the body that something is wrongo Damage to the skin and tissueso It is both physical and psychological and social (BioPsychoSocial) Biological: genetic differences Psychological: attention to pain Social; presence of othero Treatments Gate theory: blocks pain signals and you can simply treat pain by a form of stimulation, such as massaging  Hypnosis is said to be used to treat pain- Tasteo Originally you had: sweet, salty, sour, and bitter Now you have also have Umami (fresh chicken)o Taste receptors reproduce every week or two When you burn your tongueo Number of taste buds and sensitivities decreases with age - Smello Chemical sense Odorants enter the nasal cavity and stimulate the 5 million receptors that sense smell There are many different forms of smello Can be associated with memories  Connects with limbic system Strong memories are related to the sense of smell- Body Position and Movemento Kinethesis: the sense of our body parts’ position and movemento Vestibular sense: monitors the head and body’s position Wire walkingPerceptual Organization- Perceptiono Form perceptiono Depth perceptiono Perceptual constancy- Perceptual organizationo Helps us form perception Organization of the visual field into objects (figures) that stand out from their surroundings (ground)- Groupingo After distinguishing the figure from the ground, our perception needs to organize the figure into meaningful form using grouping rules Lines or shapeso Grouping and Reality Although grouping principles usually help us construct reality, they may occasionally lead us astray- Depth perceptiono Enables us to judge distanceso Gibson and Walk suggested that a human infant has depth perception- Binocular Cueso Retinal disparity: images from the two eyes differ- Monocular Cueso Relative size: if two objects are similar in