Chapter 4 Inquisitive- Sensation & Perception
Sensory systems receive; brain perceives:
SENSATION: sensory organs receive stimulus energies from environment & transduce them into electrical energy of nervous system.
TRANSDUCTION: transformation of sensory stimulus energy from environment into neural impulses. conversion of stimulus energy into electrical energy of nervous system
PERCEPTION: neural processing of electrical signals to form internal mental representation inside brain of what’s on outside. organizing, constructing and interpreting sensory info, form representation inside the brain of what it thinks is on the outside.
PSYCHOPHYSICS: focuses on relationship between physical characteristics of environmental stimuli & mental experience of them. (such as their perceived intensity)
ABSOLUTE THRESHOLDS: minimum amount of stimulation needed for a person to detect a stimulus half of the time.
SIGNAL DETECTION THEORY: used to explain how we make decisions under uncertainty. takes into account both intensity of the stimulus and psychological biases for more accurate assessment.
DIFFERENCE THRESHOLD/ JUST-NOTICEABLE DIFFERENCE (JND): minimum change in stimulus for observer to detect a difference half the time
WEBER’S LAW: observation that perception of stimulus change is proportional to the magnitude of the stimuli
ADAPTATION: when stimulus remains constant over time and eventually seems to disappear, results in enhanced detection of changes. (perceive your saliva as tasteless but if you drank someone elses you would taste it)
SENSORY ADAPTIATION: occurs at the level of sensory receptors
PERCEPTUAL ADAPTATION: occurs higher in the brain.
-Both free us to focus on changes in environment rather than on stimuli that are unchanging
AFTEREFFECTS: opposing distortions that occur after adaptation. you perceive the opposite of what your senses and brain have adapted to.
WATERFALL ILLUSION: first described by Aristotle; after gazing at a waterfall for abt a minute, when you move your gaze to the rocks at the side, they appear to be moving upwards.
-are not limited to the visual system.
-due to altered firing of neurons in parts of the brain that represents faces. instance of perceptual rather than sensory adaptation
vision- eyes of some insects capture broader spectrum of light than human eyes can.
Most species have one dominant sense organ. Humans are visual animals while bears are better smellers.
PHOTONS: basic units of all forms of electromagnetic radiation- have wavelike properties as they travel through space.
ELECTROMAGNETIC RADIATION: depending on wavelength, classified into various types of waves. radio waves to gamma rays.
ELECTROMAGNETIC SPECTRUM: outlines range of electromagnetic energy in our environments. humans perceive wavelengths within the visible spectrum which measured in nanometers or billionths of a meter.
WAVELENGTH: distance between any two consecutive crests of a wave.
-perceived as hue- color.
FREQUENCY: # of cycles per second of wave.
-longer-wavelength light has lower frequency, shorter has a higher frequency.
AMPLITUDE: height of crests of a wave.
-related to experience of intensity or brightness. distinguish the quality (color) and quantity (brightness) of light.
WAVE PROPERTIES: wavelength of light determines our experience of color, while height of wave or amplitude is perceived as brightness.
PUPIL: hole in iris where light enters
IRIS: colored muscle around pupil, controls amount of light entering eye by increasing or decreasing the size of pupil.
LENS: membrane at front of eye focuses incoming light on retina, bends light and uses the process accommodation
ACCOMMODATION: adjustment of len’s thickness by specialized muscles in order to change degree to which it bends light.
RETINA: surface on back of eye that contains photoreceptor cells.
PHOTORECEPTOR CELLS
RODS: cells that primarily support nighttime vision
CONES: cells responsible for high resolution color vision.
vision deficits:
-normal vision : eye focuses incoming light onto retina. myopia & hyperopia are common visual deficits fixed by glasses, contacts, or surgery,
MYOPIA: occurs when distant objects are projected in front of the retina
HYPEROPIA: occurs when close objects are projected behind the retina.
PHOTOPIGMENTS: inside photoreceptor cells, sensitive to light.
OPTIC NERVE: bundle of axons that converge from the retina and transmit action potentials to the brain.
BLIND SPOT: area in middle of visual field where theres no photoreceptors and no info can be received.
FOVEA: small pit in center of retina. is densely packed with cones.
-most of what we experience in vision comes from the cones in fovea.
-need the fovea to read a book.
FOVEATION: eyes move constantly in order to focus different stimuli directly onto fovea.
ACUITY: the sharpness or specificity of perception. supports discrimination of stimuli.
-cones specialize in acuity, supporting daytime vision when light is abundant- we see things in high resolution color.
SENSITIVITY: ability to detect stimulus is present.
-rods provide more sensitivity- supporting nighttime vision- light is limited and we see things in grainy shades of gray.
-farther from fovea toward the periphery of retina, the ratio of cones to rods decreases- most of rods hangout in periphery.
-Far more rods than cones- one reason rods offer more sensitivity in low light like that available for night vision.
-CONES show low convergence (acuity) RODS show high convergence (sensitivity)
CORTICAL MAGNIFICATION FACTOR: all systems have this systematic distortion. -regions that require finer discrimination receive more cortical representation.
-more direct connections (less convergence) in conjunction with more cortical space (cortical magnification) allow the cones in the fovea to convey more information to the rest of your brain.
COLOR: a psychological property made by the brain, rather than a physical property of the world. there are no colors - there are only wavelengths of light as a distinct quality- “color”.
ACHROMATIC COLORS: white, black, and any shade of grey. they do not result in distinct color or chromatic experience.
NEWTONS PRISM: using REFRACTION- the bending of light rays through a prism- to showcase the rainbow of colors visible to the human eye, Newton discovered that pure white sunlight contains all the colors we can perceive.
TRICHROMATIC THEORY: theory of color perception that three types of cone cells, each most sensitive to a specific wavelength of light, work tg to produce our perception of a multicolored world.
-one color patch can be matched by additive mixing of three lights of different wavelengths- LONG(red), MEDIUM(green), SHORT(blue)
COLORBLINDNESS: naturally occurs 1 in 50 people. result of deficiency in one of the three types of cones.
-this condition is called dichromacy
-in the dark all humans are color blind.
DICHROMACY: (having only two cones) allows for the perception of color distinctions, offers only about 1 percent of the variety a person with normal trichromacy has.
-most mammals (horses, dogs, and cats) have dichromatic vision
MONOCHROMACY: rare condition where individuals are born with only one kind of receptor. have no color perception- see all wavelengths as various shades of grey.
PURKINJE SHIFT: wavelengths at peak sensitivity of the rod photopigment, however, will appear brighter at night. this effect is called purkinje shift.
OPPONENT-PROCESS THEORY: states that information from the cones is separated into three sets of opposing or opponent channels in the ganglion cell layer.
-explains color as perceptual opposites, originating from opposite sides of the color circle
-according to theory responses of the cones are combined in the bipolar and ganglion cell layers to create 3 sets of opposing color responses: white-black, red-green, and yellow-blue.
-COLOR OPPONENCY is cue to how bipolar cells combine inputs from the diff cone types.
ganglion cells that receive inputs from cones at the red versus the green end of wavelength cancel eachother out.
COMPLEMENTARY COLORS: colors on opposite sides are the most contrasting.
-eyes cannot combine these wavelengths to form new chromatic experience, left is an experience of some shade of gray rather than color.
-they enhance eachothers hue because they do not blend.
HIERARCHICAL ANALYSIS: higher and higher brain levels of brain create more and more complete representations of what is out in the world.
-brain appears to make sense of the data it receives from the retina through this process.
PRIMARY VISUAL CORTEX: visual sensory receiving area in occipital lobe.
-RETINOTOPICALLY organized, adjacent portions of the retina connect with adjacent areas of visual cortex.
CORTICAL MAGNIFICATION: information from the fovea is given the most cortical space for analysis.
SINGLE CELL RECORDING: scientists used process to measure action potentials directly from neuron to determine certain neurons in the primary visual cortext calls- feature detectors- respond to basic features represented across retina such as LINES EDGES AND ANGLES with specific colors or movement.
FEATURE DETECTORS: specialized cell in visual cortex- responds to basic features : lines, edges, and angles.
VISUAL ASSOCIATION CORTEX: region of brain where objects are reconstructed from prior knowledge and information collected by the feature detectors. “secondary visual cortices”
PROSOPAGNOSIA: visual disorder in which individuals are unable to recognize the identity of faces.
VENTRAL PATHWAY: traverses the underside of the temporal lobe and is specialized to address the “what” questions.
-damage to ventral stream impairs recognizing what an object is while leaving intact the ability to say where it is.
DORSAL PATHWAY: flows upward to the parietal lobes and is specialized to address the where and how questions of object recognition.
-supports location, depth, and motion- influences how we interact with objects.
-people with damage- can see and recognize an object without knowing where it is or how to grasp it.
VENTRAL AND DORSAL STREAMS:
ventral: what
dorsal: where
MT: middle temporal cortex
-each mt neuron is tuned to respond to motion in particular direction
-people with damage are diagnosed with:
AKINETOPSIA: deficit in perceiving motion
PHI PHENOMENON: visual illusion where the flashing of separate images in rapid succession is perceived as fluid movement.
PITCH: perceptual quality of sounds - makes a flute sound high and a tuba sound low.
-like color, pitch is a change in quality rather than quantity of energy.
AMPLITUDE: related to the quantity of energy, corresponds with intensity or loudness of the sounds we hear.
-sound waves with large amplitudes displace air molecules more than low amplitude waves do.
HUMAN EAR: separated into the outer, middle, and inner ear. structures in ear have evolved to collect and amplify air pressure waves and transduce them into sound.
-TYMPANIC MEMBRANE “eardrum” is protected by ear canal
-tight skin like membrane located an inch into ear canal- responds to sound wave vibrations by moving in and out with corresponding pressure changes.
-this membrane is boundary line between the out and middle ear
MIDDLE EAR: portion of ear containing the eardrum and ossicles.
OSSICLES: three tiny bones in ear, hammer, anvil, and stirrup- act as levers to amplify incoming sound waves.
-forms a bridge between eardrum and another membrane called the OVAL WINDOW.
-eardrum is connected to HAMMER- joins up with anvil- which connects to stirrup- arrives at oval window
INNER EAR: innermost part of ear where cochlea resides.
-full of fluid, fluid requires more energy to move than air does.
COCHLEA: spiral structure in inner ear, basilar membrane, containing auditory sensory neurons, is located here.
BASILAR MEMBRANE: structure in cochlea where auditory cilia or auditory sensory neurons is located.
-contains thousands of hairlike cilia. vibrations of basilar membrane causes the cilia to bend back and forth triggering neural impuleses
-more than 10,000 tiny cilia in each human ear, neatly organized into rows along basilar membrane
-axons of hair cells from cochlea- bundles together to form the AUDITORY NERVE
PRIMARY AUDITORY CORTEX: located in the top portion of temporal lobe of brain.
FREQUENCY THEORY: theory of pitch and perception- proposes that the brain uses the frequency of hair cell firing to indicate pitch
PLACE THEORY: states that different pitches arise from different places along the basilar membrane.
place frequency map is created by the basilar membrane in ur ear.
-according to place theory frequency(pitch) depends on where the basilar membrane is stimulated while amplitude(loudness) depends on how much the basilar membrane is stimulated
PRIMARY AUDITORY CORTEX: region of brain where sound is processed
-located in temporal love
-place-frequency maps are found here
TONOTOPIC ORGANIZATION: arrangement of auditory cortex- nearby frequencies are processed near each other in the brain- resulting in a sound map.
-higher frequencies are processed toward back of auditory cortex
-lower frequencies toward the front
frequencies are represented tonotopically in the auditory cortex of the temporal love such that similar frequences are represented next to one another
TACTILE SENSE: the sense of touch
touch is determined by multiple receptors in the skin/epidermis
each is specialized to pick up and transduce a particular form of physical energy from the environment into electrical impulses which are all sensed in parallel and sent to the brain for analysis.
NOCICEPTOR: bare nerve ending that signals potential harm and causes withdrawl reflex.
THERMORECEPTORS: convert kinetic energy into action potentials that signal the sensation of temperature.
PRIMARY SOMATOSENSORY CORTEX: region of brain where processing of touch sensations occurs.
-touch is processed here. it is organized according to the topography of the body supporting a map of the entire body in the brain.
SOMATOSENSORY HOMUNCULUS: depiction of how the body is represented by brain, proportional to amount of cortex devoted to each body part.
SECONDARY SOMATOSENSORY CORTEX: represents more complex features, such as the sensation of motion on the skin, enables the recognition of objects.
HAPTIC PERCEPTION: examining an object by touch. supported by somatosensory association cortex.
PROPRIOCEPTION: sensory system responsible for awareness of body positions.
-sensors in joints, tendons, bones, ears, and skin enable you to know where parts of your body are in relation to one another without having to visually check.
VESTIBULAR SYSTEM: sensory system primarily responsible for balance.
-located in the inner ear.
-fluid filled canals-relay information abt body and head movements to brain - help maintain balance.
KINESTHESIS: responsible for monitoring the position and movement of body, including proprioception and the vestibular system.
INSULAR CORTEX: extension of somatosensory cortex
-interoception involves receptors that monitor the state of our internal organs and relay information about them to the brain. this is primarily supported by the insular cortex.
OLFACTION: sense of smell
-olfactory cilia- tiny hairs on olfactory receptor neurons- thousand types of receptor proteins embedded in these hairs.
EPITHELIUM: mucous membrane in the nasal cavity that contains the olfactory receptor neurons'.
-enable human beings to discern 1 trillion different odors.
OLFACTORY BULB: structure above nasal cavity where information is communicated to primary olfactory cortex via the olfactory tract.
GLOMERULI: spherical cluster of neurons in the olfactory bulb.
PRIMARY OLFACTORY CORTEX: region of brain where smell is processed
-located in the anterior temporal lobe.
GUSTATION: sense of taste
-taste receptors: sense of taste is mediated by tase receptor cells- bundled in clusters called taste buds. -sample oral concentrations of large number of molecules and report sensation of taste to brain
PRIMARY GUSTATORY CORTEX: located on insular cortex.
taste perception can be strongly influenced by what we see.
GESTALT PSYCHOLOGY: school of psychological thought- attempted to explain how various elements group together to form objects- arguing that perception is more than a simple piecing together of building blocks.
GESALT PRINCIPLES:
CONNECTEDNESS: group tg objects that are connected
CLOSURE: fill in gaps to create continuous edges, allowing us to perceive an object as a whole.
CONTINUINITY: look for smooth, continuous patterns in objects. while having a conversation we can partially ignore any interruptions and understand the sentences in a continuous manner.
SIMILARITY: group tg things that look alike.
PROXIMITY: perceive features as grouped when they are close together.
SYNCHONY: group items tg that move at the same time. in audition a similar effect takes place which is referred to as grouping by onset.
BINOCULAR CUES: depth information gathered from the separation between an individuals two eyes.
-allows brain the receive two perspectives on the same event.
BINOCULAR DISPARITY: magnitude of difference between the images projected on an individuals two eyes.
-because of this brain sees world in “stereo” & produces perception of three dimensional space by comparing the images projected on each eye.
MONOCULAR CUES: depth information that can be gathered by only one eye.
-clues to three-dimensional space that can be perceived with only one eye
RELATIVE SIZE: you can use your knowledge of the size of an object as a cue to judge its distance
RELATIVE HEIGHT: if you drive by a fiekd of sheep the sheep at the far end of field appear to be closer to horizon bc they project a to a higher point in ur visual field- you correctly perceive them as being farther away
INTERPOSITION: when viewing one object that is partially blocked by another- you perceive object behind the other to be farther from you. (it does not appear to be cut in half)
LINEAR PERSPECTIVE: instead of telling you the road is getting narrower; brain uses distortion of linear perspective to recover depth information
RELATIVE MOTION: objects tht are distant appear to move more slowly bc they are more stable on your retina then nearvy objects- rather than perceiving objects as slower or faster, your brain interprets them as differing in depth. such perceptions are the opposite of these things- actual speeds are different then what their distance makes it seem.
SIZE CONSTANCY: phenomenon where the brain adjusts its perception of distance in order to perceive an object’s actual size as constant, taking into account changed in retinal size.
COLOR CONSTANCY: phenomenon where the brain adjusts its perception of color to hold it constant, taking into account changes in lighting conditions.
PERCEPTUAL SET: predisposition that influences what we perceive based on recent experience or context.