Sensation and Perception Unit 3. Sensation and Perception

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  • Sensation and PerceptionUnit 3

  • Sensation and Perception

  • Basic concepts of SensationI. SensationThe detection of physical energy from the environment, it is then encoded into neural signalsOccurs when energy in the external environment or the body stimulates receptors in the sense organsSensory receptors- specialized cells that detect sensory stimuli (light, sound, odors) & convert them into neural impulses Found throughout body in eyes, ears, nose, mouth & joints & muscles

  • Basic concepts of SensationII. ThresholdsAbsolute threshold- the smallest amount of a stimulus that a person can sensed

    VisionThe flame from a single candle flickering about 30 miles away on a dark, clear nightHearingThe ticking of a watch placed about twenty ft. away from a listener in a quiet roomtasteAbout one teaspoon of sugar dissolved in 2 gallons of watersmellAbout one drop of perfume dispersed in a small housetouchThe wing of a bee falling on the cheek from about one centimeter away

  • Basic concepts of SensationDifference threshold (just-noticeable difference)- minimal difference in the magnitude of energy needed for people to detect a difference between stimuli (comparing) Webers law-Principle: difference thresholds grow withthe magnitude of thestimulus

    SensationWebers Constant (approximate)Saltiness of food1/5 (20%)Pressure on skin1/7Loudness of sounds1/10 (10%)odor1/20Heaviness of weights1/50 (2%)Brightness of lights1/60Pitch of sounds1/333

  • Absolute & Difference ThresholdSelect a sense Design an experiment to find an absolute threshold test the just noticeable difference for an increase or decrease in the intensity of the stimulus.Create a hypothesis about the intended results

  • Basic Concepts of SensationSignal-detection theory- detection of a stimulus depends on factors such as the intensity of the stimulus, the level of background stimulation, and the biological and physical characteristics , and expectations of the perceiver.Sensory Adaptation-process by which sensory receptors adapt to constant stimuli by becoming less sensitive to them.Sensory Deprivation-absence of normal levels of sensory stimulationSensory overload- too much stimuliASD

    Conservative or liberal

  • VisionProcess by which light energy is converted into neural impulses that the brain interprets to produce the experience of sightLight- physical energy in the form of electromagnetic radiationColors are caused by different wavelengths within the visible spectrumred = longest Violet = shortest Roy G. Biv

  • VisionThe EyeCornea- transparent covering on the eyes surface through which light enters

    Iris- regulates the size of the pupil to adjust to changes in the level of illumination Pupil- allows light to enter the eye

    Lens- focuses light rays on the retina

    Accommodation-process by which the lens changes its shape (thickness) to focus images more clearly on the retina

    Fovea- center of focus for clearer vision

  • Structure of the Eye

  • VisionRetina-Neural tissue lining the back of the eyeballs interior containing the receptors for vision; retina contains:Photoreceptors- light-sensitive cells in the eye that register lightRods- Visual receptors that are sensitive to intensity of light (dim)Cones- Visual receptors involved in color vision & fine details; humans have 3 types: blue, green, redOptic nerve- carries neural impulses generated by light stimulation from the eye to the brainBlind spot- contains no photoreceptor cells; Place where the optic nerve leaves the eye

  • Structures of the Retina

  • VisionColor vision2 major theories~Trichromatic theory- the ability to see different colors depends on the relative activity of three types of color receptors in the eye (red, green, and blue-violet) all other colors derived by a combinationOpponent-process theory-assumes that the visual system treats pairs of colors as opposing or antagonistic. Opponent-process cells are inhibited by a color, and have a burst of activity when it is removed.Afterimage- image remains after stimulus is removed; cones become tiredTrichromats-people with normal color visionMonochromats- no color visionDichromats- some color vision

    Color vision:

  • HearingAudition (sense of hearing):Travels in waves; exists only in mediums such as air, liquids, gases & solidsVibrationAmplitude, PitchAuditory LocalizationSounds from different directions are not identical as they arrive at left and right ears. The brain calculates a sounds location by using these differences.Loudness (Intensity, amplitude {height of wave}, measured in decibels)Pitch(frequency{number of cycles per second}, hertz)

  • HearingII. The Ear: structured to capture sound wavesEardrum- vibrates in response to external stimuli & transmits waves to middle earOssicles- tiny bones (hammer, anvil, & stirrup) in the middle ear that vibrate in response to eardrumCochlea- contains sensory receptors for hearingNerve (hair) cells- receptors that transform vibrations into neural impulses that are transmitted to the brain via theAuditory nerve- carries neural impulses from ear to brain

  • Hearing

  • Hearing

  • 2 types of deafness:

    Conductive Deafness: Caused by damage to middle ear; prevent people from hearing sounds that arent loud enoughHearing aids provide amplification

    Sensorineural (nerve) deafness:Can be mild, moderate or severeDamage to cells or auditory nerve in inner earCochlear implants will helpRinging sensation is nerve damage

  • Sensorineural DeafnessSensorineural deafness occurs when sounds of certain frequencies are not heard.It is usually caused by damage to the inner ear. Loud sounds can destroy neurons in the ear.Cochlear implants can help people with sensorineural deafness.Conductive DeafnessConductive deafness occurs because of damage to the middle ear, which is the part that amplifies sound.Hearing aids can provide for the function of the middle ear by amplifying sound. Deafness

  • Chemical Senses Olfaction (sense of smell)Airborne chemical molecules enter the nose and circulate through the nasal cavity. Vapors can also enter through the mouth and pass into nasal cavity.Receptors (olfactory hairs) on the roof of the nasal cavity detect these molecules. Intensity depends on # of receptors firing.Passes through the olfactory nerve, olfactory bulb, to the olfactory cortex and also structures in the Limbic System (memory and emotion)

  • Chemical SensesII. Taste Depends on odor, texture, & temperature; role in adaptation & survivalPapillae (taste receptors)taste buds- pores or openings on the tongue containing taste cells(receptors) inside the bud; 50 to 100 receptors/budRegenerate in 5-10 daysGenetic factors, expectations, and context play a significant role in taste sensitivities and preferencesFive basic tastes:SweetSaltySourBitterUmami

  • TasteDecrease with ageSupertasters- 2 or more times the taste buds,Hypersensitive, 1 in four peopleMedium tastersNon-tasters

    ALERT: receptors are actually mixed and located throughout the mouthback of throat, roof, cheeks and tongue

  • Skin SensesIII. Skin Senses (largest sensory organ)The senses of pressure, temperature, and pain that involve stimulation of sensory receptors in the skinPressureSensory receptors at the root of body hairPressure sensitivity varies throughout the bodyFingertips, lips, nose, & cheeksTemperatureReceptors are just beneath the skin (warm & cold)PainPain sensitivity variesProstaglandins: chemical that carries pain messages; Aspirin productionPain message sent from spinal cord to thalamus to cerebral cortex (somatosensory cortex)

  • Skin SensesBrain generates painPhantom PainInjured athlete doesnt feel painNo Pain???

    Gate TheoryOnly a certain amount of information can be processed by the brain at one time

  • Pain DisordersHereditary Sensory Autonomic NeuropathyPain and temp nerve fibers (receptors) never developedInsensitivity to pain means that the painful stimulus is not even perceived: a patient cannot describe the intensity or type of pain.Indifference to pain means that the patient can perceive the stimulus, but lacks an appropriate response: they will not flinch or withdraw when exposed to pain

  • Body Senses (Balance)Kinesthesis (Greek: to move & perception)- sense that informs people about the position of their bodiesSensory info is fed from receptor cells in joints, tendons and muscles to the brainAllows for navigation, movement coordination, & feel muscle contraction; interacts with vision

    Vestibular sense- movement, the sense that keeps us informed about balance and the position of our body in space, equilibrium, enables you to keep your balance; cerebellum, head positionSemicircular canals- in the inner ear; crystals; sense changes in the direction & movement of the headSenses speed, motion and balanceDizzyVestibular sacs- fluid filled, send messages to the cerebellum

  • Controversies in PerceptionSubliminal perception: perception of stimuli that are presented below the threshold of conscious awareness

  • Controversies in PerceptionParapsychology- seeks to investigate the existence and the causes of psychic abilitiesExtrasensory perception (ESP):perception that occurs without benefit of the known sensesPsychic test #1Psychic test #2Ganzfeld experimentTelepathy- communication of thoughts from one mind to another that occurs without using the known sensesClairvoyance- ability to perceive objects and events without using the known sensesPrecognition- ability to foretell the futurePsychokinesis (telekinesis)-ability to move objects by mental effort only

  • Perception