Sensation and Perception PDF

9/26/24 Study groups organized by FSS Study group information October 4th at 1:00 pm in CRX-030 1 Chapter 5 Sensation and Perception 2...

9/26/24 Study groups organized by FSS Study group information October 4th at 1:00 pm in CRX-030 1 Chapter 5 Sensation and Perception 2 Sensation and Perception SENSATION: The process through which the senses pick up visual, auditory, and other sensory stimuli and transmit them to the brain E.g. Visual sensory system detects a collection of lines, angles, shapes, & colours PERCEPTION: The process by which sensory information is actively organized and interpreted by the brain E.g. Organizing and interpreting these lines, angles, shapes, & colours as an apple 3 1  9/26/24 Sensation Sensory receptors Provide the essential links between the physical world & the brain Receive and process sensory information from the environment Respond to a distinct stimulus (e.g., light waves, sound waves, odour molecules…) 4 Sensation Transduction: The conversion of a sensory stimulus to neural impulses Stimulus is converted from one form to another E.g., Hearing: receptors in inner ear convert vibrations from sound waves into electrochemical signals (neural impulses) These neural impulses are transmitted to their own specific locations in the brain (e.g., auditory cortex) 5 Cerebral cortex Somatosensory cortex Gustatory cortex Visual cortex Olfactory cortex Auditory cortex 6 2  9/26/24 How Does Sensory Information Get to the Brain? Except smell Cerebral Energy Sensory Sensory Thalamus cortex nerve receives contains receptor transfers the processes information transduces and relays input and coded processes about the energy into a impulses to the neural environment neural signal signal information the brain (perception) Light wave Photoreceptor Optic nerve Visual cortex sound wave hair in inner ear Auditory/cochlear nerve auditory cortex odour m olecules olfactory epithelium olfactory nerve olfactory cortex 7 Stimulus detection Absolute threshold The minimum amount of sensory stimulation that can be detected 50% of the time Marks the difference between experiencing a sensation or not https://saylordotorg.github.io/text_introduction-to-psychology/s08-01-we- experience-our-world-throug.html#stangor-ch04_s01_s02_f02 8 Stimulus detection Difference threshold The smallest increase or decrease in a stimulus to produce a just noticeable difference (JND) Just Noticeable Difference The JND is the smallest change in sensation we can detect 50% of the time Weber’s Law The greater the original stimulus, the more it must be increased or decreased to notice a difference – proportion of change 1 lb 2 lbs 10 lbs 11 lbs vs. vs. 9 3  9/26/24 Perception Gestalt psychology A school of thought that aims to study how the brain organizes sensory impressions into a gestalt (German word for “form” or “whole”) The whole is more than just the sum of its parts Figure-ground relationship Principles of perceptual grouping https://research-collective.com/blog/gestalt/ 10 Figure-ground perception Figure: item of interest that stands out from the rest of the environment Ground: environment or background 11 Perceptual grouping Organize what we see using the simplest, most basic arrangement Four principles of perceptual grouping: 1. Similarity 2. Proximity 3. Continuity 4. Closure 12 4  9/26/24 Perceptual grouping Organize what we see using the simplest, most basic arrangement Four principles of perceptual grouping: 1. Similarity 2. Proximity 3. Continuity 4. Closure 13 Perceptual grouping Organize what we see using the simplest, most basic arrangement Four principles of perceptual grouping: 1. Similarity 2. Proximity 3. Continuity 4. Closure 14 Perceptual grouping Organize what we see using the simplest, most basic arrangement Four principles of perceptual grouping: 1. Similarity 2. Proximity 3. Continuity 4. Closure 15 5  9/26/24 Perceptual grouping Organize what we see using the simplest, most basic arrangement Four principles of perceptual grouping: 1. Similarity 2. Proximity 3. Continuity 4. Closure 16 Perception Depth perception The ability to see in three-dimensions (3D) and to estimate distance Binocular depth cues Monocular depth cues 17 Binocular depth cues Convergence: eyes turn inward as we focus on nearby objects Binocular disparity: Each eye sees a slightly different image 18 6  9/26/24 Monocular depth cues Visual information from one eye that allows us to perceive depth Occlusion Relative height Relative size Familiar size Atmospheric perspective Perspective convergence 19 Vision 20 Dimensions of a Wave: Light & Sound Wavelength: The distance from one peak to the next peak in a wave Amplitude: The distance between the peak and a trough of a wave Frequency: The number of waves per second Time 21 7  9/26/24 Electromagnetic radiation Long Short Only a small part of the electromagnetic spectrum is detected by the human visual system (400-700 nm) - Called the ‘visible spectrum’ - Consists of white light (light rays from sun) 22 Wavelength of light is associated with PERCEPTION of colour Long Short 23 Optics Light rays travel in straight lines until they interact with the molecules of the atmosphere and objects Reflection: Light rays bouncing off a surface Absorption: Transfer of light energy to a particle or surface (e.g., sun light on your skin, warms you up) Reflection Absorption 24 8  9/26/24 Optics Light waves that are reflected back are the ones that reach our eyes 25 The Eye The front of the eye Cornea – the tough transparent layer covering the front of the eye Function: bend the light inward and through the pupil Pupil – small dark opening in the center of the iris Function: permits light to enter the eye Iris – the circular coloured part of the eye Function: dilate and contracts the (a d a p te d fro m h ttp s://w w w.p a lm co a ste ye ce n te r.co m /re tin a l-co n d itio n s.h tm ) pupil to regulate the amount of light entering the eye 26 Focusing images Lens – suspended just behind the iris and the pupil Function: focuses on viewed objects Accommodation – flattening and bulging of the lens in order to focus on an object Flattens to focus on object far away Bulges to focus on objects that are close Retina – tissue at the back of the eye that contains the sensory receptors for vision Function: the tissue onto which the (h ttp s://w w w.p a lm co a ste ye ce n te r.co m /re tin a l-co n d itio n s.h tm ) image from the lens is projected 27 9  9/26/24 Major parts of the Eye 28 Receptors for Light and Colour: Photoreceptors Rods Cones Look like slender Shorter and more cylinders rounded 120 million 6 million Respond to black and Enable up to see colour white and fine detail Extremely sensitive Densely packed in the Allows the eye to see in fovea – clearest point of very dim light vision (https://www.webrn-maculardegeneration.com/rods-and-cones.html) 29 (https://www.newswise.com/articles/media-article/569194) 30 10  9/26/24 From the retina to the brain Rods and cones transduce the light Neural signals leave the eye via neurons (ganglion cells) that form the optic nerve The optic nerve from the two eyes meet at the optic chiasm Information from the right visual field is sent to the left side of the brain and information from the left visual field is sent to the right Travels to the thalamus, and then to the primary visual cortex in the occipital lobe https://medicine.academic.ru/88561/optic_chiasma 31 Retinotopic Maps (https://slideplayer.com/slide/5225633/) 32 Theories of colour vision Trichromatic theory Opponent-process theory 33 11  9/26/24 Trichromatic theory Three kinds of cones in the retina Red (long wavelengths) Green (medium wavelengths) Blue (short wavelengths) The three colours can then be combined to form any colour in the visible spectrum (https://psyc.ucalgary.ca/PACE/VA-Lab/colourperceptionweb/theories.htm) 34 Opponent-process theory Cells fire in an opposing fashion 1. Perceive red or green 2. Perceive blue or yellow 3. Perceive black or white Red Green Blue Yellow Black White 35 Negative afterimages 36 12  9/26/24 Hearing 37 Sound and Hearing An object makes a sound by vibrating The vibrations pass through air as sound waves by making air molecules vibrate Sound waves enter the outer ear and then cause the eardrum to vibrate 38 Frequency (Pitch) Humans can hear sounds ranging from 20-20,000 hertz https://www.youtube.com/watch?v=LNjPmhbPc9I&feature=youtu.be 39 13  9/26/24 Loudness 40 Structure of the Ear: Outer Ear Pinna Curved flap of cartilage and skin Visible part of the outer ear Auditory canal Inside the ear About 2.5 cm long Entrance lined with hairs Ends at the eardrum (tympanic membrane) that moves in response to (https://melbentgroup.com.au/otitis-externa/) the sound waves that hit it 41 Structure of the Ear: Middle Ear The eardrum marks the transition from the outer ear to the middle ear Contains the ossicles – the three smallest bones in the body - About the size of a grain of rice! - Hammer (malleus), Anvil (incus), Stirrup (stapes) - Amplify sound by 22 times! - Link the eardrum to the oval window (https://www.mayoclinic.org/diseases-conditions/hearing-loss/multimedia/ear-infections/sls-20077144?s=3) 42 14  9/26/24 Structure of the Ear: Inner Ear Begins at the inner side of the oval window Cochlea Fluid-filled, snail- shaped bony structure Basilar membrane Runs through the cochlea Contains ~15 000 hair cells (sensory receptors) 43 Structure of the ear 44 Theories of hearing Two major theories: Place Theory Frequency Theory 45 15  9/26/24 Place theory Each individual pitch that we hear is determined by the particular spot (place) along the basilar membrane that vibrates the most Place theory cannot explain how we perceive frequencies below 150 Hz (http://hyperphysics.phy-astr.gsu.edu/hbase/Sound/place.html) 46 Frequency theory Hair-cell receptors vibrate at the same frequency as the sounds that reach them A 500 Hz tone will stimulate the hair cells to vibrate 500 times per second Valid for low- and medium-frequency sounds, but cannot explain high-frequency sounds Neurons cannot fire more than 1000 times per second – cannot signal to the brain frequencies above 1000 Hz 47 Place theory vs. Frequency theory Both are correct Frequency theory best explains how we perceive low frequencies Place theory best explains how we perceive higher frequencies 48 16  9/26/24 The Chemical Senses 49 https://unsplash.com/photos/wOHH-NUTvVc Smell Olfaction Sensation of smell; the process of smell Cannot smell unless a substance’s molecules vaporize Solid/liquid à gas 10,000 odours! 50 How sense of smell works Odour molecules travel up the nostrils to the olfactory epithelium Patch of tissue at the top of each nasal cavity Nasal cavity Contains ~10 million olfactory neurons 51 17  9/26/24 How sense of smell works Odour molecules bind to specific receptors à Action potential Each olfactory receptor cell contains receptors for only one type of odour 52 How sense of smell works Axons of the olfactory receptor cells relay smell messages directly to the olfactory bulbs This is where smell sensations first register in Nasal cavity the brain Messages are then relayed to the thalamus 53 The Olfactory System 54 18  9/26/24 Taste Gustation The sensation of a taste Basic Tastes: Sweet, Sour, Salty, Bitter & Umami All five taste sensations can be detected on all locations of the tongue 55 How sense of taste works Taste buds Sensory receptor cell in mouth responsible for sense of taste Composed of 60 to 100 receptor cells Taste bud Lifespan of receptor cells is ~10 days Transduction occurs when chemicals enter taste buds 56 Skin and Body Senses 57 19  9/26/24 Skin Largest organ of the body Can detect heat, cold, pressure, pain, and a range of touch sensations Functions of the skin: Protection Temperature regulation Immunity Growth and movement Excretion Vitamin D synthesis Sensation https://unsplash.com/photos/y0OAmd_COUM 58 Somatotopic organization 59 How tactile sense works Object depresses the skin Stimulates the receptors in the skin – transduction Messages travel up the spinal cord to the brain Somatosensory cortex https://www.snoezelen.info/the-tactile-sense/ 60 20  9/26/24 Two Point Threshold How far apart two points have to be before we feel them as two separate touches The more sensitive the body part the lower the two-point threshold https://en.wikipedia.org/wiki/Two-point_discrimination#/media/File:Lawrence_1960_8.11.png 61 Pain Motivates us to tend to injuries, restrict activity, seek help Teaches us to avoid pain-producing situations Endorphins Naturally produced painkillers Block pain and produce a feeling of well-being https://creakyjoints.org/support/things-you-only-understand-if-have-chronic-pain/ 62 Pain (https://science.howstuffworks.com/life/insi de-the-mind/human-brain/pain4.htm) 63 21  9/26/24 The Kinesthetic and Vestibular Senses 64 Spatial orientation senses 65 Spatial orientation senses Kinesthetic sense Information about… Where your body parts are in relation to each other Movement in different body parts Receptors in the joints, ligaments, and muscles https://www.thinglink.com/scene/457362430729650178 66 22  9/26/24 Spatial orientation senses Vestibular sense Equilibrium / sense of balance Information about where you are in space Located in the semicircular canals (inner ear) Senses changes in motion Copyright 2017 Pearson Canada Inc. 67 23