Chapter 4 Sensation Perception All knowledge has its

Chapter 4: Sensation & Perception “All knowledge has its origins in our perceptions. ” – Leonardo Da Vinci Vision Hearing Smell Taste Touch

Definitions Sensation n process of detecting, converting, and transmitting raw sensory information eyes, ears, from the external and internal nose, tongue, environments to the brain (transduction) skin, & internal Perception n n Sense organs: process of selecting, organizing and interpreting sensory information enables us to recognize meaningful objects and events body organs Happens in the brain!

Processing Bottom-Up (parts to whole) n n Ex: you have Information processing beginning “at ingredients and the bottom” with raw sensory data that must put them together to make are sent “up” to the brain for higher something edible level analysis Data driven processing that moves from the parts to the whole Top-Down (whole to parts) n n Information processing starting “at the top” with higher level cognitive processes (such as expectations and knowledge) and then “working down” Conceptually driven processing that moves from the whole to the parts Ex: you have ingredients and a recipe & picture of a completed cake and you must recreate the cake

Top-Down Processing example Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

Top down/ bottom up Guitar player or old people Fruit or face

Sensation- Thresholds Absolute Threshold n minimum stimulation needed to detect a particular stimulus n usually defined as the stimulus needed for detection 50% of the time Difference Threshold n minimum difference between two stimuli that a subject can detect 50% of the time n just noticeable difference (JND) n increases with magnitude Ex: listen to headphones and indicate the earliest you hear a tone Easier to tell the difference between 100 & 101 Hz than 1000 & 1001 Hz Ex: listen to headphones and indicate when you hear a change in volume of sound

Sensation- Thresholds 100 Percentage of correct detections 75 When stimuli are detectable less than 50% of the time (below one’s 50 absolute threshold) Subliminal stimuli 25 0 Low Absolute threshold Intensity of stimulus Medium they are “subliminal”.

Sensation- Thresholds Weber’s Law- to perceive a difference between two stimuli, they must differ by a constant proportion n light intensity- 8% weight- 2% tone frequency- 0. 3% Sensory Adaptation: diminished sensitivity with constant stimulation - receptors higher up in sensory system get tired and fire less frequently Apply it! Come up with 3 examples

Sensation- Thresholds Signal Detection Theory n n n predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) assumes that there is no single absolute threshold High expectations- false positives Low expectations- false negatives detection depends partly on person’s -experience -expectations -motivation -level of fatigue

Vision: Physical Properties of Waves Short wavelength=high frequency (bluish colors, high-pitched sounds) Great amplitude (bright colors, loud sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Small amplitude (dull colors, soft sounds)

Perception of light and sound Transduction: conversion of one form of energy to another Wavelength: Hue (color) and pitch Amplitude: brightness and loudness Purity of wavelength: saturation of color and timbre for sound

Vision: Spectrum of Electromagnetic Energy

Vision: Parts of the Eye Cornea: transparent covering on the front of the eye Fovea: central point of focus on the back of the eye Pupil: adjustable opening in the center of the eye Iris: a ring of muscle the forms the colored portion of the eye around the pupil and controls the size of the pupil opening Lens: transparent structure behind pupil that changes shape to focus images on the retina Accommodation: change in shape of lens focus near objects Retina n Layers of neurons on inner surface of eye n light sensitive n contains rods and cones n beginning of visual information processing Blind Spot: area of retina where optic nerve leaves back of eye

Vision: Parts of the Eye

Retina’s Reaction to Light Receptors Cones n near center of retina (fovea) n fine detail and color vision n daylight or well-lit conditions Rods • Located in periphery of retina • detect black, white and gray • twilight or low light Receptors in the Human Eye Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color sensitive? Yes No

Pathways from the Eyes to the Visual Cortex

Vision Acuity: the sharpness of vision Nearsightedness n n nearby objects seen more clearly lens focuses image of distant objects in front of retina Farsightedness n n Farsighted Vision faraway objects seen more clearly lens focuses near objects behind retina Nearsighted Vision Normal Vision

Color-Deficient Vision People who suffer redgreen blindness have trouble perceiving the number within the design

Visual Information Processing Trichromatic (three color) Theory n n Young and Helmholtz The eye contains three different types of cones capable of responding to various wavelengths of light w red w green w blue

Visual Information Processing Opponent-Process Theory: opposing retinal processes enable color vision “ON” “OFF” red green red blue yellow blue black white black

The 2 Theories

Visual Perception: Gestalt- the whole is greater than the sum of its parts Gestalt Principles (gestalt = an organized whole. We tend to integrate pieces of info. into meaningful wholes) n n n n Proximity Simplicity (law of good form) Connectedness Closure Continuity Similarity Phi Phenom

x Depth Perception: The Visual Cliff n n Binocular Cues: clues about distance using two eyes w Retinal Disparity: the fact that the right and left eyes see slightly different views of the object w Convergence: the degree to which the two eyes must converge to focus on the object Monocular Cues: clues about distance based on the image in either eye w Linear Perspective: parallel lines converge in the distance w Relative Size: if two objects are the same, the larger one is seen as closer w Interposition: the nearer object overlaps the object farther in the distance w Texture Gradient: textures are coarser the closer they are w Light and shadow w Height in plane

Pictorial depth cues

Audition (Hearing) n Audition w the sense of hearing n Frequency w the number of complete wavelengths that pass a point in a given time n Pitch w a tone’s highness or lowness w depends on frequency The Stimulus Vibrations of sound waves n Amplitude: loudness n Wavelength: pitch n Purity: timbre

Audition: The Ear Outer Ear (pinna) n n Auditory Canal Eardrum Middle Ear n n n hammer anvil stirrup Inner Ear n n oval window cochlea basilar membrane hair cells (cilia)

Audition: Pitch Perception Place Theory (high pitch) n theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated Frequency Theory (low pitch) n theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch

Touch Numerous types of receptors lie in varying depths in the skin Four Basic Skin Senses n n Hot Cold Pressure Pain

Conduction Hearing Loss Audition: Loss n hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea Nerve Hearing Loss n Amplitude required for perception relative to 20 -29 year-old group hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve Older people tend to hear low frequencies well but suffer hearing loss for high frequencies 1 time 10 times 1000 times 32 64 128 256 512 1024 2048 4096 8192 16384 Frequency of tone in waves per second Low Pitch High

Taste Sensations n n sweet sour salty bitter Sensory Interaction n n the principle that one sense may influence another as when the smell of food influences its taste The Stimuli: chemical substances that are soluble The Anatomy: taste buds act as the receptors for taste (about every two weeks) Perception of taste & flavor n Numerous factors can impact the flavor of food (Ex: temperature of the food, texture, prior condition of the mouth, health state of the organism, smell)

The Tongue

Smell

Smell (Olfaction) The Stimuli: chemical substances that are soluble The Anatomy: receptors are olfactory cilia which lie on the roof of the nasal passage and sinus Sense DOES NOT get filtered by thalamus Taste and smell interact to produce flavor

How We Locate Sounds Localization of Sound n n Sound is heard in the nearest ear first Sound is heard loudest in the nearest ear

Perceptual Constancies: Size, Shape, Brightness, Color

Visual Perception: Constancies Perceptual Constancies: the ability to experience a constant perception even what is reflected on the retina changes n Color: an object will be perceived as the same color even if the color reflected on the retina changes (ex: when an object is placed in the shade) n Size: an object will be perceived as the same size even if the size reflected on the retina changes (ex: dog running toward you is not seen as growing in size) n Shape: an object will be perceived as the same shape even if the shape reflected on the retina changes (ex: door opening toward you is still perceived as rectangular)

Visual Information Processing Feature Detectors n neurons in the visual cortex respond to specific features n shape n angle n movement Cell’s responses Stimulus Parallel Processing n simultaneous processing of several dimensions through multiple pathways n color n motion n form n depth

Touch Skin Sensations n pressure w only skin sensation with identifiable receptors n n n hot cold pain

Pain Gate-Control Theory n Theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain

Body Position and Movement Kinesthesis n the system for sensing the position and movement of individual body parts Vestibular Sense the sense of body movement and body’s position relative to gravity n including the sense of balance n Semicircular canals in ears n

Parapsychology Paranormal- beyond normal telepathy, ESP, out of body experience…