Chapter 5 – Sensation Chapter 6 - Perception

Sensation Sensation Perception Bottom Up Processing Top Down Processing

Sensation- Basic Principles Psychophysics study of the relationship between physical characteristics of stimuli and our psychological experience of them Light- brightness Sound- volume Pressure- weight Taste- sweetness

Sensation- Thresholds Absolute Threshold minimum stimulation needed to detect a particular stimulus 50% of the time Difference Threshold minimum difference between two stimuli that a subject can detect 50% of the time just noticeable difference (JND)

Sensation- Thresholds Signal Detection Theory 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 because ________________________________.

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

Sensation- Thresholds Weber’s Law- to perceive a difference between two stimuli, they must differ by a constant proportion Examples: Sensory adaptation- diminished sensitivity with constant stimulation

Vision Transduction- conversion of one form of energy to another Wavelength- the distance from the peak of one wave to the peak of the next Hue- dimension of color determined by wavelength of light Intensity- amount of energy in a wave determined by amplitude brightness loudness

Vision- Spectrum of Electromagnetic Energy

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

Vision

Vision Acuity- the sharpness of vision Nearsightedness Farsightedness nearby objects seen more clearly lens focuses image of distant objects in front of retina Farsightedness faraway objects seen more clearly lens focuses near objects behind retina

Retina’s Reaction to Light- Receptors Cones near center of retina (fovea) 6 million fine detail and color vision daylight or well-lit conditions Rods peripheral retina 120 million detect black, white and gray twilight or low light

Visual Information Processing Feature Detectors Hubel & Weisel neurons in the visual cortex respond to specific features shape angle movement Stimulus Cell’s responses

Visual Information Processing Parallel Processing simultaneous processing of several dimensions through multiple pathways color motion form depth

Visual Information Processing Trichromatic (three color) Theory Young and Helmholtz three different retinal color receptors red green blue

Opponent Process- Afterimage Effect

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

Audition Audition Frequency Pitch the sense of hearing the number of complete wavelengths that pass a point in a given time Pitch a tone’s highness or lowness depends on frequency

Audition Place Theory Frequency Theory the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated Frequency Theory the 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

Audition Conduction Hearing Loss Nerve Hearing Loss hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea Nerve Hearing Loss hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve

Touch Skin Sensations pressure warmth cold pain only skin sensation with identifiable receptors warmth cold pain

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

Taste Taste Sensations Sensory Interaction sweet sour salty Bitter Umami Sensory Interaction the principle that one sense may influence another as when the smell of food influences its taste

Perception Selective Attention focus of conscious awareness on a particular stimulus

Perceptual Organization- Gestalt Visual Capture tendency for vision to dominate the other senses Grouping the perceptual tendency to organize stimuli into coherent groups

Perceptual Organization- Gestalt Gestalt- an organized whole Wertheimer, Koffka, Kohler Grouping Principles proximity- group nearby figures together similarity- group figures that are similar continuity- perceive continuous patterns closure- fill in gaps connectedness- spots, lines and areas are seen as unit when connected

Perceptual Organization- Grouping Principles

Perceptual Organization-Depth Perception ability to see objects in three dimensions allows us to judge distance Binocular cues retinal disparity images from the two eyes differ closer the object, the larger the disparity convergence neuromuscular cue two eyes move inward for near objects

Perceptual Organization-Depth Perception Visual Cliff

Perceptual Organization-Depth Perception Monocular Cues relative size smaller image is more distant interposition closer object blocks distant object relative clarity hazy object seen as more distant texture coarse --> close fine --> distant

Perceptual Organization-Depth Perception Monocular Cues (cont.) relative height higher objects seen as more distant relative motion closer objects seem to move faster linear perspective parallel lines converge with distance relative brightness closer objects appear brighter

Perceptual Constancy Perceptual Constancy perceiving objects as unchanging despite changes in retinal image color shape size

Sensory Restriction- Blakemore & Cooper, 1970 Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars.

Perceptual Interpretation Perceptual Adaptation (vision) ability to adjust to an artificially displaced visual field prism glasses Perceptual Set a mental predisposition to perceive one thing and not another

Perceptual Set- Schemas What you see in the center is influenced by perceptual set

Perception without Sensation? Extrasensory Perception controversial claim that perception can occur apart from sensory input telepathy clairvoyance precognition Parapsychology the study of paranormal phenomena ESP psychokinesis