PSYCHOLOGY Chapter 5 Sensation

 Sensation  a process by which our sensory receptors and nervous system receive and represent stimulus energy  Perception  a process of organizing and interpreting sensory information  enables us to recognize meaningful objects and events

Sensation  Bottom-Up Processing  analysis that begins with the sense receptors and works up to the brain  Top-Down Processing  information processing guided by higher-level mental processes  (construct perceptions by drawing on our experience and expectations)

Psychophysics a discipline within psychology that studies the relationship between physical stimuli and the sensations and perceptions they effect

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

Sensation- Thresholds  Subliminal  When stimuli are below one’s absolute threshold for conscious awareness LowAbsolute threshold Medium Intensity of stimulus Percentage of correct detections Subliminal stimuli

Sensation- Thresholds  Signal Detection Theory  predicts how and when we detect the presence of a stimulus (signal) amid background stimulation (noise).  assumes that there is no single absolute threshold  detection depends partly on person’s  Experience, expectations, motivatio, level of fatigue HappenedDidn’t Happen For example, when you walk to your car that is parked in an empty parking lot late at night all by yourself, you might be much more aware of noises because the situation is somewhat threatening (you are primed and listening carefully to hear anything and everything). In this case, you may hear some slight noises that you might otherwise not hear if you were in a different situation that was not as threatening. Thus, your ability to detect signals or noises has been affected by these factors

Sensation- Basic Principles  Light- brightness  Sound- volume  Pressure- weight  Taste- sweetness

Sensation- Thresholds  Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage  For example:  Weight - 2% (if you are holding a 100 lb weight, you would need to add a least 2 more lbs to notice a difference in the weight)  tone frequency- 0.3%  light intensity - 8%

Sensation- Thresholds  Sensory adaptation- diminished sensitivity as a consequence of constant stimulation

Vision  Transduction  conversion of one form of energy to another  in sensation, transforming of stimulus energies into neural impulses

Agnosia  Agnosia  Inability to recognize objects  Prosopagnosia  Inability to recognize faces

Vision  Transduction  conversion of one form of energy to another  in sensation, transforming of stimulus energies into neural impulses  Wavelength  the distance from the peak of one wave to the peak of the next

Vision  Hue  dimension of color determined by wavelength of light  Intensity  amount of energy in a wave determined by amplitude  brightness  loudness

Vision  Pupil- adjustable opening in the center of the eye  Iris- a ring of muscle that 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

Vision  Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina  Retina- the light-sensitive inner serface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

Retina’s Reaction to Light  Optic nerve- nerve that carries neural impulses from the eye to the brain  Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there  Fovea- central point in the retina, around which the eye’s cones cluster

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

Visual Information Processing  Feature Detectors  nerve cells in the brain that respond to specific features  shape  angle  movement Stimulus Cell’s responses

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

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

Visual Information Processing  Color Constancy  Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

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

Audition- The Ear  Middle Ear  chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window  Inner Ear  innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs

Audition- The Ear  Decibels  The measuring unit for sound  Cochlea  coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger impulses

Audition  Place 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

Touch  Skin Sensations  pressure  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  “gate” opened by the activity of pain signals traveling up small nerve fibers  “gate” closed by activity in larger fibers or by information coming from the brain

Taste  Taste Sensations  sweet  sour  salty  bitter  One sense may influence another  (as when the smell of food influences its taste)

Smell  Olfactory Nerve  Nerves consisting of sensory fibers that carry impulses from the nose  Olfactory Bulb  Structure involved in the perception of odors

Body Position and Movement  Kinesthesis  the system for sensing the position and movement of individual body parts  Vestibular Sense  the sense of body movement and position  including the sense of balance

PSYCHOLOGY Chapter 6 Perception

Perceptual Organization: Gestalt  Sensory Interaction  One sense affects another sense.  Synesthesia – a disorder in which senses are always overlapping  Visual Capture  tendency for vision to dominate the other senses  (MaGurk effect)

Perception  Selective Attention focus of conscious awareness on a particular stimulus Selective Attention

Perceptual Organization: Gestalt  Grouping  the perceptual tendency to organize stimuli into coherent groups  We Group by:  Proximity - closeness  Similarity – objects with close resemblance  Continuity – objects are seen as uninterrupted  Closure – the mind completes missing gaps in shapes  Connectedness – linked spts and lines are seen as one object

Perceptual Organization  Figure and Ground--organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Perceptual Organization: Depth Perception  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  Monocular Cues  relative clarity  hazy object seen as more distant

Perceptual Organization: Depth Perception  Monocular Cues  texture coarse --> close fine --> distant

Perceptual Organization: Depth Perception Relative Size  relative size  smaller image is more distant

Perceptual Organization: Depth Perception Interposition  interposition  closer object blocks distant object

Perceptual Organization: Depth Perception  Monocular Cues (cont.)  relative height  higher objects seen as more distant

Perceptual Organization: Depth Perception  Monocular Cues (cont.)  relative motion  closer objects seem to move faster  Like driving on a highway

Perceptual Organization: Depth Perception  Monocular Cues (cont.)  linear perspective  parallel lines converge with distance

Perceptual Organization: Depth Perception  Monocular Cues (cont.)  relative brightness  closer objects appear brighter

Perceptual Constancy  Perceptual Constancy  perceiving objects as unchanging even as illumination and retinal image change  color  shape  size

Visual Information Processing  Color Constancy  Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

Agnosia Inability to recognize or interpret objects in the visual field Prosopagnosia Object agnosia Famous faces

Phi phenomenon an optical illusion in which the rapid appearance and disappearance of two stationary objects such as flashing lights are perceived as the movement back and forth of a single object.

Perceptual Adaptation The brain adapts to the perception that it receives. If vision is altered slightly, the brain accounts for the difference and will allow one to perceive the world as "normal." – For example: If someone wears distortion glasses, the brain processes the “new vision” as normal. As a result of this adaptation the brain makes to this difference in perception, and the subject, is able to perform daily tasks easily – Example 2: Brain flips the world “right side up” approximately 1 week after we are born

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

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