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Ergonomics > Perception > Flashcards

Perception Flashcards

1
Q

Perception

A
  • To drive a car, fly a plane, or even just walk across a room, a person must accurately perceive the locations of objects in either two- or three-dimensional space
  • Information from gauges, indicators, and signs must be detected and interpreted correctly
  • To be successful, we need to know how we perceive the world
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2
Q

Perception of Color

A
  • Determined by the wavelength of light reflected from or emitted by an object
  • Wavelengths of light are physical, but the perception of color is purely psychological - this means the perceived color can be influenced by factors other than the wavelength
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3
Q

Spectral Colors

A
  • a color comprised of a single wavelength
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4
Q

Non-spectral Colors

A
  • a color comprised of more than one wavelength
  • Additive mixing: combinations that increase the amount of light reflected (i.e. computer monitors)
  • Subtractive mixing: combinations that reduce the amount of light reflected (i.e. paint)
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5
Q

Properties of Color

A
  • Hue: variations described by names such as red, purple, blue, orange, etc.
  • Saturation: apparent purity, vividness, or richness
  • Lightness: dark to light; physically measured in luminosity, perceived as “brightness”
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6
Q

The Color Circle

A
  • a.k.a. The Color Wheel
  • Developed by isaac Newton
  • Describes the dimensions of hue (circumference/perimeter of circle) and saturation (radius of circle)
  • Brightness/Luminosity
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7
Q

CIE Color Space

A
  • Commission Internationale de l’Eclairage
  • Describes colors based on three primaries
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8
Q

Trichromatic Theory of Color Perception

A
  • Human color vision is trichromatic
  • any hue can be matched with a combination of three primary colors
  • Theory proposes there are 3 types of photo receptors corresponding to blue, green, and red, that determine our color perception
  • supported by the fact that there are 3 types of cones in the retina
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9
Q

Trichromatic Theory: Cones

A
  • Short wavelength receptors (Blue)
  • Photopigment: cyanolabe
  • Medium wavelength receptors (Green)
  • Photopigment: chlorolabe
  • Long wavelength receptors (Red)
  • Photopigment: erythrolabe
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10
Q

Color-Blindness

A
  • 1 in every 12 men have some form of color blindness
  • Dichromatic Vision: missing one photopigment
  • Protanopia: the long wavelength (red) cones do not contain the erythrolabe
  • Deutanopia: the medium wavelength (green) cones do not contain chlorolabe
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11
Q

Opponent Process Theory of Color Perception

A
  • Developed by Ewald hering in the 1800s
  • Suggests that color perception is controlled by the activity of two opponent systems: blue-yellow and red-green
  • In these systems, only one color can be signaled at a time
  • i.e. red light will increase their firing rates and green light will decrease it
  • This works through a process of excitatory and inhibitory responses
  • Support: when we stare at a saturated color long enough then the afterimage will be its opposite (but not as saturated)
  • i.e. stare at red, afterimage is green
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12
Q

HFE Issues (regarding color perception)

A
  • Many systems contain important information conveyed by color
  • i.e. traffic lights; this is ok for most color-blind people, because even though the stop light is red, it’s also always at the top
  • Some situations are not as friendly for color-blind people (i.e. electricians need good color vision)
  • Since a good percentage of the population is color-blind, we need to account for this to reduce human error
  • The best way to design around color-blindnes: do not use color as the only dimension to distinguish signals, buttons, or commands
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13
Q

Visual Acuity

A
  • Represents the clearness or sharpness of vision
  • Usually measured with a Snellen Eye Chart
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14
Q

Contrast Sensitivity

A
  • Represents the ability of the visual system to distinguish bright and im components of a static image
  • i.e. being able to read light gray letters on a dark gray background; night driving
  • A function of both the contrast and the spatial frequency of what is being viewed
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15
Q

Perceptual Organization

A
  • The process by which we apprehend particular relationships among potentially separate stimulus elements (i.e. parts, features, dimensions)
  • How the brain determines what pieces in the visual field go together
  • We don’t perceive color patches and gray and white blobs, we perceive distinct objects
  • The world we perceive is constructed by cues such as similarities and difference of color
  • i.e. the blind spot; even though no input comes through the eye at that spot, we do not see a hole in our perceived vision. We fill it in using the surrounding visual information
    *
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16
Q

Perceptual Organization:

Figure and Ground

A
  • We effortlessly perceive scenes as objects and a background or figure and ground
  • Sometimes our perception can be fooled when the arrangements of figure and ground are ambiguous
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17
Q

Grouping Principles

A
  • Developed by Gestalt Psychologists
  • “Gestalt” means “essence or shape of an entity’s complete form”
  • Proximity: elements close together are perceived as a group
  • Similarity: similar elements (in terms of color, form, or orientation) are perceived together
  • Continuity: points connected in straight or smoothly curving lines are perceived together
  • Closure: open curves are perceived as complete forms
  • Common Fate: elements moving in the same direction are perceived as one unit
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18
Q

Artificially-Induced Grouping

A
  • Rock & Palmer (1990)
  • Common Region: an explicit boundary
  • Connectedness: explicit lines
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19
Q

Depth Perception

A
  • Used to translate physiology and a 2D image on the retina into 3D spatial information
  • Oculomotor depth cues are provided proprioceptively
  • proprioception: ability to feel what your muscles are ding and where your limbs are positioned
  • Accomodation: automatic adjustments of the lens that maintain a focused image on the retina
  • good for stimuli between 20cm and 3m
  • Vergence: degree to which the eyes are turned inward to maintain fixation on an object
  • good for up to 6m
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20
Q

Monocular Depth Cues

A
  • a.k.a. Pictorial Cues
  • Convey impressions of depth in a still image
  • Interposition: nearer objects will block the view of more distant objects if the are in the same line of vision
  • Size: the “bigness” of an object
  • if you are familiar with how big an object is supposed to be then this is called “familiar size cue”
  • if you are not familiar with how big an object is supposed to be but there are multiples of different sizes then those serve as “relative size cues”
  • Perspective: angles such as when you know something is rectangular but it appears trapezoidal
  • Motion Parallax: apparent displacement or difference in position of an object viewed along two different lines of sight
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21
Q

Binocular Depth Cues

A
  • All monocular depth cues can be perceived with two eyes but binocular depth cues can only be perceived with two eyes
  • Binocular disparity: each eye receives a slightly different image of the world because of the eye’s location
22
Q

Perception of Size and Shape

A
  • Size and Shape constancy
  • we tend to see objects as the same size despite how large the image on our retina
  • we tend to perceive objects as the same shape even if the image on the retina may be a different shape
  • Size and shape constancy can be influence by the surroundings
  • Illusions occur for many reasons including but not limited to….
  • Inaccurate perception of depth
  • Displacement of contours
  • Inaccurate eye movements
23
Q

Percepton of Motion

A
  • Object motion: external object is moving
  • with a single stimulus moving in a stationary background, we can detect movement as slow as 0.5mm per second
  • Induced motion: a stationary background causes movement to be attributed to the wrong part of a scene
  • after staring at a waterfall, other objects appear to be moving up
  • Apparent motion: discrete jumps of retinal images can produce the appearance of smooth motion
  • i.e. television frames are perceived as smooth motion
24
Q

Pattern Recognition

A
  • The ability to identify what we see
  • since we can decompose an image into features (such as color or shapes), we use the identity of those features (or patterns) to recognize the object
  • Especially important in visual search tasks
  • i.e. Where’s Waldo?; Air traffic control
  • Objects can have multiple dimensions that contribute to a feature
  • Integral dimensions: cannot specify a value on one feature dimension without specifying the value on the other dimension (i.e. the stretching or bending of an object)
  • Separable dimensions: dimensional combinations that exist independently of one another (i.e. the color and form of an object)
  • Configural Dimension: dimensions that interact to create new features. These new features can interact or interfere with the pattern recognition
  • Expectancies: perception of the object is induced by context
25
Q

Senses

A
  • Vision/sight
  • Auditory/hearing
  • Skin senses or touch
  • Smells
  • Taste
26
Q

Senses and HFE

A
  • Need to be aware of the basic properties of each of these other sensory systems and the perceptual properties and phenomena associated with them
  • Most important is generally vision
  • Second most important is generally audition (hearing)
27
Q

Hearing

A
  • Plays an important role in the communication of information (i.e. radio broadcasts, speech, etc.)
  • Sounds can be used for signaling when something needs to be fixed/changed (i.e. seatbelt) or emergency situations (i.e. smoke alarms)
  • i.e. when driving a car, sound can inform you if…..
    you need to pull over for a cop, you car’s engine is malfunctioning, your turn signal is on, etc.
  • The benefit of auditory signals is that they can be detected and perceived regardless of where they are located relative to a person - this is not true for vision
  • Auditory signals are more attention-demanding than visual signals
28
Q

Measuring Sound

A
  • Aperiodic complex waves have random amplitude across a range of frequencies and are sometimes called noise
  • White noise: equal average intensity for all component frequencies
  • Wideband noise: frequencies across most or all of the auditory spectrum
  • Narrowband noise: only a restricted range frequencies
29
Q

Auditory Sensory System: Outer Ear

A
  • Outer ear
  • At the far end of the auditory canal is the eardrum or tympanic membrane
  • Vibrates when sound pressure waves strike it
  • Damage to the eardrum results in scar tissue and thickening of the membrane
  • Separates the outer ear from the middle ear
30
Q

Auditory Sensory System: Middle Ear

A
  • Passes vibrations of the eardrum to a much smaller membrane, the oval window; provides entry into the inner ear
  • This transmission of vibrations occurs by means of 3 bones which together are called ossicles
  • Malleus: aka hammer; attached to the center of the eardrum
  • Incus: aka anvil; connects the malleus to the stapes
  • Stapes: aka stirrup; attached to the oval window
  • Since the inner ear is filled with fluid, the middle ear serves as an amplifier for the sound so that it is not dampened when the vibrations change medium
  • Connected to the throat by the Eustachian tube to keep air pressure in the middle ear equal to environmental air pressure; Has to be equal for the ear to function properly
  • Small muscles connected to the eardrum and stapes produce the acoustic reflex in the presence of loud sounds
  • reduces teh vigrations from teh outer to inner ear by making the eardrum difficult to move
  • protects inner ear from dangerous sounds
  • muffles our own noises like eating and talking
31
Q

Auditory Sensory System: Auditory nerve

A
  • Two-tone suppression: when the neural response to a sound can be suppressed by a second sound- related to auditory masking
  • Interaural time differences and interaural intensity differences allow our brains to extract spatial information
32
Q

Auditory Sensory System:
Overview

A
  • An auditory stimulus initiates a complex sequence of events that lead to the perception of sound
  1. Physical vibrations of the eardrum, ossicles, and oval window produce a wave motion in the fluid of the inner ear
  2. This wave motion causes neural signals through the bending of hair cells in the basilar membrane
  3. The auditory information is transmitted along pathways in which the neurons respond to different frequencies and other acoustic features
  4. The processing of the sensory signal performed by the auditory system provides the basis for auditory perception
33
Q

Perception of Basic Properties

A
  • Using Stevens’ law, Stevens developed a scale for measuring loudness in which the unit is called a sone
  • HFE uses this scale to measure relative loudness of noise in different contexts
  • The loudness can be influenced by the frequency of the sound which is described by the equal-loudness contours
  • Equal-loudness contours illustrates several important perceptual points
  1. To sound equally loud, sounds of different frequencies must be adjusted to different intensity levels
  2. Sounds in the range of 3-4 kHz are most easily detected because they do not have to be as intense as tones outside this range to sound as loud
  3. Low-frequency tones below approximately 200 Hz are hardest to detect
  4. The differences in loudness across the frequencies progressively diminish as intensity increases
  • Pitch: the qualitative attribute of hearing that is determine by the frequency of the sound
  • can be influenced by variables other than frequency
  • Equal pitch contours show how pitch decreases with increasing intensity below 3kHz but increases above 3kHz
  • pitch can also be influenced by duration of sound; longer durations result in a higher ability to discriminate between pitches
34
Q

HFE Concerns-Auditory Perception

A
  • Perceived loudness is a function of intensity and the length of time it was presented
  • longer sounds are perceived as louder than shorter sounds, BUT when a sound is continuously presented, the loudness diminishes
  • Loudness is also affected by the range of frequencies (or bandwidth) in the sound; loudness is not affected by an increase in range of frequencies if intensity is held constant UNTIL a critical bandwidth is reached
  • Whether or not a sound can be heard depends on other sounds in the environment
  • If a sound is audible by itself but not in the presence of other sounds, the other sounds are said to mask it
  • as mask intensity increases, stimulus intensity must increase to be detected
  • the largest masking effect happens when the stiumulus and mask are the same or similar frequencies
  • if the stimulus is lower frequency than the mask, it can be detected
  • if the stimulus is higher frequency than the mask, it is harder to detect
  • Individual differences
  • more variability than the ability to see
  • audible ranges decrease throughout the lifetime
35
Q

Theories of Pitch Perception

A
  • 1800s
  • Frequency Theory: developed by Rutherford, the basilar membrane vibrates at the frequency of the auditory stimulus which causes neurons to respond at this frequency
  • Place theory: developed by Helmholtz, the frequency of sounds affects a particular place on the basilar membrane
36
Q

Consonance and Dissonance

A
  • Consonance and dissonance refer to the degree of pleasantness of combinations of tones
  • Dissonance is a combination of notes that sound hars or unpleasant to most people
  • combinations in(side) the critical bandwidth sound dissonant
  • Consonance is a combination of notes that sound pleasant to most people when played at the same time
  • combinations outside the critical bandwidth sound consonant
37
Q

Perception of Higher-Level Properties

A

Our wide range of auditory perceptions allow us to perceive complex patterns, determine the location of stimuli, and even recognize speech; it is important to know how auditory perception is influenced by organizational factors, spatial cues, and the features of speech stiumuli

38
Q

Perceptual Organization: Auditory

A
  • Proximity: sounds close together are perceived as together
  • temporal proximity is mor important than spatial proximity
  • sounds that follow each other closely in time are perceived as together
  • Similarity: similar sounds are perceived as together
  • determined primarily by pitch of sounds
  • sounds with similar pitches are grouped together
  • Auditory stream segregation: when the auditory system perceives sounds as together or separate to make a fluid sound
  • exemplified in music when a rapid alternation between high and low frequency notes causes the perception of two distinct sounds (melody and bass)
  • this also works to fill in gaps of audition
39
Q

Perceptual Organization: Sound Localization

A
  • Sound localization: the ability to locate sounds in space
  • i.e. the dopplar effect; when a change in frequency of a wave for an observer moving relative to the source of the wave (or the source moving and the observer stationary)
  • Need to have 2 ears
  • Good at determining locations horizontally
  • Relative intensity at each ear varies as the location of the sound moves
  • Differences in intensity are caused by the sound shadow
  • To differentiate front from back:
  • the pinna causes slight distortions in sounds
  • head movements provide dynamic changes that allow a sound to be localized more accurately
  • when head movement is restricted, the most common error is when localizing between front and back sounds
  • Anything that decreases the intensity of the sound decreases the localization accuracy
40
Q

Localization

A
  • Vertical sound localization is less accurate
  • It cannot be based on enteraural differences
  • Relies on intensity of the sound and reflections of sound waves from nearby objects
41
Q

Speech Perception

A
  • First we must be able to identify complex auditory patterns
  • We do this quickly and effortlessly
  • That doesn’t mean it’s a simple process
  • Phoneme: the smallest speach segment that can alter the meaning of a word
  • Speech spectogram: can be used to examine the characteristics of different phonemes
  • Phonemes are separated by categorical perception which distinguishes differences between phonemes
  • Phonemes are not the same as converstional speech; conversational speech has no physical boundaries between words
42
Q

Speech Perception: Context

A
  • Semantic context: words are identified by what you think the speaker meant
  • Syntactic context: words are arranged in a grammatically correct fashion
  • This shows how a listener’s expectancy influences the perception of speech
43
Q

Vestibular System

A
  • Located in the inner ear
  • Allows us to feel the movement of our bodies
  • Contributes to our ability to…
  • control the position of our eyes when we move our head
  • maintain an upright posture
  • maintain balance
  • Provides information on the direction gravity is pulling and yoru own acceleration
  • Works with vision and proprioception to control movements
  • Movements due to this system are mostly involuntary (i.e. movements of your eyes to counter body motion)
  • Greatly impaired by a lack of gravity (such as in space missions)
44
Q

Somesthetic System

A
  • Detects facets of the environment that you can physically feel
  • Includes the sense of touch, pressure, vibration, temperature, pain, and proprioception
  • Sensory system:
  • Most receptors are in the skin
  • Receptors in muscle tendons and joins (as well as skin) provide proprioception of our limbs; fundamental in coordination and control of bodily movement
  • Different receptors respond to different stimuli (i.e. pain, temperature, pressure, etc.)
  • Somatosensory cortex
45
Q

Somatosensory Cortex

A
  • Adjacent areas in the skin are adjacent in the cortex
  • More sensitive areas have larger areas in the cortex
46
Q

Perception of Touch

A
  • Absolute thresholds: the smallest amount of touch that is detected, these vary across the body; lowest absolute threshold is on the face
  • Two-point thresholds: obtained by asking participants if they can determine the distance between two stimuli on their skin, when they are perceived as one stimuli then they are below the two-point threshold; lowest two-point threshold is in the fingers
  • Vibrating stimuli are easier to detect than punctat stimuli (like a poke)
  • People can use tools to acquire a tactile stimulation where using a body part might be harmful (like when wearing gloves)
  • Passive touch: the skin is stationary and an external pressure stimulus is applied to it; this is how we obtain absolute and two-point thresholds
  • Active touch: the person contacts the stimulus by moving the skin
  • Not as sensitive as vision
  • Used to provide extra feedback in systems
47
Q

Perception of Temperature

A
  • Temperature sensitivity has an almost perfect temporal and spatial summation over large areas
  • if you press a heated flat surface on your skin, it will feel hotter than if you just press the edge
  • a hot object will feel hotter if it touches you longer until you experience adaptation
  • We are not accurate at locating hot and cold stimuli on our bodies
  • we can say the general area but not as specific as a tactual stimulus
48
Q

Perception of Pain

A
  • Signals risk of physical harm if the conditions persist for any length of time
  • Important for physical HFE work
  • i.e. lower back pain; by identifying the causes, we can prevent and treat it
  • Sensitivity to pain varies across the body
  • Lowest in the tip of the nose, sole of the food, and ball of the tumb
  • Highest in the back of the knee, bend of the elbow, and neck region
  • Unlike touch and temperature, pain thresholds show little temporal or spatial summation; you either feel pain or you don’t
  • It does show adaptation during prolong(ed) stimulation; you get used to pain over time
49
Q

Chemical Systems

A
  • a.k.a. Chemical Senses
  • Taste and smell
  • the stimulus is molecules of substances in the mouth and nose
  • Both important for survival
  • things that smell or taste bad are usually poisonous
  • we add bad smells to otherwise odorless potentially harmful substances such as propane
50
Q

Chemical Systems: Taste

A
  • Taste is stimulated by substances dissolved in saliva that affect receptors in the tongue and throat
  • The receptors are called taste buds
  • There are at least 4 tase qualities:
  • Sweet
  • Salty
  • Sour
  • Bitter
  • Sensitivity to each taste does not depend on the location on the tongue
51
Q

Chemical Systems: Smell

A
  • Smells are the result of receptors in the nose detecting substances carried by air currents
  • Receptor cells in the nasal cavity are called olfactory epithelium

Ergonomics (3 decks)

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