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
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
3
Q
Spectral Colors
A
- a color comprised of a single wavelength
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)
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”
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
7
Q
CIE Color Space
A
- Commission Internationale de l’Eclairage
- Describes colors based on three primaries
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
9
Q
Trichromatic Theory: Cones
A
- Short wavelength receptors (Blue)
- Photopigment: cyanolabe
- Medium wavelength receptors (Green)
- Photopigment: chlorolabe
- Long wavelength receptors (Red)
- Photopigment: erythrolabe
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
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
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
13
Q
Visual Acuity
A
- Represents the clearness or sharpness of vision
- Usually measured with a Snellen Eye Chart
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
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
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
18
Q
Artificially-Induced Grouping
A
- Rock & Palmer (1990)
- Common Region: an explicit boundary
- Connectedness: explicit lines
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
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
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
- Physical vibrations of the eardrum, ossicles, and oval window produce a wave motion in the fluid of the inner ear
- This wave motion causes neural signals through the bending of hair cells in the basilar membrane
- The auditory information is transmitted along pathways in which the neurons respond to different frequencies and other acoustic features
- 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
- To sound equally loud, sounds of different frequencies must be adjusted to different intensity levels
- 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
- Low-frequency tones below approximately 200 Hz are hardest to detect
- 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
